Abstract:
Seasonal changes of thermal differences between the sea and the land (land-sea thermal contrast) is a key influence factor to monsoon formation, strength change, onset and retreat. Land thermal condition significantly influences atmospheric circulation at high and low level, monsoon activities and climatic anomalies. Being the largest land of the world, effects of Eurasian continent on global climate are more complicated and important, especially considering the heat source seasonal changes of the Tibetan Plateau.Based on NCEP/NCAR reanalysis data and monthly data of 160 meteorological stations in China from 1979 to 2011, the thermal characteristics over Eurasian continent are investigated. Results show that the climatic variability of surface air temperature (SAT) displays obvious difference in different regions and seasons. The SAT variability is significantly larger in south Eurasia than that in north Eurasia, and is the biggest in winter and the weakest in summer. Temporal and spatial characteristics of SAT over Eurasian continent from January to March are emphatically investigated, and it's found thermal changes are just opposite with positive (negative) anomalies in south Eurasia and negative (positive) anomalies in south Eurasia.According to the variation characteristics of temporal coefficient of the first empirical orthogonal function (EOF-PC1), 8 positive and 8 negative thermal contrast years are chosen, and the relationship between changes of the thermal variation over Eurasian continent and precipitation in China is further studied using methods of correlation and composite analysis. Results show that this thermal contrast is not only closely connected with precipitation in China from January to March, but also connected with the precipitation in the following summer. The thermal index is shown to be positively correlated with the accumulative precipitation in South China, Southwest China and middle reaches of the Huang River from January to March, and the rainfall amount of the middle and lower reaches of the Yangtze in the late summer.Finally, possible ways of thermal anomalies from January to March associated with precipitation in China are investigated. It indicates that the thermal contrast between south Eurasia and north Eurasia is closely related with AO, the east Asian trough, and the upper level jet stream in east Asia at the same time. Besides, the south Asia high, the upper level jet stream in east Asia, and Asian monsoon are also possible linkage ways between thermal contrast and the climate of China.