Ablation of Avalanched and Undisturbed Snow, Himalaya Mountains, Pakistan

Avalanche deposits represent a significant storage of winter snow on the south slope of the Himalaya Mountains, Pakistan, complicating the annual snowmelt cycle because of the differences in ablation of avalanche‐transported snow and undisturbed snow. Measurements show very high rates of melting of both snow types, particularly of avalanche snow late in the melt season. The high rates are a function of the low latitude of the study area and the low elevation of the avalanche snow deposits, as well as heat release by condensation. Air temperature was closely Correlated with daily snowmelt and appears to hold promise as a predictor, however, data constraints prevent an energy balance analysis of this relationship. Gravimetric measurements show that condensation is important in the snow surface energy exchange and can represent a significant source of energy for snowmelt. Rainfall during warm conditions also makes a more significant contribution to snowmelt than shown in previous studies. The derived temperature‐based melt factors or coefficients compare well with published figures from other mountain areas, but their confidence limits are sufficiently wide to produce significant errors in the prediction of basin snowmelt runoff.