Introduction of data assimilation procedures in the meteorological pre-processor of atmospheric dispersion models used in emergency response systems

Data assimilation (DA) procedures were developed and implemented in the frames of the meteorological pre-processor (MPP) of an emergency response system (ERS) to enable simultaneous use of different meteorological measurements (wind velocity, cloud cover, net radiation, precipitation) with Numerical Weather Prediction (NWP) data. The DA procedures were based on the optimal interpolation algorithm and the method of iterations to optimal solution, combined with methods for scaling the weighting coefficient between fields obtained by the measurements and those obtained by the NWP data. For validation purposes, the calculation by the MPP meteorological fields were compared against measurements performed in two real-scale experiments (ETEX1 and 2). Data from ground-based synoptic weather stations were used for the improvement, through DA procedures, of the first-guess fields obtained from the NWP data, while measurements from surface stations, sonic anemometer and sodar were used for comparison with the results of the MPP. The performance of the two developed DA procedures was evaluated through statistical indices (root mean square and systematic deviation of wind speed and direction) and through graphical representations. Both DA procedures improved the agreement between computed and measured meteorological fields in both examined experiments.