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Publications (8 of 8) Show all publications
Bhardwaj, A., Kumar, R. & Sam, L. (2019). Analysing Geospatial Techniques for Land Degradation Studies in Hindu Kush-Himalaya. In: Environmental Change in the Himalayan Region: (pp. 117-136). Springer
Open this publication in new window or tab >>Analysing Geospatial Techniques for Land Degradation Studies in Hindu Kush-Himalaya
2019 (English)In: Environmental Change in the Himalayan Region, Springer, 2019, p. 117-136Chapter in book (Refereed)
Place, publisher, year, edition, pages
Springer, 2019
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:ltu:diva-72987 (URN)10.1007/978-3-030-03362-0_6 (DOI)978-3-030-03361-3 (ISBN)978-3-030-03362-0 (ISBN)
Projects
Sustainable WAter Security through the Development of Artificial Glaciers (SWASDAG) in cold arid desert of Ladakh, India
Available from: 2019-02-21 Created: 2019-02-21 Last updated: 2019-07-22
Bhardwaj, A., Sam, L., Martin-Torres, J. & Zorzano Mier, M.-P. (2019). Are Slope Streaks Indicative of Global‐Scale Aqueous Processes on Contemporary Mars?. Reviews of geophysics, 57(1), 48-77
Open this publication in new window or tab >>Are Slope Streaks Indicative of Global‐Scale Aqueous Processes on Contemporary Mars?
2019 (English)In: Reviews of geophysics, ISSN 8755-1209, E-ISSN 1944-9208, Vol. 57, no 1, p. 48-77Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2019
Keywords
slope streaks, water activity, Mars, formation mechanism, deliquescence
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-73724 (URN)10.1029/2018RG000617 (DOI)000463995400003 ()2-s2.0-85059686126 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-04-12 (oliekm)

Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2019-10-10Bibliographically approved
Sam, L., Kumar, R. & Bhardwaj, A. (2019). Climate and Remotely Sensed Markers of Glacier Changes in the Himalaya. In: Environmental Change in the Himalayan Region: (pp. 65-88). Springer
Open this publication in new window or tab >>Climate and Remotely Sensed Markers of Glacier Changes in the Himalaya
2019 (English)In: Environmental Change in the Himalayan Region, Springer, 2019, p. 65-88Chapter in book (Refereed)
Abstract [en]

The study of past and future climatic variations in the Hindu Kush–Himalayan (HKH) region is a well-documented topic of scientific research. Recent studies have highlighted the significantly higher rates of warming in the HKH region compared to the global average. The HKH region has the largest reserves of glacial ice outside the poles. These glaciers are predominantly known to be sensitive indicators of changing regional and global climate. The large geographical extent, high elevation and perennial inclemency in weather conditions project remote sensing as the only viable option to study glacial characteristics periodically on a regional scale. The present chapter starts with a review of significant studies to assess the extent of climate change in the HKH. Climate-sensitive glacial markers which can be studied using remote sensing are identified. The chapter focuses on the key markers such as changes in glacier extents, glacier facies and supraglacial debris, and mass balance and thickness. The chapter examines these markers separately with respect to changing climate through recent remote sensing-based studies. It provides an overview of recent studies which deal with regional scale glaciological monitoring and assessment. The conclusive section of the chapter suggests the future role of remote sensing applications in studying these markers of climate change. The chapter uses recent studies to highlight key aspects that should be kept in perspective while undertaking remotely sensed glacial assessments.

Place, publisher, year, edition, pages
Springer, 2019
National Category
Climate Research
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-72986 (URN)10.1007/978-3-030-03362-0_4 (DOI)978-3-030-03362-0 (ISBN)978-3-030-03361-3 (ISBN)
Projects
Sustainable WAter Security through the Development of Artificial Glaciers (SWASDAG) in cold arid desert of Ladakh, India
Available from: 2019-02-21 Created: 2019-02-21 Last updated: 2019-07-22
Bhardwaj, A., Sam, L., Martin-Torres, J. & Zorzano Mier, M.-P. (2019). Discovery of recurring slope lineae candidates in Mawrth Vallis, Mars. Scientific Reports, 9, Article ID 2040.
Open this publication in new window or tab >>Discovery of recurring slope lineae candidates in Mawrth Vallis, Mars
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 2040Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Astronomy, Astrophysics and Cosmology Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-72894 (URN)10.1038/s41598-019-39599-z (DOI)000458619600040 ()2-s2.0-85061571667 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-27 (johcin)

Available from: 2019-02-14 Created: 2019-02-14 Last updated: 2019-02-27Bibliographically approved
Bhardwaj, A., Sam, L., Martin-Torres, J. & Zorzano Mier, M.-P. (2019). Distribution and Morphologies of Transverse Aeolian Ridges in ExoMars 2020 Rover Landing Site. Remote Sensing, 11(8), Article ID 912.
Open this publication in new window or tab >>Distribution and Morphologies of Transverse Aeolian Ridges in ExoMars 2020 Rover Landing Site
2019 (English)In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 11, no 8, article id 912Article in journal (Refereed) Published
Abstract [en]

Aeolian processes are believed to play a major role in the landscape evolution of Mars. Investigations on Martian aeolian landforms such as ripples, transverse aeolian ridges (TARs), and dunes, and aeolian sediment flux measurements are important to enhance our understanding of past and present wind regimes, the ongoing dust cycle, landscape evolution, and geochemistry. These aeolian bedforms are often comprised of loose sand and sharply undulating topography and thus pose a threat to mobility and maneuvers of Mars rovers. Here we present a first-hand account of the distribution, morphologies, and morphometrics of TARs in Oxia Planum, the recently selected ExoMars 2020 Rover landing site. The gridded mapping was performed for contiguous stretches of TARs within all the landing ellipses using 57 sub-meter high resolution imaging science experiment (HiRISE) scenes. We also provide the morphological descriptions for all types of TARs present within the landing ellipses. We use HiRISE digital terrain models (DTMs) along with the images to derive morphometric information for TARs in Oxia Planum. In general, the average areal TAR coverage was found to be 5.4% (±4.9% standard deviation), increasing from west to east within the landing ellipses. We report the average TAR morphometrics in the form of crest–ridge width (131.1 ± 106.2 m), down-wind TAR length (17.6 ± 10.1 m), wavelength (37.3 ± 11.6 m), plan view aspect ratio (7.1 ± 2.3), inter-bedform spacing (2.1 ± 1.1), slope (10.6° ± 6.1°), predominant orientations (NE-SW and E-W), and height (1.2 ± 0.8 m). While simple TARs are predominant, we report other TAR morphologies such as forked TAR, wavy TAR with associated smaller secondary ripples, barchan-like TAR, networked TAR, and mini-TARs from the region. Our results can help in planning the rover traverses in terms of both safe passage and scientific returns favoring aeolian research, particularly improving our understanding of TARs.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
transverse aeolian ridge (TAR), ExoMars 2020, Oxia Planum, HiRISE, mapping
National Category
Physical Sciences Astronomy, Astrophysics and Cosmology
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-73660 (URN)10.3390/rs11080912 (DOI)000467646800022 ()2-s2.0-85065019154 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-05-29 (oliekm)

Available from: 2019-04-15 Created: 2019-04-15 Last updated: 2019-08-19Bibliographically approved
Singh, S., Bhardwaj, A., Singh, A., Sam, L., Shekhar, M., Martin-Torres, J. & Zorzano Mier, M.-P. (2019). Quantifying the Congruence between Air and Land Surface Temperatures for Various Climatic and Elevation Zones of Western Himalaya. Remote Sensing, 11(24), Article ID 2889.
Open this publication in new window or tab >>Quantifying the Congruence between Air and Land Surface Temperatures for Various Climatic and Elevation Zones of Western Himalaya
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2019 (English)In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 11, no 24, article id 2889Article in journal (Refereed) Published
Abstract [en]

The surface and near-surface air temperature observations are primary data for glacio-hydro-climatological studies. The in situ air temperature (Ta) observations require intense logistic and financial investments, making it sparse and fragmented particularly in remote and extreme environments. The temperatures in Himalaya are controlled by a complex system driven by topography, seasons, and cryosphere which further makes it difficult to record or predict its spatial heterogeneity. In this regard, finding a way to fill the observational spatiotemporal gaps in data becomes more crucial. Here, we show the comparison of Ta recorded at 11 high altitude stations in Western Himalaya with their respective land surface temperatures (Ts) recorded by Moderate Resolution Imagining Spectroradiometer (MODIS) Aqua and Terra satellites in cloud-free conditions. We found remarkable seasonal and spatial trends in the Ta vs. Ts relationship: (i) Ts are strongly correlated with Ta (R2 = 0.77, root mean square difference (RMSD) = 5.9 °C, n = 11,101 at daily scale and R2 = 0.80, RMSD = 5.7 °C, n = 3552 at 8-day scale); (ii) in general, the RMSD is lower for the winter months in comparison to summer months for all the stations, (iii) the RMSD is directly proportional to the elevations; (iv) the RMSD is inversely proportional to the annual precipitation. Our results demonstrate the statistically strong and previously unreported Ta vs. Ts relationship and spatial and seasonal variations in its intensity at daily resolution for the Western Himalaya. We anticipate that our results will provide the scientists in Himalaya or similar data-deficient extreme environments with an option to use freely available remotely observed Ts products in their models to fill-up the spatiotemporal data gaps related to in situ monitoring at daily resolution. Substituting Ta by Ts as input in various geophysical models can even improve the model accuracy as using spatially continuous satellite derived Ts in place of discrete in situ Ta extrapolated to different elevations using a constant lapse rate can provide more realistic estimates. 

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
Himalaya, land surface temperature, air temperature, topography, MODIS
National Category
Meteorology and Atmospheric Sciences Aerospace Engineering
Research subject
Atmospheric science; Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-77066 (URN)10.3390/rs11242889 (DOI)
Note

Validerad;2019;Nivå 2;2019-12-10 (johcin)

Available from: 2019-12-04 Created: 2019-12-04 Last updated: 2019-12-10Bibliographically approved
Bhardwaj, A., Sam, L., Martín-Torres, F. J. & Zorzano, M.-P. (2019). Revisiting enigmatic Martian slope streaks. Earth Space and Science News - Editors Vox, 100
Open this publication in new window or tab >>Revisiting enigmatic Martian slope streaks
2019 (English)In: Earth Space and Science News - Editors Vox, Vol. 100Article in journal, News item (Other academic) Published
Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2019
National Category
Geosciences, Multidisciplinary Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-72563 (URN)10.1029/2019EO113611 (DOI)
Available from: 2019-01-15 Created: 2019-01-15 Last updated: 2019-02-28Bibliographically approved
Bhardwaj, A., Sam, L., Martin-Torres, J., Zorzano Mier, M.-P. & Ramírez Luque, J. A. (2019). UAV Imaging of a Martian Brine Analogue Environment in a Fluvio-Aeolian Setting. Remote Sensing, 11(18), Article ID 2104.
Open this publication in new window or tab >>UAV Imaging of a Martian Brine Analogue Environment in a Fluvio-Aeolian Setting
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2019 (English)In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 11, no 18, article id 2104Article in journal (Refereed) Published
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

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
unmanned aerial vehicle (UAV), photogrammetry, salt flat, geomorphometry, analogue research
National Category
Geosciences, Multidisciplinary Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-75922 (URN)10.3390/rs11182104 (DOI)000489101500034 ()2-s2.0-85072630275 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-09-10 (johcin)

Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-10-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3181-2960

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