EGU2020-11363
https://doi.org/10.5194/egusphere-egu2020-11363
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Revealing snow cover dynamics in the Hindu Kush Himalaya over the past decades

Kathrin Naegeli1, Carlo Marin2, Valentina Premier2, Gabriele Schwaizer3, Martin Stengel4, Xiaodan Wu1,5, and Stefan Wunderle1
Kathrin Naegeli et al.
  • 1University of Bern, Institut of Geography and Oeschger Center for Climate Change Research, Bern, Switzerland (kathrin.naegeli@giub.unibe.ch)
  • 2Eurac Institute for Earth Observation, Bolzano, Italy
  • 3ENVEO – Environmental Earth Observation IT GmbH, Innsbruck, Austria
  • 4Deutscher Wetterdienst, Offenbach, Germany
  • 5College of Earth and Environmental Sciences, Lanzhou University, China

Knowledge about the snow cover distribution is of high importance for climate studies, weather forecast, hydrological investigations, irrigation or tourism, respectively. The Hindu Kush Himalayan (HKH) region covers almost 3.5 million km2 and extends over eight different countries. The region is known as ‘water tower’ as it contains the largest volume of ice and snow outside of the polar ice sheets and it is the source of Asia’s largest rivers. These rivers provide ecosystem services, the basis for livelihoods and most importantly living water for drinking, irrigation, energy production and industry for two billion people, a fourth of the world’s population, living in the mountains and downstream.

The spatio-temporal variability of snow cover in the HKH is high and studies reported average snow-covered area percentage of 10–18%, with greater variability in winter (21–42%) than in summer (2–4%). However, no study systematically investigated snow cover metrics, such as snow cover area percentage (SCA), snow cover duration (SCD) or snow cover onset (SCOD) and melt-out day (SCMD), for the entire region so far. Here, we thus present unique in-sights of regional and sub-regional snow cover dynamics for the HKH based on almost four decades, an exceptionally long and in view of the climate modelling community valuable timeseries, of satellite data obtained within the ESA CCI+ Snow project.

Our results are based on Advanced Very High Resolution Radiometer (AVHRR) data, collected onboard the polar orbiting satellites NOAA-7 to -19, providing daily, global imagery at a spatial resolution of 5 km. Calibrated and geocoded reflectance data and a consistent cloud mask pre-processed and provided by the ESA Cloud_cci project as global 0.05° composites are used. The retrieval of snow extent considers the high reflectance of snow in the visible spectra and the low reflectance values in the short-wave infrared expressed in the Normalized Difference Snow Index (NDSI). Additional thresholds related to topography and land cover are included to derive the fractional snow cover of every pixel. A temporal gap-filling was applied to mitigate the influence of clouds. Reference snow maps from high-resolution optical satellite data as well as in-situ station data were used to validate the time series.

How to cite: Naegeli, K., Marin, C., Premier, V., Schwaizer, G., Stengel, M., Wu, X., and Wunderle, S.: Revealing snow cover dynamics in the Hindu Kush Himalaya over the past decades, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11363, https://doi.org/10.5194/egusphere-egu2020-11363, 2020

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Presentation version 1 – uploaded on 30 Apr 2020
  • AC1: Very brief summary, Kathrin Naegeli, 04 May 2020

    This contribution highlights the high value and potential of a global snow cover FCDR produced in the frame of the ESA CCI+ Snow project and based on AVHRR GAC data.