ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 46 Issue 10 > 2020,46(10):1375-1384. DOI:10.7519/j.issn.1000-0526.2020.10.011 Prev Next
Features and Possible Causes for the Boreal Spring Climate Anomalies in 2020
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Abstract:
In boreal spring 2020 (March-April-May), the average temperature in China is 11.5℃ ranking the fifth since 1961.The temperature is above or near average in most China. The mean precipitation is 137 mm, lower by 4% than climatology. The characteristic precipitation in East China is featured with enhanced precipitation in North and South China and suppressed in central China. The positive anomalies are mainly in most of Northeast, eastern North China, eastern Inner Mongolia, southern Jiangnan and most of South China. The negative is pronounced in the JiangHuai Region. The subseasonal variation of precipitation is significant. During boreal spring (mainly in April and May) in midhigh latitudes, the signal of the pattern in the upper troposphere is two troughs and one ridge which is characterized by one blockage over west Lake Baikal and two troughs located over northwest Ural Mountains and the Sea of Japan, respectively. In low troposphere northerly anomaly prevails in eastern China with strong meridional circulation. An anticyclone in low troposphere is located at Northwest Pacific Ocean while the WesternNorth Pacific subtropical high (WPSH) is much stronger and its ridge line is more southwestward. The water vapor is divergent over most Eastern China with deficient precipitation. In March 2020 the zonal circulation dominates midhigh latitudes of Asia and WPSH exhibits stronger and northward, resulting in positive precipitation anomaly in Jiangnan and South China. The influence of tropical SST forcing shows that the Indian Ocean Basin warming (IOBW) and West Pacific play important roles in the sustained strengthening and westward trend of WPSH in spring in the decaying 2019/2020 weak Modoki ENSO. The North Atlantic SST dipole (NASD) mode shows good spatial persistence from February-March to April-May 2020. NASD in early boreal spring can be an important predictor that impacts the midhigh latitude circulation with blocking over west Lake Baikal during April-May.
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