Recent Observing System Experiments on the impact of ERS scatterometer wind data on numerical weather simulations of cold surge

This study examines the impact of scatterometer wind data from the ERS satellite on the performance of a numerical weather prediction (NWP) model in simulating the planetary-scale characteristics of cold surge during the northern winter. A comprehensive set of Observing System Experiments (OSEs) were carried out using the Meteorological Service Singapore's (MSS) data assimilation and forecasting system. The period chosen for the OSEs was during a cold surge which occurred from 13 Nov 1995 to 23 Nov 1995. Two experiments, with ten day forecasts from 00 UTC, were carried out every day for this period: (1) control experiment, which uses both the conventional weather observations and the ERS scatterometer wind data, and (2) without ERS data experiment, which uses only the conventional weather observations. The comparison of the results from these experiments allows the authors to assess the impact of ERS scatterometer wind data on the data assimilation and forecasting system of MSS in simulating the characteristics of cold surge. Overall, the impacts on the performance of the NWP model in simulating the planetary-scale characteristics of cold surges are neutral albeit an observed small positive impact on the lower and upper level forecast wind fields during the developing stage of the surge. The authors' expect the impact of the scatterometer wind data in numerical forecasts to be more significant from the improvement in the wind scatterometer model, the assimilation method and the resolution of the NWP model.