Study On Drought Monitoring Of Spring Maize In Northeast China Based On Optimum Remote Sensing Index

Drought has the characteristics of long duration,wide range of influence and strong harmfulness.Howvever,it has become one of the most serious natural disasters in the world.As an important spring maize planting area in China,Northeast China is frequently affected by drought in its growing season,which has posed a serious threat to agricultural production and economic development.At present,there are many drought indexes,and the drought remote sensing index has been recognized by scholars for its real-time,fast and accurate advantages.Therefore,the applicability of different drought remote sensing indexes may be affected by many factors,such as regional differences,time scale differences,crop types and phenology differences.Therefore,the most appropriate drought remote sensing index is selected to monitor the drought in the spring maize planting area of Northeast China It is of great significance to study the law of drought in the growing season of spring maize for improving the yield of Spring Maize in Northeast China.In this study,the northeast spring maize planting area was selected as the research area,and the growth season of spring maize in typical dry years was selected.The sensitivity and applicability of eight remote sensing indexes for drought monitoring of northeast spring maize were analyzed by using Relevance(R),determination coefficient(R~2),Root Mean Square Error(RMSE),and the optimum remote sensing index was selected to monitor the growth season of spring maize in Northeast China Spatial and temporal characteristics of drought in growing season.The main results of this study are as follows:(1)The correlation analysis between the eight typical remote sensing indexes and the relative soil moisture content(RSM)of different soil layers in the spring maize growing season of2017 and 2018 shows that the eight remote sensing indexes can monitor the drought in the spring maize growing season of Northeast China when the planting area is in different farmland environment,but the sensitivity of TVDI and VTCI is higher than that of the others The accuracy of TVDI is higher than that of VTCI.(2)Taking the 2018 for instance,the analyzes sensitive period of TVDI-N constructed by NDVI\LST feature space and TVDI-E constructed by EVI\LST feature space for drought monitoring,as well as their drought judgment and accuracy.The results show that TVDI-N is more sensitive than TVDI-E in the early growth stage of spring maize,and TVDI-N is more accurate than TVDI-E 33.3 percentage points;in the middle stage of spring maize growth,it is the period of sensitivity conversion,and TVDI-E is 12.5 percentage points higher than TVDI-N;in the late stage of spring maize growth,TVDI-E is more sensitive than TVDI-N,and TVDI-E is 8.7 and 39.2 percentage points higher than TVDI-N respectively.(3)From 2003 to 2018,the northeast region showed an obvious trend of aridity,and the trend became more and more obvious.The frequency of aridity was high and the influence scope was wide.In terms of time,the severe drought in the study area is April to May.In June to July,the overall drought situation slows down,but the regional differences are large.In August,the drought area decreases,but the drought area is increased compared with that in the earlier stage.In space,the drought area above light drought level fluctuates between 15%and 45%,above medium drought level fluctuates between 10%and 30%,except this,above heavy drought level The product fluctuates between 5%and 15%.The arid areas are mainly concentrated in the west of Northeast China,including the west of Liaoning Province,the west of Jilin Province and the southwest of Heilongjiang Province.The conclusion of this study is that although the eight remote sensing indexes can be used for drought monitoring of spring maize planting area in Northeast China,the sensitivity and accuracy of TVDI are generally higher than those of the other seven indexes,and TVDI-N is suitable for the early stage of spring maize growth,and TVDI-E is suitable for the middle and late stage of spring maize growth.The frequency of drought is high and the influence range is wide in the growing season of spring maize planting area in Northeast China,but the drought level is mainly light drought,and the drought area is mainly in the west of the study area,and the drought is most serious from April to May.