Aerosol optical properties over marine and continental sites of India during pre-monsoon season

Ground and satellite based measurements of spectral optical properties of aerosols have been carried out at Dehradun (DDN) in the Indo-Gangetic Plain (IGP) and Kavaratti (KVT) at Lakshadweep in southern Arabian Sea during pre-monsoon season (March-May) 2012. The measurements illustrate distinct seasonal impact on aerosol properties with maximum dust loading during May in conjunction with anthropogenic aerosols over DDN and marine aerosols over KVT. Aerosol optical depth (AOD) values have been observed maximum in May (0.72 +/- 0.03) over DDN and in April (0.77 +/- 0.05) over KVT. The high AOD at DDN during May is associated with low alpha and high beta, means higher loading in May is associated with coarse mode aerosols, may be dust loading as evident from SSA and volume size distribution. Similarly, high AOD at KVT during March and April are associated with high alpha and low beta, may be due to anthropogenic influence as evident from BT analysis as well as SSA and volume size distribution. However, influence of marine aerosols is also noticeable over KVT during May as indicated by the lower values of alpha with high turbidity coefficient beta. Comparison between sunphotometer and MODIS AOD observations indicates good statistical agreement with the minimal error.