scholarly journals Analysis of snow bidirectional reflectance from ARCTAS spring-2008 campaign

2009 ◽  
Vol 9 (5) ◽  
pp. 21993-22040 ◽  
Author(s):  
A. Lyapustin ◽  
C. K. Gatebe ◽  
R. Kahn ◽  
R. Brandt ◽  
J. Redemann ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Phase Function ◽  
Full Range ◽  
Arctic Region ◽  
The Arctic ◽  
Bidirectional Reflectance ◽  
International Polar Year ◽  
Sensing Applications ◽  
Synthetic Phase ◽  
Best Fit

Abstract. The spring 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment was one of the major intensive field campaigns of the International Polar Year, aimed at detailed characterization of atmospheric physical and chemical processes in the Arctic region. Part of this campaign was a unique snow bidirectional reflectance experiment on the NASA P-3B aircraft conducted on 7 and 15 April by the Cloud Absorption Radiometer (CAR) jointly with airborne Ames Airborne Tracking Sunphotometer (AATS) and ground-based Aerosol Robotic Network (AERONET) sunphotometers. The CAR data were atmospherically corrected to derive snow bidirectional reflectance at high 1° angular resolution in view zenith and azimuthal angles along with surface albedo. The derived albedo was generally in good agreement with ground albedo measurements collected on 15 April. The CAR snow bidirectional reflectance factor (BRF) was used to study the accuracy of analytical Ross-Thick Li-Sparse (RTLS), Modified Rahman-Pinty-Verstraete (MRPV) and Asymptotic Analytical Radiative Transfer (AART) BRF models. Except for the glint region (azimuthal angles φ<40°), the best fit MRPV and RTLS models fit snow BRF to within ±0.05. The plane-parallel radiative transfer (PPRT) solution was also analyzed with the models of spheres, spheroids, randomly oriented fractal crystals, and with a synthetic phase function. The latter merged the model of spheroids for the forward scattering angles with the fractal model in the backscattering direction. The PPRT solution with synthetic phase function provided the best fit to measured BRF in the full range of angles. Regardless of the snow grain shape, the PPRT model significantly over-/underestimated snow BRF in the glint/backscattering regions, respectively, which agrees with other studies. To improve agreement with the experiment, we introduced a model of macroscopic snow surface roughness by averaging the PPRT solution over the slope distribution function and by adding a simple model of shadows. With macroscopic roughness described by two parameters, the AART model achieved an accuracy of about ±0.05 with a possible bias of ±0.03 in the spectral range 0.4–2.2 μm. This high accuracy holds at view zenith angles below 55–60° covering the practically important range for remote sensing applications, and includes both glint and backscattering directions.

scholarly journals Analysis of snow bidirectional reflectance from ARCTAS Spring-2008 Campaign

2010 ◽  
Vol 10 (9) ◽  
pp. 4359-4375 ◽  
Author(s):  
A. Lyapustin ◽  
C. K. Gatebe ◽  
R. Kahn ◽  
R. Brandt ◽  
J. Redemann ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Phase Function ◽  
Full Range ◽  
Arctic Region ◽  
The Arctic ◽  
Bidirectional Reflectance ◽  
International Polar Year ◽  
Sensing Applications ◽  
Synthetic Phase ◽  
Best Fit

Abstract. The spring 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment was one of major intensive field campaigns of the International Polar Year aimed at detailed characterization of atmospheric physical and chemical processes in the Arctic region. A part of this campaign was a unique snow bidirectional reflectance experiment on the NASA P-3B aircraft conducted on 7 and 15 April by the Cloud Absorption Radiometer (CAR) jointly with airborne Ames Airborne Tracking Sunphotometer (AATS) and ground-based Aerosol Robotic Network (AERONET) sunphotometers. The CAR data were atmospherically corrected to derive snow bidirectional reflectance at high 1° angular resolution in view zenith and azimuthal angles along with surface albedo. The derived albedo was generally in good agreement with ground albedo measurements collected on 15 April. The CAR snow bidirectional reflectance factor (BRF) was used to study the accuracy of analytical Ross-Thick Li-Sparse (RTLS), Modified Rahman-Pinty-Verstraete (MRPV) and Asymptotic Analytical Radiative Transfer (AART) BRF models. Except for the glint region (azimuthal angles φ<40°), the best fit MRPV and RTLS models fit snow BRF to within ±0.05. The plane-parallel radiative transfer (PPRT) solution was also analyzed with the models of spheres, spheroids, randomly oriented fractal crystals, and with a synthetic phase function. The latter merged the model of spheroids for the forward scattering angles with the fractal model in the backscattering direction. The PPRT solution with synthetic phase function provided the best fit to measured BRF in the full range of angles. Regardless of the snow grain shape, the PPRT model significantly over-/underestimated snow BRF in the glint/backscattering regions, respectively, which agrees with other studies. To improve agreement with experiment, we introduced a model of macroscopic snow surface roughness by averaging the PPRT solution over the slope distribution function and by adding a simple model of shadows. With macroscopic roughness described by two parameters, the AART model achieved an accuracy of about ±0.05 with a possible bias of ±0.03 in the spectral range 0.4–2.2 μm. This high accuracy holds at view zenith angles below 55–60° covering the practically important range for remote sensing applications, and includes both glint and backscattering directions.

scholarly journals Analysis of IASI tropospheric O<sub>3</sub> data over the Arctic during POLARCAT campaigns in 2008

2012 ◽  
Vol 12 (16) ◽  
pp. 7371-7389 ◽  
Author(s):  
M. Pommier ◽  
C. Clerbaux ◽  
K. S. Law ◽  
G. Ancellet ◽  
P. Bernath ◽  
...  
Keyword(s):  
Arctic Region ◽  
Anthropogenic Sources ◽  
The Arctic ◽  
International Polar Year ◽  
Air Masses ◽  
Infrared Radiance ◽  
In Situ Data ◽  
Clean Air ◽  
International Polar

Abstract. Ozone data retrieved in the Arctic region from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI) on board the MetOp-A European satellite are presented. They are compared with in situ and lidar observations obtained during a series of aircraft measurement campaigns as part of the International Polar Year POLARCAT activities in spring and summer 2008. Different air masses were sampled during the campaigns including clean air, polluted plumes originating from anthropogenic sources, forest fire plumes from the three northern continents, and stratospheric-influenced air masses. The comparison between IASI O3 [0–8 km], [0–12 km] partial columns and profiles with collocated aircraft observations is achieved by taking into account the different sensitivity and geometry of the sounding instruments. A detailed analysis is provided and the agreement is discussed in terms of vertical sensitivity and surface properties at the location of the observations. Overall, IASI O3 profiles are found to be in relatively good agreement with smoothed in situ and lidar profiles in the free troposphere with differences of less than 40% (25% over sea for both seasons) and 10%, respectively. The correlation between IASI O3 retrieved partial columns and the smoothed aircraft partial columns is good with DC-8 in situ data in spring over North America (r = 0.68), and over Greenland with ATR-42 lidar measurements in summer (r = 0.67). Correlations with other data are less significant highlighting the difficulty of IASI to capture precisely the O3 variability in the Arctic upper troposphere and lower stratosphere (UTLS). This is particularly noted in comparison with the [0–12 km] partial columns. The IASI [0–8 km] partial columns display a low negative bias (by less than 26% over snow) compared to columns derived from in situ measurements. Despite the relatively high biases of the IASI retrievals in the Arctic UTLS, our analysis shows that IASI can be used to identify, using O3 / CO ratios, stratospheric intrusions.

scholarly journals Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013

Ocean Science ◽  
2017 ◽  
Vol 13 (1) ◽  
pp. 123-144 ◽  
Author(s):  
Jiping Xie ◽  
Laurent Bertino ◽  
François Counillon ◽  
Knut A. Lisæter ◽  
Pavel Sakov
Keyword(s):  
Data Assimilation ◽  
Sea Ice ◽  
Quality Assessment ◽  
Arctic Region ◽  
Ocean Model ◽  
Observation Time ◽  
The Arctic ◽  
Bias Estimation ◽  
International Polar Year ◽  
Near Surface

Abstract. Long dynamical atmospheric reanalyses are widely used for climate studies, but data-assimilative reanalyses of ocean and sea ice in the Arctic are less common. TOPAZ4 is a coupled ocean and sea ice data assimilation system for the North Atlantic and the Arctic that is based on the HYCOM ocean model and the ensemble Kalman filter data assimilation method using 100 dynamical members. A 23-year reanalysis has been completed for the period 1991–2013 and is the multi-year physical product in the Copernicus Marine Environment Monitoring Service (CMEMS) Arctic Marine Forecasting Center (ARC MFC). This study presents its quantitative quality assessment, compared to both assimilated and unassimilated observations available in the whole Arctic region, in order to document the strengths and weaknesses of the system for potential users. It is found that TOPAZ4 performs well with respect to near-surface ocean variables, but some limitations appear in the interior of the ocean and for ice thickness, where observations are sparse. In the course of the reanalysis, the skills of the system are improving as the observation network becomes denser, in particular during the International Polar Year. The online bias estimation successfully maintains a low bias in our system. In addition, statistics of the reduced centered random variables (RCRVs) confirm the reliability of the ensemble for most of the assimilated variables. Occasional discontinuities of these statistics are caused by the changes of the input data sets or the data assimilation settings, but the statistics remain otherwise stable throughout the reanalysis, regardless of the density of observations. Furthermore, no data type is severely less dispersed than the others, even though the lack of consistently reprocessed observation time series at the beginning of the reanalysis has proven challenging.

scholarly journals Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013

2016 ◽  
Author(s):  
Jiping Xie ◽  
Laurent Bertino ◽  
Francois Counillon ◽  
Knut A. Lisæter ◽  
Pavel Sakov
Keyword(s):  
Data Assimilation ◽  
Sea Ice ◽  
Quality Assessment ◽  
Arctic Region ◽  
Ocean Model ◽  
The Arctic ◽  
Bias Estimation ◽  
International Polar Year ◽  
Near Surface ◽  
The North

Abstract. Long dynamical atmospheric reanalyses are widely used for climate studies, but data assimilative reanalyses of the Arctic ocean and sea ice are less common. TOPAZ4 is a coupled ocean and sea ice data assimilation system for the North Atlantic and the Arctic that is based on the HYCOM ocean model and the Ensemble Kalman Filter data assimilation method using 100 dynamical members. A 23-years reanalysis has been completed for the period 1991–2013. This study presents its quantitative quality assessment, compared to both assimilated and unassimilated observations available in the whole Arctic region in order to document the strengths and weaknesses of the system for potential users. It is found that TOPAZ4 performs well with respect to near surface ocean variables, but some limitations appear in the interior of the ocean and for ice thickness, where observations are sparse. In the course of the reanalysis, the skills of the system are improving as the observation network becomes denser, in particular during the International Polar Year. The online bias estimation successfully maintains a low bias in our system.

Process-Based Decomposition of the Decadal Climate Difference between 2002–13 and 1984–95

2017 ◽  
Vol 30 (12) ◽  
pp. 4373-4393 ◽  
Author(s):  
Xiaoming Hu ◽  
Yana Li ◽  
Song Yang ◽  
Yi Deng ◽  
Ming Cai
Keyword(s):  
Radiative Transfer ◽  
Heat Storage ◽  
Decomposition Analysis ◽  
Arctic Region ◽  
The Arctic ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Model Calculations ◽  
Surface Warming ◽  
Decadal Climate

This study examines at the process level the climate difference between 2002–13 and 1984–95 in ERA-Interim. A linearized radiative transfer model is used to calculate the temperature change such that its thermal radiative cooling would balance the energy flux perturbation associated with the change of an individual process, without regard to what causes the change of the process in the first place. The global mean error of the offline radiative transfer model calculations is 0.09 K, which corresponds to the upper limit of the uncertainties from a single term in the decomposition analysis. The process-based decomposition indicates that the direct effect of the increase of CO2 (0.15 K) is the largest contributor to the global warming between the two periods (about 0.27 K). The second and third largest contributors are the cloud feedback (0.14 K) and the combined effect of the oceanic heat storage and evaporation terms (0.11 K), respectively. The largest warming associated with the oceanic heat storage term is found in the tropical Pacific and Indian Oceans, with relatively weaker warming over the tropical Atlantic Ocean. The increase in atmospheric moisture adds another 0.1 K to the global surface warming, but the enhancement in tropical convections acts to reduce the surface warming by 0.17 K. The ice-albedo and atmospheric dynamical feedbacks are the two leading factors responsible for the Arctic polar warming amplification (PWA). The increase of atmospheric water vapor over the Arctic region also contributes substantially to the Arctic PWA pattern.

The 9th Circumpolar Remote Sensing Symposium

Polar Record ◽  
2007 ◽  
Vol 43 (4) ◽  
pp. 289-289
Author(s):  
Carl Markon
Keyword(s):  
Remote Sensing ◽  
New Technology ◽  
Panel Discussion ◽  
The Arctic ◽  
International Polar Year ◽  
Sensing Applications ◽  
International Polar ◽  
Remote Sensing Symposium ◽  
Circumpolar Arctic ◽  
Oral Presentations

Most of the papers in this issue of Polar Record are a result of research performed by a cadre of scientists specifically dealing with remote sensing applications in the Arctic environments. These studies, and other similar activities, were presented originally at the 9th Circumpolar Remote Sensing Symposium held in Seward, Alaska, from 15–19 May 2006. The symposium provided a forum to the 40 international scientists attending it for the exchange of current applied research, the presentation of new technology, and the advancement of internal co-operation in the circumpolar Arctic and Antarctic regions. Oral presentations in the 10 plenary sessions focused on snow, ice, and cryosphere studies, climate and the environment, environmental monitoring, arctic vegetation inventory, monitoring and analysis, databases, data processing and GIS. In addition there was a special plenary session on remote sensing for the International Polar Year. At the end of the symposium, there was a special panel discussion on recommendations for future sensors for boreal and polar remote sensing.

The International Geophysical Year

1957 ◽  
Vol 10 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Harold Spencer Jones
Keyword(s):  
Arctic Region ◽  
The Arctic ◽  
Polar Regions ◽  
International Polar Year ◽  
International Geophysical Year ◽  
Primary Object ◽  
International Polar ◽  
Meteorological Observations ◽  
One Year ◽  
The Arctic Region

In 1874, the Austrian arctic scientist, Weyprecht, on his return from an Austro-Hungarian polar expedition stated that, though many countries had sent expeditions into the polar regions at great expense and involving appreciable hazards to those participating, no important contributions to knowledge had resulted from them. They had done a certain amount of mapping and obtained a few meteorological observations but the primary object had been, as a matter of national prestige, to plant the flag nearer to the Pole than had been reached before. In his opinion what was needed for the advancement of knowledge about the polar regions was that nations should collaborate in sending expeditions to various parts of the arctic region to make observations throughout the whole of one year. Largely because of his persistent advocacy of this view, the value of the proposal came to be recognized, and as a result the enterprise known as the First International Polar Year was developed. A number of countries combined to send expeditions to establish observing stations at selected points in the arctic region to make observations throughout the year 1882–3 in meteorology and geomagnetism and also of the aurora. The observations made during this Polar Year contributed appreciably to knowledge of geomagnetism and of meteorology.

scholarly journals Absorption, scattering and single scattering albedo of aerosols obtained from in situ measurements in the subarctic coastal region of Norway

2011 ◽  
Vol 11 (1) ◽  
pp. 2161-2182 ◽  
Author(s):  
E. Montilla ◽  
S. Mogo ◽  
V. Cachorro ◽  
J. Lopez ◽  
A. de Frutos
Keyword(s):  
Coastal Region ◽  
Arctic Region ◽  
Single Scattering ◽  
Mean Value ◽  
In Situ Measurements ◽  
Single Scattering Albedo ◽  
The Arctic ◽  
Rural Site ◽  
International Polar Year

Abstract. In situ measurements of aerosol optical properties were made in summer 2008 at the ALOMAR station facility (69°16 N, 16°00 E), located at a rural site in the North of the island of Andøya (Vesterålen archipelago), about 300 km north of the Arctic Circle. The extended three months campaign was part of the POLAR-CAT Project of the International Polar Year (IPY-2007-2008), and its goal was to characterize the aerosols of this sub-Arctic area which frequently transporte to the Arctic region. The ambient light-scattering coefficient, σs(550 nm), at ALOMAR had a hourly mean value of 5.412 Mm−1 (StD = 3.545 Mm−1) and the light-absorption coefficient, σa(550 nm), had an hourly mean value of 0.400 Mm−1 (StD = 0.273 Mm−1). The scattering/absorption Ångström exponents, αs,a, are used for detailed analysis of the variations of the spectral shape of σs,a. The single scattering albedo, &amp;omega0, ranges from 0.622 to 0.985 (mean = 0.913, StD = 0.052) and the relation of this property to the absorption/scattering coefficients and the Ångström exponents is presented. The relationships between all the parameters analyzed, mainly those related to the single scattering albedo, allow us to describe the local atmosphere as extremely clean.

scholarly journals Soviet experience of development of the Soviet Arctic in view of modern problems. Review of Zubkov K.I., Karpov V.P. Development of the Russian Arctic: Soviet experience in the context of current national strategy (on the example of the Ural Far North and Western Siberia). Moscow: Political encyclopedia, 2019. 367 p.

2020 ◽  
pp. 180-185
Author(s):  
M.G. Agapov
Keyword(s):  
Large Scale ◽  
Western Siberia ◽  
Full Range ◽  
Arctic Region ◽  
The Arctic ◽  
National Strategy ◽  
Russian Arctic ◽  
Far North ◽  
The Arctic Region ◽  
Soviet Experience

Discussed in this review are the results of the research presented in the monograph of specialists in North-ern studies K.I. Zubkov and V.P. Karpov «Development of the Russian Arctic: Soviet experience in the context of current national strategy (on the example of the Ural Far North and Western Siberia)». The reviewer notes that, in general, the study follows the pattern of state-centrism, teleologism and geopolitical alarmism typical for modern Russian Arctic historiography. Among the most important theses of the authors of this peer-reviewed monograph, are the following ones: (1) the transport and economic development was the basis of the Russian / Soviet Arctic exploration program; (2) the Soviet strategy of the Far North development dictated mainly the technocratic and commodity character of the territory exploitation; (3) modern Russia inherits the definition of the priorities of the state policy in the Arctic Region from the Soviet Union and relies on the territorial and production complexes cre-ated back in the USSR. The reviewer expresses serious doubts about the scientific productivity of the classic geopolitical paradigm used by the authors of the monograph: geared towards large-scale generalizations, it is simply unable to capture the full range of contradictions arising in the process of exploration of the Arctic Region. Hence the authors’ tendency to present the entire process of Arctic Region exploration as predetermined, while in reality the history of the Russian Arctic Region colonization is full of collisions; it is more intermittent than consis-tent. In particular, draws attention the constant reproduction of the same topoi in the rhetoric of Arctic Region ex-ploration. For example, from age to age, it has been repeated that the Northern Sea Route is just about to be-come the largest transnational waterway. The reviewer notes the ambiguity of practical recommendations of the authors. Thus, repeatedly expressing the idea of Russia’s interest in the international cooperation in the develop-ment of the Arctic, the authors are concerned to the same extent that foreign partners may force Russia out of the region. The review is aimed at opening a debate on approaches to understanding the Soviet experience in the Arctic Region development.

scholarly journals Analysis of IASI tropospheric O<sub>3</sub> data over Arctic during POLARCAT campaigns in 2008

2011 ◽  
Vol 11 (12) ◽  
pp. 33127-33171
Author(s):  
M. Pommier ◽  
C. Clerbaux ◽  
K. S. Law ◽  
G. Ancellet ◽  
P. Bernath ◽  
...  
Keyword(s):  
Forest Fire ◽  
Arctic Region ◽  
Anthropogenic Sources ◽  
The Arctic ◽  
International Polar Year ◽  
Air Masses ◽  
Infrared Radiance ◽  
In Situ Data ◽  
International Polar

Abstract. Ozone data retrieved in the Arctic region from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI) on board the MetOp-A European satellite are presented. They are compared with in situ and lidar observations obtained during a series of aircraft measurement campaigns as part of the International Polar Year (IPY) POLARCAT activities in spring and summer 2008. Different air masses were sampled during the campaigns including clean air, polluted plumes originating from anthropogenic sources, forest fire plumes from the three northern continents, and stratospheric-influenced air masses. The comparison between IASI O3 [0–8 km], [0–12 km] partial columns and profiles with collocated aircraft observations is achieved by taking into account the different sensitivity and geometry of the sounding instruments. A detailed analysis is provided and the agreement is discussed in terms of information content and surface properties at the location of the observations. Overall, IASI O3 profiles are found to be in relatively good agreement in the free troposphere with smoothed in situ and lidar profiles with differences less than 40% (25% over the sea for both seasons) and 10%, respectively. The correlation between IASI O3 retrieved partial columns and the smoothed aircraft partial columns is good with DC-8 in situ data in spring over North American forest fire regions (r = 0.68), and over Greenland with ATR-42 lidar measurements in summer (r = 0.67). Correlations with other data are less significant highlighting the difficulty with which IASI is able to capture O3 variability in the Arctic upper troposphere and lower stratosphere (UTLS) with sufficient precision as noted in comparison with the [0–12 km] partial columns. However the [0–8 km] partial columns show good results with IASI which displays a negative bias (maximum of 26% over snow) compared to columns derived from in situ measurements. Despite these difficulties in the Arctic UTLS, this work also shows that IASI can be used to study particular cases where stratospheric intrusions are present using a O3/CO ratio diagnostic.

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