Drought Monitoring Of Spring Maize In Northeast China

In order to comprehensively analyze the drought situation of spring maize in Northeast China,based on the data spatial interpolation of monthly and daily minimum temperature,maximum temperature,relative humidity,air pressure,sunshine hours,wind speed,precipitation and other data of 105 main meteorological stations in Northeast China and its surrounding areas,the Standardized Precipitation Evapotranspiration Index(SPEI)of 1,3,6,12 and 24 month scale in 1989-2018 was calculated.The law of drought occurrence and evolution in Northeast China and the difference of dominant meteorological factors in different months of spring maize growing season were analyzed.In 2018,when the drought is more serious in Northeast China,based on the daily meteorological element data and the measured ground drought data,and based on the Crop Water Deficit Index(CWDI),crop coefficient(K_c)and classification threshold were improved.The K_c is estimated on a daily basis using the subsection function,and then the daily cumulative CWDI is calculated.At the same time,the critical threshold value of drought degree classification is estimated on a daily basis by using subsection function,and the dynamic classification standard of drought degree changes with the development process of spring maize is constructed.Using MODIS data to calculate the vegetation index and extract the spatial distribution of spring maize.The response characteristics of spring maize to disaster factors under the condition of drought in 2018 were analyzed.The main results are as follows:(1)From 1989 to 2018,the drought change in Northeast China has certain regularity,and the main factors of drought in different periods of spring maize growing season are different.From 1989 to 2018,there was a regular pattern of normal drought normal 10 years in Northeast China,and the drought situation was more serious in 2000-2010.The high drought frequency month in spring maize growing season in Northeast China occurred in May,and the drought frequency was higher in western Jilin,east Inner Mongolia and southwest Heilongjiang.The dominant factors of drought in different months were different,except for precipitation It also includes relative humidity,maximum temperature and sunshine hours.June is the relative humidity,sunshine hours and minimum temperature,July is the relative humidity and sunshine hours,August is the maximum temperature and average temperature,September is the relative humidity and maximum temperature,and the whole spring corn growth season is the maximum air temperature,sunshine hours and relative humidity.(2)The improved CWDI index can be used for the continuous dynamic monitoring of spring maize drought.The drought monitoring results of spring maize in 2018 by using the improved CWDI have a high coincidence with the ground survey results,with the overall judgment rate reaching 75.7%,which is 8.1%higher than the drought judgment rate of the CWDI,and has a better spatial continuity.The improved CWDI is more sensitive to the change of precipitation factors.The monitoring results show that the drought in Northeast China is serious in 2018.(3)Spring maize will have a certain degree of response to the occurrence of meteorological drought.The planting area of spring corn in Northeast China is vast and mostly concentrated in the vast plains of the central region.In 2018,the growth season of spring maize in central Jilin province lagged behind.The impact of the meteorological drought process in 2018 on non-arid areas The correlation coefficient between TVDI and 8-day synthetic improved CWDI(CWDI8)is the largest in southwest Heilongjiang,central Jilin and northwest Liaoning,and the maximum correlation coefficient reaches 0.717,the correlation coefficient decreases from north to south,and the response of TVDI is mainly in CWDI8monitoring areas above severe drought.The study on the temporal and spatial characteristics of drought in long time series has a certain reference value for clarifying the drought risk and interannual change in Northeast China.The short time scale monitoring of spring maize drought disaster process and the analysis of spring maize drought response are conducive to the formulation and implementation of drought prevention and mitigation strategies in the actual production process of spring maize,which has certain guiding significance for spring maize production.