Validation and Accuracy Assessment of MODIS C6.1 Aerosol Products over the Heavy Aerosol Loading Area

Abstract

The aim of this study is to evaluate the accuracy of MODerate resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) products over heavy aerosol loading areas. For this analysis, the Terra-MODIS Collection 6.1 (C6.1) Dark Target (DT), Deep Blue (DB) and the combined DT/DB AOD products for the years 2000–2016 are used. These products are validated using AErosol RObotic NETwork (AERONET) data from twenty-three ground sites situated in high aerosol loading areas and with available measurements at least 500 days. The results show that the numbers of collections (N) of DB and DT/DB retrievals were much higher than that of DT, which was mainly caused by unavailable retrieval of DT in bright reflecting surface and heavy pollution conditions. The percentage falling within the expected error (PWE) of the DT retrievals (45.6%) is lower than that for the DB (53.4%) and DT/DB (53.1%) retrievals. The DB retrievals have 5.3% less average overestimation, and 25.7% higher match ratio than DT/DB retrievals. It is found that the current merged aerosol algorithm will miss some cases if it is determined only on the basis of normalized difference vegetation index. As the AOD increases, the value of PWE of the three products decreases significantly; the undervaluation is suppressed, and the overestimation is aggravated. The retrieval accuracy shows distinct seasonality: the PWE is largest in autumn or winter, and smallest in summer. The most severe overestimation and underestimation occurred in the summer. Moreover, the DT, DB and DT/DB products over different land cover types still exhibit obvious deviations. In urban areas, the PWE of DB product (52.6%) is higher than for the DT/DB (46.3%) and DT (25.2%) products. The DT retrievals perform poorly over the barren or sparsely vegetated area (N = 52). However, the performance of three products is similar over vegetated area. On the whole, the DB product performs better than the DT product over the heavy aerosol loading area.

Validation of MODIS C6.1 and MERRA-2 AOD Using AERONET Observations: A Comparative Study over Turkey

“…However, with a focus on storm episodes of mineral dust over four sunphotometer ground-based sites in Australia, Mukkavilli et al [49] found overestimation in MEERA-2 AOD. In addition, with respect to MODIS DB/DT and DT algorithms in comparison with AERONET, significant overestimations in AOD were found by Shaheen et al [41] and Tian et al [50], respectively. A larger deviation in RMB is found in the present study for MODIS than MERRA-2, with respect to both monthly and daily averaging (Figure 1).…”

Aerosols over the Foothills of the Eastern Himalayan Region during Post-monsoon and Winter Seasons

“…Compared to Aqua MODIS, Terra MODIS shows better agreement with the ground observation which is indicated by the higher R 2 value. The evaluation of these products over other areas in the Asian region show results with lower R 2 values (Bilal et al, 2018;Huang et al, 2020;Sharma et al, 2021;Tian and Gao, 2019). This may be attributed to the lower number of data samples in the present study, and the difference in the spatial and temporal window size taken for collocation.…”

Changing patterns in aerosol vertical distribution over South and East Asia

“…Comparison between AOD obtained from satellite-borne (MODIS and CALIOP) and ground-based remote sensing instruments (Lidar) revealed very good consistency 23 . Several studies already reported good consistency between the MODIS AOD and AOD obtained from AERONET measurements 48,49 . We further compared MODIS AOD with the AERONET observations over Kanpur (26.5° N, 80.2° E) where continuous observations are available during 2000-2018 and is shown in Supplementary Fig.…”