Abstract:

The Arctic is a highly climate-sensitive area. In recent years, the Arctic temperature has increased at twice the rate of the global average, and aerosols have a significant impact on Arctic warming. To explore the optical characteristics of aerosols over the Arctic, we analyze the characteristics of the spatial and temporal distributions of the Arctic aerosol optical depth (AOD) based on Moderate-resolution Imaging Spectroradiometer (MODIS) 10-km and 3-km AOD products from March 2000 to October 2018 and validate these products via comparisons with the ground-based Aerosol Robotic Network (AERONET). The results indicate that the correlation coefficients between the MODIS 10-km and 3-km AODs and the AERONET base station points are 0.840 and 0.853, respectively, and that the root mean square error is less than 0.1. Both the 10-km and 3-km AODs are in good agreement with the ground-based observations. The results for the correlation coefficient, root mean square error, relative mean bias, and expected error between the two AOD products and the AERONET data all show that, overall, the accuracy of MODIS 10-km AOD products in the Arctic region is higher than 3-km AOD , and both are more accurate in the Eastern Hemisphere of the Arctic than in other regions. Moreover, the accuracy of the MODIS 10-km AOD increases as the latitude increases in the Western Hemisphere of the Arctic, although no consistent pattern is observed in the 3-km AOD. Additionally, the two AOD products typically exhibit greater accuracy in May, September, and October and are slightly more accurate in spring than in summer. Moreover, remarkable AOD differences are detected between low and high latitudes in the Arctic, where AOD increases unevenly as the latitude decreases. The Arctic MODIS AOD exhibits obvious seasonal variations. Spring AOD values generally range from 0.1 to 0.3 and peak in the Nordic region in April. In summer, high AOD values extend to larger areas from June to August, while the AOD values are typically smaller than 0.1 in autumn. Moreover, the two MODIS AOD products exhibit different patterns over Arctic land and ocean areas. The MODIS 10-km AOD is usually larger over the Arctic Ocean, while the MODIS 3-km AOD is generally larger over the Arctic land areas.

Key words: Arctic, MODIS, AOD, distribution characteristics