Temporal Variability of Extreme Precipitation in Jiangxi during 1961-2018

Using 58 years (1961 to 2018) of daily rainfall data, this study focuses on determining trends in the annual and seasonal precipitation extremes of Jiangxi, China, by choosing four extreme precipitation indices, including strong precipitation amount (SPA), mean precipitation intensity (MPI), strong precipitation days (SPD), and strong precipitation frequency (SPF). The monotonic trends are tested by using the Mann-Kendall test for the trends and Sen’s method for the magnitude of the trends. The effective sample size (ESS) method was used to eliminate the influence of serial correlation in the Mann-Kendall test. The results indicated that station Zixi had the strongest extreme precipitation, while Wanzai had the weakest. The trends for each index showed an obvious regional feature over Jiangxi. Increasing trends in annual extreme precipitation indices were found at almost all stations, and the annual variability of the extreme precipitation indices was pronounced, especially for the mean precipitation intensity and the strong precipitation frequency;the majority of these positive trends were shown by the statistical tests. In spring, four indices exhibited significant increasing trends in Northeast and Southwest Jiangxi;however, in summer, only MPI had a remarkable positive trend across almost all of Jiangxi. For the other indices, few stations had remarkable trends. In autumn, MPI and SPF showed remarkable increasing trends in most regions of Jiangxi, while SPA and SPD showed increasing trends at only 6 stations and 3 stations, respectively, which were scattered in the northern and middle parts. In winter, the stations with remarkable upward trends in SPA and SPD were mainly located in the middle of the region, whereas the significant patterns of MPI and SPF were located in the south and middle of the region.

IMPACTS OF MONTHLY ANOMALIES OF INTRASEASONAL OSCILLATION OVER SOUTH CHINA SEA AND SOUTH ASIA ON THE ACTIVITY OF SUMMER MONSOON AND RAINFALL IN EASTERN CHINA

The impact of strong(weak) intraseasonal oscillation(ISO) over South China Sea(SCS) and South Asia(SA)in summer on the SCS and SA summer monsoon and the summer rainfall in Eastern China are studied by using the NCEP-NCAR analysis data and the rainfall data of 160 stations in China from 1961 to 2010.It is found that the impacts are significantly different in different months of summer.The study shows that in June and July cyclonic(anticyclonic) atmospheric circulation over SCS and SA corresponds to strong(weak) ISO over SCS.In August,however,strong(weak) ISO over SCS still corresponds to cyclonic(anticyclonic) atmospheric circulation over SA.In June and August cyclonic(anticyclonic) atmospheric circulation over South Asia corresponds to strong(weak) ISO over SA while a strong(weak) ISO corresponds to anticyclonic(cyclonic) atmospheric circulation over SA in July.Besides,in June the strong(weak) ISO over SA corresponds to cyclonic(anticyclonic) atmospheric circulation over SCS,while in July and August the atmospheric circulation is in the same phase regardless of whether the ISO over SA is strong or weak.The impacts of the strong(weak)ISO over SCS on the rainfall of eastern China are similar in June and July,which favors less(more) rainfall in Yangtze-Huaihe Rivers basin but sufficient(deficient) rainfall in the south of Yangtze River.However,the impacts are not so apparent in August.In South Asia,the strong(weak) ISO in July results in less(more)rainfall in the south of Yangtze River but sufficient(deficient) rainfall in Yangtze-Huaihe Rivers basin.The influence on the rainfall in eastern China in June and August is not as significant as in July.