Interannual Variations of TOA Albedo over Arctic, Antarctic and Tibetan Plateau in 2000-2019

Abstract:

Recent changes in Earth’s climate system have significantly affected the radiation budget and its year-to-year variations at top of the atmosphere (TOA) over the polar regions and High Mountain Asia (HMA). The amount of shortwave solar energy absorbed in these regions depends largely on the surface and cloud albedo. The interannual variability of these albedos determines the TOA flux variations, which in turn drives the next cycle of variations in the atmosphere and cryosphere through energy redistribution and interactions with dynamics. Observing high-latitude TOA fluxes is still challenging from space, because spatial inhomogeneity of surface/atmospheric radiative processes and spectral variability can reflect sunlight very differently. In this study we analyze the 20-year TOA flux and albedo data from CERES and MISR over the Arctic, the Antarctic, and Tibetan Plateau (TP), and found overall great consistency in the TOA albedo trend and interannual variations. The observations reveal a lagged correlation between the Arctic and subarctic albedo fluctuations. The observed year-to-year variations are further used to evaluate the reanalysis data, which exhibit substantial shortcomings in representing the polar TOA flux variability. The observed Arctic flux variations are highly correlated with cloud fraction (CF), except in the regions where CF > 90% or where the surface is covered by ice. An empirical orthogonal function (EOF) analysis shows that the first five EOFs can account for ~50% of the Arctic TOA variance, whereas the correlation with climate indices suggests that Sea Ice Extent (SIE), North Atlantic Oscillation (NAO) and 55^°N-65^°N cloudiness are the most influential processes in driving the TOA flux variabilities.