Comparative study on the characteristics of spatial-temporal variations between rainy season over North of Huaihe area and Meiyu in the yangze-huaihe region

In this article, precipitation and subtropical high ridge axis of 500hPa are adapted for the new definition of North Huaihe-River Rainy Season (NHRS). The annual precipitation in NHRS and Meiyu (YHMY) from 1961 to 2009 is calculated by the summer daily rainfall in East China. The beginning day and ending day, as well as duration time in 49 years are also analyzed in this article for the two Rainy Seasons. The spatial-temporal distribution characteristics of NHRS and YHMY are investigated in terms of REOF methods. Results show that: (1) The average duration time of NHRS is similar to YHMY, while its average dates of beginning day and ending day is a week later than YHMY. (2) The rainfall center of NHRS located in Huaihe-River basin and its northern area between 33° N and 37°N, the center of YHMY located mainly in the South 33° N. (3) The average precipitation of NHRS is slightly less than YHMY´s, the yearly precipitation variation of the two Rainy Seasons are similar with no obvious increasing or decreasing trend in the 49 years, but with distinguish inter-annual and inter-decadal variations.