A Dark Target Method for Himawari-8/AHI Aerosol Retrieval: Application and Validation
A Dark Target Method for Himawari-8/AHI Aerosol Retrieval: Application and Validation
复制标题
Himawari-8/AHI 气溶胶反演的暗目标方法：应用与验证
DOI：
10.1109/tgrs.2018.2854743
复制
发表时间：
2019-01-01
影响因子：
8.2
通讯作者：
Qie, Lili
中科院分区：
文献类型：
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作者：
Ge, Bangyu;Li, Zhengqiang;Qie, Lili
Himawari-8（H8）是一颗地球同步轨道卫星，每10分钟观测一次地球的全圆盘图像，是研究大气气溶胶时间变化的有力工具。H8机载的先进的himawari成像仪（AHI）具有与中分辨率成像光谱仪（MODIS）相似的几个光谱波段。因此，利用MODIS暗目标（DT）方法，可以从AHI数据中反演气溶胶光学厚度（AOD）。通过对这两种卫星红外波段的统计研究，发现DT地区AHI（2.3 μ m）和MODIS（2.12 μ m）的短波红外波段差异可以忽略。同时，对于AHI传感器，从0.86 μ m（而不是传统的1.24 μ m）和2.3 μ m计算的归一化差分植被指数（NDVI）也可以很好地指示地表光谱反射率。因此，本文首先提出了一种新的AHI传感器NDVI，以改进基于DT反演方法的地表反射率估计。然后，使用查找表策略检索DT区域的AOD，并基于2015年8月至2016年7月中国地区的AHI观测进行检验。所有检索结果均通过气溶胶机器人网络和太阳天空辐射计观测网络的地面测量进行验证。AHI反演和地面观测网观测的AOD结果与R-2值0.81吻合较好。AHI和MODIS DT AOD产品之间的相互比较也显示出良好的一致性，R-2为0.92。
Himawari-8 (H8), as a geostationary satellite, observing the full disk image of the earth per 10 min, is a very powerful tool to investigate atmospheric aerosol temporal variations. The advanced himawari imager (AHI) onboard H8 has several spectral bands similar with those of Moderate Resolution Imaging Spectroradiometer (MODIS). Aerosol optical depth (AOD) is thus possible to be retrieved from AHI data using the dark target (DT) method of MODIS. Based on a statistics study of infrared bands of these two satellite instruments, we found that the difference of shortwave infrared hands between AHI (2.3 mu m) and MODIS (2.12 mu m) in DT area can be ignored for our purpose. Meanwhile, for AHI sensor, the normalized difference vegetation index (NDVI) calculated from 0.86 mu m (instead of traditional 1.24 mu m) and 2.3 mu m can also be a good indicator of surface spectral reflectance. Therefore, first, a new NDVI of AHI sensor is proposed in this paper to improve the estimation of surface reflectance based on DT retrieval method. Then, AOD over DT area was retrieved using a lookup table strategy and tested based on AHI observation over China region from August 2015 to July 2016. All retrieved results are validated against ground-based measurements of the aerosol robotic network and the sun-sky radiometer observation network. The coincident AOD results between AHI retrieval- and ground-based network measurements show good agreements with R-2 of 0.81. The intercomparison between AHI and MODIS DT AOD products also shows a good agreement with R-2 of 0.92.