Changes in Andes Mountains Snow Cover from MODIS Data 2000-2014

The Andes Mountains in South America span a length of 7,000 km, and many parts of the mountain range develop a snowpack that is important for sustaining regional water supplies. Changes in snow cover in the Andes Mountains have not been studied in detail due to sparse and unevenly distributed climate data. We calculate the snow persistence (SP) as the fraction of time with snow cover for each year between 2000-2014 from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensors, which provide 500m, 8-day maximum snow cover extent. We ran Mann-Kendall trend analyses to identify areas of decrease, increase, or no change in SP over the study time period and evaluated whether these trends related to temperature and precipitation obtained from University of Delaware dataset. In the northern part of the study region, limited snow cover is present, and few trends in snow persistence were detected. A large area (70,515 km2) between 29-36°S is affected by a significant loss of snow cover (2-5 day less day of snow per year). In this latitude range, most of the land surface area with snow loss (62%) is on the east side of the Andes. This loss of snow correlates with both declining precipitation and increasing temperature over the study time period in this latitude range. The relative importance of each of these climate variables changes across elevation and latitude. Precipitation has greater relative importance at lower elevations, whereas temperature has greater relative importance at higher elevations.