In this article, a new definition for the North Huaihe River rainy season (NHRS) is presented using summer daily precipitation in East China and subtropical high ridge axis at 500 hPa. By calculating the annual precip...In this article, a new definition for the North Huaihe River rainy season (NHRS) is presented using summer daily precipitation in East China and subtropical high ridge axis at 500 hPa. By calculating the annual precipitation amounts in the NHRS and Meiyu of the Yangtze-Huaihe Rivers basin (YHMY) from 1961 to 2009, the dates of precipitation beginning and ending as well as the duration of the two rainy seasons in the 49 years are analyzed. Atmospheric circulation characteristics in positive and negative precipitation anomaly years during the NHRS are also studied. Results are shown as follows. (1) The new definition for the NHRS is much easier to use. It involves only two meteorological factors, making its application more practical. It can also distinguish two rainy periods of the NHRS more objectively. (2) The average duration of the NHRS is similar to that of the YHMY, except that its average dates of beginning and ending are about one week later than those of the YHMY. The average precipitation of the NHRS is slightly less than that of the YHMY, and the yearly precipitation variation of the two rainy seasons are similar to each other with no obvious increasing or decreasing trend in the 49 years, but with distinguished decadal and inter-annual variations. (3) In positive precipitation anomaly years, the South Asian high moves more northward and more eastward, the western Pacific subtropical high is located more northward and westward, and the summer monsoon is stronger than normal, resulting in the convergence of the warm and moist southwesterly airflow from the west side of the subtropical high and the cold air from the north side of the northeast trough in North Huaihe River basin.展开更多
基金National Basic Research Program of China (2010CB950401)Natural Science Foundation of Jiangsu Province (07KJA7020)
文摘In this article, a new definition for the North Huaihe River rainy season (NHRS) is presented using summer daily precipitation in East China and subtropical high ridge axis at 500 hPa. By calculating the annual precipitation amounts in the NHRS and Meiyu of the Yangtze-Huaihe Rivers basin (YHMY) from 1961 to 2009, the dates of precipitation beginning and ending as well as the duration of the two rainy seasons in the 49 years are analyzed. Atmospheric circulation characteristics in positive and negative precipitation anomaly years during the NHRS are also studied. Results are shown as follows. (1) The new definition for the NHRS is much easier to use. It involves only two meteorological factors, making its application more practical. It can also distinguish two rainy periods of the NHRS more objectively. (2) The average duration of the NHRS is similar to that of the YHMY, except that its average dates of beginning and ending are about one week later than those of the YHMY. The average precipitation of the NHRS is slightly less than that of the YHMY, and the yearly precipitation variation of the two rainy seasons are similar to each other with no obvious increasing or decreasing trend in the 49 years, but with distinguished decadal and inter-annual variations. (3) In positive precipitation anomaly years, the South Asian high moves more northward and more eastward, the western Pacific subtropical high is located more northward and westward, and the summer monsoon is stronger than normal, resulting in the convergence of the warm and moist southwesterly airflow from the west side of the subtropical high and the cold air from the north side of the northeast trough in North Huaihe River basin.
