Characteristics Of Climate Change In Jialing River Basin In Recent 55 Years

The Jialing River,an important tributary of the upper reaches of the Yangtze River,has had a serious impact on the ecological environment of the basin and the economic development of the surrounding areas as a result of natural disasters and the involve of human activities has also caused damage of the basin ecology to a certain extent.Therefore,under the influence of global warming,analyzing the characteristics of climate change of the basin has certain realistic significance for predicting and preventing the occurrence of meteorological disasters,protecting the ecological environment and developing the economy.This paper selects the data of monthly temperature and precipitation 11 meteorological stations processed from 1961 to 2015 in the Jialing River Basin,applies linear propensity rate method,Mann-Kendall nonparametric test,EEMD decomposition analysis,R/S trend forecast and Kriging.Spatial interpolation and other methods to analyze the spatial and temporal distribution of meteorological elements in the basin,and the main conclusions are below:(1)The average temperature of the Jialing River Basin from 1961 to 2015 had showed a significant upward trend(Z=3.24)for around 55 years,and the increase rate was 0.15°C/10 a and the average lowest temperature per year increase rate(0.20°C/10a)was greater than The average maximum temperature per year increase rate(0.16 °C/10a).In terms of seasonal variation,the average temperature and average highest temperature per year comparison were autumn>spring>winter>summer,while the average minimum temperature per year was extremely obvious,and the Z value was greater than 2.32.The average temperature,the highest average temperature and the lowest average temperature per year in the basin all changed in the 1990 s suddenly.After that,the temperature tended to rise to a significant increase level.The three different temperature characteristics value mutation of the spring all happened in 2004 and the summer is concentrated in 2000,while the autumn and winter have different points of mutation.The difference laws of average temperature,the average maximum temperature as well as the average minimum temperature per year were relatively significant.They were characterized by the trend of rising first,then decreasing and then raising,and the annual and seasonal Hurst indices of the three indicators are larger than 0.5 which indicated that there was a certain continuity between future temperature trends and past trends.The main periods of average temperature and average maximum temperature per year were quasi-4a and quasi-7a,and the average minimum temperature period was mainly quasi-4a and 8a which had been decreasing first and then rising throughout the period.The average temperature per year had a period of quasi-3a,quasi-7a and quasi-14 a in spring,and quasi-4a,6a and 18 a periods mainly in summer,and quasi-4a and 9a mainly in autumn,and 2a and quasi-8a in winter.The largest contribution of annual average temperature of the highest temperature spring was made by quasi-3a and quasi-7a,the change period of 3a,6a and 18 a in summer,the quasi-4a and 6a periods in autumn,and 3a and quasi-7a in winter.The average annual minimum temperature was the quasi-3a and quasi-7a,the summer is quasi-4a,the quasi 7a and 18 a,while the autumn was dominated by quasi 3a and quasi 8a,while the winter was affected by the 2a and 9a cycles.The spatial variation of the annual mean temperature in the Jialing River Basin was characterized by the gradual decrease from the southeast to west,north and east.The annual mean temperature of basin in the spring,autumn and winter increases(Z>0),and the overall summer rising temperature,but there existed the temperature differences in each region.The average temperature of the highest temperature and the lowest temperature per year wa1 s consistent with the average temperature.Since the 21 st century,the temperature values have risen by varying degrees.The area with the most up range of annual mean temperature and the minimum temperature is Mianyang,which is higher than the average value by 0.7 °C-0.8 °C,and the highest annual temperature rises by 0.5 °C.(2)The annual precipitation in the Jialing River Basin decreased at a rate of 6.22mm/10 a,and the downward trend was weak(Z=-0.56).The precipitation increased from 1960 s to 1980 s per year,and began to decrease in the 1990 s,up to 913.3mm,the lowest of all years.The annual precipitation in 1962 showed a sudden change from high to low.The seasonal variation of precipitation was obvious.The precipitation in spring and autumn decreases,while the precipitation in summer and winter increases,and the summer was the season with the most concentrated precipitation,accounting for 48.3% of the annual precipitation,and the winter entered the period with less rain.There are different oscillation periods of precipitation.The annual precipitation changes mainly in the period of quasi-3a and 5a,showing a gradual decline waving trend.The four seasons also had different periodic characteristics.The spring was mainly 5a and 6a,and the autumn 5a and quasi 8a,winter quasi-5a and quasi-14 a,summer 2a,quasi-6a annual scale and 28 a annual scale period.Precipitation changed in the basin in the next year,spring and autumn will continue to decrease to some extent,while precipitation in the summer and winter will continue to increase.The spatial distribution of precipitation in the basin was uneven,and it was gradually reduced from the southeast to the northwest due to the influence of altitude and terrain.The precipitation changes during the year were concentrated in the downstream.The downward trend of precipitation in Suining area was the most obvious in spring(Z=-1.86),and the most significant rise in summer(Z=2.49).The increase was also the largest since 2000.The precipitation in Wudu area increased in autumn(Z>0),and the rest of the areas showed a downward trend.The Z value in each area in winter was either positive or negative,and the change trend was not obvious.(3)The number of precipitation days in the basin was significantly reduced in the fluctuation changes(Z=-3.39),and the decreasing rate was 2.8d/10 a.It gradually decreased after 1980 s,and reached the lowest after 2000 at 125.1d.The number of precipitation days changed suddenly in 1992.In the seasonal changes,the number of precipitation days decreased in spring,summer and autumn,and increased in winter,mainly concentrated in summer,accounting for 29.5% of the annual precipitation days,and the least in winter accounting for 15.5% of the annual precipitation days.The mutation time,2 years later than the annual mutation,was 1994,and there were multiple mutation points in summer and winter.The initial occurrence was 1962,and the autumn mutation point was 1976.The periodic characteristics of the annual precipitation days were quasi-4a and 9a.The period of precipitation days in each season was dominated by annual scales.There were quasi-3a and quasi-7a in spring,2a and quasi-6a in summer,and quasi-4a and 6a in autumn as well as the winter change period of 4a and quasi 8a.In the future trend change,there exists a Hurst phenomenon in the number of precipitation days,which has a long-term positive correlation with past changes.The annual precipitation period of the basin was consistent with the spatial variation of annual precipitation,which decreased from southeast to northwest.The most significant reduction area was Liang Ping area(Z=-3.37),while the largest decrease area in spring was Bazhong.