Targeting Optimal Use of GPS Humidity Measurements in Meteorology


The TOUGH project is now finished. It has been a succesful project. The main results from TOUGH are now being utilised in the systems for operational use of near real time ground based GPS data in meteorology that are emerging. Both when it comes to establishing a GPS delay observing system (see E-GVAP) and regarding use of GPS delays in numerical weather prediction. To study in various degrees of detail the results from TOUGH follow the links under "Results" en the left-hand column.


    Knowledge of the atmospheric distribution of water vapour is of key importance in weather prediction and climate research. It is tightly coupled to processes like energy transfer, precipitation, and is an important greenhouse gas. However, currently there is lack of knowledge about the actual humidity field, both due to a shortage of observations and a sub-optimal handling of humidity in the data assimilation systems, which are used to make estimates of the actual atmospheric field. Such fields are used to start numerical weather prediction and for climate monitoring. Global Positioning System (GPS) signals are particularly sensitive to water vapour. In the TOUGH project we have developed and refined methods enabling optimal use of GPS data from existing European GPS stations in numerical weather prediction models, and assessed the impact of such data upon the skill of weather forecasts.

  • TOUGH was an interdiciplinary project between 15 institutes with expertise in the GPS system and meteorological institutes, coordinted by the Danish Meteorological Institute (DMI). It ran from February 2003 to January 2006

  • TOUGH is a shared-cost project (contract EVG1-CT-2002-00080) co-funded by the Research DG of the European Commission within the RTD activities of the Environment and Sustainable Development sub-programme (5'th Framework Programme).

  • TOUGH is open to collaboration with other institutes working in the field. An important part of the project is to make other potential users of ground based GPS atmospheric products aware of this type of observations.

  • For further information, please, utilise the links on the TOUGH homepage or contact the TOUGH team at

  • Example
    These figures shows a case with significant improvement of a forecast when ground based GPS observations are included among the observations specifying the field from which the computer calculates the exptected future weather. To the left is the observed rain over a 12 hour period. Below are the predicted amounts over the same period. Green, yellow, red, and violet colors indicate severe large amounts of rain, with violet being the highest.

    Observed rain

    Forecast rain with GPS

    Forecast rain without GPS