Variation Features of Hourly Precipitation in Shandong Province in Flood Season During 1961-2012
Based on the hourly precipitation data from 74 meteorological stations in Shandong Province during 1961-2012, the spatiotemporal and diurnal variation characteristics of hourly extreme rainfalls in Shandong during the flood season (May to September) were analyzed. The results show that the hourly extreme rainfall amount and frequency in Shandong are roughly in zonal distributions, decreasing from the southeast to the northwest inland. The intensity of hourly extreme precipitation in the west central part is larger than that in other parts of Shandong. The precipitation in the west, northwest, southwest and western peninsula accounts for a higher proportion. The regional average extreme precipitation, precipitation frequency and intensity show no significant upward trends. The increasing trend of precipitation in the south, northwest, northeast and northeastern peninsula is evident, and the precipitation intensity in the south, southeast, west and eastern central part of the peninsula rises obviously. The period from 15:00 to 20:00 BT is the main occurrence period of hourly extreme precipitation in Shandong Province. The amount and frequency of precipitation decline during the period from 11:00 to 18:00 BT, while in other periods the trends are upward. Precipitation intensity in the morning shows a downward trend while at other times it is in an opposite way. The hourly precipitation and frequency are the largest in July with two highvalue centers in the day time. During the two periods of 21:00-02:00 BT and 03:00-08:00 BT, the average extreme precipitation and rainfall at most of the stations show ascending trends.