Evaluation of Terra Modis C6 and C6.1 Aerosol Products Against Beijing, Xianghe, and Xinglong Aeronet Sites in China During 2004 2014
Journal Article - Open Access
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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In this study, Terra-MODIS Moderate Resolution Imaging Spectroradiometer Collections 6 and 6.1 C6 and C6.1 aerosol optical depth AOD retrievals with the recommended high-quality flag QF 3 were retrieved from Dark-Target DT, Deep-Blue DB and merged DT and DB DTB level-2 AOD products for verification against Aerosol Robotic Network AERONET Version 3 Level 2.0 AOD data obtained from 2004-2014 for three sites located in the Beijing-Tianjin-Hebei BTH region. These are Beijing, located over mixed bright urban surfaces, XiangHe located over suburban surfaces, and Xinglong located over hilly and vegetated surfaces. The AOD retrievals were also validated over different land-cover types defined by static monthly NDVI Normalized Difference Vegetation Index values obtained from the Terra-MODIS level-3 product MOD13A3. These include non-vegetated surfaces NVS, NDVI 0.2, partially vegetated surfaces PVS, 0.2 NDVI 0.3, moderately vegetated surfaces MVS, 0.3 NDVI 0.5 and densely vegetated surfaces DVS, NDVI 0.5. Results show that the DT, DB, and DTB-collocated retrievals achieve a high correlation coefficient of 0.90-0.97, 0.89-0.95, and 0.86-0.95, respectively, with AERONET AOD. The DT C6 and C6.1 collocated retrievals were comparable at XiangHe and Xinglong, whereas at Beijing, the percentage of collocated retrievals within the expected error EE increased from 21.4 to 35.5 , the root mean square error RMSE decreased from 0.37 to 0.24, and the relative percent mean error RPME decreased from 49 to 27 . These results suggest significant relative improvement in the DT C6.1 product. The percentage of DB-collocated AOD retrievals EE was greater than 70 at Beijing and Xinglong, whereas less than 66 was observed at XiangHe. Similar to DT AOD, DTB AOD retrievals performed well at XiangHe and Xinglong compared with Beijing.