Radiative Impact of Cryosphere on the Climate of Earth and Mars.

Cryosphere;Snow albedo;Mars;Engineering (General);Engineering;Atmospheric, Oceanic and Space Sciences

Singh, DeepakMartinez, German ;

University of Michigan

关键词: Cryosphere;    Snow albedo;    Mars;    Engineering (General);    Engineering;    Atmospheric, Oceanic and Space Sciences;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/133296/sdeepak_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Snow- and ice-covered surfaces are the most reflective regions on Earth and Mars, and their extent can change substantially with small changes in climate. The presence of Earth’s cryosphere greatly alters the planet’s albedo and changes in cryospheric extent and reflectivity therefore partially determine the sensitivity of climate to anthropogenic and external forcings. Carbon dioxide ice is abundant on the Martian surface, and plays an important role in the planet’s energy budget.Firstly, we quantify the shortwave Cryosphere Radiative Effect (CrRE) on Earth. Relatively high resolution (0.05°×0.05°) MODIS data along with radiative kernel datasets are used to estimate the global land shortwave CrRE. We perform multiple analyses to determine the sensitivity of our estimates to the use of different thresholds for snow cover determinations, different climatologies for missing data, and radiative kernels generated with different distributions of clouds produced with various versions of the Community Atmosphere Model. We estimate a global land-based CrRE of about -2.6 W/m2 during 2001-2013, with about 59% of the effect originating from Antarctica.Secondly, we adapt the terrestrial Snow, Ice, and Aerosol Radiation (SNICAR) model to simulate CO2 snow albedo across the solar spectrum (0.2-5.0 μm). We apply recent laboratory derived refractive indices of CO2 ice, which produce higher broadband CO2 snow albedo (0.93–0.98) than previously estimated. We perform multiple analyses to determine the sensitivity of cryosphere spectral albedo to the amount and type of dust, co-presence of CO2 and H2O ices, ice grain size, snow layer thickness, and solar zenith angle. In addition, we also compare our simulations with observed Mars surface albedo, and achieved a reasonable fit between the two.Finally, SNICAR is implemented with the Laboratoire de Météorologie Dynamique Mars GCM to prognostically determine ice cap (both H2O and CO2) albedos interactively in the model. We then explore the impact of dust on surface cryosphere albedo and its impact on Mars’ shortwave energy flux. After integrating SNICAR into the Mars GCM, we find that the impact caused by dust is about 1.5 times the impact caused by the presence of snow itself on shortwave flux at the surface.