Title: Discernable role of dust in the spatial heterogeneity of observed snowmelt over Himalayas.
Chandan Sarangi is an Assistant Professor at the Department of Civil Engineering, IIT Madras, Chennai, Tamil Nadu, India. He completed his Post Doctorate Research from the Pacific Northwest National Laboratory (PNNL), Richland, WA, USA, and has extensive experience as a Construction Engineer. His research interests are; Aerosol-cloud-climate interactions; Impact of climate change on Cloud systems and rainfall; Impact of aerosols on Evapotranspiration and land-atmosphere interactions; Effect of dust deposition on snow darkening and Himalayan glaciers; Urban heat island effect and air quality over megacities; Extreme rainfall and coupling with aerosols and urbanization, and Cloud seeding research.
High-mountain Asia (HMA) is commonly known as the third pole of Earth, however, the snow cover and glacier mass is reducing at an unprecedented rate in recent decades. While climate change has been believed to be the primary reason for these reducing trends, light-absorbing particles (LAPs), mainly dust and black carbon, can also significantly impact the heterogeneity in snowmelt and regional water availability within HMA. In this talk, I will discuss the significance of dust deposition on snow albedo reduction and snowmelt over Himalayas. Westerly-driven, long-range transportation of dust particles via elevated aerosol layers (EALs) is a persistent phenomenon during spring and summer over the Indian subcontinent. During the snow accumulation season EALs transport ~100-1000 µg/m3 of dust to the snow-covered slopes Himalayas. Using unique satellite estimates of snow albedo changes due to these impurities, I will demonstrate a robust physical association between the EALs and aerosol-induced snow darkening over Himalayas. Further, results from fully coupled chemistry Weather Research and Forecasting (WRF-Chem) regional model simulations will also be discussed to reinforce the satellite observations. Results reveal that LAPs can induce high magnitudes of snow albedo reduction (4 %–8 %) in pre-monsoon seasons, which eventually leads to a snow-mediated radiative forcing of ∼ 30–50 W m-2 at the surface. Consequently, the western Himalayas hold the most vulnerable glaciers and mountain snowpack to LAP impacts within HMA. More interestingly, a distinct elevational signature is found in dust- and black carbon-induced snow darkening over Himalayas in both observations and simulations. Specifically, the influence of dust on snow darkening is greater than that of black carbon above 4000 m. Thus, these findings suggest a discernable role of dust in the spatial heterogeneity of observed snowmelt and snowline trends over HMA and implicate an increasing contribution of dust to snowmelt as the snow line rises under future warming.