D16    Bias reduction scheme

Responsible partner
Due date

The bias reduction scheme is developed as part of work-package 3100, the purpose of which is:

Comparison of ground-based GPS measurements with forecast models data and with radiosonde data have revealed that the GPS measurements may be affected by systematic errors (error biases). Early data assimilation experiments have indicated that it is necessary to apply bias reduction algorithms in order to avoid detrimental effects of these error biases on, for example, precipitation forecasts. Ideally, these error bias problems should be avoided by applying remedy actions as close as possible to source of the information, e.g. at the GPS station or by improving the pre-processing algorithms. It is foreseen, however, that the need for bias reduction schemes will remain. Statistical comparison between GPS Zenith Total Delay measurements and the operational SMHI HIRLAM model will be carried out for at least one year of data, to include possible seasonal variations, and for data from a network distributed all over Europe, to include possible geographical variations. Data compiled by the GPS data producers within the project will be utilized. Various predictor variables that might explain systematic differences between modelled and measured data will be investigated, for example geographical position, season, time of the day, tropospheric temperature and moisture content. Furthermore, the possibility to use an adaptive bias reduction algorithm based on Kalman filtering will be investigated.

The efficiency of the developed bias reduction scheme will be tested through data assimilation and forecast experiments with and without application of the bias reduction scheme.

The report on the bias reduction scheme can be obtained here: Report_d16_d17.pdf