scholarly journals Comparison of different methods to retrieve effective snow grain size in central Antarctica

2017 ◽  
Author(s):  
Tim Carlsen ◽  
Gerit Birnbaum ◽  
André Ehrlich ◽  
Johannes Freitag ◽  
Georg Heygster ◽  
...  
Keyword(s):  
Grain Size ◽  
Measurement System ◽  
Surface Albedo ◽  
Austral Summer ◽  
Surface Energy Budget ◽  
Research Station ◽  
Polar Regions ◽  
Radiation Measurement ◽  
In Situ Observations

Abstract. The effective size of snow grains (reff) affects the reflectivity of snow surfaces and thus the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA) was monitored for a two-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS, ground-based) and the Spectral Modular Airborne Radiation measurement sysTem (SMART, airborne). The Snow Grain Size and Pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified and applied to the ground-based and airborne observations collected in this study. Furthermore, spectral ratios of surface albedo at 1280 nm and 1100 nm wavelength were used to reduce the retrieval uncertainty. Additionally, the algorithm originally developed for cloudless conditions was adapted to handle overcast conditions. Optical in situ observations of SSA utilizing an IceCube device were used to validate the retrieval results. The SSA retrieved from CORAS observations varied between 27 m2 kg-1 and 86 m2 kg-1. Snowfall events caused distinct SSA maxima which were often followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of fresh fallen ice crystals (vice versa for reff). SSA retrieved by data from CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved by the airborne SMART observations underestimated the ground-based observations by a factor of 2.1 (overestimation of reff).

scholarly journals Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

2017 ◽  
Vol 11 (6) ◽  
pp. 2727-2741 ◽  
Author(s):  
Tim Carlsen ◽  
Gerit Birnbaum ◽  
André Ehrlich ◽  
Johannes Freitag ◽  
Georg Heygster ◽  
...  
Keyword(s):  
Grain Size ◽  
Measurement System ◽  
Surface Albedo ◽  
Surface Energy Budget ◽  
Research Station ◽  
Polar Regions ◽  
Radiation Measurement ◽  
In Situ Observations ◽  
The Impact

Abstract. The optical-equivalent snow grain size affects the reflectivity of snow surfaces and, thus, the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA), from which the optical snow grain size is derived, was observed for a 2-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of ground-based spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS) and airborne observations with the Spectral Modular Airborne Radiation measurement sysTem (SMART). The snow grain size and pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified in order to reduce the impact of the solar zenith angle on the retrieval results and to cover measurements in overcast conditions. Spectral ratios of surface albedo at 1280 and 1100 nm wavelength were used to reduce the retrieval uncertainty. The retrieval was applied to the ground-based and airborne observations and validated against optical in situ observations of SSA utilizing an IceCube device. The SSA retrieved from CORAS observations varied between 27 and 89 m2 kg−1. Snowfall events caused distinct relative maxima of the SSA which were followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of freshly fallen ice crystals. The ability of the modified algorithm to include measurements in overcast conditions improved the data coverage, in particular at times when precipitation events occurred and the SSA changed quickly. SSA retrieved from measurements with CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved from the airborne SMART data slightly underestimated the ground-based results.

scholarly journals Integrative and comprehensive Understanding on Polar Environments (iCUPE): the concept and initial results

2020 ◽  
Author(s):  
Tuukka Petäjä ◽  
Ella-Maria Duplissy ◽  
Ksenia Tabakova ◽  
Julia Schmale ◽  
Barbara Altstädter ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Natural Resources ◽  
Satellite Remote Sensing ◽  
Integrated Approach ◽  
The Arctic ◽  
Polar Regions ◽  
Comprehensive Understanding ◽  
In Situ Observations ◽  
Initial Results

Abstract. The role of polar regions increases in terms of megatrends such as globalization, new transport routes, demography and use of natural resources consequent effects of regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project iCUPE – integrative and Comprehensive Understanding on Polar Environments to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth Observations (EO) and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns and satellites to deliver data products, metrics and indicators to the stakeholders concerning the environmental status, availability and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and provision of novel data in atmospheric pollution, local sources and transboundary transport, characterization of arctic surfaces and their changes, assessment of concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, quantification of emissions from natural resource extraction and validation and optimization of satellite Earth Observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of integration of comprehensive in situ observations, satellite remote sensing and multiscale modeling in the Arctic context.

scholarly journals Measurement and interpretation of gas phase formaldehyde concentrations obtained during the CHABLIS campaign in coastal Antarctica

2008 ◽  
Vol 8 (14) ◽  
pp. 4085-4093 ◽  
Author(s):  
R. A. Salmon ◽  
S. J.-B. Bauguitte ◽  
W. Bloss ◽  
M. A. Hutterli ◽  
A. E. Jones ◽  
...  
Keyword(s):  
Gas Phase ◽  
Austral Summer ◽  
Research Station ◽  
Steady State Analysis ◽  
Sources And Sinks ◽  
Data Coverage ◽  
Absolute Concentrations ◽  
Instrumental Detection Limit ◽  
Phase Production

Abstract. Gas phase formaldehyde concentrations were measured during the 2004–2005 CHABLIS campaign at Halley research station, Antarctica. Data coverage span from May 2004 through to January 2005, thus capturing the majority of the year, with a wintertime minimum of near or below the instrumental detection limit rising to between 50 and 200 pptv during the austral summer. Factors controlling HCHO concentration include local chemical sources and sinks, and exchange with the snow surface. The measured seasonality is in line with previous observations from Neumayer station, with maximum in summer and minimum during the winter months, but with lower absolute concentrations throughout the year. The gas-phase production of HCHO was dominated by methane oxidation and a steady-state analysis showed that reactions of iodine and bromine species substantially reduced the predicted HCHO levels based upon in situ chemistry. This indicates a substantial additional HCHO source to be present that could be explained by a snowpack source.

scholarly journals In situ observations of black carbon in snow and the corresponding spectral surface albedo reduction

2015 ◽  
Vol 120 (4) ◽  
pp. 1476-1489 ◽  
Author(s):  
C. A. Pedersen ◽  
J.-C. Gallet ◽  
J. Ström ◽  
S. Gerland ◽  
S. R. Hudson ◽  
...  
Keyword(s):  
Black Carbon ◽  
Surface Albedo ◽  
In Situ Observations

scholarly journals The Energy Budget of the Polar Atmosphere in MERRA

2012 ◽  
Vol 25 (1) ◽  
pp. 5-24 ◽  
Author(s):  
Richard I. Cullather ◽  
Michael G. Bosilovich
Keyword(s):  
Energy Budget ◽  
The Arctic ◽  
Polar Regions ◽  
Polar Cap ◽  
The South ◽  
Atmospheric Energy ◽  
In Situ Observations ◽  
Energy Convergence ◽  
South Polar

Abstract Components of the atmospheric energy budget from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) are evaluated in polar regions for the period 1979–2005 and compared with previous estimates, in situ observations, and contemporary reanalyses. Closure of the budget is reflected by the analysis increments term, which indicates an energy surplus of 11 W m−2 over the North Polar cap (70°–90°N) and 22 W m−2 over the South Polar cap (70°–90°S). Total atmospheric energy convergence from MERRA compares favorably with previous studies for northern high latitudes but exceeds the available previous estimate for the South Polar cap by 46%. Discrepancies with the Southern Hemisphere energy transport are largest in autumn and may be related to differences in topography with earlier reanalyses. For the Arctic, differences between MERRA and other sources in top of atmosphere (TOA) and surface radiative fluxes are largest in May. These differences are concurrent with the largest discrepancies between MERRA parameterized and observed surface albedo. For May, in situ observations of the upwelling shortwave flux in the Arctic are 80 W m−2 larger than MERRA, while the MERRA downwelling longwave flux is underestimated by 12 W m−2 throughout the year. Over grounded ice sheets, the annual mean net surface energy flux in MERRA is erroneously nonzero. Contemporary reanalyses from the Climate Forecast Center (CFSR) and the Interim Re-Analyses of the European Centre for Medium-Range Weather Forecasts (ERA-I) are found to have better surface parameterizations; however, these reanalyses also disagree with observed surface and TOA energy fluxes. Discrepancies among available reanalyses underscore the challenge of reproducing credible estimates of the atmospheric energy budget in polar regions.

scholarly journals CLARA-SAL: a global 28-yr timeseries of Earth's black-sky surface albedo

2012 ◽  
Vol 12 (9) ◽  
pp. 25573-25615 ◽  
Author(s):  
A. Riihelä ◽  
T. Manninen ◽  
V. Laine ◽  
K. Andersson ◽  
F. Kaspar
Keyword(s):  
Sea Ice ◽  
Surface Albedo ◽  
Greenland Ice Sheet ◽  
Open Water ◽  
Atmospheric Effect ◽  
Clear Sky ◽  
Product Features ◽  
In Situ Observations

Abstract. We present a novel 28-yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS), as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR.

scholarly journals Wintertime enhancements of sea salt aerosol in polar regions consistent with a sea ice source from blowing snow

2017 ◽  
Vol 17 (5) ◽  
pp. 3699-3712 ◽  
Author(s):  
Jiayue Huang ◽  
Lyatt Jaeglé
Keyword(s):  
Sea Ice ◽  
Open Ocean ◽  
Sea Salt ◽  
The Arctic ◽  
Polar Regions ◽  
Blowing Snow ◽  
In Situ Observations ◽  
Frost Flowers ◽  
Mass Concentrations

Abstract. Sea salt aerosols (SSA) are generated via air bubbles bursting at the ocean surface as well as by wind mobilization of saline snow and frost flowers over sea-ice-covered areas. The relative magnitude of these sources remains poorly constrained over polar regions, affecting our ability to predict their impact on halogen chemistry, cloud formation, and climate. We implement a blowing snow and a frost flower emission scheme in the GEOS-Chem global chemical transport model, which we validate against multiyear (2001–2008) in situ observations of SSA mass concentrations at three sites in the Arctic, two sites in coastal Antarctica, and from the 2008 ICEALOT cruise in the Arctic. A simulation including only open ocean emissions underestimates SSA mass concentrations by factors of 2–10 during winter–spring for all ground-based and ship-based observations. When blowing snow emissions are added, the model is able to reproduce observed wintertime SSA concentrations, with the model bias decreasing from a range of −80 to −34 % for the open ocean simulation to −2 to +9 % for the simulation with blowing snow emissions. We find that the frost flower parameterization cannot fully explain the high wintertime concentrations and displays a seasonal cycle decreasing too rapidly in early spring. Furthermore, the high day-to-day variability of observed SSA is better reproduced by the blowing snow parameterization. Over the Arctic (> 60° N) (Antarctic, > 60° S), we calculate that submicron SSA emissions from blowing snow account for 1.0 Tg yr−1 (2.5 Tg yr−1), while frost flower emissions lead to 0.21 Tg yr−1 (0.25 Tg yr−1) compared to 0.78 Tg yr−1 (1.0 Tg yr−1) from the open ocean. Blowing snow emissions are largest in regions where persistent strong winds occur over sea ice (east of Greenland, over the central Arctic, Beaufort Sea, and the Ross and Weddell seas). In contrast, frost flower emissions are largest where cold air temperatures and open leads are co-located (over the Canadian Arctic Archipelago, coastal regions of Siberia, and off the Ross and Ronne ice shelves). Overall, in situ observations of mass concentrations of SSA suggest that blowing snow is likely to be the dominant SSA source during winter, with frost flowers playing a much smaller role.

scholarly journals Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000–2013)

2014 ◽  
Vol 8 (6) ◽  
pp. 2293-2312 ◽  
Author(s):  
P. M. Alexander ◽  
M. Tedesco ◽  
X. Fettweis ◽  
R. S. W. van de Wal ◽  
C. J. P. P. Smeets ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Temporal Variability ◽  
Surface Albedo ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Elevation ◽  
In Situ Observations ◽  
Spatio Temporal

Abstract. Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo during June, July, and August (JJA) for the period 2000–2013. We use two remote sensing products derived from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS), as well as outputs from the Modèle Atmosphérique Régionale (MAR) regional climate model (RCM) and data from in situ automatic weather stations. Our results point to an overall consistency in spatio-temporal variability between remote sensing and RCM albedo, but reveal a difference in mean albedo of up to ~0.08 between the two remote sensing products north of 70° N. At low elevations, albedo values simulated by the RCM are positively biased with respect to remote sensing products by up to ~0.1 and exhibit low variability compared with observations. We infer that these differences are the result of a positive bias in simulated bare ice albedo. MODIS albedo, RCM outputs, and in situ observations consistently indicate a decrease in albedo of −0.03 to −0.06 per decade over the period 2003–2013 for the GrIS ablation area. Nevertheless, satellite products show a decline in JJA albedo of −0.03 to −0.04 per decade for regions within the accumulation area that is not confirmed by either the model or in situ observations. These findings appear to contradict a previous study that found an agreement between in situ and MODIS trends for individual months. The results indicate a need for further evaluation of high elevation albedo trends, a reconciliation of MODIS mean albedo at high latitudes, and the importance of accurately simulating bare ice albedo in RCMs.

Sign in / Sign up

Export Citation Format

Share Document