Aerosol distribution around Svalbard during intense easterly winds

Abstract. This paper reports on backscatter and depolarization measurements by an airborne lidar in the Arctic during the ASTAR 2004 campaign. A unique weather situation facilitated the observation of the aerosol concentration under strongly forced atmospheric conditions. The vigorous easterly winds distorted the flow past Svalbard in such a way that mesoscale features were visible in the remote-sensing observations: The formation of a well-mixed aerosol layer inside the Adventdalen and the subsequent thinning of the aerosol plume were observed over the Isfjorden. Additionally, mobilization of sea salt aerosols due to a coastal low-level jet at the northern tip of Svalbard resulted in a sloped boundary layer toward north. Mesoscale numerical modelling was applied to identify the sources of the aerosol particles and to explain the observed patterns.

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Lidar characterization of the Arctic atmosphere during ASTAR 2007: four cases studies of boundary layer, mixed-phase and multi-layer clouds

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-2847-2010 ◽

2010 ◽

Vol 10 (6) ◽

pp. 2847-2866 ◽

Cited By ~ 9

Author(s):

A. Lampert ◽

C. Ritter ◽

A. Hoffmann ◽

J.-F. Gayet ◽

G. Mioche ◽

...

Keyword(s):

Boundary Layer ◽

Case Studies ◽

Airborne Lidar ◽

Mixed Phase ◽

Spherical Particles ◽

The Arctic ◽

Free Troposphere ◽

Atmospheric Conditions ◽

Raman Lidar ◽

Tropospheric Aerosol

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR), which was conducted in Svalbard in March and April 2007, tropospheric Arctic clouds were observed with two ground-based backscatter lidar systems (micro pulse lidar and Raman lidar) and with an airborne elastic lidar. In the time period of the ASTAR 2007 campaign, an increase in low-level cloud cover (cloud tops below 2.5 km) from 51% to 65% was observed above Ny-Ålesund. Four different case studies of lidar cloud observations are analyzed: With the ground-based Raman lidar, a layer of spherical particles was observed at an altitude of 2 km after the dissolution of a cloud. The layer probably consisted of small hydrated aerosol (radius of 280 nm) with a high number concentration (around 300 cm−3) at low temperatures (−30 °C). Observations of a boundary layer mixed-phase cloud by airborne lidar and concurrent airborne in situ and spectral solar radiation sensors revealed the localized process of total glaciation at the boundary of different air masses. In the free troposphere, a cloud composed of various ice layers with very different optical properties was detected by the Raman lidar, suggesting large differences of ice crystal size, shape and habit. Further, a mixed-phase double layer cloud was observed by airborne lidar in the free troposphere. Local orography influenced the evolution of this cloud. The four case studies revealed relations of cloud properties and specific atmospheric conditions, which we plan to use as the base for numerical simulations of these clouds.

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Airborne observations of a subvisible midlevel Arctic ice cloud: microphysical and radiative characterization

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-595-2009 ◽

2009 ◽

Vol 9 (1) ◽

pp. 595-634

Author(s):

A. Lampert ◽

A. Ehrlich ◽

A. Dörnbrack ◽

O. Jourdan ◽

J.-F. Gayet ◽

...

Keyword(s):

Remote Sensing ◽

Thermal Infrared ◽

Airborne Lidar ◽

Radiative Properties ◽

The Arctic ◽

Cloud Base ◽

Effective Diameter ◽

Ice Cloud ◽

Tropospheric Aerosol

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed at around 3 km altitude south of Svalbard. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in-situ instruments. Collocated airborne lidar remote-sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in-situ sensors roughly 30 min later. From individual ice crystal samples detected with the Cloud Particle Imager and the ensemble of particles measured with the Polar Nephelometer, we retrieved the single-scattering albedo, the scattering phase function as well as the volume extinction coefficient and the effective diameter of the crystal population. Furthermore, a lidar ratio of 21 (±6) sr was deduced by two independent methods. These parameters in conjunction with the cloud optical thickness obtained from the lidar measurements were used to compute spectral and broadband radiances and irradiances with a radiative transfer code. The simulated results agreed with the observed spectral downwelling radiance within the range given by the measurement uncertainty. Furthermore, the broadband radiative simulations estimated a net (solar plus thermal infrared) radiative forcing of the subvisible midlevel ice cloud of −0.4 W m−2 (−3.2 W m−2 in the solar and +2.8 W m−2 in the thermal infrared wavelength range).

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Microphysical and radiative characterization of a subvisible midlevel Arctic ice cloud by airborne observations – a case study

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-2647-2009 ◽

2009 ◽

Vol 9 (8) ◽

pp. 2647-2661 ◽

Cited By ~ 34

Author(s):

A. Lampert ◽

A. Ehrlich ◽

A. Dörnbrack ◽

O. Jourdan ◽

J.-F. Gayet ◽

...

Keyword(s):

Remote Sensing ◽

Thermal Infrared ◽

Airborne Lidar ◽

Radiative Properties ◽

The Arctic ◽

Cloud Base ◽

Effective Diameter ◽

Ice Cloud ◽

Tropospheric Aerosol

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed south of Svalbard at around 3 km altitude. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in situ instruments. Collocated airborne lidar remote sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in situ sensors roughly 30 min later. From individual ice crystal samples detected with the Cloud Particle Imager and the ensemble of particles measured with the Polar Nephelometer, microphysical properties were retrieved with a bi-modal inversion algorithm. The best agreement with the measurements was obtained for small ice spheres and deeply rough hexagonal ice crystals. Furthermore, the single-scattering albedo, the scattering phase function as well as the volume extinction coefficient and the effective diameter of the crystal population were determined. A lidar ratio of 21(±6) sr was deduced by three independent methods. These parameters in conjunction with the cloud optical thickness obtained from the lidar measurements were used to compute spectral and broadband radiances and irradiances with a radiative transfer code. The simulated results agreed with the observed spectral downwelling radiance within the range given by the measurement uncertainty. Furthermore, the broadband radiative simulations estimated a net (solar plus thermal infrared) radiative forcing of the subvisible midlevel ice cloud of −0.4 W m−2 (−3.2 W m−2 in the solar and +2.8 W m−2 in the thermal infrared wavelength range).

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Airborne Lidar Observations of Wind, Water Vapor, and Aerosol Profiles During The NASA Aeolus Cal/Val Test Flight Campaign

10.5194/amt-2020-475 ◽

2020 ◽

Author(s):

Kristopher M. Bedka ◽

Amin R. Nehrir ◽

Michael Kavaya ◽

Rory Barton-Grimley ◽

Mark Beaubien ◽

...

Keyword(s):

Remote Sensing ◽

Optical Properties ◽

Water Vapor ◽

European Space Agency ◽

Airborne Lidar ◽

Horizontal Wind ◽

Atmospheric Conditions ◽

Horizontal Wind Speed ◽

Wide Range ◽

Test Flight

Abstract. Lidars are uniquely capable of collecting high precision and high spatio-temporal resolution observations that have been used for atmospheric process studies from the ground, aircraft, and space for many years. The Aeolus mission, the first space-borne Doppler wind lidar, was developed by the European Space Agency and launched in August 2018. Its novel Atmospheric LAser Doppler INstrument (ALADIN) observes profiles of the component of the wind vector and aerosol/cloud optical properties along the instrument’s line-of-sight (LOS) direction on a global scale. Two airborne lidar systems have been developed at NASA Langley Research Center in recent years that collect measurements in support of several NASA Earth Science Division focus areas. The coherent Doppler Aerosol WiNd (DAWN) lidar measures vertical profiles of LOS velocity along selected azimuth angles that are combined to derive profiles of horizontal wind speed and direction. The High Altitude Lidar Observatory (HALO) measures high resolution profiles of atmospheric water vapor (WV), and aerosol and cloud optical properties. Because there are limitations in terms of spatial and vertical detail and measurement precision that can be accomplished from space, airborne remote sensing observations like those from DAWN and HALO are required to fill these observational gaps as well as to calibrate and validate space-borne measurements. Over a two-week period in April 2019 during their Aeolus Cal/Val Test Flight campaign, NASA conducted five research flights over the Eastern Pacific Ocean with the DC-8 aircraft. The purpose was to demonstrate: 1) DAWN and HALO measurement capabilities across a range of atmospheric conditions, 2) Aeolus Cal/Val flight strategies and comparisons of DAWN and HALO measurements with Aeolus to gain an initial perspective of Aeolus performance, and 3) how atmospheric dynamic processes can be resolved and better understood through simultaneous observations of wind, WV, and aerosol profile observations, coupled with numerical model and other remote sensing observations. This paper provides a brief description of the DAWN and HALO instruments, discusses the synergistic observations collected across a wide range of atmospheric conditions sampled during the DC-8 flights, and gives a brief summary of the validation of DAWN, HALO, and Aeolus observations and comparisons.

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Airborne lidar observations of wind, water vapor, and aerosol profiles during the NASA Aeolus calibration and validation (Cal/Val) test flight campaign

Atmospheric Measurement Techniques ◽

10.5194/amt-14-4305-2021 ◽

2021 ◽

Vol 14 (6) ◽

pp. 4305-4334

Author(s):

Kristopher M. Bedka ◽

Amin R. Nehrir ◽

Michael Kavaya ◽

Rory Barton-Grimley ◽

Mark Beaubien ◽

...

Keyword(s):

Remote Sensing ◽

Optical Properties ◽

Water Vapor ◽

European Space Agency ◽

Airborne Lidar ◽

Horizontal Wind ◽

Atmospheric Conditions ◽

Spatiotemporal Resolution ◽

Wide Range ◽

Test Flight

Abstract. Lidars are uniquely capable of collecting high-precision and high spatiotemporal resolution observations that have been used for atmospheric process studies from the ground, aircraft, and space for many years. The Aeolus mission, the first space-borne Doppler wind lidar, was developed by the European Space Agency (ESA) and launched in August 2018. Its novel Atmospheric LAser Doppler INstrument (ALADIN) observes profiles of the component of the wind vector and aerosol/cloud optical properties along the instrument's line-of-sight (LOS) direction on a global scale. A total of two airborne lidar systems have been developed at NASA Langley Research Center in recent years that collect measurements in support of several NASA Earth Science Division focus areas. The coherent Doppler Aerosol WiNd (DAWN) lidar measures vertical profiles of LOS velocity along selected azimuth angles that are combined to derive profiles of horizontal wind speed and direction. The High Altitude Lidar Observatory (HALO) measures high resolution profiles of atmospheric water vapor (WV) and aerosol and cloud optical properties. Because there are limitations in terms of spatial and vertical detail and measurement precision that can be accomplished from space, airborne remote sensing observations like those from DAWN and HALO are required to fill these observational gaps and to calibrate and validate space-borne measurements. Over a 2-week period in April 2019, during their Aeolus Cal/Val Test Flight campaign, NASA conducted five research flights over the eastern Pacific Ocean with the DC-8 aircraft. The purpose was to demonstrate the following: (1) DAWN and HALO measurement capabilities across a range of atmospheric conditions, (2) Aeolus Cal/Val flight strategies and comparisons of DAWN and HALO measurements with Aeolus, to gain an initial perspective of Aeolus performance, and (3) ways in which atmospheric dynamic processes can be resolved and better understood through simultaneous observations of wind, WV, and aerosol profile observations, coupled with numerical model and other remote sensing observations. This paper provides a brief description of the DAWN and HALO instruments, discusses the synergistic observations collected across a wide range of atmospheric conditions sampled during the DC-8 flights, and gives a brief summary of the validation of DAWN, HALO, and Aeolus observations and comparisons.

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Evidence of Arctic-wide Atmospheric Aerosols from DMSP Visible Imagery

Journal of Climate and Applied Meteorology ◽

10.1175/0733-3021-23.10.1459 ◽

1984 ◽

Vol 23 (10) ◽

pp. 1459-1464 ◽

Cited By ~ 6

Author(s):

Keith P. Shine ◽

David A. Robinson ◽

Ann Henderson-Sellers ◽

George Kukla

Keyword(s):

Remote Sensing ◽

Atmospheric Aerosols ◽

Large Scale ◽

Radiation Budget ◽

Shortwave Radiation ◽

The Arctic ◽

Potential Importance ◽

Transfer Scheme ◽

Aerosol Distribution ◽

Visible Imagery

Abstract Recent work has emphasized the potential importance of atmospheric aerosols in the Arctic. This paper presents results indicating the large-scale presence of arctic aerosols during late spring. Their screening effect may be sufficient to alter significantly the shortwave radiation budget. The ratios of brightness over sea and snow covered ice surfaces are shown to be considerably lower, using DMSP shortwave imagery, than those calculated for clear skies using a radiative transfer scheme. Our analysis shows that aerosols are the most likely cause of the discrepancy. With additional calibration the method offers the potential for remote sensing of the aerosol distribution and concentration over the Arctic.

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Terrestrial Laser Scanning for Vegetation Analyses with a Special Focus on Savannas

Remote Sensing ◽

10.3390/rs13030507 ◽

2021 ◽

Vol 13 (3) ◽

pp. 507

Author(s):

Tasiyiwa Priscilla Muumbe ◽

Jussi Baade ◽

Jenia Singh ◽

Christiane Schmullius ◽

Christian Thau

Keyword(s):

Remote Sensing ◽

Vegetation Structure ◽

Laser Scanning ◽

Spatial Scales ◽

Terrestrial Laser Scanning ◽

Point Clouds ◽

Parameter Extraction ◽

Airborne Lidar ◽

Special Focus ◽

Vegetation Parameter

Savannas are heterogeneous ecosystems, composed of varied spatial combinations and proportions of woody and herbaceous vegetation. Most field-based inventory and remote sensing methods fail to account for the lower stratum vegetation (i.e., shrubs and grasses), and are thus underrepresenting the carbon storage potential of savanna ecosystems. For detailed analyses at the local scale, Terrestrial Laser Scanning (TLS) has proven to be a promising remote sensing technology over the past decade. Accordingly, several review articles already exist on the use of TLS for characterizing 3D vegetation structure. However, a gap exists on the spatial concentrations of TLS studies according to biome for accurate vegetation structure estimation. A comprehensive review was conducted through a meta-analysis of 113 relevant research articles using 18 attributes. The review covered a range of aspects, including the global distribution of TLS studies, parameters retrieved from TLS point clouds and retrieval methods. The review also examined the relationship between the TLS retrieval method and the overall accuracy in parameter extraction. To date, TLS has mainly been used to characterize vegetation in temperate, boreal/taiga and tropical forests, with only little emphasis on savannas. TLS studies in the savanna focused on the extraction of very few vegetation parameters (e.g., DBH and height) and did not consider the shrub contribution to the overall Above Ground Biomass (AGB). Future work should therefore focus on developing new and adjusting existing algorithms for vegetation parameter extraction in the savanna biome, improving predictive AGB models through 3D reconstructions of savanna trees and shrubs as well as quantifying AGB change through the application of multi-temporal TLS. The integration of data from various sources and platforms e.g., TLS with airborne LiDAR is recommended for improved vegetation parameter extraction (including AGB) at larger spatial scales. The review highlights the huge potential of TLS for accurate savanna vegetation extraction by discussing TLS opportunities, challenges and potential future research in the savanna biome.

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The model of an information system for monitoring remote sensing data of the Arctic region

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/678/1/012043 ◽

2021 ◽

Vol 678 (1) ◽

pp. 012043

Author(s):

Makar Bizyukin ◽

Gennady Abrahamyan

Keyword(s):

Remote Sensing ◽

Information System ◽

Remote Sensing Data ◽

Arctic Region ◽

The Arctic ◽

Sensing Data ◽

The Arctic Region

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Remote Sensing of Snow Cover Variability and Its Influence on the Runoff of Sápmi’s Rivers

Geosciences ◽

10.3390/geosciences11030130 ◽

2021 ◽

Vol 11 (3) ◽

pp. 130

Author(s):

Sebastian Rößler ◽

Marius S. Witt ◽

Jaakko Ikonen ◽

Ian A. Brown ◽

Andreas J. Dietz

Keyword(s):

Remote Sensing ◽

Snow Cover ◽

Air Temperature ◽

Kendall Test ◽

The Arctic ◽

Boreal Winter ◽

Snowmelt Runoff ◽

River Catchment ◽

Catchment Areas ◽

Runoff Model

The boreal winter 2019/2020 was very irregular in Europe. While there was very little snow in Central Europe, the opposite was the case in northern Fenno-Scandia, particularly in the Arctic. The snow cover was more persistent here and its rapid melting led to flooding in many places. Since the last severe spring floods occurred in the region in 2018, this raises the question of whether more frequent occurrences can be expected in the future. To assess the variability of snowmelt related flooding we used snow cover maps (derived from the DLR’s Global SnowPack MODIS snow product) and freely available data on runoff, precipitation, and air temperature in eight unregulated river catchment areas. A trend analysis (Mann-Kendall test) was carried out to assess the development of the parameters, and the interdependencies of the parameters were examined with a correlation analysis. Finally, a simple snowmelt runoff model was tested for its applicability to this region. We noticed an extraordinary variability in the duration of snow cover. If this extends well into spring, rapid air temperature increases leads to enhanced thawing. According to the last flood years 2005, 2010, 2018, and 2020, we were able to differentiate between four synoptic flood types based on their special hydrometeorological and snow situation and simulate them with the snowmelt runoff model (SRM).

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