Analysis on Characteristics of Rainfall Change in Dali Prefecture in Recent 54 Years

Abstract

Through the method of Linear trend, Cumulative anomaly and Morlet wavelet, the interdecadal variation, annual, seasonal, monthly variation, abrupt change of climate and cycle of rainfall in Dali Prefecture from 1962 to 2015 were analyzed. The start date of rainy season occurred on May 8th, 2001 is the earliest; The start date of rainy season occurred on July 1st, 2015 is the latest; The average value of the start date of rainy season from 1962 to 2015 is May 31st. During the past 54 years, the annual, seasonal and monthly rainfall showed the different degrees of reduction. Linear trend analysis showed that the trend of annual rainfall was decreasing with linear trend rate of -14.02 mm/10a, the annual rainfall decreases with the number of years is not significant. Seasonal rainfall decrease with the year number is not significant. The rainfall in summer and autumn decreased with the year number. The decreasing trend of rainfall in summer is greater than that in autumn. The rainfall in Winter and Spring increased with the year number. The increasing trend of rainfall in summer is greater than that in autumn. By using the method of cumulative anomaly and Morlet wavelet, the abrupt change of annual rainfall was analyzed, and the change of annual rainfall were found in 1974, 2002 and 2008. The annual rainfall was mainly in the period of 6 and 30. On the 6a and 10a period scales, the annual rainfall from 2015 to 2019 is increasing, which predicts that Dali Prefecture is in the wet period from 2015 to 2019.