Characteristics of Inter-Annual and Seasonal Changes in Temperature and Precipitation over the Nantong Region during the Period 1960-2007

Over the past half century,temperature rising has been observed in most parts of China,but temporal-spatial distribution of temperature change varies among different regions. In general,precipitation shows a greater regional difference than temperature,but the trend is not prominent. Examining trends in temperature and precipitation in Nantong located in the north wing of the Yangtze River delta would be greatly useful in predicting future climate change. There were 4 meteorological variables,i.e.,average temperature,average maximum temperature,average minimum temperature,and precipitation at the monthly scale obtained from seven meteorological stations across the study region for use in this analysis. Methods of linear trend,moving average methods,Mann-Kendall nonparametric,moving T-test,and wavelet analysis were employed to examine trend,mutation,and cycle changes in temperature and precipitation at inter-annual and seasonal scales across the Nantong Region during the period 1960 to 2007. Results show that 1) linear rates of annual average temperature,annual average maximum temperature,and annual average minimum temperature were 0.29℃/10a,0.24℃/10a,and 0.54℃/10a,respectively. Years of mutation in annual average temperature,annual average maximum temperature,and annual average minimum temperature were detected to be 1997,2001,and 1988,respectively;2) Linear rates of average temperature in spring,autumn,and winter were 0.37℃/10a,0.27℃/10a,and 0.43℃/10a,respectively. Average temperature in summer didn’t pass the test. Linear rates of average minimum temperature in autumn and winter were 0.85℃/10a and 0.54℃/10a,respectively,and the value in spring and summer didn’t pass the test. Linear rates of precipitation only passed the test in winter,showing a value of 13.84 mm/10a. Years of mutation in average temperature in spring,summer,autumn,and winter were in 2000,2003,1996-1997,and 1991,respectively. Years of mutation in average maximum temperature in summer and autumn were in 2000 and 1994,while they were not significant in spring and winter. The year of mutation in average minimum temperature in winter was found to be 1987,while the other seasons were not significant. Precipitation changes in autumn and winter occurred in 1991 and 1989,respectively;they decreased in autumn but increase in winter. Characteristics of seasonal change showed a significant increase in average minimum temperature in autumn and winter,precipitation in winter,and an earlier warming mutation in autumn and winter;3) For cycle change,temperature and precipitation showed stable changes at a longer time scale,such as cycle changes of annual average temperature in 21-30 years and precipitation in 14-25 years. Cycles in a small scale(e.g.,10 years) changed frequently,but not stable. Overall,mutation in temperature in the Nantong Region was later than western and central regions of China,while that in precipitation was not significant at inter-annual or seasonal scales.