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Publications (10 of 29) Show all publications
Wolf, V., Völger, P., Kuhn, T. & Gumbel, J. (2019). ANALYSIS OF PARTICLE SHAPE, DEPOLARIZATION AND LIDAR RATIO IN ARCTIC CIRRUS CLOUDS: A CASE STUDY. In: : . Paper presented at The 29th International Laser Radar Conference (ILRC29).
Open this publication in new window or tab >>ANALYSIS OF PARTICLE SHAPE, DEPOLARIZATION AND LIDAR RATIO IN ARCTIC CIRRUS CLOUDS: A CASE STUDY
2019 (English)Conference paper, Published paper (Refereed)
National Category
Natural Sciences Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:ltu:diva-73537 (URN)
Conference
The 29th International Laser Radar Conference (ILRC29)
Available from: 2019-04-09 Created: 2019-04-09 Last updated: 2019-05-03
Wolf, V., Kuhn, T., Milz, M., Völger, P., Krämer, M. & Rolf, C. (2018). Arctic ice clouds over northern Sweden: microphysical properties studied with the Balloon-borne Ice Cloud particle Imager B-ICI. Atmospheric Chemistry And Physics, 18(23), 17371-17386
Open this publication in new window or tab >>Arctic ice clouds over northern Sweden: microphysical properties studied with the Balloon-borne Ice Cloud particle Imager B-ICI
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2018 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 18, no 23, p. 17371-17386Article in journal (Refereed) Published
Abstract [en]

Ice particle and cloud properties such as particle size, particle shape and number concentration influence the net radiation effect of cirrus clouds. Measurements of these features are of great interest for the improvement of weather and climate models, especially for the Arctic region. In this study, balloon-borne in situ measurements of Arctic cirrus clouds have been analysed for the first time with respect to their origin. Eight cirrus cloud measurements have been carried out in Kiruna (68 N), Sweden, using the Balloon-borne Ice Cloud particle Imager (B-ICI). Ice particle diameters between 10 and 1200 µm have been found and the shape could be recognized from 20 µm upwards. Great variability in particle size and shape is observed. This cannot simply be explained by local environmental conditions. However, if sorted by cirrus origin, wind and weather conditions, the observed differences can be assessed. Number concentrations between 3 and 400 L−1 have been measured, but the number concentration has reached values above 100 L−1 only for two cases. These two cirrus clouds are of in situ origin and have been associated with waves. For all other measurements, the maximum ice particle concentration is below 50 L−1 and for one in situ origin cirrus case only 3 L−1. In the case of in situ origin clouds, the particles are all smaller than 350 µm diameter. The PSDs for liquid origin clouds are much broader with particle sizes between 10 and 1200 µm. Furthermore, it is striking that in the case of in situ origin clouds almost all particles are compact (61 %) or irregular (25 %) when examining the particle shape. In liquid origin clouds, on the other hand, most particles are irregular (48 %), rosettes (25 %) or columnar (14 %). There are hardly any plates in cirrus regardless of their origin. It is also noticeable that in the case of liquid origin clouds the rosettes and columnar particles are almost all hollow.

Place, publisher, year, edition, pages
Copernicus Publications, 2018
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-72316 (URN)10.5194/acp-18-17371-2018 (DOI)000452384100002 ()2-s2.0-85058149311 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-08 (johcin)

Available from: 2018-12-18 Created: 2018-12-18 Last updated: 2019-04-19Bibliographically approved
Kuhn, T., Wolf, V., Völger, P., Stanev, M. & Gumbel, J. (2017). Comparison of In-Situ Balloon-Borne and Lidar Measurement of Cirrus Clouds. In: Proceedings of the 23rd ESA Symposium on European Rocket and Balloon Programmes and Related Research: . Paper presented at 23rd ESA Symposium on European Rocket and Balloon Programmes and Related Research, Visby, 11-15 June 2017. Noordwijk, The Netherlands, Article ID A-091kuhn.
Open this publication in new window or tab >>Comparison of In-Situ Balloon-Borne and Lidar Measurement of Cirrus Clouds
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2017 (English)In: Proceedings of the 23rd ESA Symposium on European Rocket and Balloon Programmes and Related Research, Noordwijk, The Netherlands, 2017, article id A-091kuhnConference paper, Published paper (Other academic)
Abstract [en]

A series of in-situ balloon-borne experiments con- ducted at Kiruna, Sweden (68°N), is studying upper- tropospheric, cold ice clouds in arctic latitudes. Ex- periments are launched from Esrange Space Center and collect ice particles with an in-situ imaging instrument. One of the aims with these measurements is to improve satellite remote sensing of cold ice clouds. Such clouds can be observed by lidar. Therefore, when possible, concurrent ground-based lidar measurements have been carried out with two available lidar systems to accom- pany the balloon-borne measurements. The Esrange lidar is located at Esrange Space Center, approximately 500 m from the in-situ launch site on the balloon pad; the IRF lidar is located about 29 km to the west of Esrange Space Center (operated by the Swedish Institute of Space Physics, IRF). Here we present results from these lidar measurements and compare them to ice particle proper- ties determined during the in-situ measurements. 

Place, publisher, year, edition, pages
Noordwijk, The Netherlands: , 2017
Keywords
Cirrus; ice clouds; lidar; ice particles; in-situ; balloon-borne; Arctic; high latitude measurements
National Category
Natural Sciences Earth and Related Environmental Sciences Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-66461 (URN)
Conference
23rd ESA Symposium on European Rocket and Balloon Programmes and Related Research, Visby, 11-15 June 2017
Funder
Swedish National Space Board
Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2019-04-19Bibliographically approved
Barabash, V., Ejemalm, J., Kuhn, T., Milz, M., Molin, S., Johansson, J. & Westerberg, L.-G. (2017). Masters Programs in Space Science and Engineering in Northern Sweden. In: : . Paper presented at 68th International Astronautical Congress, Adelaide, Australia, 25 – 29 September 2017 (pp. 11179-11191).
Open this publication in new window or tab >>Masters Programs in Space Science and Engineering in Northern Sweden
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2017 (English)Conference paper, Published paper (Refereed)
Keywords
rymd, space, Master, education, engineering
National Category
Aerospace Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Industrial Electronics; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-65521 (URN)2-s2.0-85051439897 (Scopus ID)9781510855373 (ISBN)
Conference
68th International Astronautical Congress, Adelaide, Australia, 25 – 29 September 2017
Projects
342
Available from: 2017-09-07 Created: 2017-09-07 Last updated: 2018-08-23Bibliographically approved
Kuhn, T. & Gultepe, I. (2016). Ice Fog and Light Snow Measurements Using a High-Resolution Camera System (ed.). Pure and Applied Geophysics, 173(9), 3049-3064
Open this publication in new window or tab >>Ice Fog and Light Snow Measurements Using a High-Resolution Camera System
2016 (English)In: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 173, no 9, p. 3049-3064Article in journal (Refereed) Published
Abstract [en]

Ice fog, diamond dust, and light snow usually form over extremely cold weather conditions, and they affect both visibility and Earth’s radiative energy budget. Prediction of these hydrometeors using models is difficult because of limited knowledge of the microphysical properties at the small size ranges due to measurement issues. These phenomena need to be better represented in forecast and climate models; therefore, in addition to remote sensing accurate measurements using ground-based instrumentation are required. An imaging instrument, aimed at measuring ice fog and light snow particles, has been built and is presented here. The ice crystal imaging (ICI) probe samples ice particles into a vertical, tapered inlet with an inlet flow rate of 11 L min−1. A laser beam across the vertical air flow containing the ice crystals allows for their detection by a photodetector collecting the scattered light. Detected particles are then imaged with high optical resolution. An illuminating LED flash and image capturing are triggered by the photodetector. In this work, ICI measurements collected during the fog remote sensing and modeling (FRAM) project, which took place during Winter of 2010–2011 in Yellowknife, NWT, Canada, are summarized and challenges related to measuring small ice particles are described. The majority of ice particles during the 2-month-long campaign had sizes between 300 and 800 μm. During ice fog events the size distribution measured had a lower mode diameter of 300 μm compared to the overall campaign average with mode at 500 μm.

Keywords
Ice fog, snow, precipitation, ice particles, fall speed, optical imaging, Earth sciences - Atmosphere and hydrosphere sciences, Geovetenskap - Atmosfärs- och hydrosfärsvetenskap
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-2909 (URN)10.1007/s00024-016-1343-7 (DOI)000382941400005 ()2-s2.0-84986620977 (Scopus ID)0a4144d5-c9bd-4686-8bab-f783b6fceab3 (Local ID)0a4144d5-c9bd-4686-8bab-f783b6fceab3 (Archive number)0a4144d5-c9bd-4686-8bab-f783b6fceab3 (OAI)
Note

Validerad; 2016; Nivå 2; 2016-10-12 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Kuhn, T. & Heymsfield, A. J. (2016). In Situ Balloon-Borne Ice Particle Imaging in High-Latitude Cirrus (ed.). Pure and Applied Geophysics, 173(9), 3065-3084
Open this publication in new window or tab >>In Situ Balloon-Borne Ice Particle Imaging in High-Latitude Cirrus
2016 (English)In: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 173, no 9, p. 3065-3084Article in journal (Refereed) Published
Abstract [en]

Cirrus clouds reflect incoming solar radiation, creating a cooling effect. At the same time, these clouds absorb the infrared radiation from the Earth, creating a greenhouse effect. The net effect, crucial for radiative transfer, depends on the cirrus microphysical properties, such as particle size distributions and particle shapes. Knowledge of these cloud properties is also needed for calibrating and validating passive and active remote sensors. Ice particles of sizes below 100 µm are inherently difficult to measure with aircraft-mounted probes due to issues with resolution, sizing, and size-dependent sampling volume. Furthermore, artefacts are produced by shattering of particles on the leading surfaces of the aircraft probes when particles several hundred microns or larger are present. Here, we report on a series of balloon-borne in situ measurements that were carried out at a high-latitude location, Kiruna in northern Sweden (68N 21E). The method used here avoids these issues experienced with the aircraft probes. Furthermore, with a balloon-borne instrument, data are collected as vertical profiles, more useful for calibrating or evaluating remote sensing measurements than data collected along horizontal traverses. Particles are collected on an oil-coated film at a sampling speed given directly by the ascending rate of the balloon, 4 m s−1. The collecting film is advanced uniformly inside the instrument so that an always unused section of the film is exposed to ice particles, which are measured by imaging shortly after sampling. The high optical resolution of about 4 µm together with a pixel resolution of 1.65 µm allows particle detection at sizes of 10 µm and larger. For particles that are 20 µm (12 pixel) in size or larger, the shape can be recognized. The sampling volume, 130 cm3 s−1, is well defined and independent of particle size. With the encountered number concentrations of between 4 and 400 L−1, this required about 90- to 4-s sampling times to determine particle size distributions of cloud layers. Depending on how ice particles vary through the cloud, several layers per cloud with relatively uniform properties have been analysed. Preliminary results of the balloon campaign, targeting upper tropospheric, cold cirrus clouds, are presented here. Ice particles in these clouds were predominantly very small, with a median size of measured particles of around 50 µm and about 80 % of all particles below 100 µm in size. The properties of the particle size distributions at temperatures between −36 and −67 °C have been studied, as well as particle areas, extinction coefficients, and their shapes (area ratios). Gamma and log-normal distribution functions could be fitted to all measured particle size distributions achieving very good correlation with coefficients R of up to 0.95. Each distribution features one distinct mode. With decreasing temperature, the mode diameter decreases exponentially, whereas the total number concentration increases by two orders of magnitude with decreasing temperature in the same range. The high concentrations at cold temperatures also caused larger extinction coefficients, directly determined from cross-sectional areas of single ice particles, than at warmer temperatures. The mass of particles has been estimated from area and size. Ice water content (IWC) and effective diameters are then determined from the data. IWC did vary only between 1 × 10−3 and 5 × 10−3 g m−3 at temperatures below −40 °C and did not show a clear temperature trend. These measurements are part of an ongoing study.

Keywords
small ice particles, cirrus, in situ measurements, volume extinction, balloon-borne, Earth sciences - Atmosphere and hydrosphere sciences, Geovetenskap - Atmosfärs- och hydrosfärsvetenskap
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-7503 (URN)10.1007/s00024-016-1324-x (DOI)000382941400006 ()2-s2.0-84986550413 (Scopus ID)5e5db84f-dc26-4e5f-8754-75ceef750aff (Local ID)5e5db84f-dc26-4e5f-8754-75ceef750aff (Archive number)5e5db84f-dc26-4e5f-8754-75ceef750aff (OAI)
Note

Validerad; 2016; Nivå 2; 2016-10-12 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Gultepe, I., Zhou, B., Milbrandt, J. A., Bott, A., Li, Y., Heymsfield, A. J., . . . Cermak, J. (2015). A review on ice fog measurements and modeling (ed.). Paper presented at . Atmospheric research, 151, 2-19
Open this publication in new window or tab >>A review on ice fog measurements and modeling
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2015 (English)In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 151, p. 2-19Article in journal (Refereed) Published
Abstract [en]

The rate of weather-related aviation accident occurrence in the northern latitudes is likely 25 times higher than the national rate of Canada. If only cases where reduced visibility was a factor are considered, the average rate of occurrence in the north is about 31 times higher than the Canadian national rate. Ice fog occurs about 25% of the time in the northern latitudes and is an important contributor to low visibility. This suggests that a better understanding of ice fog prediction and detection is required over the northern latitudes. The objectives of this review are the following: 1) to summarize the current knowledge of ice fog microphysics, as inferred from observations and numerical weather prediction (NWP) models, and 2) to describe the remaining challenges associated with measuring ice fog properties, remote sensing microphysical retrievals, and simulating/predicting ice fog within numerical models. Overall, future challenges related to ice fog microphysics and visibility are summarized and current knowledge is emphasized.

National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-4874 (URN)10.1016/j.atmosres.2014.04.014 (DOI)000343786500002 ()2-s2.0-84910056608 (Scopus ID)2e03f514-b132-40c4-8360-cbab6836c943 (Local ID)2e03f514-b132-40c4-8360-cbab6836c943 (Archive number)2e03f514-b132-40c4-8360-cbab6836c943 (OAI)
Note
Validerad; 2014; Nivå 2; 20140515 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Ekman, J., Antti, M.-L., Martin-Torres, J., Emami, R., Törlind, P., Kuhn, T., . . . Fakhardji, W. (2015). Projekt: Rymdforskarskolan. Paper presented at .
Open this publication in new window or tab >>Projekt: Rymdforskarskolan
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2015 (English)Other (Other (popular science, discussion, etc.))
Abstract [en]

The Graduate School of Space Technology

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Materials Engineering Aerospace Engineering Other Engineering and Technologies not elsewhere specified Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Chemical Process Engineering
Research subject
Industrial Electronics; Engineering Materials; Atmospheric science; Onboard space systems; Product Innovation; Machine Elements; Chemical Technology; Entrepreneurship and Innovation
Identifiers
urn:nbn:se:ltu:diva-36154 (URN)8c1c49e5-8fd1-4b50-992e-abd48bc5619c (Local ID)8c1c49e5-8fd1-4b50-992e-abd48bc5619c (Archive number)8c1c49e5-8fd1-4b50-992e-abd48bc5619c (OAI)
Note

Publikationer: Opportunities and Challenges for Additive Manufacturing in Space Applications; Status: Ongoing; Period: 01/01/2015 → …; End date: 31/12/2018

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2019-05-03Bibliographically approved
Gultepe, I., Kuhn, T., Pavolonis, M. J., Calvert, C., Gurka, J. J., Heymsfield, A. J., . . . Bernstein, B. C. (2014). Ice fog in arctic during fram-ice fog project aviation and nowcasting applications (ed.). Paper presented at . Bulletin of The American Meteorological Society - (BAMS), 95(2), 211-226
Open this publication in new window or tab >>Ice fog in arctic during fram-ice fog project aviation and nowcasting applications
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2014 (English)In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 95, no 2, p. 211-226Article in journal (Refereed) Published
Abstract [en]

Increased understanding of ice fog microphysics can improve frost and ice fog prediction using forecast models and remote-sensing retrievals, thereby reducing potential hazards to aviation

National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-4881 (URN)10.1175/BAMS-D-11-00071.1 (DOI)000333725400006 ()2-s2.0-84898661945 (Scopus ID)2e2814eb-48d2-4ea4-b0f6-74644f783d8c (Local ID)2e2814eb-48d2-4ea4-b0f6-74644f783d8c (Archive number)2e2814eb-48d2-4ea4-b0f6-74644f783d8c (OAI)
Note
Validerad; 2014; 20140502 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Kuhn, T. & Heymsfield, A. J. (2014). Vertical distributions of small cirrus cloud particles from balloon-borne in-situ measurements: Oral presentation (ed.). Paper presented at EGU General Assembly 2014 : 27/04/2014 - 02/05/2014. Paper presented at EGU General Assembly 2014 : 27/04/2014 - 02/05/2014.
Open this publication in new window or tab >>Vertical distributions of small cirrus cloud particles from balloon-borne in-situ measurements: Oral presentation
2014 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

Thin and cold ice clouds are important for the radiative budget, yet they are difficult to measure. They are often high in the troposphere where they reflect incoming sunlight, creating a cooling effect. At the same time these clouds absorb longwave radiation from Earth, creating a greenhouse effect. Knowledge of the net effect is crucial and depends on the microphysical properties of the clouds, which at these altitudes and temperatures are often composed of small particles of 100 μm or less in size. Most of in-situ data reported in the literature have been sampled with aircraft probes, which have known issues with such small particles due to sizing and shattering prob- lems, in addition to having also a small and size-dependent sampling volume for these particles.A series of balloon-borne in-situ measurements, currently being carried out from a high-latitude location in north- ern Sweden (Kiruna, 68N 21E), combined with previous balloon-borne measurements from other locations, are used to study properties of small cloud ice particles at a variety of temperatures and altitudes. Among other prop- erties, size distributions and concentrations are analysed as a function of height within the cloud layer. Results are compared to literature data from aircraft probes to shed more light on the uncertainties related to the difficulties of these probes in measuring small particles.

Keywords
ice clouds, cirrus, small ice particles, Earth sciences - Atmosphere and hydrosphere sciences, Geovetenskap - Atmosfärs- och hydrosfärsvetenskap
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-35510 (URN)a0f9418a-2fca-4574-a2e8-26d5d07b0396 (Local ID)a0f9418a-2fca-4574-a2e8-26d5d07b0396 (Archive number)a0f9418a-2fca-4574-a2e8-26d5d07b0396 (OAI)
Conference
EGU General Assembly 2014 : 27/04/2014 - 02/05/2014
Note
Godkänd; 2014; 20140505 (thokuh)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3701-7925

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