Changes in atmospheric aerosol loading from space-based measurements and model simulations for the decade 2001-2010
Tuesday, 16 December 2014
This study presents long-term trend estimates of aerosol optical thickness (AOT) retrieved from the space-born instruments (MODIS-Terra, MISR-Terra, SeaWiFS-OrbView-2, and MODIS-Aqua) and simulated by the atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC) for the decade 2001-2010. The satellite-retrieved AOT trends are estimated using the weighted trend method that minimizes the uncertainty effect of unrepresentative monthly means induced by frequent cloud occurrence in cloudy seasons because the AOT products are retrieved from cloud-free radiances by the visible imager. The EMAC simulations distinguish various aerosols components (i.e. black carbon, organic carbon, dust, aerosol water, sea salt, and water soluble compounds) for selected regions and the decomposed trends for each of them. A significant decrease in the satellite-retrieved AOT is estimated over Western Europe (i.e. by up to about -6.59 ± 5.30% per year with a 95% confidence interval) due to the decreasing water-soluble compounds (i.e. ammonium, nitrate and sulphate) and aerosol water content. In contrast, a statistically significant increase is observed over East China (about +5.66 ± 4.14% per year), which is attributed to the increase in black carbon, water-soluble compounds, and aerosol water.