Abstract ID: 3.12859 | Accepted as Talk | Talk | TBA | TBA

Snow darkening by deposited light-absorbing particles (LAP) has the potential to accelerate snowmelt, affecting the timing and magnitude of snowmelt. The sensitivity of the seasonal snow cover duration to changes in LAP at a high-altitude valley site in the Central Himalayas, India, is here investigated. An approach included a first step of mimicking the variation of the albedo of the seasonal snow using two seasons of automatic weather station (AWS) data and adapting a field-based deposition of LAP to the snow. Secondly, the number of days with snowmelt were evaluated based on the net energy budget of the seasonal snow cover and the derived surface temperature. The influence on the energy budget by LAP combined with the melt-day analysis resulted in relations to determine the contribution of LAP to the number of days with snowmelt. Above a concentration of 1 ng g-1 in equivalent LAP (LAPeq) , in new snow, the number of days with snowmelt can be estimated by; days=0.0109(log⁡(〖LAP〗_eq )+1)PP±0.0033(log⁡(〖LAP〗_eq )+1)PP, where PP is the seasonal precipitation in mm snow water equivalent. A change in LAPeq by a factor of two corresponds to about 1/3 of a day per 100 mm precipitation. Although the change in the number of days with melt caused by the changes in LAPeq is small, the estimated total change in the snow melt-out date by LAP can be significant. For our realistic base case scenario for the Sunderdhunga Valley, Central Himalayas, India, of LAPeq=100 ng g-1 and PP=400 mm, this yields in an advancement of the melt-out date of about 13 days.