Drought Monitoring In Beijing-Tianjin-Hebei Region Based On MODIS And TRMM Downscaling Data

With global warming and the greenhouse effect,drought disasters have had a serious impact on social and economic development and ecological environment due to their long duration and wide distribution.The Beijing-Tianjin-Hebei region is an important political and cultural center in my country,of which Hebei Province is a key production base for grain crops in China and one of the thirteen major grain producing areas in China.To carry out drought monitoring in this area and build a drought monitoring model that can accurately analyze the temporal and spatial variation characteristics of drought is of great significance to ensure the healthy growth of crops in this area.This thesis takes Beijing-Tianjin-Hebei as the study area,and based on the downscaling study of TRMM data,combined with meteorological station data and MODIS image data,SDCI is constructed,and the temporal and spatial distribution and evolution of drought conditions in the study area are analyzed and discussed.(1)The accuracy of the downscaling results of geographically weighted regression has been significantly improved compared with the results of statistical downscaling.After the downscaling results are calibrated by the geographic difference analysis method and processed by the proportional index method,the accuracy of the annual downscaling data has been significantly improved.The correlation of monthly precipitation data increased from 0.92 to 0.94,the relative error and root mean square error were also significantly reduced,and the downscaled data could more finely show the spatial distribution characteristics of precipitation in the study area.(2)Through the analysis of the variation law of TRMM precipitation data after downscaling in the Beijing-Tianjin-Hebei region,it is found that the precipitation in the study area varies greatly from 2005 to 2019,with an average annual precipitation of 511mm;the precipitation in different months shows a trend of increasing first and then decreasing.,the precipitation is mainly concentrated in June to September;the average precipitation in the study area for many years shows the distribution of the northeast wet and the northwest dry in space.(3)Based on the ergodic method and semi-empirical method,the normalized drought state index was constructed,and the SDCI of 0.4PCI,0.4TCI and 0.2VCI weighted combined components was finally determined as the optimal drought monitoring index in the study area based on the meteorological drought index.(4)The SDCI drought monitoring results in the Beijing-Tianjin-Hebei region from2005 to 2019 show that: the inter-annual drought is generally mild drought,and the drought has been alleviated;the seasonal SDCI mean results show that: summer >autumn > spring > winter,the summer drought is the lightest;through the monthly scale The monitoring results showed that the drought in the study area was greatly affected by precipitation,and the SDCI value showed a trend of first increasing and then decreasing,and the drought was the lightest in July.In the spatial distribution of SDCI,the overall drought situation shows a decreasing trend from south to north,and extreme drought occurs more frequently in Langfang and other places;drought disasters occur frequently in spring and winter,and the drought situation in summer and autumn is significantly relieved.Mild or no drought conditions;the results of the spatial distribution of drought conditions on a monthly scale show that the study area showed no drought in July,and severe drought disasters occurred in January and December.(5)Using the trend analysis method,the coefficient of variation method and the gravity center migration method to analyze the SDCI results of each year,it is found that the drought situation in the Beijing-Tianjin-Hebei region has been significantly improved in the past 15 years,and the area of the area where the drought situation has been alleviated accounts for 55.57%;the drought situation in the study area is relatively stable,53.48% of the area showed low volatility and low volatility;the results of the migration of the center of gravity of the drought-prone areas showed that the drought conditions in the study area moved to the southwest as a whole.