Snowline Altitude 8. A critical task in determining these eight variables is the lapse-rate of the temperature observed at the valley stations, to the glacier, which for South Cascade Glacier is at an altitude 1300 meters higher than the temperature station. Two coefficients determine the intercepts of the lines that relate lapse-rate to temperature range, and two coefficients are the slopes of these lines. Accumulation Snow accumulation at each altitude interval is determined by calculated precipitation and temperature. Beginning on October 1, snowfall is cumulated at each altitude interval until the following September 30.
Rain is assumed to occur as direct runoff.
Ablation Four coefficients are required to calculate snow and ice ablation. Both the mean daily temperature and the diurnal temperature range are used in these algorithms. For only ice ablation, a short wave, radiative ablation factor is calculated from the diurnal temperature range, which is a rough measure of cloudiness, or solar radiation. Total ablation is the sum of these two components. Each altitude interval is treated as a separate entity and its mass balance is independently calculated.