ROLE OF SNOW DEPTH IN THE INFLUENCE OF EL NIÑO ON SUMMER CLIMATE ANOMALIES OVER EAST ASIA

Abstract

With the datasets of Global Land Data Assimilation System (GLDAS) NOAH land surface model, GPCC monthly mean rainfall, and NCAR/NCEP global monthly mean reanalysis from 1948 to 2010, by using methods of filtering, composite and linear regression and correlation, the characteristics of Eurasian snow depth anomalies in El Niño mature winter, its influences on soil moisture after snow melting, and finally on East Asian summer monsoon are investigated, and the main conclusions are as follows: In El Niño mature winter, snow depth in regions of the Iranian Plateau, the northeast of Lake Balkhash and the southern Tibetan Plateau increases remarkably, so are the related snow melting and soil moisture. The above-mentioned three regions are identified as the key regions for snow depth to store and extend the El Niño signals. In spring, the snow begins to melt, and the soil moisture increases correspondingly, thus the El Niño signals are transmitted from winter snow depth to soil moisture in spring. As a result, sensible heat flux decreases and latent heat flux increases, and the atmospheric circulations are greatly influenced. The anomalous soil moisture in the Iranian plateau is most important for the East Asian summer monsoon in El Niño decaying summer, since it has similar impact pattern on the anomalous summer precipitation as the El Niño composite. The spring and summer soil moisture in both the southern Tibetan plateau and the northeast of Lake Balkhash increase simultaneously, which significantly contribute to the increased precipitation in North China. Therefore, to investigate and predict the East Asian summer monsoon variability by using El Niño signal, the roles of snow depth in storing and modulating El Niño impacts in those key regions should be considered.