A Statistical Analysis Of The Temporal-Spatial Changing Characteristics Of Extreme Climate Events Over China: 1955～2004

Based on the observational data of daily precipitation and temperature in the period of 1955~2004,the temporal-spacial Changing characteristics of frequency and density of extreme climte events have been analyzed systemically.Thereby,some major conclusions can be revealed.The researches about the extreme precipitation events indicate that long-term change of annual extreme precipitation events has two periods.Significant decreases were detected in the annual number of extreme precipitation days and in the total amount and density of extreme precipitation during 1955~1982a,with significant increases in the period of 1976 ~2004a.The long-term change is different in different areas.The extensive increases appear in the basin of Yangtze river and over the south of Yangtze river in 1955~1982a.In most parts of the northeast china and north china,slight negative trends were dominant from1976 to 2004a.The indexes of extreme precipitation events appear strongly increases over the Gobi and desert of northwest china in 1955~1982a.However,during 1976~2004a ,the positive trends of this area were reducing,even became negative trends in some regions.The results of extreme temperature events show that the density and frequency of annual extreme minimum temperature events was decreased strongly. Slight change was detected in density and frequency of diurnal extreme maximum temperature annually in 1955~2004a.But there was apparent difference in two periods: 1955~1982a, 1976~2004a.The study on the spacial distribution of trend coefficient of annual extreme temperature events points out that the trends in the annual hot days and cold nights are most significant,especially cold nights.Hot daysbecame increasing since the Middle of 1980s and strong trends appear in the most parts of northern china (other than west Xinjiang) and in the small parts of southeast china.The temperature of extreme minimum temperature events at night was significantly positive trend and the trends in the southern china were stronger than that in the northern china.The relation between the extreme climate events and the mean and variability of average temperature is : 1) the mean and variability of seasonal average temperature was closelier relation to the extreme climate events than that of annual average temperature 2) the relationship between the extreme temperature events and the mean> variability of seasonal average temperature is better than the extreme precipitation events,especially the frequency of extreme temperature events. 3) the interdecadal relation between the mean n variability of average temperature in summer and the extreme maximum temperature events is weak.But interdecadal change of the mean and variability of average temperature in winter has strong influence on the extreme minimum temperature,specially cold nights.