Study On The Variations Of Temperature And Precipitation Of Chongqing Urban From 1951 To 2014

The regional characteristic of climate change is one of the important issues of climate change research. It is very important to estimate the trend of regional climate change correctly and to explore its causes. Taking Chongqing urban as the study area and the meteorological data of 1981-2010 as the climate background value, this paper analyzes the annual and seasonal variations of temperature and precipitation from 1951 to 2014, based on the daily monitoring data from the meteorological stations in Shapingba, Beibei and Banan.Decadal analysis is carried out to illustrate the periodic characteristics of annual and seasonal variations of temperature and precipitation of Chongqing urban. Using Mann-Kendall test combined with the accumulative anomaly curve to ascertain the abrupt change of climate. The mult-scales characteristics of temperature and precipitation variability are analyzed by ensemble empirical mode decomposition(EEMD) method.The result shows that:(1)The change of temperature and precipitation in Chongqing urban has obvious phased characteristics.The inter-annual fluctuations of temperature and precipitation in Chongqing urban are relatively large since 21 st century, which increase the frequency of extreme weather. Integrated the two aspects of temperature and precipitation, the climate in Chongqing urban tends to be warmer and more dry, as well as the summer climate, while winter, spring and autumn tends to be warmer and more humid.(2)Annual average temperature inversion mutation happened in 2000, the annual precipitation had no obvious mutation. Abrupt changes of precipitation in spring appeared in 1967, while that occurred in summer in 1956 and 1992. In autumn, the abrupt change of temperature happened in 1997, and the precipitation occurred in 1952, 1955 and 1984 respectively.(3)Annual average temperature shows a trend of decreased at the first and then keeps increasing on the whole. The inter-annual oscillations of quasi 2a, 6a play a leading role to the variation. The oscillation of 24 a makes main contributation to the warming mutation in 2000, after the abrupt, oscillation amplitude of each scale reduces obviously, especially on the large scale. Spring temperature change is mainly influenced by the general increasing trend and the periodic variation of quasi 3a and quasi 12 a. Summer temperature in the 50 s to the early 21 st century has been a downward trend, it began a slow upward trend in the 2000 s. The temperature change is mainly affected by the inter-annual oscillation of quasi 3a and the decadal oscillation of quasi 13 a, 28 a. In autumn, the temperature is decreased firstly and then increased, and the temperature change is mainly dominated by the oscillations of quasi 3a, quasi 5a and quasi 25 a. The warming mutation in 1997 is dominated by decadal oscillations, and the response of each scale is concentrated on the increase of amplitude, and the performance of large scale is more significant. Winter temperature rises since the 1960 s. The inter-annual oscillation of quasi 4a and quasi 7a together with the long-term warming trend play a leading role to the variation.(4)The annual precipitation shows an increasing trend from 1951 to 2014. The inter-annual oscillations of quasi 6a and quasi 3a together with the decadal oscillation of quasi 13 a are in the dominant position in the long term variation of annual precipitation. The annual precipitation will increase in the coming years. Spring precipitation, in the 1950 s to the mid 1970 s, was decreasing, and began to show an increasing trend at the beginning of 1980 s. The oscillations of quasi 2a, quasi 7a and quasi 12 a are dominant in precipitation variation. The increase abrupt of precipitation in 1967 is mainly reflected in the periodic oscillations of quasi 7a and quasi 12 a. Summer precipitation showing a tendency of reduction from 1951 to the early 1990 s, has presented a slowly increasing trend after 2000.The precipitation change is mainly dominated by the oscillations of quasi 2a, quasi 6a and quasi 11 a. Autumn precipitation is increasing since the late 1960 s. The reduced mutation of the precipitation in 1951 is mainly dominated by the periodic oscillation of quasi 3a and quasi 16 a.The mutation in 1956 is mainly influenced by the quasi-periodic of 3a and 16 a, while mutation in 1984 by the inter-annual oscillations of quasi 3a and quasi 6a. Winter precipitation shows a rising trend closing to linear on the whole. The inter-annual oscillations of quasi 3a, 6a and 10 a are playing leading role to the variation. At present, the precipitation is less than normal stage on the inter-annual time scale, and will have more rainfall on decadal scale.