All-sky infrared radiance data assimilation has been challenging,due to nonlinear features and complex error statistics.Covariance localization,which is essential for an ensemble Kalman filter applied to high-dimensio...All-sky infrared radiance data assimilation has been challenging,due to nonlinear features and complex error statistics.Covariance localization,which is essential for an ensemble Kalman filter applied to high-dimensional geophysical systems,needs to consider the characteristics of all-sky radiances.To effectively extract information from all-sky radiances that are sensitive to clouds,two adaptive localizations are proposed here.Compared to the previously proposed global group filter(GGF-FS)that adaptively estimates localization lengthscales based on sample correlations,one simultaneously takes the vertical location and localization lengthscales into account(GGF-VS),and the other further considers the impacts of cloud top pressure and brightness temperature on the adaptive localization parameters(GGF-VLS).Both GGF-VS and GGF-VLS have broader vertical localization lengthscales and better capture the TC structure than GGF-FS,and GGF-VLS has larger variations of localization parameters than GGF-VS.Data assimilation experiments for assimilating all-sky infrared radiances confirm that GGF-VS has smaller errors of state variables than GGF-FS,and GGF-VLS further reduces the errors compared to GGF-FS and GGF-VS.Moreover,the more detailed adaptive localization parameters are beneficial for the TC intensity forecast.GGF-VS and GGF-VLS produce smaller errors and ensemble spread for the minimum sea level pressure and maximum wind speed than GGF-FS.GGF-VLS further improves the TC intensity forecast than GGF-VS,and both produce more coherent TC structures that are favored for intensified TC than GGF-FS,including the stronger warm core,more moisture at low levels,and enhanced primary and secondary circulations.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42450168)the Science and Technology Innovation Project of Laoshan Laboratory(Grant No.LSKJ202203303)+2 种基金the Science and Technology Project of State Grid Zhejiang Electric Power Engineering Research Institute(Grant No.5211DS25000L)the Fundamental Research Funds for the Central Universities-Cemac“Geo X”Interdisciplinary Program(Grant No.020714380207)the Fund for Postgraduate Research and Practice Innovation Program of Jiangsu Province(Grant No.KYCX22_0114)。
文摘All-sky infrared radiance data assimilation has been challenging,due to nonlinear features and complex error statistics.Covariance localization,which is essential for an ensemble Kalman filter applied to high-dimensional geophysical systems,needs to consider the characteristics of all-sky radiances.To effectively extract information from all-sky radiances that are sensitive to clouds,two adaptive localizations are proposed here.Compared to the previously proposed global group filter(GGF-FS)that adaptively estimates localization lengthscales based on sample correlations,one simultaneously takes the vertical location and localization lengthscales into account(GGF-VS),and the other further considers the impacts of cloud top pressure and brightness temperature on the adaptive localization parameters(GGF-VLS).Both GGF-VS and GGF-VLS have broader vertical localization lengthscales and better capture the TC structure than GGF-FS,and GGF-VLS has larger variations of localization parameters than GGF-VS.Data assimilation experiments for assimilating all-sky infrared radiances confirm that GGF-VS has smaller errors of state variables than GGF-FS,and GGF-VLS further reduces the errors compared to GGF-FS and GGF-VS.Moreover,the more detailed adaptive localization parameters are beneficial for the TC intensity forecast.GGF-VS and GGF-VLS produce smaller errors and ensemble spread for the minimum sea level pressure and maximum wind speed than GGF-FS.GGF-VLS further improves the TC intensity forecast than GGF-VS,and both produce more coherent TC structures that are favored for intensified TC than GGF-FS,including the stronger warm core,more moisture at low levels,and enhanced primary and secondary circulations.
