Analysis of the temporal-spatial changes in surface radiation budget over the Antarctic sea ice region

The surface radiation budget (SRB) of the Antarctic sea ice region (ASIR) is important for the climate change in Antarctica, which partly explains the global warming. Long-term (1982-2015) satellite-derived (EUMETSAT Satellite Application Facility on Climate Monitoring, CLARA-A2) and reanalysis (European Centre for Medium-Range Weather Forecasts, ERA-Interim) datasets provided high quality and global coverage surface radiation products, which enabled us to quantify the SRB of the ASIR and widen our understanding of the polar climate. The downwelling longwave (LW) and shortwave (SW) radiation from the two datasets were validated at two Baseline Surface Radiation Network Stations (i.e., Neumayer and Syowa). Cloud LW emission dominated over cloud SW reflection and absorption due to high-albedo over the sea ice surface, thereby leading to a positive all-wave cloud radiative forcing (CRF) within 0-100 W m^-2. This result indicated a warming effect on the surface of the ASIR, except during the austral summer. Compared with the all sky, substantial solar radiation was absorbed by the surface which under the clear sky will result in the increasing of temperature and sea ice melting during the austral summer; hence, the SW CRF had a major influence on all-wave CRF and caused more than -150 W m^-2 of cooling near the edge of the sea ice. The summer averages of all-wave CRF over the ASIR surface were - 43.02 and - 35.74 W m^-2 for the ERA-Interim and CLARA-A2 datasets, respectively. Contrary to the effect of CRF, the surface net LW radiation (LWnet) exhibited a cooling effect over the ASIR surface throughout the year and peaks at -47.21 W m^-2 for CLARA-A2 dataset in December. Meanwhile, a warming effect was caused by the surface net SW radiation (SWnet) peaks at 101.52 and 104.09 W m^-2 for the ERA-Interim and CLARA-A2 datasets, respectively. In summer, the warming effect caused by the surface net all-wave radiation in East Antarctica was deeper than that in West Antarctica. The time series and trend analysis showed that the surface net radiation and CRF over the entire ASIR basically exhibited a decreasing trend. The descending speed of SWnet (-3.652 W m^-2 decade^-1) about five times faster than that of LWnet (-0.722 W m^-2 decade^-1). Although a significant trough appeared in 1993/1994 of the time series curves of All-wave CRF, it had a deeply negative trend with about -3.443 W m^-2 decade^-1. Detailed analysis on the five longitudinal sectors around Antarctica (the Weddell Sea, the Indian Ocean, the Pacific Ocean, the Ross Sea, and the Bellingshausen-Amundsen Sea) can further help us understand the SRB of the ASIR.