Assessing spatiotemporal variations of AOD in Japan based on Himawari-8 L3 V31 aerosol products: Validations and applications

The next-generation geostationary meteorological Himawari-8 satellite has a high temporal resolution of 10 min and thus provides a huge advantage for monitoring aerosol optical depths (AOD) in real-time. The newly released Himawari-8 Level 3 Version 31 aerosol products include the ??ngstro??m exponent (AE) and three categories of AOD of AOD_L2_Mean, AOD_Pure, and AOD_Merged on an hourly basis. In this study, we evaluated the accuracy of these aerosol products in Japan where with low AOD using the Aerosol robotic network (AERONET), SKYNET, and moderate resolution image spectroradiometer (MODIS) AODs. The results showed that the AOD_L2_Mean had the lowest correlation coefficients and the highest RMSE with the available AODs (AERONET: R:0.558, RMSE:0.230; SKYNET: R:0.674, RMSE:0.246; MODIS: R:0.525, RMSE:0.195) while the other two had similar performances. The result also indicated that although the AOD_Pure and AOD_Merged showed good agreements with the ground observations in terms of time series, they were, unfortunately, overestimated in most cases. In comparison, the AOD_L2_Mean values were nevertheless frequently overestimated. On an hourly basis, the AOD_Merged product had the best performance. Furthermore, the spatiotemporal analysis revealed that the AOD_Merged has traced the spatial and temporal variations well in Japan, with higher loadings in spring and summer and lower values in winter. In addition, the mean AOD loading across years was high in the Seto Inland Sea in Japan. The evaluation offered in this study can contribute to understanding the error sources on retrieving AHI AOD and the spatiotemporal variations of AOD in Japan, which have frequently been ignored in current assessment studies.

Automated summary

The high temporal resolution of the Himawari-8 satellite allows for real-time monitoring of aerosol optical depths (AOD). This study evaluated the accuracy of the newly released Himawari-8 Level 3 Version 31 aerosol products in Japan using ground observations. The results showed that the AOD_Merged product had the best performance in tracking the spatial and temporal variations of AOD in Japan.