Modified Temperature Index Method Using Near-Surface Soil and Air Temperatures for Modeling Snowmelt in the Canadian Prairies

Abstract

A modified temperature index snowmelt model (SDSM-MTI), based on both near-surface soil temperature ( Tg ) and air temperature ( Ta ) , was proposed and successfully tested at the Paddle River Basin (PRB) of Alberta. By using a weighted average of Tg and Ta and introducing a melt-rate adjustment factor Mrf , SDSM-MTI could simulate more accurate snowmelt runoff, snow water equivalent, and snow depth at PRB than the standard temperature index approach operated either under fixed or seasonally variable melt factor ( Mr ) independently calibrated with Ta only. This is partly because at PRB the primary energy fluxes responsible for snowmelt correlate more closely with Tg than Ta , especially at a daily time step, and partly because when Tg<0°C , Mrf of SDSM-MTI is much less than one that reduces Mr to a very small value, and hence we can more effectively control the timing of major snowmelt for PRB, which usually happens only when Tg⩾0°C .