Abstract:

With the daily precipitation data derived from 35 weather stations in the Three Gorges Reservoir Area from 1960 to 2008, the extreme precipitation threshold for different stations were defined by centesimal value method,and then the concentration degree and the concentration period were calculated to indicate the temporal distribution features of extreme precipitation. Based on the two new indices,inhomogeneity of extreme precipitation in the Three Gorges Reservoir Area was analyzed.The results showed that there was less extreme precipitation in southwestern and northeastern parts but more in central and southeastern parts.A little discrepancy appeared for the spatial distribution between concentration degree and concentration period of extreme precipitation. The extreme precipitation events happened more frequently in northeastern and western parts than in central part relatively.The period of accruing extreme precipitation in the Three Gorges Reservoir Area was usually from the end of June to July 15th,and it was later in northeastern and western parts while earlier in central regions.The concentration degree and the concentration period of extreme precipitation showed a positive correlation with the amounts of extreme precipitation in flood season.If the amounts of extreme precipitation were less,the concentration degree was higher and the concentration period was earlier especially in the northeast parts,vice versa.After impound of the Three Gorges Reservoir,the concentration degree was uniform in different parts for whole area, but some obvious changes happened for concentration period and the amounts of extreme precipitation.More extreme precipitation appeared and the concentration period was earlier in the northeastern parts,while what happened in the southwestern parts was reversed