ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Impact of early and late onset of El Ni?o on summer precipitation in China
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Abstract:
Based on the monthly rainfall of 643 stations in China, NCEP reanalysis data and NOAA ERSST sea surface temperature data from 1961 to 2023, impacts of early and late onset of El Ni?o on summer precipitation in China are analyzed. The results are as followed. Westerly wind anomalies in the equatorial west-central Pacific are more pronounced in June-August of years with early El Ni?o onset than in years with late El Ni?o onset, resulting in a more obvious warming of the sea surface temperature in the equatorial east-central Pacific in earlier onset years, the sea surface temperature in the quarter continues to rise. However, the positive anomaly of sea surface temperature in the equatorial east-central Pacific Ocean in the later onset years is not obvious and changes slowly. There is obvious differences in summer precipitation in central and eastern China between the El Ni?o earlier onset years and the El Ni?o later onset years, especially in July and August. In the El Ni?o earlier onset years, the Western North Pacific anticyclone (WNPAC) generally appears around August, the summer precipitation in central and eastern China is distributed in "-+-" from south to north, with more precipitation than normal in Jianghuai Region, and less precipitation than normal in other areas. In June, the Western Pacific Ocean is an abnormal cyclone, the precipitation in most of China’s central and eastern parts is less than normal. In July, the abnormal cyclone in the Western Pacific Ocean retreats southward significantly, the precipitation in regions of the Jiangnan, Northwest and North China continues to be less than normal. And the abnormal anticyclone to the east of Japan significantly extends westward and presses southward, the southeast coastal areas of China turns to abnormal southerly winds, leading to precipitation along the southern China coast, Jianghuai basin turn to more than normal. In August, Northwest Pacific Ocean turns into an anomalous anticyclone, WNPAC begins to appear, the precipitation over the middle and lower reaches of the Yangtze River and most parts of its south is more than normal, while the precipitation in most parts of northern China is less than normal. In the later onset years, WNPAC usually appears in October or later, the Western Pacific Ocean has been an abnormal cyclone from June to August. The summer precipitation in the central and eastern regions of China is distributed in "+-+" from south to north, and the precipitation persistence characteristics of each month are obvious.
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