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Study Uses WRF Model to Analyze Extreme Weather Event and Enhance Precipitation Predictions

Changes in rainfall patterns directly impact hydrological processes in general and the timing and magnitude of floods in particular. Therefore, it is necessary to have accurate predictions of precipitation timings and amounts, along with their impact on resulting runoff to produce reliable flash flood guidance.

Prof. Volker Wulfmeyer, a First Cycle Awardee of the UAE Rain Enhancement Program (UAEREP) and Managing Director and Chair of Physics and Meteorology at the Institute of Physics and Meteorology of the University of Hohenheim in Stuttgart, co-led a study that investigated an extreme weather event that impacted the UAE in March 2016, and produced thunderstorms, strong winds, large hail, and severe flooding caused by a low pressure system that passed from the UAE and Oman to southeastern Iran. The study used the Weather Research and Forecasting model coupled with its hydrological modeling extension package (WRF-Hydro).

The weather event was simulated from both standalone WRF and fully coupled WRF-Hydro model configurations and compared to station observations and high-resolution satellite products. The main objective of the study was to investigate the added value of coupled land surface–atmospheric modeling for precipitation forecasts over the hyper-arid environment of the UAE, as a limited number of studies utilizing the WRF model focused on areas in the Middle East region, and employed current modeling tools to aid in operational forecasting efforts in the region.

Using ground and satellite observations over the UAE to validate the model results, the study expanded the ongoing research efforts addressing the prediction of extreme hydrometeorological events in arid regions and investigated the potential of coupling atmospheric and hydrological processes in short-term prediction.

The results showed reductions of 24 % and 13 % in RMSE and rBIAS measures, respectively, for precipitation forecasts from the coupled model configuration. Furthermore, the coupled WRF-Hydro system was found to outperform the Integrated Multi-satellite Retrievals from the Global Precipitation Measurement Mission (IMERG GPM) at several ground stations including Abu Dhabi and Jabal Mebreh. The demonstrated improvement in coupled precipitation simulation, at the local scale, greatly enhances the accuracy of hydrologic forecasts and flash flood guidance systems.

The study recommends to focus future work on in-situ soil moisture data assimilation to enhance the model accuracy – both overland and in the atmosphere through the captured soil moisture-precipitation feedback.

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