With the successful installation and commissioning of aerosol observations from Mt Saraswati (32.78° N, 78.95° E, 4520 m amsl), Hanle in the trans-Himalayas, on 09 Aug 2009, in collaboration with the scientists/engineers from the Indian Institute of Astrophysics, ARFI attained another distinction of being the first and only atmospheric observatory in India, having regular aerosol measurements from the highest location. First ever continuous measurements of aerosol black carbon and number size distribution of ultra-fine, fine and accumulation mode aerosols from this free tropospheric Himalayan location have shown new particle formation (apparently driven by photochemistry) with a strong solar control on the processes: first step to aerosol life cycle. The highest values of BC over Hanle during spring highlighted the influence of the advection from West and Southwest Asia. The columnar AOD depicts very low values with a mean of ~ 0.08 ± 0.03 at 500 nm. The vertical profiles of extinction coefficients, from CALIPSO, indicate the presence of elevated aerosol layers attributed mainly to the influence of long range transport of aerosols from the west Asian and Indian desert region.
Thus it is of paramount interest to quantify the spatio-temporal heterogeneities of aerosols over the Himalayan region. Besides this, the free tropospheric sites would be indicative of the background level and are useful for the study of background atmospheric aerosols. Thus, in view of the importance of the aerosol studies in the free-tropospheric Himalayas and in view of its significance to regional and global climate, the observation from another high-altitude site 'Himansh' in the Lahaul and Spiti valley, located close to major glaciers in the western part of Himalayas, provided valuable information on the characteristics of aerosols. As the observational site Himansh is remotely located with no anthropogenic activities and is elevated at an altitude of 4080 m a.s.l, almost similar altitude of free troposphere over plains, the site represents a background free-tropospheric region.
In addition to the above, series of aerosol measurments from the the chain of ARFINET observatories across across the complex terrain of Himalayas, popularly known as the ‘Third Pole’, is made for understanding spatio-temporal variability of aerosol mass loadings, their seasonal behavior, sources, possible transport pathways and effects on snow pack energy budgets and climate over distinct mountainous and foothill regions, extending from the west to the east.
Deposition of absorbing aerosols (mainly BC and dust) on highly reflecting surfaces (like snow or ice) could reduce the surface albedo by absorbing more sunlight, which may exacerbate warming and glacier/ snow melting. Extensive field campaigns were carried out to understand the Black Carbon properties over the Himalayan and Polar (Arctic and Antarctic) regions and its implications on snow melting.
Recent field campaigns to the glaciers and long-term measurements from high altitude stations are used to understand the BC induced snow albedo forcing over southern slopes of Himalayas. Following a synthesis of measurements from the Himalayan ARFINET stations with those during a scouting experiment to a glacier, and models of snow and ice, coupled with radiative transfer schemes, this study highlighted the overwhelming role of snow-albdedo forcing over direct forcing; the effect being higher for aged snow than for fresh snow. This has revealed a complex dependence of absorbing aerosols in the snow, the snow microphysics and other processes in determining the impact - the first major step towards understanding the aerosol-cryosphere interactions.
Few chain of observatories have been identified over the Himalayas to make extensive investigations on aerosol-cryosphere interaction processes using in-situ data collected through field experiments.