The effect of boundary layer dynamics on aerosol properties at the Indo-Gangetic plains and at the foothills of the Himalayas

Previous studies have noted that aerosols originating from the polluted Indo-Gangetic plains can reach high altitudes at the Indian Himalayas and thereby have an effect on the south Asian monsoon. Here we examine the transport of pollutions by comparing aerosol properties from a Himalayan foothill measurement site and a site at the Indo-Gangetic plains. Gual Pahari is a polluted semi-urban background measurement site at the Indo-Gangetic plains close to New Delhi and Mukteshwar is a relatively clean background measurement site at the foothills of the Himalayas about 270 km NE from Gual Pahari and about 2 km above the nearby plains. The data set has more than two years of simultaneous measurements including meteorological parameters and aerosol mass concentrations. Modeled backward trajectories and Planetary Boundary Layer (PBL) heights are also used to examine the origin or air masses and the extent of the vertical mixing. The comparison shows that aerosol concentrations at the foothill site are correlated with the average PBL height. Together with the favorable synoptic scale circulation, this suggests a contribution of air mass transport from the plains.