Research And Application Of PM_2.5 Concentrations Estimation Method For Himawari-8

In recent years,more and more people are concerned about air pollution.PM_2.5,as a major pollutant in the atmosphere,the change of concentrations is an important indicator can reflect the air pollution situation.At present,the PM_2.5 concentrations data released by most online platforms are mainly from the ground-level PM_2.5 concentrations across the country.Although the ground-level PM_2.5 concentrations can ensure the data accuracy,due to the limited number and distribution of ground observation stations,it can only provide PM_2.5concentrations data in a limited space scale.Satellite remote sensing has the characteristics of wide coverage,less restricted conditions,abundant historical data,continuous time series and so on,which can be used for large-scale monitoring of air pollution.At present,it is common to use polar-orbit satellites to estimate the PM_2.5 concentrations,however,due to polar-orbiting satellites can only make limited observations of the same region once or twice a day,it can't enable relevant departments and the public to obtain the near-real-time pollution information.Therefore,this paper used the prominent advantage of high temporal resolution for the Himawari-8 geostationary satellite to carry out the estimation method research and application of PM_2.5 concentrations.The main work of the paper was as follows:?1?Aiming at the problem of inaccurate cloud identification in the retrieval algorithm,a dynamic threshold cloud mask algorithm based on time series was proposed.The primary prerequisite for estimating PM_2.5 concentrations by remote sensing is to obtain reliable aerosol optical thickness products.This paper utilized the characteristics of multispectral and high time resolution for Himawari-8 to add band types for cloud recognition.A dynamic threshold cloud mask algorithm based on time series was proposed to improve the accuracy of cloud recognition and reduce the phenomenon that the low values of aerosol optical thickness are overestimated and the value of non-cloud pixel missing in retrieval results.The Dark Target aerosol retrieval algorithm was used to realize aerosol optical thickness solution for pixels passing through the cloud mask algorithm.The regression analysis of the retrieval results and the ground-based data showed that the R was 0.87 and the RMSE was 0.13.?2?In order to obtain the PM_2.5 concentrations in a continuous long time series,In this paper,a method for estimating PM_2.5 concentrations based on geographically weighted regression model was improved to enable the model to estimate PM_2.5 concentrations for Himawari-8 aerosol optical thickness.Used this paper's Himawari-8 aerosol optical thickness products,combined with meteorological data such as height of the planetary boundary,relative humidity and ground-level PM_2.5 concentrations to construct geographically weighted regression model,trained the regression coefficients between PM_2.5 concentrations and parameters at different geographic locations.Finally,PM_2.5 concentrations was estimated through these regression coefficients combined with inverse distance weighting method.In this paper,the PM_2.5concentrations in eastern China in July 2018 was estimated by this model,and the fitting regression analysis was carried out with the ground-level PM_2.5 concentrations?R=0.74?.The results showed that it was feasible to estimate the PM_2.5 concentrations of by using Himawari-8 aerosol optical thickness based on the geographically weighted regression model.?3?Aiming at the application requirement of environmental monitoring in Henan Province,Henan Environmental Monitoring Center put forward an air-space-earth integration environmental information monitoring system.In this paper,the improved Himawari-8 aerosol optical thickness retrieval algorithm and PM_2.5 concentrations estimation method based on geographically weighted regression model were used as the algorithm interface to apply to the environmental information monitoring system.It helps the system to process 0-2 level remote sensing data,and produces visual products such as aerosol optical thickness,PM_2.5and haze monitoring for business needs.By establishing the monitoring model of the linkage between remote sensing satellite and atmospheric air quality,the system effectively improves the information service level and rapid response ability of environmental monitoring,and is conducive to strengthening the level of atmospheric environmental supervision in Henan Province.The research and application of atmospheric remote sensing algorithm for Himawari-8 make full use of Himawari-8's outstanding advantage of high temporal resolution,which is conducive to the study and analysis of the temporal and spatial distribution characteristics and change trends of particulate matter under long time series,to reflect accurately and timely the latest status of global air pollution in the study area,and to satisfy the near-real-time demand of air quality data acquisition.