| With the global warming,drought as the most common and most influential natural disasters in the world,which frequency and intensity are increased,the losses of direct economic and indirect economic are also increased,drought has a profound impact for social stability and economic development.In recent years,with the rapid development of national economy,population growth and urban construction process was speeding up,the scope and areas of drought and floods had been from agriculture,rural development to urban area and ecosystem.In this context,it is of great significance to reduce the risk of agricultural production and improve the living standard o f peasants by making disaster risk assessment and management of drought disaster and building disaster prevention and mitigation system of different crops in different regions and mitigating the adverse effects of drought disaster on crops.The crops were seriously affected and disaster rate is high in C hongqing,because of Chongqing`s unique geographical location and climate environment,and there are a variety of frequent disasters,coupled with poor agricultural infrastructure,less investment in agricultural capital,agricultural capacity to resist natural disasters is low.Therefore,the study of the spatiotemporal distribution characteristics and regularity of drought is to study the occurrence and development of drought in C hongqing,to monitor and forecast,to provide scientific basis and reference for safe production and avoid disadvantages.This paper uses the daily precipitation data of 1961-2010 cities in 34 national meteorological stations in Chongqing,based on the local standard "Meteorologica l Disaster Standard" of Chongqing,uses the mathematical statistics method to analyze the arid types and their grades in 34 districts and counties in C hongqing from 1961 to 2010,uses the Hurst exponential method,the sliding t mutation test method,the Morlet wavelet analysis method to analyze the time series,and the Arc GIS spatial interpolation method is used to analyze the seasonal drought,the number of days of drought,the number of days of drought,the ratio of dry stations and the comprehensive intensity of drought;The temporal and spatial distribution characteristics and regularity of annual drought intensity index were analyzed.The main conclusions of the study are as follows:(1)Seasonal drought in the county have different trends in time,there are obvious interdecadal changes.In the past 50 years(1961-2010),the drought last days of spring drought and winter drought were decreased in C hongqing;the drought last days of summer drought and midsummer drought and autumn drought were increased in Chongqing.During the period from 1961 to 2010,there were obvious interdecadal changes in the drought last days and drought standing ratio in C hongqing.The scope occurrence of spring drought was the largest in the 1960 s,and the scope occurrence of spring drought was the smallest in the 1990 s.The scope occurrence of summer drought was the largest in the 1990 s,and the scope occurrence of summer drought was the smallest in the 1970 s.The scope occurrence of midsummer drought was the largest in the 1970 s,and the scope occurrence of midsummer drought was the smallest in the 1980 s.The scope occurrence of autumn drought was the largest in the 1980 s,and the scope occurrence of autumn drought was the smallest in the 21 st century.The scope occurrence of winter drought was the largest in the 1960 s,and the scope occurrence of winter drought was the smallest in the early 21 st century.(2)The spatial distribution of seasonal drought frequency was quite different.The West of Chongqing such as Tongnan District,Dazu District,Rongchang District,the central part of Chongqing such as Fengdu County,Zhongxian County and the northeast of C hongqing such as Yunyang County,Wuxi County were the main area of spring drought,spring drought frequency was bigger;the South-East of Chongqing and the central part of Chongqing such as C hangshou District,Wansheng,the frequency of spring drought was smaller.The West of Chongqing such as Tongnan District,Dazu District,Rongchang District,the North-East of Chongqing such as Fengjie County,Wuxi County and Wushan County,summer drought frequency was bigger;the South-East of C hongqing and the vast central area of C hongqing,the frequency of summer drought was smaller.The West of C hongqing,the central part along the Yangtze River area were the main area of midsummer drought,high frequency of midsummer drought;the North-East of Chongqing such as Chengkou County and South-West of Chongqing such as Wansheng,the frequency of midsummer drought was low.The North-East of C hongqing such as Wuxi County,Wushan County,Fengjie County,the South-East of Chongqing such as Xiushan County,Youyang County and the East of Chongqing such as Tongnan District were the main area of autumn drought,high frequency of autumn drought.The North-East of C hongqing such as Yunyang County,Fengjie County,Wuxi County were the main area of winter drought,high frequency of winter drought.(3)The spatial distribution of the total intensity of seasonal drought in the districts and counties was quite different.The high-value area of the total intensity of spring drought was mainly in the West of C hongqing such as Tongnan District,Dazu District,Rongchang District and the North-East of Chongqing such as Yunyang County;the low value area was mainly in the South-East of Chongqing such as Xiushan County,Youyang County,the North-East of C hongqing such as Chengkou County and the South-West of C hongqing such as Wansheng.The high-value area of the total intensity of summer drought was mainly in the West of Chongqing such as Tongnan District,Tongliang District,Dazu District,Rongchang District,Yongchuan District and the North-East of C hongqing such as C hengkou County,Wuxi County;the low-value area was mainly in the South-East of C hongqing such as Xiushan County,Youyang County,Qianjiang District,Pengshui County and the central part of Chongqing such as Wansheng,Nanchuan District,Changshou District,Fengdu County,Zhongxian.The high-value area of the total intensity of midsummer drought was mainly in the West of Chongqing such as Jiangjin District and the central area of Chongqing such as Fuling District;the low-value areas was mainly in the central area of Chongqing Wansheng and the North-East of C hongqing such as C hengkou County.The high-value area of the total intensity of autumn drought was mainly in the North-East of Chongqing such as Yunyang County,Fengjie County,Wushan County,Wuxi County;the low-value areas was mainly in the West of Chongqing such as Tongliang District,the central area of Chongqing such as Banan District,Wansheng,Nanchuan District,Changshou District,Fuling District,Dianjiang County,Zhongxian.The high-value area of the total intensity of winter drought was mainly the North-East of C hongqing such as Yuyang County,Wushan County,Wuxi County;the low-value areas were mian in the vast central of Chongqing and the western of Chongqing.(4)The annual drought intensity of the district and county was declining in time,and the spatial distribution of the average annual drought intensity was high in the middle and low in the north and south.Time characteristics: In the past 50 years(1961-2010)Chongqing city and county drought intensity showed a slight downward trend.Spatial distribution characteristics: the West of C hongqing such as Tongnan District,Bishan District,the central part of C hongqing such as Fuling District,Wulong District and the North-East of C hongqing such as Wuxi County,Wushan County,drought intensity was heavy;in the central part of C hongqing such as Nanchuan District,Wansheng,the South-East of C hongqing such as Youyang County,Xiushan County and the North-East of Chongqing such as Chengkou County,drought intensity was lighter.(5)The intensity of drought intensity of C hongqing was declined,it had obvious stage,and there were multiple time scales of oscillation period.In the past 50 years(1961-2010),the annual drought intensity of Chongqing showed a slight decrease trend,the change tendency was-7.89 / 10 a.The annual drought of C hongqing was the strongest in the 1970 s,and the drought intensity was the lowest in the 1990 s.There was a mutation point of annual drought intensity in C hongqing,and the annual drought intensity was weakened from enhancement to weakening around 1979.The drought intensity of C hongqing has three oscillation periods,such as quasi 2a,5a and 18 a,and the drought intensity of C hongqing had experienced weak ? strong ? weak ? strong ? weak ? strong from 1961 to 2010. |
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