FY-3D MERSI-II云顶产品算法及精度检验

RETRIEVAL AND VALIDATION OF FY-3D MERSI-II CLOUD TOP PRODUCTS

关键词:  FY-3  云顶温度  云顶高度  云顶压强  精度检验

Key words:  FY-3  cloud top temperature  cloud top height  cloud top pressure  quality validation

摘要:

云顶温度和云顶高度作为基本的云参数，在云的热辐射强迫估计，航空气象保障，数值天气预报，天气气候研究等方面具有十分重要的意义。FY-3D/ MERSI-II云顶温度产品基于云在红外波段的发射率假设，利用两个红外分裂窗通道(11.0 μm、12.0 μm)结合一维变分方法寻找最优云顶温度层，再利用数值天气预报廓线产品插值反演对应的云顶高度和压强。利用AQUA/MODIS所提供的云产品数据对FY-3D/MERSI-II云顶温度、云顶高度、云顶压强产品进行精度检验，结果表明：FY-3D/MERSI-II水云云顶温度精度为-1.2±4.6 K，云顶高度精度为1.4±1.8 km，云顶压强精度为-140.9±114.5 hPa；厚冰云云顶温度精度为7.0±6.0 K，云顶高度精度为-1.0±0.9 km，云顶压强精度为37.1±36.0 hPa；混合云云顶温度精度为1.5±8.5 K，云顶高度精度为0.8±2.2 km，云顶压强精度为-87.4±157.8 hPa，单层卷云和多层云的反演偏差较大。辐射传输模式在云顶性质反演中有十分关键的作用，但目前对冰云特别是卷云的性质认识不足，因此如何精确描述冰晶辐射特性，提高冰云特别是卷云辐射传输的模拟精度将是下一步的工作重点。

Abstract:

As basic cloud parameters, cloud top temperature and cloud top height are of great significance to the estimation of cloud thermal radiative forcing, aviation meteorological support, numerical weather prediction and climate research. In the present research, we employ the FY-3D/MERSI-II cloud-top temperature products based on the assumption of cloud emissivity in the infrared band and two channels (11 μm and 12 μm) to find the optimal cloud-top temperature layer using the 1DVar method, and then interpolate the corresponding cloud-top height and pressure by using the numerical weather prediction profile product. Then we adopt the AQUA/MODIS cloud products to evaluate the retrieved products, and the results show that: for water cloud, the precision of cloud top temperature is -1.2±4.6 K, the precision of cloud top height is 1.4±1.8 km, and the precision of cloud top pressure is -140.9±114.5 hPa; for thick ice, the precision of cloud top temperature is 7.0±6.0 K, the precision of cloud top height is -1.0±0.9 km, and the precision of cloud top pressure is 37.1±36.0 hPa; for mixed cloud, the precision of cloud top temperature is 1.5±8.5 K, the precision of cloud top height is 0.8±2.2 km, the precision of cloud top pressure is -87.4±157.8 hPa, and the precision of the products for cirrus and multi-layer cloud is poor. The radiative transfer model plays a key role in the retrieval of cloud top properties; however, there is insufficient understanding of the nature of ice cloud especially cirrus cloud. Therefore, accurate description of the radiation characteristics of ice crystals and improvement in the simulation accuracy of radiation transfer of ice cloud, especially cirrus cloud, will be the focus of the following research.