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In order to understand the regional climate implications of aerosols over Indo-Gangetic Plains (IGP), a major Indo-US field experiment, Ganges Valley Aerosol Experiment (GVAX) was conducted during 2011-12. Atmospheric Radiation Measurement (ARM) mobile facility (AMF) was deployed at the northern Indo-Gangetic Plain over the high-altitude site, Manora Peak, Nainital (29°21'33.84"N, 79°27'29.27"E, 1980 m amsl) in Central Himalayas, for an year-round meas- urement of aerosols, clouds and other climate-relevant atmospheric parameters. One of the objectives of GVAX was examining the ability of models to simulate aerosols over Indian region and validate the simulations. In part-1 of this two-part paper, we examine use of the chemical transport model 'CHIMERE' to simulate aerosol fields over Indian region (4-37.5°N; 67-88.5°E) for multiple years (2006, 2007 and 2008) by simulating the spatial and temporal distribution of PM10, BC mass concentrations and OC/BC ratios. It is seen that the model successfully captures the broad features of the regional distribution of aerosols, including the most conspicuous IGP hotspot and its seasonality. [ABSTRACT FROM AUTHOR]

During a series of measurements, simultaneous measurements were made of spectral aerosol optical depths (AOD), black carbon (BC) mass concentration, total and size segregated composite aerosol mass concentrations at the second campus of Indian Institute of Science (IISc), Challakere, Karnataka. Surprisingly, most of the aerosol mass is found in the submicron size range, which is unusual for a dry region. Unexpectedly large enhancement in BC aerosol concentration was observed during the morning hours (6-8 a.m.), both during summer and winter, which is mysterious and hence requires further study. However, BC mass fraction, which is one of the most important climaterelevant parameters was 3.3% of total aerosol mass, implying a significantly low aerosol-induced absorption of solar radiation and hence consequent atmospheric warming. Based on our initial measurements as well as 11 years of satellite data analysis, we conclude that this location is best suited for establishing a climate observatory. [ABSTRACT FROM AUTHOR]

Atmospheric chemistry is a branch of atmospheric science where major focus is the composition of the Earth's atmosphere. Knowledge of atmospheric composition is essential due to its interaction with (solar and terrestrial) radiation and interactions of atmospheric species (gaseous and particulate matter) with living organisms. Since atmospheric chemistry covers a vast range of topics, in this article the focus is on the chemistry of atmospheric aerosols with special emphasis on the Indian region. I present a review of the current state of knowledge of aerosol chemistry in India and propose future directions. [ABSTRACT FROM AUTHOR]

The RAWEX-GVAX field campaign has been carried out from June 2011 to March 2012 over a high altitude site Manora Peak, Nainital (29.4°N; 79.2°E; 1958 m amsl) in the central Himalayas to assess the impacts of absorbing aerosols on atmospheric thermodynamics and clouds. This paper presents the preliminary results of the observations and data analysis of the Doppler Lidar, installed at Nainital. Strong updrafts with vertical winds in the range of ~2-4 ms-1 occurred during the daytime and throughout the season indicating thermally driven convection. On the other hand during nighttime, weak downdrafts persisted during stable conditions. Plan Position Indicator scan of Doppler Lidar showed north-northwesterly winds in the boundary layer. The mixing layer height, derived from the vertical velocity variance, showed diurnal variations, in the range ~0.7-1 km above ground level during daytime and very shallow during nighttime. [ABSTRACT FROM AUTHOR]