Measuring near-surface snow temperatures changes over terrain

ABSTRACT: The energy balance at the snow surface results in substantial diurnal temperature fluctuations within the top portion of the snowpack. These temperature fluctuations, which vary both spatially and over time, can have important effects on stability. During the winters of 2005 and 2006, field data for a near-surface warming study were collected on a treeline knoll located in the Columbia Mountains of British Columbia. Thermocouple arrays placed on the top and at different locations on the knoll side slopes recorded temperatures within the top 30 cm of the snowpack. During each test period, nearby measurements of incoming short and long wave radiation were collected, as were periodic observations of cloud cover, air temperature and the snow surface temperature at each array. The study aims to use field data to identify when, and to what extent, near-surface warming occurs on different aspects. Instrumentation challenges encountered in accurately measuring near-surface snow temperatures are also presented. Preliminary analysis of the data shows a significant correlation between aspect and the maximum daytime increase in near-surface snow temperatures. In one experiment, the magnitude of daytime warming measured at 10 cm depth was almost 7 ºC greater on the south aspect than the north aspect. The aspect dependent differences in daily temperature change decreased with increased cloud cover