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  • 51.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sam, Lydia
    Department of Environmental Science, Sharda University.
    Bhardwaj, Akanksha
    Banaras Hindu University, Varanasi.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    LiDAR remote sensing of the cryosphere: Present applications and future prospects2016In: Remote Sensing of Environment, ISSN 0034-4257, E-ISSN 1879-0704, Vol. 177, p. 125-143Article in journal (Refereed)
    Abstract [en]

    The cryosphere consists of frozen water and includes lakes/rivers/sea ice, glaciers, ice caps/sheets, snow cover, and permafrost. Because highly reflective snow and ice are the main components of the cryosphere, it plays an important role in the global energy balance. Thus, any qualitative or quantitative change in the physical properties and extents of the cryosphere affects global air circulation, ocean and air temperatures, sea level, and ocean current patterns. Due to the hardships involved in collecting ground control points and field data for high alpine glaciers or vast polar ice sheets, several researchers are currently using remote sensing. Satellites provide an effective space-borne platform for remotely sensing frozen areas at the global and regional scales. However, satellite remote sensing has several constraints, such as limited spatial and temporal resolutions and expensive data acquisition. Therefore, aerial and terrestrial remote sensing platforms and sensors are needed to cover temporal and spatial gaps for comprehensive cryospheric research. Light Detection and Ranging (LiDAR) antennas form a group of active remote sensors that can easily be deployed on all three platforms, i.e., satellite, aerial, and terrestrial. The generation of elevation data for glacial and snow-covered terrain from photogrammetry requires high contrast amongst various reflective surfaces (ice, snow, firn, and slush). Conventional passive optical remote sensors do not provide the necessary accuracy, especially due to the unavailability of reliable ground control points. However, active LiDAR sensors can fill this research gap and provide high-resolution and accurate Digital Elevation Models (DEMs). Due to the obvious advantages of LiDAR over conventional passive remote sensors, the number of LiDAR-based cryospheric studies has increased in recent years. In this review, we highlight studies that have utilised LiDAR sensors for the cryospheric research of various features, such as snow cover, polar ice sheets and their atmospheres, alpine glaciers, and permafrost. Because this technology shows immense promise for applications in future cryospheric research, we also emphasise the prospects of utilising LiDAR sensors. In this paper, a large compilation of relevant references is presented to allow readers to explore particular topics of interest.

  • 52.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sam, Lydia
    Institut für Kartographie, Technische Universität Dresden.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Rock glaciers as proxies for identifying terrestrial and analogous Martian permafrost2016In: XI. International Conference On Permafrost: Book of Abstracts / [ed] Günther, F. and Morgenstern, A., Potsdam: Bibliothek Wissenschaftspark Albert Einstein , 2016, p. 535-537Conference paper (Refereed)
  • 53.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sam, Lydia
    Institut für Kartographie, Technische Universität Dresden.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Zorzano Mier, Maria-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Fonseca, Ricardo
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martian slope streaks as plausible indicators of transient water activity2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 7074Article in journal (Refereed)
    Abstract [en]

    Slope streaks have been frequently observed in the equatorial, low thermal inertia and dusty regions of Mars. The reason behind their formation remains unclear with proposed hypotheses for both dry and wet mechanisms. Here, we report an up-to-date distribution and morphometric investigation of Martian slope streaks. We find: (i) a remarkable coexistence of the slope streak distribution with the regions on Mars with high abundances of water-equivalent hydrogen, chlorine, and iron; (ii) favourable thermodynamic conditions for transient deliquescence and brine development in the slope streak regions; (iii) a significant concurrence of slope streak distribution with the regions of enhanced atmospheric water vapour concentration, thus suggestive of a present-day regolith-atmosphere water cycle; and (iv) terrain preferences and flow patterns supporting a wet mechanism for slope streaks. These results suggest a strong local regolith-atmosphere water coupling in the slope streak regions that leads to the formation of these fluidised features. Our conclusions can have profound astrobiological, habitability, environmental, and planetary protection implications

  • 54.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sam, Lydia
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institut für Kartographie, Technische Universität Dresden, Dresden, Germany. Department of Environmental Science, Sharda University, Greater Noida, India.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC ‐ UGR), Armilla, Spain. UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK.
    Zorzano Mier, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA-CSIC), Madrid, Spain.
    Are Slope Streaks Indicative of Global‐Scale Aqueous Processes on Contemporary Mars?2019In: Reviews of geophysics, ISSN 8755-1209, E-ISSN 1944-9208, Vol. 57, no 1, p. 48-77Article in journal (Refereed)
    Abstract [en]

    Slope streaks are prevalent and intriguing dark albedo surface features on contemporary Mars. Slope streaks are readily observed in the equatorial and subequatorial dusty regolith regions with low thermal inertia. They gradually fade over decadal timescales. The proposed mechanisms for their formation vary widely based on several physicochemical and geomorphological explanations. The scientific community is divided in proposing both dry and wet mechanisms for the formation of slope streaks. Here we perform a systematic evaluation of the literature for these wet and dry mechanisms. We discuss the probable constraints on the various proposed mechanisms and provide perspectives on the plausible process driving global‐scale slope streak formation on contemporary Mars. Although per our understanding, a thorough consideration of the global distribution of slope streaks, their morphology and topography, flow characteristics, physicochemical and atmospheric coincidences, and terrestrial analogies weighs more in favor of several wet mechanisms, we acknowledge that such wet mechanisms cannot explain all the reported morphological and terrain variations of slope streaks. Thus, we suggest that explanations considering both dry and wet processes can more holistically describe all the observed morphological variations among slope streaks. We further acknowledge the constraints on the resolutions of remote sensing data and on our understanding of the Martian mineralogy, climate, and atmosphere and recommend continuous investigations in this direction using future remote sensing acquisitions and simulations. In this regard, finding more wet and dry terrestrial analogs for Martian slope streaks and studying them at high spatiotemporal resolutions can greatly improve our understanding.

  • 55.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sam, Lydia
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Zorzano Mier, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Discovery of recurring slope lineae candidates in Mawrth Vallis, Mars2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 2040Article in journal (Refereed)
    Abstract [en]

    utside of established RSL regions and further prompt the inclusion of a new geographical region within the RSL candidate group. Our inferences on the RSL candidates are based on several morphological and geophysical evidences and analogies: (i) the dimensions of the RSL candidates are consistent with confirmed mid-latitude RSL; (ii) albedo and thermal inertia values are comparable to those of other mid-latitude RSL sites; and (iii) features are found in a summer season image and on the steep and warmest slopes. These results denote the plausible presence of transient liquid brines close to the previously proposed landing ellipse of the ExoMars rover, rendering this site particularly relevant to the search of life. Further investigations of Mawrth Vallis carried out at higher spatial and temporal resolutions are needed to identify more of such features at local scales to maximize the scientific return from the future Mars rovers, to prevent probable biological contamination during rover operations, to evade damage to rover components as brines can be highly corrosive, and to quantify the ability of the regolith at mid-latitudes to capture atmospheric water which is relevant for in-situ-resource utilization.

  • 56.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sam, Lydia
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Zorzano Mier, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ramírez Luque, Juan Antonio
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    UAV Imaging of a Martian Brine Analogue Environment in a Fluvio-Aeolian Setting2019In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 11, no 18, article id 2104Article in journal (Refereed)
    Abstract [en]

    Understanding extraterrestrial environments and landforms through remote sensing and terrestrial analogy has gained momentum in recent years due to advances in remote sensing platforms, sensors, and computing efficiency. The seasonal brines of the largest salt plateau on Earth in Salar de Uyuni (Bolivian Altiplano) have been inadequately studied for their localized hydrodynamics and the regolith volume transport across the freshwater-brine mixing zones. These brines have recently been projected as a new analogue site for the proposed Martian brines, such as recurring slope lineae (RSL) and slope streaks. The Martian brines have been postulated to be the result of ongoing deliquescence-based salt-hydrology processes on contemporary Mars, similar to the studied Salar de Uyuni brines. As part of a field-site campaign during the cold and dry season in the latter half of August 2017, we deployed an unmanned aerial vehicle (UAV) at two sites of the Salar de Uyuni to perform detailed terrain mapping and geomorphometry. We generated high-resolution (2 cm/pixel) photogrammetric digital elevation models (DEMs) for observing and quantifying short-term terrain changes within the brines and their surroundings. The achieved co-registration for the temporal DEMs was considerably high, from which precise inferences regarding the terrain dynamics were derived. The observed average rate of bottom surface elevation change for brines was ~1.02 mm/day, with localized signs of erosion and deposition. Additionally, we observed short-term changes in the adjacent geomorphology and salt cracks. We conclude that the transferred regolith volume via such brines can be extremely low, well within the resolution limits of the remote sensors that are currently orbiting Mars, thereby making it difficult to resolve the topographic relief and terrain perturbations that are produced by such flows on Mars. Thus, the absence of observable erosion and deposition features within or around most of the proposed Martian RSL and slope streaks cannot be used to dismiss the possibility of fluidized flow within these features

  • 57.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sam, Lydia
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martín-Torres, F. Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Zorzano, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Revisiting enigmatic Martian slope streaks2019In: Earth Space and Science News - Editors Vox, Vol. 100Article in journal (Other academic)
  • 58.
    Bhardwaj, Anshuman
    et al.
    TERI University, New Delhi.
    Sam, Lydia
    Department of Environmental Science, Sharda University.
    Singh, Shaktiman
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Kumar, Ramesh
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Automated detection and temporal monitoring of crevasses using remote sensing and their implications for glacier dynamics2016In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 57, no 71, p. 81-91Article in journal (Refereed)
    Abstract [en]

    Detailed studies on temporal changes of crevasses and their linkage with glacier dynamics are scarce in the Himalayan context. Observations of temporally changing surficial crevasse patterns and their orientations are suggestive of the processes that determine seasonal glacier flow characteristics. In the present study, on a Himalayan valley glacier, changing crevasse patterns and orientations were detected and mapped on Landsat 8 images in an automated procedure using the ratio of Thermal Infrared Sensor (TIRS) band 10 to Optical Land Imager (OLI) shortwave infrared (SWIR) band 6. The ratio was capable of mapping even crevasses falling under mountain shadows. Differential GPS observations suggested an average error of 3.65% and root-mean-square error of 6.32m in crevasse lengths. A year-round observation of these crevasses, coupled with field-based surface velocity measurements, provided some interesting interpretations of seasonal glacier dynamics.

  • 59.
    Bhardwaj, Anshuman
    et al.
    Snow and Avalanche Study Establishment, Defence Research and Development Organization (DRDO), Him Parisar, Sector-37A, Chandigarh.
    Singh, Mritunjay Kumar
    Snow and Avalanche Study Establishment, Defence Research and Development Organization (DRDO), Him Parisar, Sector-37A, Chandigarh.
    Joshi, Prakash C.
    Space Applications Centre, ISRO, Ahmedabad, Atmospheric and Oceanic Sciences Group, Space Applications Centre, Indian Space Research Organisation, Ahmedabad.
    Snehmani, Snehmani
    Snow and Avalanche Study Establishment, Defence Research and Development Organization (DRDO), Him Parisar, Sector-37A, Chandigarh.
    Singh, Shaktiman
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Sam, Lydia
    Department of Environmental Science, Sharda University.
    Gupta, R.D.
    Snow and Avalanche Study Establishment, Defence Research and Development Organization (DRDO), Him Parisar, Sector-37A, Chandigarh.
    Kumar, Rajesh
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    A lake detection algorithm (LDA) using Landsat 8 data: A comparative approach in glacial environment2015In: International Journal of Applied Earth Observation and Geoinformation, ISSN 0303-2434, Vol. 38, p. 150-163Article in journal (Refereed)
    Abstract [en]

    Glacial lakes show a wide range of turbidity. Owing to this, the normalized difference water indices (NDWIs) as proposed by many researchers, do not give appropriate results in case of glacial lakes. In addition, the sub-pixel proportion of water and use of different optical band combinations are also reported to produce varying results. In the wake of the changing climate and increasing GLOFs (glacial lake outburst floods), there is a need to utilize wide optical and thermal capabilities of Landsat 8 data for the automated detection of glacial lakes. In the present study, the optical and thermal bandwidths of Landsat 8 data were explored along with the terrain slope parameter derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model Version2 (ASTER GDEM V2), for detecting and mapping glacial lakes. The validation of the algorithm was performed using manually digitized and subsequently field corrected lake boundaries. The pre-existing NDWIs were also evaluated to determine the supremacy and the stability of the proposed algorithm for glacial lake detection. Two new parameters, LDI (lake detection index) and LF (lake fraction) were proposed to comment on the performances of the indices. The lake detection algorithm (LDA) performed best in case of both, mixed lake pixels and pure lake pixels with no false detections (LDI = 0.98) and very less areal underestimation (LF= 0.73). The coefficient of determination (R-2) between areal extents of lake pixels, extracted using the LDA and the actual lake area, was very high (0.99). With understanding of the terrain conditions and slight threshold adjustments, this work can be replicated for any mountainous region of the world.

  • 60.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Singh, Shaktiman
    Institut für Kartographie, Technische Universität Dresden.
    Sam, Lydia
    Institut für Kartographie, Technische Universität Dresden.
    Bhardwaj, Akanksha
    Banaras Hindu University, Varanasi.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Singh, Atar
    Department of Environmental Science, Sharda University.
    Kumar, Rajesh
    Department of Environmental Science, Sharda University.
    MODIS-based estimates of strong snow surface temperature anomaly related to high altitude earthquakes of 20152017In: Remote Sensing of Environment, ISSN 0034-4257, E-ISSN 1879-0704, Vol. 188, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The high levels of uncertainty associated with earthquake prediction render earthquakes some of the worst natural calamities. Here, we present our observations of MODerate resolution Imaging Spectroradiometer (MODIS)-derived Land Surface Temperature (LST) anomaly for earthquakes in the largest tectonically active Himalayan and Andean mountain belts. We report the appearance of fairly detectable pre-earthquake Snow Surface Temperature (SST) anomalies. We use 16 years (2000–2015) of MODIS LST time-series data to robustly conclude our findings for three of the most destructive earthquakes that occurred in 2015 in the high mountains of Nepal, Chile, and Afghanistan. We propose the physical basis behind higher sensitivity of snow towards geothermal emissions. Although the preliminary appearance of SST anomalies and their amplitudes vary, we propose employing a global-scale monitoring system for detecting and studying such spatio-temporal geophysical signals. With the advent of improved remote sensors, we anticipate that such efforts can be another step towards improved earthquake predictions.

  • 61.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Department of Environmental Science, Sharda University.
    Singh, Shaktiman
    Department of Environmental Science, Sharda University,.
    Sam, Lydia
    Department of Environmental Science, Sharda University,.
    Joshi, PK
    School of Environmental Sciences, Jawaharlal Nehru University, New Delhi.
    Bhardwaj, Akanksha
    Banaras Hindu University.
    Martín-Torres, Javier F.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Kumar, Rajesh
    Department of Environmental Science, Sharda University.
    A review on remotely sensed land surface temperature anomaly as an earthquake precursor2017In: International Journal of Applied Earth Observation and Geoinformation, ISSN 0303-2434, Vol. 63, p. 158-166Article in journal (Refereed)
    Abstract [en]

    The low predictability of earthquakes and the high uncertainty associated with their forecasts make earthquakes one of the worst natural calamities, capable of causing instant loss of life and property. Here, we discuss the studies reporting the observed anomalies in the satellite-derived Land Surface Temperature (LST) before an earthquake. We compile the conclusions of these studies and evaluate the use of remotely sensed LST anomalies as precursors of earthquakes. The arrival times and the amplitudes of the anomalies vary widely, thus making it difficult to consider them as universal markers to issue earthquake warnings. Based on the randomness in the observations of these precursors, we support employing a global-scale monitoring system to detect statistically robust anomalous geophysical signals prior to earthquakes before considering them as definite precursors.

  • 62.
    Birman, Camille
    et al.
    Météo-France-CNRS, Toulouse .
    Mahfouf, Jean-François
    Météo-France-CNRS, Toulouse.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. IRV.
    Mendrok, Jana
    Chalmers University of Technology, Gothenburg, Sweden.
    Buehler, Stefan A.
    University of Hamburg, Hamburg.
    Brath, Manfred
    University of Hamburg, Hamburg .
    Information content on hydrometeors from millimeter and sub-millimeter wavelengths2017In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 69, no 1, article id 1271562Article in journal (Refereed)
    Abstract [en]

    This study examines the information content on hydrometeors that could be provided by a future HYperspectralMicrowave Sensor (HYMS) with frequencies ranging from 6.9 to 874 GHz (millimeter and sub-millimeter regions). Through optimal estimation theory the information content is expressed quantitatively in terms of degrees of freedom for signal (DFS). For that purpose the Atmospheric Radiative Transfer Simulator (ARTS) and its Jacobians are used with a set of 25 cloudy and precipitating profiles and their associated errors from the European Centre for Medium-range Weather Forecasting (ECMWF) global numerical weather prediction model.

    In agreement with previous studies it is shown that frequencies between 10 and 40 GHz are the most informative ones for liquid and rain water contents. Similarly, the absorption band at 118 GHz contains significant information on liquid precipitation. A set of new window channels (15.37-, 40.25-, 101-GHz) could provide additional information on the liquid phase. The most informative channels on cloud icewater are the window channels at 664 and 874GHz and thewater vapour absorption bands at 325 and 448 GHz. Regarding snow water contents, the channels having the largest DFS values are located inwindow regions (150-, 251-, 157-, 101-GHz). However it is necessary to consider 90 channels in order to represent 90% of the DFS. The added value of HYMS has been assessed against current Special Sensor Microwave Imager/Sounder (SSMI/S) onboard the Defense Meteorological Satellite Program (DMSP) and future (Microwave Imager/Ice Cloud Imager (MWI/ICI) onboard European Polar orbiting Satellite – Second Generation (EPS-SG)) microwave sensors. It appears that with a set of 276 channels the information content on hydrometeors would be significantly enhanced: the DFS increases by 1.7 against MWI/ICI and by 3 against SSMI/S. A number of tests have been performed to examine the robustness of the above results. The most informative channels on solid hydrometeors remain the same over land and over ocean surfaces. On the other hand, the database is not large enough to produce robust results over land surfaces for liquid hydrometeors. The sensitivity of the results to the microphysical properties of frozen hydrometeors has been investigated. It appears that a change in size distribution and scattering properties can move the large information content of the channels at 664 and 874 GHz from cloud ice to solid precipitation.

  • 63.
    Bish, D.L.
    et al.
    Indiana University, Department of Geological Sciences, Bloomington.
    Blake, D.F.
    NASA Ames.
    Vaniman, D.T.
    Planetary Science Institute, Tucson.
    Chipera, S.J.
    CHK Energy.
    Morris, R.V.
    NASA Johnson Space Center, Houston.
    Ming, D.W.
    NASA Johnson Space Center, Houston.
    Treiman, A.H.
    Lunar and Planetary Institute, Houston.
    Sarrazin, P.
    In-Xitu, Campbell, California.
    Morrison, S.M.
    Department of Geology, University of Arizona, Tucson.
    Downs, R.T.
    Department of Geology, University of Arizona, Tucson.
    Achilles, C.N.
    ESCG/UTC Aerospace Systems, Houston.
    Yen, A.S.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Bristow, T.F.
    NASA Ames.
    Crisp, J.A.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Morookian, J.M.
    NASA Jet Propulsion Laboratory, Pasadena.
    Farmer, J.D.
    Department of Geological Sciences, Arizona State University, Tempe.
    Rampe, E.B.
    NASA Johnson Space Center, Houston.
    Stolper, E.M.
    California Institute of Technology, Pasadena.
    Spanovich, N.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Martin-Torres, Javier
    Centro de Astrobiología (CAB).
    X-ray diffraction results from Mars Science Laboratory: Mineralogy of Rocknest at Gale Crater2013In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 341, no 6153, article id 1238932Article in journal (Refereed)
    Abstract [en]

    The Mars Science Laboratory rover Curiosity scooped samples of soil from the Rocknest aeolian bedform in Gale crater. Analysis of the soil with the Chemistry and Mineralogy (CheMin) x-ray diffraction (XRD) instrument revealed plagioclase (~An57), forsteritic olivine (~Fo62), augite, and pigeonite, with minor K-feldspar, magnetite, quartz, anhydrite, hematite, and ilmenite. The minor phases are present at, or near, detection limits. The soil also contains 27 ± 14 weight percent x-ray amorphous material, likely containing multiple Fe3+- and volatile-bearing phases, including possibly a substance resembling hisingerite. The crystalline component is similar to the normative mineralogy of certain basaltic rocks from Gusev crater on Mars and of martian basaltic meteorites. The amorphous component is similar to that found on Earth in places such as soils on the Mauna Kea volcano, Hawaii.

  • 64.
    Blanco, Enrique
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    DESIGN OF A SCALABLE, ADAPTABLE AND RELIABLE DEORBITING MECHANISM2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 65.
    Borovoi, Anatoli
    et al.
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Reichard, Jens
    Richard-Aβmann-Observatorium, DWD, Lindenberg, Germany.
    Görsdorf, Ulrich
    Richard-Aβmann-Observatorium, DWD, Lindenberg, Germany.
    Wolf, Veronika
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Richard-Aβmann-Observatorium, DWD, Lindenberg, Germany.
    Konoshonkin, Alexander
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Shishko, Victor
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Kustova, Natalia
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Retrieving microphysics of cirrus clouds from data measured with raman lidar ramses and a tilted ceilometer2018In: EPJ Web of Conferences, ISSN 2101-6275, E-ISSN 2100-014X, Vol. 176, article id 08002Article in journal (Refereed)
    Abstract [en]

    To develop a microphysical model of cirrus clouds, data obtained by Raman lidar RAMSES and a tilted ceilometer are studied synergistically. The measurements are interpreted by use of a data archive containing the backscattering matrixes as well as the depolarization, color and lidar ratios of ice crystals of different shapes, sizes and spatial orientations calculated within the physical-optics approximation.

  • 66.
    Bridges, N.T.
    et al.
    Johns Hopkins University Applied Physics Laboratory, Laurel.
    Blaney, D.L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Day, M.D.
    Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin.
    Herkenhoff, K.E.
    U.S. Geological Survey, Flagstaff.
    Lanza, N.L.
    Los Alamos National Laboratory.
    Mouélic, S. Le
    CNRS/Université de Nantes.
    Martin-Torres, Javier
    Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Maurice, S.
    IRAP, CNRS-Université Toulouse.
    Newman, C.E.
    Ashima Research, Pasadena.
    Newsom, H.E.
    Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque.
    Wiens, R.C.
    Los Alamos National Laboratory.
    Zorzano, M.-P.
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Rock abrasion and landscape modification by windblown sand as documented by the MSL Curiosity rover2015Conference paper (Refereed)
  • 67.
    Bruns, M.
    et al.
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Burrows, J.P.
    Universität Bremen, Institute of Environmental Physics.
    Richter, A.
    Universität Bremen, Institute of Environmental Physics.
    Rozanov, A.
    Universität Bremen, Institute of Environmental Physics.
    Wang, P.
    Royal Netherlands Meteorological Institute (KNMI), De Bilt.
    Heue, K. P.
    University of Heidelberg, Institute of Environmental Physics.
    Platt, U.
    University of Heidelberg, Institute of Environmental Physics.
    Pundt, I.
    University of Heidelberg, Institute of Environmental Physics.
    Wagner, T.
    University of Heidelberg, Institute of Environmental Physics.
    NO2 profile retrieval using airborne multi axis UV-visible skylight absorption measurements over central Europe2006In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 6, no 10, p. 3049-3058Article in journal (Refereed)
  • 68.
    Bruns, Marco
    et al.
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Burrows, John P.
    Universität Bremen, Institute of Environmental Physics.
    Heue, Klaus-Peter
    University of Heidelberg, Institute of Environmental Physics.
    Platt, Ulrich
    University of Heidelberg, Institute of Environmental Physics.
    Pundt, Irene
    University of Heidelberg, Institute of Environmental Physics.
    Richter, Andreas
    Universität Bremen, Institute of Environmental Physics.
    Rozanov, Alexej
    Universität Bremen, Institute of Environmental Physics.
    Wagner, Thomas
    University of Heidelberg, Institute of Environmental Physics.
    Wang, Ping
    Universität Bremen, Institute of Environmental Physics.
    Retrieval of profile information from airborne multiaxis UV-visible skylight absorption measurements2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 22, p. 4415-4426Article in journal (Refereed)
    Abstract [en]

    A recent development in ground-based remote sensing of atmospheric constituents by UV-visible, absorption measurements of scattered light is the simultaneous use of several horizon viewing directions in addition to the traditional zenith-sky pointing. The different light paths through the atmosphere enable the vertical distribution of some atmospheric absorbers, such as NO2, BrO, or O-3, to be retrieved. This approach has recently been implemented on an airborne platform. This novel instrument, the airborne multiaxis differential optical absorption spectrometer (AMAXDOAS), has been flown for the first time. In this study, the amount of profile information that can be retrieved from such measurements is investigated for the trace gas NO2. Sensitivity studies on synthetic data are performed for a variety of representative measurement conditions including two wavelengths, one in the UV and one in the visible, two different surface spectral reflectances, various lines of sight (LOSs), and for two different flight altitudes. The results demonstrate that the AMAXDOAS measurements contain useful profile information, mainly at flight altitude and below the aircraft. Depending on wavelength and LOS used, the vertical resolution of the retrieved profiles is as good as 2 km near flight altitude. Above 14 km the profile information content of AMAXDOAS measurements is sparse. Airborne multiaxis measurements are thus a promising tool for atmospheric studies in the troposphere and the upper troposphere and lower stratosphere region.

  • 69.
    Brändström, U.
    et al.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Enell, C-F
    Sodankylä Geophysical Observatory, University of Oulu.
    Widell, O.
    SSC, ESRANGE, Kiruna.
    Hansson, T.
    SSC, ESRANGE, Kiruna.
    Whiter, D.
    Finnish Meteorological Institute, Helsinki.
    Mäkinen, S.
    Finnish Meteorological Institute, Helsinki.
    Mikhaylova, Daria
    Swedish Institute of Space Physics / Institutet för rymdfysik , Polar Atmospheric Research, Swedish Institute of Space Physics, Box 812, 98128, Kiruna.
    Axelsson, Katarina
    Swedish Institute of Space Physics.
    Sigernes, F.
    The Kjell Henriksen Observatory, UNIS, Longyearbyen.
    Gulbrandsen, N.
    Tromsø University.
    Schlatter, N.M.
    School of Electrical Engineering, Royal Institute of Technology, Stockholm.
    Gjendem, A.G.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cai, L.
    Department of Physics, University of Oulu.
    Reistad, J.P.
    University of Bergen.
    Daae, M.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Demissie, D.D.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Andalsvik, Y.L.
    Department of Physics, University of Oslo.
    Roberts, O.
    Aberystwyth University.
    Polyuanov, S.
    Polar Geophysical Institute, Murmansk.
    Chernouss, S.
    Polar Geophysical Institute, Apatity.
    Results from the intercalibration of optical low light calibration sources 20112012In: Geoscientific Instrumentation, Methods and Data Systems, ISSN 2193-0856, E-ISSN 2193-0864, Vol. 1, no 1, p. 43-51Article in journal (Refereed)
    Abstract [en]

    Following the 38th Annual European Meeting onAtmospheric Studies by Optical Methods in Siuntio in Finland,an intercalibration workshop for optical low light calibrationsources was held in Sodankyl¨a, Finland. The mainpurpose of this workshop was to provide a comparable scalefor absolute measurements of aurora and airglow. All sourcesbrought to the intercalibration workshop were compared tothe Fritz Peak reference source using the Lindau CalibrationPhotometer built by Wilhelm Barke and Hans Lauche in1984. The results were compared to several earlier intercalibrationworkshops. It was found that most sources were fairlystable over time, with errors in the range of 5–25 %. To furthervalidate the results, two sources were also intercalibratedat UNIS, Longyearbyen, Svalbard. Preliminary analysis indicatesagreement with the intercalibration in Sodankyl¨a withinabout 15–25 %.

  • 70.
    Buch, Aranaud
    et al.
    LGPM, Ecole Centrale Paris, Chatenay-Malabry.
    Freissinet, Caroline
    NASA Goddard Space Flight Center.
    Szopa, Cyril
    LATMOS, Université Pierre et Marie Curie, Université Versailles Saint-Quentin & CNRS, Guyancourt.
    Glavin, Danny
    NASA Goddard Space Flight Center.
    Coll, Patrice
    Laboratoire Interuniversitaire des Systèmes Atmosphériques, Université Paris-Est Créteil, Université Paris Diderot and CNRS, Créteil.
    Cabane, Michel
    LATMOS, Université Pierre et Marie Curie, Université Versailles Saint-Quentin & CNRS, Guyancourt.
    Eigenbrode, Jen
    NASA Goddard Space Flight Center.
    Navarro-Gonzalez, Rafael
    Universidad Nacional Autónoma de México.
    Stern, Jen
    NASA Goddard Space Flight Center.
    Coscia, David
    LATMOS, Université Pierre et Marie Curie, Université Versailles Saint-Quentin & CNRS, Guyancourt.
    Teinturier, Samuel
    LATMOS, Université Pierre et Marie Curie, Université Versailles Saint-Quentin & CNRS, Guyancourt.
    Dworkin, Jason
    NASA Goddard Space Flight Center.
    Mahaffy, Paul
    NASA Goddard Space Flight Center.
    Martin-Torres, Javier
    Centro de Astrobiología (CSIC-INTA), Madrid.
    Wet Chemistry on SAM: How it Helps to Detect Organics on Mars2013Conference paper (Refereed)
  • 71.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Atmospheric radiative-transfer simulator2006In: Thermal Microwave Radiation: Applications for Remote Sensing, London: Institution of Engineering and Technology, 2006, p. 54-56Chapter in book (Other academic)
  • 72. Buehler, Stefan
    Cloud ice water submillimeter imaging radiometer (CIWSIR): ESA earth explorer mission proposal2005Report (Other academic)
  • 73. Buehler, Stefan
    International Symposium on Sub-Millimeter Wave Earth Observation from Space--III: proceedings of the Third International Symposium on Sub-Millimeter Wave Earth Observation from Space, held at the Hanse Institute for Advanced Study, Delmenhorst, Germany, October 8 and 9, 20012001Collection (editor) (Other academic)
  • 74. Buehler, Stefan
    JEM / SMILES: the superconducting submillimeter-wave limb-emission sounder on the Japanese experimental module of the international space station2005Report (Other academic)
  • 75. Buehler, Stefan
    Microwave Limb Sounding2002In: Remote sensing of atmosphere and ocean from space: models, instruments and techniques, Dordrecht & Boston: Encyclopedia of Global Archaeology/Springer Verlag, 2002Chapter in book (Other academic)
  • 76. Buehler, Stefan
    Remote sensing of atmospheric composition for climate applications: Habilitationschrift2004Doctoral thesis, comprehensive summary (Other academic)
  • 77. Buehler, Stefan
    Upper tropospheric humidity and ice from meteorological operational sensors (UTH-MOS)2005In: Results of the German Atmospheric Research Programme - AFO2000, Markgraf-Verlag , 2005Chapter in book (Other academic)
  • 78. Buehler, Stefan
    Upper tropospheric humidity and ice from meteorological operational sensors (UTH-MOS)2003In: AFO 2000 newsletter, no 4Article in journal (Other academic)
  • 79.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    UTH-MOS: Wasserdampf und Cirren in der oberen Troposphäre aus operationellen meteorologischen Satellitendaten2006Report (Other academic)
  • 80. Buehler, Stefan
    et al.
    Courcoux, N.
    Universität Bremen, Institute of Environmental Physics.
    The impact of temperature errors on perceived humidity supersaturation2003In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 30, no 14, p. 1759-Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo method is used to study the propagation of temperature uncertainties into relative humidity with respect to ice (RH i ) calculated from specific humidity. For a flat specific humidity distribution and Gaussian temperature uncertainties the resulting RH i distribution drops exponentially at high RH i values—much slower than a Gaussian. This agrees well with the RH i distribution measured by the Microwave Limb Sounder (MLS), which means that such remotely measured RH i distributions can be explained, at least partly, by temperature uncertainties.

  • 81.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Courcoux, N.
    Universität Bremen, Institute of Environmental Physics.
    John, Viju Oommen
    University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami.
    Radiative transfer calculations for a passive microwave satellite sensor: comparing a fast model and a line-by-line model2006In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 111, no 20, p. 20304-Article in journal (Refereed)
    Abstract [en]

    A comparison between the fast radiative transfer model Radiative Transfer for the TIROS Operational Vertical Sounder (RTTOV-7) and the physical radiative transfer model Atmospheric Radiative Transfer Simulator ( ARTS) was carried out. Radiances were simulated for the sounding channels of the Advanced Microwave Sounding Unit B (AMSU-B) for the whole globe for a single time of a single day ( 1 January 2000, 0000 UT). Temperature, pressure, and specific humidity profiles from the reanalysis data set ERA-40 of the European Centre for Medium-Range Weather Forecasts (ECMWF) were used as input for both models; geopotential height profiles were also used but only as input for ARTS. The simulations were made for two different surface emissivities, 0.60 and 0.95. The low surface emissivity case exhibits the larger radiance differences. Although the global values of the mean difference and standard deviation are small ( for example, the global mean difference for channel 18 is 0.014 K and the standard deviation is 0.232 K), the examination of the geographical distribution of the differences shows that large positive or negative values are observed over dry regions of high northern and southern latitudes and over dry elevated regions. The origin of these differences was found to be due to errors introduced by the transmittance parametrization used in RTTOV.

  • 82.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Defer, E.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Evans, F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eliasson, Salomon
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Erikssson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lee, C.
    Met Office Hadley Centre, Exeter.
    Jimenez, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Prigent, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Crewell, S.
    Institute for Geophysics and Meteorology, University of Cologne.
    kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Bennartz, R.
    Atmospheric and Oceanic Sciences, University of Wisconsin.
    Gasiewski, A.J.
    NOAA-CU Center for Environmental Technology (CET), Department of Electrical and Computer Engineering, University of Colorado at Boulder.
    Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 82012In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, no 7, p. 1529-1549Article in journal (Refereed)
    Abstract [en]

    Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized 'essential climate variable' ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  • 83. Buehler, Stefan
    et al.
    Engeln, A. von
    Universität Bremen, Institute of Environmental Physics.
    Brocard, E.
    Universität Bremen, Institute of Environmental Physics.
    John, Viju Oommen
    Universität Bremen, Institute of Environmental Physics.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. University of Köln, Physikalisches Institut.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Recent developments in the line-by-line modeling of outgoing longwave radiation2006In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 98, no 3, p. 446-457Article in journal (Refereed)
    Abstract [en]

    High frequency resolution radiative transfer model calculations with the Atmospheric Radiative Transfer Simulator (ARTS) were used to simulate the clear-sky outgoing longwave radiative flux (OLR) at the top of the atmosphere. Compared to earlier calculations by Clough and coworkers the model used a spherical atmosphere instead of a plane parallel atmosphere, updated spectroscopic parameters from HITRAN, and updated continuum parameterizations from Mlawer and coworkers. These modifications lead to a reduction in simulated OLR by approximately 4.1%, the largest part, approximately 2.5%, being due to the absence of the plane parallel approximation. As a simple application of the new model, the sensitivity of OLR to changes in humidity, carbon dioxide concentration, and temperature were investigated for different cloud-free atmospheric scenarios. It was found that for the tropical scenario a 20% change in humidity has a larger impact than a doubling of the carbon dioxide concentration. The sensitive altitude region for temperature and humidity changes is the entire free troposphere, including the upper troposphere where humidity data quality is poor.

  • 84. Buehler, Stefan
    et al.
    Engeln, Axel von
    Universität Bremen, Institute of Environmental Physics.
    Kuenzi, Klaus
    Universität Bremen, Institute of Environmental Physics.
    Retrieval of atmospheric mixing ratio profiles from mm/sub-mm limb sounder data: accuracy requirements on line broadening parameters1996In: Atmospheric Spectroscopy Applications. Workshop proceedings, 1996, p. 155-158Conference paper (Refereed)
  • 85. Buehler, Stefan
    et al.
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Universität Bremen, Institute of Environmental Physics.
    Engeln, Axel von
    Universität Bremen, Institute of Environmental Physics.
    Verdes, C.
    Universität Bremen, Institute of Environmental Physics.
    ARTS: the atmospheric radiative transfer simulator2005In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 91, no 1, p. 65-93Article in journal (Refereed)
    Abstract [en]

    RTS is a modular program that simulates atmospheric radiative transfer. The paper describes ARTS version 1.0, which is applicable in the absence of scattering. An overview over all major parts of the model is given: calculation of absorption coefficients, the radiative transfer itself, and the calculation of Jacobians. ARTS can be freely used under a GNU general public license. Unique features of the program are its scalability and modularity, the ability to work with different sources of spectroscopic parameters, the availability of several self-consistent water continuum and line absorption models, and the analytical calculation of Jacobians.

  • 86. Buehler, Stefan
    et al.
    Eriksson, PatrickChalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Atmospheric millimeter and sub-millimeter wave radiative transfer modeling2007Collection (editor) (Other academic)
  • 87. Buehler, Stefan
    et al.
    Eriksson, PatrickChalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Atmospheric millimeter and sub-millimeter wave radiative transfer modeling 22001Collection (editor) (Other academic)
  • 88.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lemke, Oliver
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Absorption lookup tables in the radiative transfer model ARTS2011In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, no 10, p. 1559-1567Article in journal (Refereed)
    Abstract [en]

    We describe the lookup table approach that is used to store pre-calculated absorption data in the radiative transfer model ARTS. The table stores absorption cross sections as a function of frequency, pressure, temperature, and the water vapor volume mixing ratio, where the last dimension is only included for those gas species that require it. The table is used together with an extraction strategy, which uses polynomial interpolation, with recommended interpolation orders between five and seven. We also derived recommended default settings for grid spacings and interpolation orders, and verified that the approach gives very accurate results with these default settings. The tested instrument setups were for AMSU-B, HIRS, and Odin, three well-known satellite remote sensing instruments covering a wide range of frequencies and viewing geometries. Errors introduced by the lookup table were found to be always below a few millikelvin, in terms of the simulated brightness temperature.

  • 89. Buehler, Stefan
    et al.
    Eyring, Veronika
    DLR-Institut für Physik der Atmosphäre, Oberpfaffenhofen.
    Wehr, Tobias
    Kuenzi, Klaus
    Universität Bremen.
    Limits imposed on millimeter and sub-millimeter wave limb sounders by continuum emissions1996In: Atmospheric ozone: proceedings of the XVIII Quadrennial Ozone Symposium L'Aquila, Italy, 12-21 September 1996 / [ed] Rumen D. Bojkov; Guido Visconti, L'Aquila: Parco Scientifico e Tecnologici d'Abruzzo , 1996, p. 883-886Conference paper (Refereed)
  • 90.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Jimenez, C.
    Evans, K. F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Rydberg, B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Heymsfield, A.
    NCAR, Boulder, Colorado.
    Stubenrauch, C.
    CNRS/IPSL - Laboratoire de Meteorologie Dynamique, Ecole Polytechnique, Palaiseau.
    Lohmann, U.
    ETH Zurich, Institute for Atmospheric and Climate Science.
    Emde, C.
    Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen.
    John, V. O.
    Met Office Hadley Centre, Exeter.
    Sreerekha, T. R.
    Met Office Hadley Centre, Exeter.
    Davis, C. P.
    School of Geosciences, University of Edinburgh.
    A concept for a satellite mission to measure cloud ice water path, ice particle size, and cloud altitude2007In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, no Suppl.2, p. 109-128Article in journal (Refereed)
    Abstract [en]

    A passive satellite radiometer operating at submillimetre wavelengths can measure cloud ice water path (IWP), ice particle size, and cloud altitude. The paper first discusses the scientific background for such measurements. Formal scientific mission requirements are derived, based on this background and earlier assessments. The paper then presents a comprehensive prototype instrument and mission concept, and demonstrates that it meets the requirements. The instrument is a conically scanning 12-channel radiometer with channels between 183 and 664 GHz, proposed to fly in tandem with one of the Metop satellites. It can measure IWP with a relative accuracy of approximately 20% and a detection threshold of approximately 2 g m-2. The median mass equivalent sphere diameter of the ice particles can be measured with an accuracy of approximately 30 µm, and the median IWP cloud altitude can be measured with an accuracy of approximately 300 m. All the above accuracies are median absolute error values; root mean square error values are approximately twice as high, due to rare outliers.

  • 91. Buehler, Stefan
    et al.
    John, V. O.
    Universität Bremen, Institute of Environmental Physics.
    A simple method to relate microwave radiances to upper tropospheric humidity2005In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 110, no 2, p. D02110-Article in journal (Refereed)
    Abstract [en]

    A brightness temperature (BT) transformation method can be applied to microwave data to retrieve Jacobian weighted upper tropospheric relative humidity (UTH) in a broad layer centered roughly between 6 and 8 km altitude. The UTH bias is below 4% RH, and the relative UTH bias below 20%. The UTH standard deviation is between 2 and 6.5% RH in absolute numbers, or between 10 and 27% in relative numbers. The standard deviation is dominated by the regression noise, resulting from vertical structure not accounted for by the simple transformation relation. The UTH standard deviation due to radiometric noise alone has a relative standard deviation of approximately 7% for a radiometric noise level of 1 K. The retrieval performance was shown to be of almost constant quality for all viewing angles and latitudes, except for problems at high latitudes due to surface effects. A validation of AMSU UTH against radiosonde UTH shows reasonable agreement if known systematic differences between AMSU and radiosonde are taken into account. When the method is applied to supersaturation studies, regression noise and radiometric noise could lead to an apparent supersaturation even if there were no supersaturation. For a radiometer noise level of 1 K the drop-off slope of the apparent supersaturation is 0.17% RH−1, for a noise level of 2 K the slope is 0.12% RH−1. The main conclusion from this study is that the BT transformation method is very well suited for microwave data. Its particular strength is in climatological applications where the simplicity and the a priori independence are key advantages.

  • 92.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Kottayil, Ajil
    Milz, Mathias
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Efficient radiative transfer simulations for a broadband infrared radiometer: combining a weighted mean of representative frequencies approach with frequency selection by simulated annealing2010In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, no 4, p. 602-615Article in journal (Refereed)
    Abstract [en]

    We present a method to efficiently simulate the measurements of a broadband infrared instrument. The High Resolution Infrared Radiation Sounder (HIRS) instrument is used as example to illustrate the method. The method uses two basic ideas. Firstly, the channel radiance can be approximated by a weighted mean of the radiance at some representative frequencies, where the weights can be determined by linear regression. Secondly, a near-optimal set of representative frequencies can be found by simulated annealing.The paper does not only describe and analyze the method, it also describes how the method was used to derive optimized frequency grids for the HIRS instruments on the satellites TIROS N, NOAA 6-19, and Metop A. The grids and weights, as well as the optimization algorithm itself are openly available under a GNU public license.

  • 93.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Universität Bremen, Institute of Environmental Physics.
    Bauer, Agnes
    Institute of Environmental Physics, University of Bremen.
    Corrigendum to 'Water vapor continuum: Absorption measurements at 350 GHz and model calculations' [JQSRT 2002;74:545-62]2008In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 109, no 9, p. 1743-1744Article in journal (Other academic)
  • 94. Buehler, Stefan
    et al.
    Kuvatov, M.
    Universität Bremen, Institute of Environmental Physics.
    John, V. O.
    Universität Bremen, Institute of Environmental Physics.
    Scan asymmetries in AMSU-B data2005In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 32, no 24, p. L2481-Article in journal (Refereed)
    Abstract [en]

    A simple method of averaging measurements for different scan positions was used to quantify scan asymmetries in AMSU-B brightness temperatures for the sensors on the satellites NOAA 15, 16, and 17. The method works particularly well for the sounding channels 18 to 20. The asymmetries are small in most cases. In particular, asymmetries for Channel 18 are below 1.90, −0.53, and 0.49 K for NOAA 15, 16, and 17, respectively. On the other hand, it was found that the instrument on NOAA 15 has significant asymmetries for Channels 19 and 20, which seem to be related to the known radio frequency interference problem for this instrument. The use of the appropriate set of interference correction coefficients significantly reduces the asymmetry.

  • 95. Buehler, Stefan
    et al.
    Kuvatov, M.
    Universität Bremen, Institute of Environmental Physics.
    John, V. O.
    Universität Bremen, Institute of Environmental Physics.
    Leiterer, U.
    Meteorological Observatory Lindenberg, German Weather Service, Lindenberg.
    Dier, H.
    Meteorological Observatory Lindenberg, German Weather Service, Lindenberg.
    Comparison of microwave satellite humidity data and radiosonde profiles: a case study2004In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 109, no 13, p. S13103-Article in journal (Refereed)
    Abstract [en]

    This article documents a case study comparing radiosonde humidity data to Advanced Microwave Sounding Unit (AMSU) satellite humidity data. The study had two goals: first, to develop a robust method for such a comparison, and second, to check the quality and mutual consistency of radiosonde data, radiative transfer model, and AMSU data. The radiosonde data used are Vaisala RS80 data from the station Lindenberg of the German Weather Service (DWD), which have been subject to several corrections compared to the standard data processing. The radiative transfer model is the Atmospheric Radiative Transfer Simulator ( ARTS), and the AMSU data are those of the satellites NOAA 15 and 16 for the time periods 2001 and 2002. The comparison was done in radiance space, using a radiative transfer model to simulate AMSU radiances from the radiosonde data. The overall agreement is very good, with radiance biases below 1.5 K and standard deviations below 2 K. The main source of "noise'' in the comparison is atmospheric inhomogeneity on the 10-km scale. While the radiosonde correction performed at Lindenberg significantly reduces the bias between simulated and measured AMSU radiance, there still remains a slope in the radiance difference. Possible reasons for this were investigated. Most likely, the radiosondes underestimate the relative humidity under extremely dry conditions, showing 0 % RH when the true value is 2 - 4 % RH.

  • 96.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuvatov, M.
    Institut für Umweltphysik (Institute for Environmental Physics) (IUP), University of Bremen.
    John, V. O.
    Meteorology and Physical Oceanography, Rosenstiel School for Marine and Atmospheric Science (RSMAS), University of Miami.
    Milz, Mathias
    Soden, B.J.
    Meteorology and Physical Oceanography, Rosenstiel School for Marine and Atmospheric Science (RSMAS), University of Miami.
    Jackson, D.L.
    Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, NOAA Earth System Research Laboratory.
    Norholt, J.
    Institut für Umweltphysik (Institute for Environmental Physics) (IUP), University of Bremen.
    An upper tropospheric humidity data set from operational satellite microwave data2008In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, no 14, p. D14110-Article in journal (Refereed)
    Abstract [en]

    183.31 GHz observations from the Advanced Microwave Sounding Unit B (AMSUB) instruments onboard the NOAA 15, 16, and 17 satellites were used to derive a new data set of Upper Tropospheric Humidity (UTH). The data set consist of monthly median and mean data on a 1.5 degrees latitude-longitude grid between 60 degrees S and 60 degrees N, and covers the time period of January 2000 to February 2007. The data from all three instruments are very consistent, with relative difference biases of less than 4% and relative difference standard deviations of 7%. Radiometric contributions by high ice clouds and by the Earth's surface affect the measurements in certain areas. The uncertainty due to clouds is estimated to be up to approximately 10%RH in areas with deep convection. The uncertainty associated with contamination from surface emission can exceed 10%RH in midlatitude winter, where the data therefore should be regarded with caution. Otherwise the surface influence appears negligible. The paper also discusses the UTH median climatology and seasonal cycle, which are found to be broadly consistent with UTH climatologies from other sensors. Finally, the paper presents an initial validation of the new data set against IR satellite data and radiosonde data. The observed biases of up to 9%RH (wet bias relative to HIRS) were found to be broadly consistent with expectations based on earlier studies. The observed standard deviations against all other data sets were below 6%RH. The UTH data are available to the scientific community on http://www.sat.ltu.se.

  • 97.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuvatov, Mashrab
    IUP, University of Bremen.
    Sreerekha, T. R.
    UK Met Office, Exeter.
    John, Viju Oommen
    RSMAS, University of Miami.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Notholt, Justus
    IUP, University of Bremen.
    A cloud filtering method for microwave upper tropospheric humidity measurements2007In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, no 21, p. 5531-5542Article in journal (Refereed)
    Abstract [en]

    The paper presents a cloud filtering method for upper tropospheric humidity (UTH) measurements at 183.31±1.00 GHz. The method uses two criteria: a viewing angle dependent threshold on the brightness temperature at 183.31±1.00 GHz, and a threshold on the brightness temperature difference between another channel and 183.31±1.00 GHz. Two different alternatives, using 183.31±3.00 GHz or 183.31±7.00 GHz as the other channel, are studied. The robustness of this cloud filtering method is demonstrated by a mid-latitudes winter case study. The paper then studies different biases on UTH climatologies. Clouds are associated with high humidity, therefore the possible dry bias introduced by cloud filtering is discussed and compared to the wet biases introduced by the clouds radiative effect if no filtering is done. This is done by means of a case study, and by means of a stochastic cloud database with representative statistics for midlatitude conditions. Both studied filter alternatives perform nearly equally well, but the alternative using 183.31±3.00 GHz as other channel is preferable, because that channel is less likely to see the Earth's surface than the one at 183.31±7.00 GHz. The consistent result of all case studies and for both filter alternatives is that both cloud wet bias and cloud filtering dry bias are modest for microwave data. The recommended strategy is to use the cloud filtered data as an estimate for the true all-sky UTH value, but retain the unfiltered data to have an estimate of the cloud induced uncertainty. The focus of the paper is on midlatitude data, since atmospheric data to test the filter for that case were readily available. The filter is expected to be applicable also to subtropical and tropical data, but should be further validated with case studies similar to the one presented here for those cases.

  • 98.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Eliasson, Salomon
    Upper tropospheric humidity and cloud ice: comparing global climate models and satellite observations2008In: 2008 European Geosciences Union General Assembly, Austria Center Vienna, Vienna (Austria), 13-18 Apr 2008, European Geosciences Union (EGU), 2008Conference paper (Other academic)
    Abstract [en]

    Upper tropospheric humidity (UTH) and cloud ice (measured as ice water content IWC or vertically integrated ice water path IWP) are parameters of the climate system on which current global climate models do not agree well. This is illustrated by intercomparing the models in the IPCC AR4 archive. It is then discussed, to what extent different satellite measurements agree on these parameters. The focus is on passive observations from different infrared (HIRS, IASI) and microwave (AMSU-B, HSB) sensors.

  • 99. Buehler, Stefan
    et al.
    Sinnhuber, Björn-Martin
    Universität Bremen.
    Instrumental requirements for a submillimeter-wave limb sounder1999In: International workshop on submillimeter-wave observation of Earth's atmosphere from space, National Space Development Agency of Japan , 1999, p. 209-220Conference paper (Other academic)
  • 100. Buehler, Stefan
    et al.
    Verdes, C.L.
    Universität Bremen, Institute of Environmental Physics.
    Tsujimaru, S.
    National Institute of Information and Communication Technology, Tokyo.
    Kleinbohl, A.
    Universität Bremen, Institute of Environmental Physics.
    Bremer, H.
    Universität Bremen, Institute of Environmental Physics.
    Sinnhuber, M.
    Universität Bremen, Institute of Environmental Physics.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Expected performance of the superconducting submillimeter-wave limb emission sounder compared with aircraft data2005In: Radio Science, ISSN 0048-6604, E-ISSN 1944-799X, Vol. 40, no 3, p. RS3016/1-RS3016/13Article in journal (Refereed)
    Abstract [en]

    The simulated retrieval performance of a submillimeter wave limb sounder was compared with that of an up-looking instrument with identical observation frequency bands and comparable noise temperature. The frequency bands were 624.32-626.32 and 649.12-650.32 GHz, and the retrieval simulations focused on the key trace gas species O-3, HCl, and ClO. As expected, the limb geometry leads to a better altitude resolution and larger measurement altitude range. The same retrieval setup was applied to measured spectra, taken by the up-looking Airborne Submillimeter Radiometer ( ASUR) instrument on 4 September 2002 at 19.11 degrees E, 71.90 degrees N and on 19 September 2002 at 44.10 degrees E, 4.10 degrees S. The observed structures in the fit residual near the HCl spectral lines at 625.9 GHz lead to the conclusion that the pressure shift parameter of HCl is likely to be higher than the value in the HITRAN spectroscopic database. Depending on the assumed temperature dependence of the shift, the HCl pressure shift value consistent with the ASUR data is 0.090-0.117 MHz/hPa instead of the 0.030 MHz/hPa reported in HITRAN. This result is in good agreement with very recent independent laboratory work which suggests a value of 0.110 MHz/hPa for the shift.

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