RESEARCH ARTICLES CURRENT SCIENCE, VOL. 112, NO. 6, 25 MARCH 2017 1208 *For correspondence. (e-mail: kamal.kant@sase.drdo.in) Estimation of snow accumulation on Samudra Tapu glacier, Western Himalaya using airborne ground penetrating radar K. K. Singh 1, *, H. S. Negi 1 , A. Kumar 2 , A. V. Kulkarni 3 , S. K. Dewali 1 , P. Datt 1 , A. Ganju 1 and S. Kumar 1 1 Snow and Avalanche Study Establishment, Chandigarh 160 036, India 2 National Institute of Technology, Kurukshetra 136 119, India 3 Divecha Centre for Climate Change, Indian Institute of Science, Bengaluru 560 012, India In this study an airborne ground penetrating radar (GPR) is used to estimate spatial distribution of snow accumulation in the Samudra Tapu glacier (the Great Himalayan Range), Western Himalaya, India. An impulse radar system with 350 MHz antenna was mounted on a helicopter for the estimation of snow depth. The dielectric properties of snow were meas- ured at a representative site (Patseo Observatory) using a snow fork to calibrate GPR data. The snow depths estimated from GPR signal were found to be in good agreement with those measured on ground with an absolute error of 0.04 m. The GPR survey was conducted over Samudra Tapu glacier in March 2009 and 2010. A kriging-based geostatistical interpolation method was used to generate a spatial snow accumula- tion map of the glacier with the GPR-collected data. The average accumulated snow depth and snow water equivalent (SWE) for a part of the glacier were found to be 2.23 m and 0.624 m for 2009 and 2.06 m and 0.496 m for 2010 respectively. Further, the snow accumulation data were analysed with various topo- graphical parameters such as altitude, aspect and slope. The accumulated snow depth showed good cor- relation with altitude, having correlation coefficient varying between 0.57 and 0.84 for different parts of the glacier. Higher snow accumulation was observed in the north- and east-facing regions, and decrease in snow accumulation was found with an increase in the slope of the glacier. Thus, in this study we generate snow accumulation/SWE information using airborne GPR in the Himalayan terrain. Keywords: Glacier, ground penetrating radar, snow accumulation, snow water equivalent. IN the Himalaya snow and glaciers cover a large geo- graphical area and influence climate and environment of the region. Recent studies carried out using satellite images suggest approximately 40,800 sq. km area is cov- ered by glaciers in the Great Himalaya and Karakoram mountain ranges 1 . These glaciers are a perennial and vital source of freshwater to the countries around the Himalayan chain. In recent years, glaciers and seasonal snow cover in this region have been significantly influ- enced by climate change 2–7 ; therefore, it is useful to mon- itor the spatial and temporal changes of snow thickness. Estimation of snow thickness using field-based methods such as snow stakes, automatic sensors, etc. provides mostly point-specific information. However, ground penetrating radar (GPR), a non-destructive technique, can be used to collect both point as well as spatial distribution of snow thickness. It has been widely used in ground mode, for snow and ice thickness measurements 8–15 , snowpack stratigraphic delineation 16 and to study the subsurface properties of other strata 17 . Forte et al. 18,19 reported the applications of GPR data in determining the density and electromagnetic (EM) wave velocity for snow, firn and ice. Colucci et al. 20 used GPR profiles in combination with LiDAR data to calculate the volumetric and mass variations in the body of the ice. Apart from ground mode, GPR survey has also been conducted using air- borne mode. Machguth et al. 21 and Sold et al. 22 used heli- copter-borne GPR on alpine glaciers to study the spatial variability of snow accumulation and compared the re- sults with ground observations. Conway et al. 23 detected the bed topography of a temperate glacier using airborne GPR with a 2 MHz antenna. Recently, the airborne GPR has been used to obtain different cryospheric information (ice depth, snow layer, snow erosion due to wind, etc.) of the Antarctic region 24–26 . In the Himalaya, GPR has been mostly used in ground mode to estimate ice/glacier depth and detection of cre- vasses in different glaciers 27–30 . The ground-based GPR systems are difficult to operate in the rugged glaciated terrain of the Himalaya 31 . In addition, a large number of buried/hidden crevasses and hostile weather conditions pose limitations on ground-based field surveys. To over- come the above constraints, an airborne GPR technique was used by Negi et al. 32 , which was suitable for snow depth estimation and detection of buried objects. The snow depth information from the Himalayan gla- ciers is limited, though it is important for glacier health studies. Therefore, the present study is aimed at estimating