Analysis Of Drought Situation In Heilongjiang Province Based On MODIS Data

Drought is a potential natural disaster.It is a natural disaster with complex causes.The loss of crops is huge,far more than other meteorological disasters.As a large agricultural country,China's agricultural economy is the ballast of China's modern economy,supporting the normal development of China's national economy.At the same time,Heilongjiang Province,as a major grain producing province,is affected by monsoon climate and natural conditions,with high drought frequency,high drought intensity and long duration.Drought has seriously affected the normal growth and development of the main food crops in Heilongjiang Province.At present,many fields begin to apply modern information technology to solve the problem,to make up for the shortcomings of traditional data acquisition methods in terms of collection speed and information quantity.Compared with the traditional data acquisition methods,the modern remote sensing information technology has a faster data update speed and a larger and deeper data coverage area.When monitoring the drought,it can obtain the drought development status in real time and accurately,analyze and process the remote sensing data through the relevant software,and predict the drought development trend,which is helpful for the relevant government departments to make disaster prevention and mitigation decisions,and provides a scientific and reliable basis for the formulation of drought relief programs.Based on the previous drought monitoring research results,the spatial and temporal characteristics of drought distribution in Heilongjiang Province were analyzed by using MODIS data,and the temperature vegetation drought index model was constructed,and carries out correlation analysis according to the soil moisture content data in Heilongjiang Province.The reliability of the temperature vegetation drought index model of each weather station in Heilongjiang Province was verified,combined with the historical drought event data and spring moisture index of Heilongjiang Province,the distribution of drought area and spring drought area in Heilongjiang Province were analyzed and verified,and the following conclusions are summarized:(1)The LST / NDVI characteristic space of Heilongjiang Province was constructed.The results showed that: the scatter plot of Heilongjiang Province took the normalized vegetation index(NDVI)and surface temperature(LST)as the abscissa and ordinate,but when the angelica normalized vegetation index was larger or smaller,there were fewer pixels on the scatter plot,which indicated that the soil moisture content could not meet the demand of dry soil in Heilongjiang Province when the surface was completely covered by vegetation and bare soil Therefore,this paper selects vegetation index between 0.2 and 0.8 to establish LST / NDVI feature space.(2)When dealing with the historical data of Heilongjiang Province from 1990 to 2007,two methods were used to evaluate the drought grade of Heilongjiang Province from 1990 to 2007,the rate of grain loss due to drought and the ratio of crop disaster area.In practical application,it was found that the rate of grain loss due to drought was more suitable for evaluating the drought grade of Heilongjiang Province.(3)Through the analysis of drought grade distribution map in Heilongjiang Province,the distribution of spring drought area in Heilongjiang Province is obtained,the spring drought area of Heilongjiang Province is divided into severe spring drought area,moderate spring drought area and mild spring drought area and it is verified by the spring humidity coefficient C,which proves that the distribution of spring drought area in Heilongjiang Province has a certain reliability.(4)Combining with the historical data and the drought grade distribution map of Heilongjiang Province obtained by remote sensing,the regional distribution map of drought situation in Heilongjiang Province is obtained,the drought prone areas of Heilongjiang Province can be divided into frequent drought areas,occasional drought areas and occasional drought area.The division of drought prone areas in Heilongjiang Province is verified by rainfall anomaly method,which proves that the division of drought prone areas in Heilongjiang Province has certain reliability.