Spatial distributions and seasonal cycles of aerosols in India and China seen in global climate-aerosol model

A climate-aerosol model is employed to study spatial and temporal variability of aerosol properties over India and China for recent (year 2006) and future conditions (year 2020) under different emission pathways. We present results for aerosol mass concentration in different size classes and optical properties for the five different aerosol species treated by the model. Aerosol mass concentration and optical depth have significant contributions from both anthropogenic and natural aerosols. Different species have maxima in different regions, with the highest anthropogenic aerosol concentrations found in Kolkata and elsewhere in the Ganges basin in India and on the northern part of the east coast and in the Sichuan basin in China. In India, natural aerosols have a maximum in the summer due to higher wind speeds, whereas anthropogenic aerosols have a maximum in the winter due to less efficient wet removal. Surface concentrations also tend to be higher in winter due to the additional reason of lower average boundary layer height. In China, seasonal cycles are weaker with natural aerosols having a maximum in the spring and sulfate contribution to the aerosol optical depth (AOD) being higher in the latter half of the year. MODIS AOD spatial distributions are reproduced well by the model, except for the Ganges valley with high absorption and for the Thar desert with high dust concentrations. Seasonal cycles compare qualitatively well with MODIS measurements.