Application Of New Geostationary Satellite Data In Autumn Drought Monitoring In Hebei Province

Hebei Province is located in the North China region,and drought has occurred frequently in recent years.In the autumn of 2018,a continuous meteorological drought occurred in Hebei Province.As an important grain producing area in China,this severely restricted local agricultural production.Therefore,timely,accurate and effective drought monitoring is necessary.This paper uses FY-4 AGRI(Advanced Geostationary Radiation Imager)data to monitor the drought conditions in Hebei Province in the autumn of 2018,and explores the processing methods of AGRI data,and compares it with the data of Himawari-8 AHI(Advanced Himawari Imager)in the same period,and analyzes the performance of the two sensors in drought monitoring.At present,there are not many applications of FY-4 satellite data.This study has positive significance for the promotion and use of a new generation of domestic satellite data.A lot of work has been done on drought monitoring based on AGRI and AHI data.Firstly,the ASTM-E490 solar spectrum was selected,and the spectral response function of the sensor was used to calculate the atmospheric average spectral irradiance value(ESUN_b)of the atmospheric and near-infrared bands of the AGRI and AHI sensors.The spectral response function of HJ-1A/1B was used to verify that the relative error between the average solar spectrum irradiance and the official value calculated based on the ASTM-E490 solar spectrum is only between 0.191%and 0.571%.In this study,cloud detection and water detection of images uses the threshold method.The cloud detection adopts the red reflectance combined with the near-infrared-red light ratio reflectance method,and the water detection uses the red light reflectance combined with the NDVI threshold method.The results show that the method has a good effect on cloud and water detection,and can identify all cloud-covered pixels except the cloud water boundary.The soil moisture automatic extraction algorithm combined with the vertical drought index PDI was used to monitor the autumn drought conditions in Hebei Province in 2018,and the PDI index was graded in the drought conditions in Hebei Province.Finally,the applicability of the two sensor data to drought monitoring is analyzed.The results showed that the overall trend of drought in Hebei Province in 2018 was arid.The drought mainly occurs in most parts of the southeast and a few parts of the northwest and northeast.The PDI index of the vegetation area in the northwestern and southwestern of China is not obvious,and the response of the North China Plain to the PDI is more obvious.Using the measured soil moisture data and the PDI index for correlation analysis,the PDI values of the sensor inversion are negatively correlated with the measured data,and the correlation is generally above 0.5.The AHI sensor has a higher correlation at 20 cm soil depth,but at 10 cm soil depth,the correlation between AGRI and measured relative soil moisture data is more stable.In general,the correlation between soil moisture data and PDI of 20cm is stronger than that of10cm,and the PDI value of the site of AGRI inversion is similar to the trend of AHI inversion.It shows that the application of the new domestic satellite data(AGRI)in the drought monitoring business is feasible.