最新一代地球同步氣象衛星—向日葵八號（Himawari-8, H-8）已於2014年發射，並在2015年7月4日正式運作，其裝載著高像素成像儀（Advanced Himawari Imager, AHI），可提供高達16個可見光和紅外波段的光學頻道、1公里空間解析度以及涵蓋整個東亞和太平洋地區每10分鐘超高時間解析度的觀測資料，因此若能建立氣膠光學厚度（Aerosol Optical Depth, AOD）的反演模式，對於時、空變化劇烈之大氣懸浮微粒濃度與空氣品質的即時監測極具效益，此亦為本研究的主要目標。基於氣膠的散射與吸收效應在影像所造成的模糊效應，配合參考影像之反射率及氣膠光學厚度資料之建置，本研究嘗試以時間序列疊代的對比演算法，應用H-8觀測影像即時反演目標區域之氣膠光學厚度。 在與MODerate-resolution Imaging Spectroradiometer（MODIS）的氣膠產品比較後，顯示本研究可有效地提供氣膠的空間分布特性，而相對於地面測站AErosol Robotic NETwork（AERONET）點的觀測資料，雖有有些微高、低估的情形發生，研判為受到移動視窗內的雲蔭比例以及地物種類複雜程度之影響，導致反演過程中有些許的誤差產生，但整體的反演結果還是具備相當之準確性。後續亦將改進移動視窗像元的篩選及太陽入射透射率的修正，期能藉由地球同步衛星H-8的觀測協助，準確地提供大範圍高時間解析的氣膠光學厚度動態資料，以利空氣品質的即時監測應用。 ;The new generation geostationary weather satellite Himawari-8 (H-8) was launched in 2014, and operated on 4 July 2015. The onboard Advanced Himawari Imager (AHI) can provide 16 optical spectral bands with higher spatial resolution (1km x 1km) over East Asian and West Pacific areas every 10 minutes. The broad and highly frequent observations are powerful to monitor the large scale atmospheric environment instantaneously, such as the particle matter (PM) concentration in terms of aerosol optical depth (AOD). Therefore, this study focuses on retrieving AOD from AHI images. Based on the pre-constructed datasets of clear-sky reflectance and AOD as the reference, the Contrast Reduction Method (CRM) with Time Series Iteration Algorithm (TSIA) is explored for AOD retrievals from AHI image after cloud masking. The results show the consistency with MODerate-resolution Imaging Spectroradiometer (MODIS) AOD products in the pattern of spatial distribution. Although the magnitude of retrieved AODs is slightly underestimated/overestimated compared to AErosol Robotic NETwork (AERONET) in situ measurements, which principally caused from the effects of surface texture and cloud proportion in each moving window, the overall accuracy still indicates high practicability of proposed algorithm in providing different spectral bands AOD distribution from AHI/H-8 data. The improvement of proposed approach for H-8 AOD retrieval will keep working on, such as the pixel filtering within the moving window and the correction of solar incoming transmittance. Then the application to instantaneous monitor of the regional particle matter (PM) concentration for air quality with AHI/H-8 data could be expected.
