Articles | Volume 9, issue 5
The Cryosphere, 9, 1879–1893, 2015

Special issue: Interactions between climate change and the Cryosphere: SVALI,...

The Cryosphere, 9, 1879–1893, 2015

Research article 24 Sep 2015

Research article | 24 Sep 2015

Satellite observations of changes in snow-covered land surface albedo during spring in the Northern Hemisphere

K. Atlaskina1, F. Berninger2, and G. de Leeuw1,3 K. Atlaskina et al.
  • 1Department of Physics, University of Helsinki, Helsinki, Finland
  • 2Department of Forest Sciences, University of Helsinki, Helsinki, Finland
  • 3Finnish Meteorological Institute, Helsinki, Finland

Abstract. Thirteen years of Moderate Resolution Imaging Spectroradiometer (MODIS) surface albedo data for the Northern Hemisphere during the spring months (March–May) were analyzed to determine temporal and spatial changes over snow-covered land surfaces. Tendencies in land surface albedo change north of 50° N were analyzed using data on snow cover fraction, air temperature, vegetation index and precipitation. To this end, the study domain was divided into six smaller areas, based on their geographical position and climate similarity. Strong differences were observed between these areas. As expected, snow cover fraction (SCF) has a strong influence on the albedo in the study area and can explain 56 % of variation of albedo in March, 76 % in April and 92 % in May. Therefore the effects of other parameters were investigated only for areas with 100 % SCF. The second largest driver for snow-covered land surface albedo changes is the air temperature when it exceeds a value between −15 and −10 °C, depending on the region. At monthly mean air temperatures below this value no albedo changes are observed. The Enhanced Vegetation Index (EVI) and precipitation amount and frequency were independently examined as possible candidates to explain observed changes in albedo for areas with 100 % SCF. Amount and frequency of precipitation were identified to influence the albedo over some areas in Eurasia and North America, but no clear effects were observed in other areas. EVI is positively correlated with albedo in Chukotka Peninsula and negatively in eastern Siberia. For other regions the spatial variability of the correlation fields is too high to reach any conclusions.

Short summary
Snow cover explained most of the spring surface albedo changes in the Northern Hemisphere in the years 2000−2012. However, there are vast areas where albedo changed up to ±0.2 under full snow-covered conditions. We found that if in these areas, the mean monthly air temperature exceeds a value between -15°C and -10°C, depending on the region, albedo decreases with an increase of the temperature. The complexity of processes involved in surface albedo changes is discussed.