Snow-cover variability in central Asia between 2000 and 2011 derived from improved MODIS daily snow-cover products

Abstract

In this study, the daily snow-cover time series has been analysed for the whole of central Asia after cloud coverage was removed. Snow-cover duration (SCD), snow-cover start (SCS), and snow-cover melt (SCM) have been derived for each hydrological year from 2000/2001 to 2010/2011 and mean conditions were extracted that identify a distinct north–south gradient of these parameters. The snow-cover index (SCI), which depicts a moderate variability with maximum deviations of ∼20%, has been included for major hydrological catchments. The hydrological year 2001/2002 stands out due to minimum SCD caused by late SCS and early SCM while 2002/2003 constitutes maximum SCD initiated by late SCM. Although the time series of 11 years of data is too short to calculate possible trends of snow-cover characteristics, the results can be used to describe the average snow-cover conditions and compare single years against these values. Large divergences can indicate deficits or excesses of snow, which may lead to abnormal run-off situations, including natural disasters such as floods, landslides, or droughts. The latter, especially, can have severe negative economic impacts in a region.

Acknowledgements

This study was funded by the German Federal Foreign Office in the context of the Central Asian Water (CAWa) Project (http://www.cawa-project.net/). MODIS snow-cover data were provided by the NSIDC, Boulder, Colorado, USA, from their web site at nsidc.org/. Landsat 7 data were provided by the US Geological Survey (http://landsat.usgs.gov/index.php). SRTM data were provided by CGIAR-CSI SRTM 90 m Database (http://www.cgiar-csi.org/).