Features of Temperature and Precipitation Change during1951-2000 of Nanchong and Causal Analysis of Sudden Weather Change

Based on the data between1951 and2000 concerning the yearly and monthly temperature and precipitation in Nachong, an in-depth analysis is made of the temperature and precipitation change to find out about the relevant changing fea- tures through the methods of linear regression, anomaly analysis and moving average. It turned out that the yearly average temperature in Nanchong city was of a fluctuant decreasing trend as a whole by the rate of-0. 086℃/10a with the acutest de- crease found in the1980s. The drop of temperature in summer contributed most to the yearly average temperature of the city, next to which was the temperature drop in spring and winter, with the autumn having the least influence on the yearly tempera- ture change. The same thing is found to happen in terms of the annual precipitation with a climate tendency rate of-19. 6mm/ 10a. The autumn precipitation reduction was the main factor leading to the annual precipitation drop, next to which was sum- mer and the last was spring, and the precipitation in winter was found to have a slight rise, though hard to notice. Based on such findings, a Mann-Kendall sudden change test was made of the annual average temperature and precipitation of the city and it is found that the abrupt change of the annual mean temperature took place in1975 and no abrupt change is detected in terms of the annual precipitation.