S. Kumar’s scientific contributions

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 measured 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 accumulation 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 correlation 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.

Identification and mapping of crevasses in glaciated regions is important for safe movement. However, the remote and rugged glacial terrain in the Himalaya poses greater challenges for field data collection. In the present study crevasse signatures were collected from Siachen and Samudra Tapu glaciers in the Indian Himalaya using ground-penetrating radar (GPR). The surveys were conducted using the antennas of 250 MHz frequency in ground mode and 350 MHz in airborne mode. The identified signatures of open and hidden crevasses in GPR profiles collected in ground mode were validated by ground truthing. The crevasse zones and buried boulder areas in a glacier were identified using a combination of airborne GPR profiles and SAR data, and the same have been validated with the high-resolution optical satellite imagery (Cartosat-1) and Survey of India mapsheet. Using multi-sensor data, a crevasse map for Samudra Tapu glacier was prepared. The present methodology can also be used for mapping the crevasse zones in other glaciers in the Himalaya.

The snowpack variability is one of the most widely studied subjects of snow science in recent times. The subject holds importance due to role of variability in decision making about snowpack stability. This study is an attempt to understand the evolution pattern of spatial and temporal variability within snowpack especially with respect to snowpack depth and ram-resistance profile. Under this study detailed observations were made over the snow-covered slopes in Gulmarg region of Indian Himalaya for two consecutive snow seasons (2006-07 and 2007-08). The place may be characterized as one of maritime climate. The observations involve multiple snowpack resistance profiles and stratigraphy over all the four main aspects (north, east, south and west) at different points of time during each season. The analysis of these observations revealed some interesting results. Snowpack depth was found to be reasonably uniform at slope scale for all the slopes.Also all the other slopes, except southerly, were found to resemble with level ground snowpack in terms of snowpack stratification, but absolute resistance values of specific layers and snowpack depth varied considerably. Most importantly, the spatial variability was observed to be increasing or reducing near the snowpack surface only, i.e., once buried, the variability (low or high) persisted until it got exposed again, implying that above-surface meteorological conditions are the main cause of variability. Further, dry layers exhibited low variability compared to moist layers. The study significantly adds to the understanding of the snowpack variability pattern in regions of maritime climate and thus may prove vital in interpreting the stability tests results.

The high Himalayan mountains in the north of India are important sources for generating and maintaining the climate over the entire northern belt of the Indian subcontinent. They also influence extreme weather events, such as the western disturbances over the region during winter. The work presented here describes some current trends in weather and climate over the western Himalaya and suggests some possible explanations in the context of climate change. The work also shows how the special features of Indian orography in the western Himalaya affect climate change in the long term, changing the pattern of precipitation over the region. Data analysis of different ranges of the western Himalaya shows significant variations in temperature and snowfall trends in the past few decades. Possible explanations for the changing climate over the western Himalaya are proposed, in terms of variations in cloudiness. The possible effects of climate change on the number of snowfall days and the occurrences of western disturbances over the western Himalaya are also analysed.