Rainstorms are a major category of meteorological disaster,and thus research on their spatiotemporal distributions and trends is important in reducing or even preventing their adverse impacts.In this study,precipitation data gathered from meteorological observation stations over seven counties in Longyan during a 54-year period from 1960 to 2013 were used to study the spatial distribution characteristics of rainstorms.Further analysis was made by dividing the seven counties of Longyan into southern and northern counties.The main analytical methods used were the Mann-Kendall (M-K) method and Morlet wavelet power spectrum analysis [for the change or long-term trends of precipitation,and multi-scale analysis of the temporal (annual,seasonal,monthly) distribution of precipitation,respectively].
The results showed that the annual precipitation duration at seven meteorological observation stations had an increasing tendency during the 54-year time period,but this tendency was not statistically significant.An obvious change-point occurred around 1975,after which the annual precipitation increased by 101.2 mm.Moreover,based on the Morlet wavelet power spectrum analysis,the southern and northern counties had different significant time-scale cycles,as well as variation in the strength of cycle over time.The precipitation amount at the seven observation stations was greatest in spring,accounting for around 38.2% of the annual precipitation,followed by summer and autumn.However,each of the four seasons demonstrated distinct changes,and change ranges,in different years.For example,spring precipitation changed significantly around 1999,according to analysis using the M-K test,decreasing by 7.1% after that year.
Combined with the spatial distribution of rainfall duration,the precipitation over the northern counties was greater than that in the southern counties in spring and winter,less than that over southern counties in autumn,and nearly the same in summer.At the same time,however,neither the northern counties or southern counties showed a significant change in seasonal precipitation under the 95% confidence level.
Through further data analysis,it was found that the monthly precipitation over the seven meteorological observation stations had an increasing trend in the time period from January to June,and a decreasing trend in the time period from August to December.Monthly precipitation was concentrated from March to June (being greatest in June),amounting to 17.3% of the total precipitation in a year.Comparing the monthly precipitation between the northern and southern counties,it was clear that-except for the period from July to September-monthly precipitation in the northern counties was greater than that in the southern counties.