China Collection 1.1: an aerosol optical depth dataset at 1km resolution over mainland China retrieved from satellite data

NASA's Moderate Resolution Imaging Spectro-radiometer (MODIS) sensors have been observing the Earth from polar orbit, from Terra since early 2000 and from Aqua since mid-2002._MODIS is uniquely suited for characterization of aerosols, combining broad swath size, multi-band spectral coverage and moderately high spatial resolution imaging. By using MODIS data, many algorithms have showed excellent competence at the aerosol distribution and properties retrieval. However, in China, many regions are not satisfied with the dark density pixel condition. In this paper, aerosol optical depth (AOD) datasets (China Collection 1.1) at 1 km resolutions have been derived from the MODIS data using the Synergetic Retrieval of Aerosol Properties (SRAP) method over mainland China for the period from August 2002 to now, comprising AODs at 470, 550, and 660 nm. We compared the China Collection 1.1 AOD datasets for 2010 with AERONET data. From those 2460 collocations, representing mutually cloud-free conditions, we find that 62% of China Collection 1.1 AOD values comparing with AERONET-observed values within an expected error envelop of 20% and 55% within an expected error envelop of 15%. Compared with MODIS Level 2 aerosol products, China Collection 1.1 AOD datasets have a more complete coverage with fewer data gaps over the study region.