Analysis on Characteristic of Precipitation in Poyang Lake Basin from 1959 to 2008

Based on the daily precipitation observational data in 78 counties and municipalities in Jiangxi province in Poyang Lake Basin from 1959 to 2008, day-to-day observation data of the past 50 year are firstly completed with inverse distance weighting (IDW) and complete day-to-day precipitation observation data on PoYang Lake Basin has been established; Secondly, Mexican Hat wavelet analysis is used on periodic law of annual rainfall and precipitation in flood season in this basin. Spatial distribution of annual rainfall and precipitation in flood season in this basin is technically analyzed with GIS geo-statistics; variation tendency of total annual rainfall, sprinkle, downfall, rainstorm days and successive no-rain days are studied respectively with linear regression and credit analysis is also made on these variation tendencies. Results show that: (1) No significant changes have taken place on annual rainfall and precipitation in flood season in this basin in the past 50 years and periodic fluctuation is presented. Wavelet analysis reveals that annual rainfall has a quasi-period of 20 years and precipitation in flood season has a quasi-period of 6 years. (2) Annual rainfall and precipitation in flood season are featured by basically similar spatial distribution. Areas with heavy precipitation are concentrated in Raohe basin and Xinjiang basin in the northeast of Jiangxi province. (3) Total rainfall days and days of sprinkle in this basin are in a descending tendency; on the contrary, accumulated longest time of no rainfall in all observation station are in an ascending tendency; which indicates that risks of draught and flood occurrence in this basin are in an ascending tendency. (4) Spatial distribution of total rainfall days and mean annual precipitation differs a lot; Total rainfall days in west Jinggangshan area and central and east part of the basin are the most; spatial distribution of rainstorm days and mean annual precipitation are similar. Areas with the most rainstorm days are also concentrated in Raohe basin and Xinjiang basin in the northeast of Jiangxi province. It can be seen from this that spatial distribution of mean annual precipitation, storm rainfall and rainstorm days are closely linked with each other.