Aerosols characteristics, trends and their climatic implications over Northeast India and adjoining South Asia

Aerosol characteristics and climatic implications derived for selected locations of the north‐eastern region of India and adjoining locations Thimphu (THM), Dhaka (DAC) and Banmauk between 22–30°N and 88–98°E are reported. The region is found to reveal a distinct spatio‐temporal variability in aerosol distribution, with highest climatological mean aerosol optical depth at 550 nm (AOD 550 ) at DAC (0.65 ± 0.07) and lowest at the high altitude location THM (0.19 ± 0.02). Seasonally the maximum AOD 550 is observed in the pre‐monsoon season. Moderate resolution imaging spectroradiometer Level‐3 Collection 6 AOD 550 and Ångström exponent (AE) exhibit a significant and simultaneous increasing trend in the range of ∼0.003 year −1 to 0.012 year −1 and ∼−0.001 year −1 to 0.020 year −1 , respectively, during the period 2001–2014. Together with AE, increasing trend of total ozone mapping spectrometer and ozone monitoring instrument‐retrieved aerosol index (∼0.001 year −1 to 0.007 year −1 during 1979–2014) signifies an increase in anthropogenic aerosol loading, leading to an increase in number density of cloud condensation nuclei and decrease/increase of cloud effective radius /cloud optical depth (COD). This is further associated with overall decreasing trends of rainfall rate over this complex monsoon region. A slow increase in maximum temperature ( T max ) (∼0.008 °C year −1 to 0.049 °C year −1 ) compared to that in minimum temperature ( T min ) (∼0.007 °C year −1 to 0.068 °C year −1 ) is attributed to solar dimming due to increasing aerosol loading and COD (∼0.056 year −1 to 0.15 year −1 ). A decrease in high‐level cloud (COD high ) counteracts decreasing trends of ground reaching solar radiation over a few locations, including Dibrugarh. This study is important from an aerosol radiation interaction and aerosol cloud interaction viewpoint, which facilitates in reaching a closure of model simulated present day climate change and future climate projections.