基于IASI双二氧化碳通道的一种不同高度云检测算法
投稿时间:2018-10-12  修订日期:2019-01-11  点此下载全文
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作者单位E-mail
李琪 南京信息工程大学 2801417001@qq.com 
邹晓蕾 马里兰大学 地球系统科学交叉学科中心 xzou1@umd.edu 
基金项目:国家自然科学基金
中文摘要:利用卫星红外探测仪来探测大气不同垂直层内的云具有一定难度,尤其对于和背景场差别较小的光学厚度比较薄的云而言。在前人发展的云检测算法基础上,利用红外高光谱探测仪(IASI)在二氧化碳吸收带的长短波红外通道对云反应程度的不同来探测云。依据不同通道的权重函数峰值高度和云不敏感层高度将IASI长短波红外通道进行配对,成功配对的长短波红外通道晴空亮温之间建立线性回归模型,即通过长波红外通道亮温可以线性回归得到配对的短波通道亮温,将短波通道的晴空回归亮温和观测亮温之差定义为云指数(CESI)。权重函数峰值高度位于383 hPa的云指数空间分布和云成分为冰的空间分布较为一致,尤其在赤道和低纬度地区。权重函数峰值高度位于790 hPa的云指数空间分布和低云云顶气压也有较好的一致性。
中文关键词:红外高光谱探测仪  长短波红外通道  权重函数  云不敏感层  云指数
 
A different layer cloud detection algorithm based on IASI double CO2 bands
Abstract:Detection of clouds in different vertical layers of the atmosphere using satellite infrared instruments is challenging, especially for those optically thin clouds due to their small thermal contrasts to the background. Based on the cloud detection algorithm developed by the predecessors, the Atmospheric Sounding Interferometer (IASI) is used for cloud detection by using the different responses to clouds between longwave and shortwave channels at CO2 bands. IASI longwave channels are first paired with shortwave channels based on weighing function altitudes and sensitivity to clouds. A linear relationship of brightness temperatures between each paired channels is then established for predicting the shortwave channel from the longwave channel in clear sky conditions. A cloud emission and scattering index (CESI) can finally be defined as the difference of the paired shortwave channel between the regression model predicted and the observed brightness temperatures. The spatial distribution of CESIs with weighting functions peak around 383 hPa is consistent with the distribution of the cloud phase of ice, especially in the equator and low latitudes. The spatial distribution of CESIs with weighting functions peak around 790 hPa agrees well with the distribution of the low cloud top pressure.
keywords:IASI  Longwave and shortwave infrared channels  Weighting function  Cloud-insensitive level  CESI
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