Seasonal division of 850 hPa South China Sea based on multi-element atmospheric condition similarity

Abstract

Comprehensive consideration of multiple meteorological elements for the objective identification and division of seasonal changes is important in the field of climate monitoring and diagnostic analysis. The development of relevant identification and classification methods will help us better understand the new characteristics of seasonal transitions against the background of climate change. Based on reanalysis data from the National Centers for Environmental Prediction from 1950 to 2015, we used the multi-element atmospheric condition similarity method to seasonally divide the average climatological conditions at 850 hPa over the South China Sea, and analyzed the annual mean results of the onset of seasons and annual mean seasonal variations of meteorological elements in this region. The results show the following. First, the seasonal division results based on multi-element atmospheric condition similarity coincide with the seasonal variation times of each meteorological element with atmospheric conditions comprising five meteorological elements. When the four seasons change, the meteorological elements at 850 hPa in the South China Sea have obvious seasonal variation, and atmospheric circulation and surface upward long-wave radiation change conspicuously with seasonal transformation. This confirms the validity of the method as applied to seasonal divisions in the South China Sea. Second, when the climate system translates from winter to summer in the South China Sea, thermal elements change greatly and rapidly. Changes to thermal elements in spring provide climate conditions for the onset of summer and the onset of the summer monsoon in the South China Sea. Third, when the climate system shifts from summer to winter in the South China Sea, changes to wind elements are obvious and rapid. In autumn, changes in thermal conditions between the Eurasian continent and the Pacific Ocean lead to major changes in atmospheric circulation and wind. In addition, seasonal divisions are no longer just nodes of time. Rather, they can be used as important indicators for further studies of atmospheric circulation changes, short-term climate predictions, and seasonal changes of other climate systems.