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Jun Li, W. Paul Menzel, Zhongdong Yang, Richard A. Frey, and Steven A. Ackerman

Abstract

A method for automated classification of surface and cloud types using Moderate Resolution Imaging Spectroradiometer (MODIS) radiance measurements has been developed. The MODIS cloud mask is used to define the training sets. Surface and cloud-type classification is based on the maximum likelihood (ML) classification method. Initial classification results define training sets for subsequent iterations. Iterations end when the number of pixels switching classes becomes smaller than a predetermined number or when other criteria are met. The mean vector in the spectral and spatial domain within a class is used for class identification, and a final 1-km-resolution classification mask is generated for such a field of view in a MODIS granule. This automated classification refines the output of the cloud mask algorithm and enables further applications such as clear atmospheric profile or cloud parameter retrievals from MODIS and Atmospheric Infrared Sounder (AIRS) radiance measurements. The advantages of this method are that the automated surface and cloud-type classifications are independent of radiance or brightness temperature threshold criteria, and that the interpretation of each class is based on the radiative spectral characteristics of different classes. This paper describes the ML classification algorithm and presents daytime MODIS classification results. The classification results are compared with the MODIS cloud mask, visible images, infrared window images, and other observations for an initial validation.

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Chaohua Dong, Jun Yang, Wenjian Zhang, Zhongdong Yang, Naimeng Lu, Jinming Shi, Peng Zhang, Yujie Liu, and Bin Cai

FengYun-3A (FY-3A), the first satellite in the second generation of the Chinese polar-orbiting meteorological satellites, was launched at Taiyuan, China, launching center on 27 May 2008. Equipped with both sounding and imaging payloads, enabling more powerful observations than the first generation of the FY-1 series, FY-3A carries 11 instruments. Two of them are the same as those on FY-1C/D, while the others, whose spectral bands cover violet, visible, near-infrared, infrared, and microwave spectral regions, are all newly developed. FY-3A instruments can be used to detect and study weather, clouds, radiation, climate, atmosphere, land, ocean, and other environmental features. FY-3A check out took about 5 months following its launch; FY-3A has been operational since January 2009. The plan for the future FY-3 series is to operate two polar-orbiting spacecraft—one in the morning and the other in the afternoon orbit—with different payloads for each spacecraft. This orbit configuration will be further coordinated with the World Meteorological Organization (WMO). One low-inclination orbit spacecraft is under consideration for radar and passive microwave precipitation measurement missions. Details are under discussion and yet to be determined. An overview of the first launch, FY-3A (the second generation of the Chinese meteorological satellites), and its imaging and sounding capabilities and potential applications are given in this paper.

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