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ICDC
CENIntegrated Climate Data Center ICDC

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Snow water equivalent from ESA GlobSnow

Sample maps of SWE on the northern hemisphere from the ESA-GlobSnow project for winter 2010/2011Sample maps of SWE on the northern hemisphere from the ESA-GlobSnow project for winter 2010/2011
Sample maps of SWE on the northern hemisphere from the ESA-GlobSnow project for winter 2010/2011. Copyright: UHH/CEN/S. Kern

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Access

RESTRICTED: This link to the data set is only available for a restricted user group.  The data set is only accessible in CEN/MPI net or accessible from external nets with a customer account.  Please contact ICDC if you would like to access this data from outside the network.

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Description

Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave/Imager (SSM/I), and Advanced Microwave Scanning Radiometer aboard EOS (AMSR-E) data have been used to produce a data set of the snow water equivalent (SWE) gridded onto a Lambert-Azimuthal Equal Area grid with 25 km grid resolution. For each grid cell, the data set includes daily and monthly values of SWE.

First, using an empirical relationship between brightness temperatures and snow properties wet / melting snow areas are masked out.  Next, snow depth is obtained from brightness temperatures for grid cells co-located with weather station data using an emission model. This model uses the snow grain size as a scalable input parameter which is chosen such that the difference between observed and computed snow depth becomes minimal. The set of grain sizes obtained together with the snow depth is used to construct a kriging interpolated distribution of  the effective snow grain size which is subsequently used in the emission model inversion to obtain the snow depth distribution. Observed snow density values are finally used to convert snow depth into SWE. More details about the used approach can be found in the references in the Product User Guide (note: this guide is for version 2.0, we didn't reveice the one for version 3.0 yet).

Please also read the data quality section further below.

We are offering daily and monthly average data. For months February through May also a bias-corrected version is available.

The main product terminates 2018-12-31. A near-real-time (NRT) product with daily temporal resolution exists. We offer this product beginning in 2018-01-01 with one year overlap to the quality controlled CDR.

This is version 3.0 / and its NRT extension of the product.

Last update of data set at ICDC: September 12, 2024.

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Parameters

Parameters of the  monthly and daily SWE data sets
NameUnit
SWE mm

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Coverage, spatial and temporal resolution

Period and temporal resolution:

  • Typically for October through May, sometimes longer
  • 1979-01-01 to 2018-05-31 (Daily)
  • 1979-01 to 2018-05 (Monthly)
  • NRT-product: 2018-01-01 to 2024-07-31 (Daily only)

Coverage and spatial resolution:

  • Northern Hemisphere
  • Spatial resolution: 25 km x 25 km, EASE-Grid
  • Geographic latitude: 35°N to 85°N
  • Geographic longitude: 180°W to 180°E
  • Dimension: 721 columns x 721 rows
  • Altitude: following terrain, mountains are excluded

Format:

  • NetCDF

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Data quality

The data set does not contain information about the uncertainty. Users should be aware of a number of error sources; the approach itself (cannot be adapted to local snow property changes as e.g. a high fraction of depth hoar) as well as the coarse spatial resolution (grid resolution is 25 km) can cause further uncertainties if not even a bias. In particular SWE values above about 200 to 250 mm are underestimated.

Furthermore, problems arise in forested areas and mountains, in regions covered with many lakes and in areas with highly varying snow properties (dry <--> wet) or a high fraction of depth hoar relative to the total snow depth.

The retrieval approach of version 3.0 is similar to version 2.0, but with an updated snow emission model (new version of the HUT snow emission model in the SWE retrieval), updated forest canopy consideration and forest aux-data layer, and updated synoptic snow depth input data used in the retrieval (added observations and homogenized through the long term time-series).

Note, that in the data set offered here

  • Years 1978-1989 have substantially more data gaps and sometimes dubious SWE distributions particularly in Europe.
  • The used kriging interpolation regionally also causes artifacts. A visual inspection of the data for the respective region of interest is recommended.

More details about the data quality and about where and under which circumstances a SWE underestimation can occur can be found in the product user guide and in the scientific articles listed in the references section.

The nrt product is not as quality controlled as the CDR ending in 2018. It exhibits more missing dates but includes months June through September.

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Contact

Stefan Kern
University of Hamburg
E-Mail: stefan.kern (at) uni-hamburg.de

Kari Luojus
Finish Meteorological Institute (FMI)
Helsinki
Finland
email: kari.luojus (at) fmi.fi

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References

Literature:

Websites:

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Data citation

Please cite the data as follows:

Takala, M., Luojus, K., Pulliainen, J., Derksen, C., Lemmetyinen, J., Kärnä, J.-P., Koskinen, J. and Bojkov, B., Estimating northern hemisphere snow water equivalent for climate research through assimilation of space-borne radiometer data and ground-based measurements, Remote Sensing of Environment, 115(12), 3517-3529, 2011, http://doi.org/10.1016/j.rse.2011.08.014 

Pulliainen, J., Luojus, K., Derksen, C., Mudryk, L., Lemmetyinen, J., Salminen, M., Ikonen, J., Takala, M., Cohen, J., Smolander, T., and Norberg, J.: Patterns and trends of Northern Hemisphere snow mass from 1980 to 2018. Nature, 581(7808), 294-298, 2020, https://doi.org/10.1038/s41586-020-2258-0

Luojus, K., Pulliainen, J., Takala, M., Lemmetyinen, J., and Moisander, M.: GlobSnow v3.0 snow water equivalent (SWE). PANGAEA, 2020, https://doi.org/10.1594/PANGAEA.911944, last access: September 14, 2021.

or for the NRT product:

Takala, M., Luojus, K., Pulliainen, J., Derksen, C., Lemmetyinen, J., Kärnä, J.-P., Koskinen, J. and Bojkov, B., Estimating northern hemisphere snow water equivalent for climate research through assimilation of space-borne radiometer data and ground-based measurements, Remote Sensing of Environment, 115(12), 3517-3529, 2011, http://doi.org/10.1016/j.rse.2011.08.014

GlobSnow v3.0 NearRealTime (NRT) obtained from https://www.globsnow.info/swe(nrt/ [last access date: August 30, 2024]

and with the following acknowledgments:

Thanks to ICDC, CEN, University of Hamburg for data support.

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