This app shows the snow cover duration anomaly of the current snow season in comparison with the average snow cover duration over the same period of the year between 2000-2021. The snow cover is obtained from Nasa’s Terra/MODIS satellite observations. The app is automatically updated when new observations are available. Click here to view in full screen.
New: we provide here an experimental application which shows the current snow cover area in comparison with a 30-year climatology that was generated by machine learning from the UERRA reanalysis (documentation under preparation). The plots will appear below after a 1 minute load time. You can select the entire Alps or a river basin subregion.
- The daily NDSI is extracted from the MOD10A1.006 collection (~500 m spatial resolution). Missing values are filled using a linear interpolation in the time dimension .
- The resulting series of daily gap-free NDSI is converted to a series of binary snow maps (snow / no-snow) using the threshold NDSI>0.2.
- The snow duration is the sum of the snow maps along the time axis.
- The snow maps over 2000-2021 were pre-computed and stored as an asset to reduce the app loading time (but it’s still slow).
 Although more sophisticated algorithms exist to fill gaps in MODIS snow cover maps, the linear interpolation in the time dimension is a good trade-off between efficiency and accuracy (Gascoin et al. 2015).