Risk Assessment Of Agricultural Drought Disasters In Northwest China

Drought disasters are one of the most frequent,largest,and most severe natural disasters in the world.They have caused great harm to the economic life and property safety of human society,especially agricultural production and life.Northwest China is the arid and semi-arid region with the largest distribution area in China,drought disasters occur all year round,which has a profound impact on agricultural production and life in the region.Clarifying the spatiotemporal evolution characteristics of agricultural drought-causing factors in Northwest China and analyzing the distribution of agricultural drought disaster risk in the region are the core content of formulating reasonable and effective drought risk management policies to prevent major droughts.This article takes Northwest China as the research area,using Mann-Kendall mutation test method,sliding average method,analytic hierarchy process,inverse distance weighting method,wavelet period analysis and other methods to analyze the time series trends,spatial distribution characteristics and abrupt characteristics of precipitation and temperature in Northwest China.Analyze the temporal and spatial distribution and periodic change characteristics of agricultural drought disasters;Pearson correlation coefficient and wavelet cross analysis method are used to analyze the response of MCI to ENSO events,Arctic Oscillation and other large-scale climate factors;Based on the disaster risk theory,the tomographic analysis method is used to determine the weight of agricultural drought disaster risk index and each factor in the northwest region.The agricultural drought disaster risk indicators in the research area are analyzed on the GIS platform.The main conclusions are as follows:(1)From 1970 to 2016,the multi-year average precipitation in Northwest China was356.03 mm,and the annual average precipitation increased at a rate of 8.223mm/10 a.The four seasons of the northwestern region show a significant increase in precipitation,with the largest increase trend in summer and the smallest increase trend in winter.From the perspective of spatial distribution characteristics,the annual average precipitation in Northwest China gradually decreases from east to west and from south to north,and the spatial distribution of precipitation in each season shows a decrease from east to west.From 1970 to 2016,the linear trend rate of the multi-year average temperature in Northwest China was 0.40?/10 a.The average temperature in the northwestern region has been on the rise for many years,with the highest growth rate in spring and the smallest growth rate in summer.In terms of spatial distribution,the multi-year average temperature in Northwest China is the highest in Xinjiang and Shaanxi in the east and west,and Qinghai has the lowest multi-year average temperature.(2)From 1970 to 2016,the trend rate of the comprehensive meteorological drought index in Northwest China was 0.022?/10 a.The drought seasons are mostly in late spring,summer and early autumn,and the frequency of light drought and heavy drought is relatively high.The MCI of each region has an upward trend for a period of time after 2016 a,and experienced 7-9 cycles of change in 47 a.In terms of spatial distribution,the annual average drought frequency of the stations in the northwestern region is between 1% and 35%,which is roughly characterized by the distribution characteristics of high in the middle and low in the east and west.Gansu has a relatively high frequency of droughts,while southwestern Xinjiang has the least frequency of droughts.The frequency of arid products is highest in summer and autumn,and the frequency of drought in spring is the lowest.The spatial distribution of drought frequency in each season is more consistent.(3)The duration of meteorological drought is positively correlated with the duration of extreme events.The MCI index of each region is correlated with the Arctic Oscillation indices are all positively correlated,of which Ningxia has the strongest response to the Arctic Oscillation Index;the Pacific Interdecadal Oscillation Index has the strongest impact on the meteorological drought in Shaanxi,and is positively correlated,and the rest of the region has a negative correlation with the Pacific Interdecadal Oscillation Index;The Asian Zonal Circulation Index has the greatest impact on the meteorological drought in Xinjiang,and it is positively correlated.The Asian Meridional Circulation Index has the greatest impact on the meteorological drought in Gansu,and the resonance period between MCI and the Asian Meridional Circulation Index are Similar in all regions.The response of the meteorological drought in the northwest to the Asian zonal circulation is greater than that of the Asian meridional circulation;the number of sunspots affects Shaanxi and Ningxia.The number of sunspots has close influence on the meteorological drought in Shaanxi and Ningxia,obviously stronger than other regions.The MCI index of Shaanxi and Gansu is positively correlated with the number of sunspots,and the index of Ningxia and Qinghai is negatively correlated with the number of sunspots.The influence of sunspot number on meteorological drought in Xinjiang is related to whether it is in the same period or not,and there is a positive correlation when MCI index lags behind sunspot number.(4)The areas with higher drought risk in Northwest China are distributed in the Kunlun Mountains,the Hexi Corridor area and the Qaidam Basin.The drought intensity in this area is high,and the hazard factors are high.The grain output per unit area and the agricultural population account for a large proportion,and the exposure of disaster-bearing bodies is high.The natural population growth rate and slope are large,the river network density is small,and the disaster-pregnant environment is highly vulnerable.The output value of agriculture,forestry,animal husbandry and fishery accounts for a large proportion,the total power of agricultural machinery and the effective irrigation rate are low,and the reliability of disaster prevention capabilities is low;The risk of drought in southern Shaanxi,Guanzhong,eastern Qinghai and eastern Xinjiang is relatively small.This area has a relatively large population,a large natural population growth rate,a relatively large proportion of grain output per unit area and agricultural population,and high exposure to disaster-bearing bodies and high vulnerability of the disaster-pregnant environment.Due to the high level of agricultural mechanization,the disaster prevention capability in the region is at a high level;Most areas of Ningxia,western Gansu and southern Xinjiang have the lowest comprehensive drought risk.There are few drought sites,low natural population growth rate,and high effective irrigation rate in this area,making it a low-risk area for drought.