Estimation and Long-term Trend Analysis of Surface Solar Radiation in Antarctica: A Case Study of Zhongshan Station

Long-term, ground-based daily global solar radiation (DGSR) at Zhongshan Station in Antarctica can quantitatively reveal the basic characteristics of Earth's surface radiation balance and validate satellite data for the Antarctic region. The fixed station was established in 1989, and conventional radiation observations started much later in 2008. In this study, a random forest (RF) model for estimating DGSR is developed using ground meteorological observation data, and a high-precision, long-term DGSR dataset is constructed. Then, the trend of DGSR from 1990 to 2019 at Zhongshan Station, Antarctica is analyzed. The RF model, which performs better than other models, shows a desirable performance of DGSR hindcast estimation with an R-2 of 0.984, root-mean-square error of 1.377 MJ m(-2), and mean absolute error of 0.828 MJ m(-2). The trend of DGSR annual anomalies increases during 1990-2004 and then begins to decrease after 2004. Note that the maximum value of annual anomalies occurs during approximately 2004/05 and is mainly related to the days with precipitation (especially those related to good weather during the polar day period) at this station. In addition to clouds and water vapor, bad weather conditions (such as snowfall, which can result in low visibility and then decreased sunshine duration and solar radiation) are the other major factors affecting solar radiation at this station. The high-precision, long-term estimated DGSR dataset enables further study and understanding of the role of Antarctica in global climate change and the interactions between snow, ice, and atmosphere.