Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Method to estimate SCA in boreal forest area using Terra/MODIS-data

A method to estimate the real fraction of snow covered area (SCA) using
Terra/MODIS-data is described here. The method is based on a semi-empirical reflectance model, which expresses the reflectance from target area as a function of three reflectance contributors (wet snow, dense coniferous forest and snow-free ground), apparent forest transmissivity and SCA. In addition to MODIS, the method can be adapted to any optical sensor. The method is especially designed to be applied in boreal forest zone. The forest canopy does not hamper the estimation: the apparent transmissivites just have to be estimated using MODIS data under full dry snow conditions.

Dissemination and use potential:
The produced SCAs may be disseminated as numerical files or thematic maps.
At the moment, as the method is operatively applied in Finland, the results are presented related to Finnish natinal coordinate grid, but also other coordinate systems can be used, depending on the application area.

The use potential is high, as the method can be applied to work with any calculation area larger than MODIS pixel (0.5km x 0.5km) and anywhere in boreal forest zone.

Key innovative features:
- The relatively simple reflectance model is easy to apply for any optical sensor
- The method does not need auxiliary land use data except information on water areas (which are very easy to classify using summertime satellite images)
- A novel method where forests are concerned via forest transmissivity, which is calculated using the same kind of satellite data as, is used for the SCA-estimation.

Current status:
The method will be tested using in situ SCA-information at wether stations and snow courses in Finland. Good results are expected, as SCA-estimates produced by applying NOAA/AVHRR-data are proved to be accurate, when validated against those in situ observations.

Use of the method:
The method now used to provide sca to be assimilated with Finnish national hydrological modelling system.When applied outside Finland, hydrologists are able to use the Method to produce SCA-estimates in a way most beneficial for their needs.

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