The study computes degree-day factor for snow and ice over the Dokriani glacier (4000 m altitude) in Garhwal Himalayas. The effect of natural dusting on degree-day factor is also examined. Information on the degree-day factor for snow and ice is required for the estimation of snow and ice melt runoff from a glacierized basin.
As a part of the study, natural dust available at the experiment site was uniformly spread over the surface of snow and ice blocks to form a 2 mm thick layer. Observations were taken of the melt runoff from the snow and ice blocks as also of the air temperature at 2m above the surface. The mean degree-day factor for clean and dusted snow blocks were computed as 5.75 and 6.41 mm oC-1d-1, respectively, whereas for clean and dusted ice the values were 7.33 and 7.97 mm oC-1d-1, respectively.
The mean daily melt factors for dusted snow and dusted ice are found to be higher than the corresponding dust free snow and ice blocks. A sharp rise and fall has been observed in the hourly melt runoff from the ice blocks and consequently, in the hourly melt factor of ice melt.
The average maximum hourly value of melt factor for the clean and dusted snow blocks were computed to be 0.706 and 0.871 mm oC-1hr-1, respectively, while the minimum value was zero in all the cases. In case of ice, the average maximum hourly ice melt factor was observed to be 0.919 and 1.057, respectively. The maximum hourly value ice melt factor occurred at about 12 hours for both the blocks. A comparison of degree-day factors for snow and ice is made with the existing information from literature.
No significant change in degree-day factors in snow and ice, with dust or without dust, was found when average temperature of the day was used as a mean of daily maximum and minimum temperatures, instead of values of average of 24 hours. This confirms that the average temperature of the day computed as mean of maximum and minimum temperatures is a good approach for snow melt and glacier melt runoff calculations when hourly data are not available.
The approach should be extended to study seasonal variation in degree-day factors under different conditions in the Himalayan region.
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