Causes of Temperature Anomaly and Analysis on Low Temperature Process in Qinghai Plateau in Spring
Using the temperature observation data in Qinghai, NCEP monthly mean reanalysis data, 74 pieces of circulation characteristics materials provided by National Climate Centre of China Meteorological Administration (CMA) and 52 pieces of climate indices from U.S. National Oceanic and Atmospheric Administration (NOAA) from 1961 to 2012, temperature anomaly characteristic and its impact factor in spring Qinghai Plateau were studied. The results show that the spring temperature in Qinghai Plateau presents a remarkable increasing trend, having obvious interdecadal variation features. The winter Eurasian pattern (EU) teleconnection pattern in Northern Hemisphere has very good indicative meanings to the temperature amomaly in the next spring. When it is in the EU pattern, the sping temperature is prone to be lower. The Ural pressure ridge, East Asian trough, subtropical high and polar vortex indices in Northern Hemisphere and Plateau height field, all affect the spring temperature. At the same time, the spring temperature has good response to the SST in SomaliaArabian SeaBay of Bengal of North Indian Ocean, Northwest Pacific and Equatorial Pacific. When the SST is colder (warmer), spring is colder (warmer). The continuous low temperature process is the direct cause for low temperatures in Qinghai in spring. The main impact system of frequent low temperature process is the low pressure in area south to Lake Baikal. As it develops significantly, Qinghai Plateau lies in the northwest airflow in front of ridge and behind trough then the plateau height field is lower. Thus, frequent cold airs tend to cause the persistent low temperature process. Otherwise, the situation is opposite.