Abstract
Abstract. The western Mediterranean Sea area is frequently affected in autumn by heavy precipitation events (HPEs). These severe meteorological episodes, characterized by strong offshore low-level winds and heavy rain in a short period of time, can lead to severe flooding and wave-submersion events. This study aims to progress towards an integrated short-range forecast system via coupled modeling for a better representation of the processes at the air–sea interface. In order to identify and quantify the coupling impacts, coupled ocean–atmosphere–wave simulations were performed for a HPE that occurred between 12 and 14 October 2016 in the south of France. The experiment using the coupled AROME-NEMO-WaveWatchIII system was notably compared to atmosphere-only, coupled atmosphere–wave and ocean–atmosphere simulations. The results showed that the HPE fine-scale forecast is sensitive to both couplings: the interactive coupling with the ocean leads to significant changes in the heat and moisture supply of the HPE that intensify the convective systems, while coupling with a wave model mainly leads to changes in the low-level dynamics, affecting the location of the convergence that triggers convection over the sea. Result analysis of this first case study with the AROME-NEMO-WaveWatchIII system does not clearly show major changes in the forecasts with coupling and highlights some attention points to follow (ocean initialization notably). Nonetheless, it illustrates the higher realism and potential benefits of kilometer-scale coupled numerical weather prediction systems, in particular in the case of severe weather events over the sea and/or in coastal areas, and shows their affordability to confidently progress towards operational coupled forecasts.
Highlights
In the last decade, improving the forecast of intense weather events involving air–sea interactions has motivated operational forecast centers to develop and operate ocean– atmosphere–wave coupled modeling platforms for shortand medium-range weather predictions (see, for instance, the Geophysical Fluid Dynamics Laboratory (GFDL) model used at the National Weather Service, Bender et al, 2007, the Coupled Ocean/Atmosphere Mesoscale Prediction System for Tropical Cyclones (COAMPS-TC) operated at the Naval Research Laboratory for hurricane prediction, Doyle et al, 2014, the global ocean–ice–atmosphere coupled prediction system run at Environment and Climate Change Canada, Smith et al, 2018, and the recent developments at the European Centre for Medium-Range Weather Forecasts, Magnusson et al, 2019)
The present study describes a new kilometric regional coupled system involving the Météo-France high-resolution operational numerical weather prediction (NWP) model AROME-France, the WaveWatch III wave model and the NEMO ocean model, which paves the way to the future coupled regional convection-resolving NWP system of Météo-France
This study presents the ocean–atmosphere–wave coupled system, developed using the NWP model AROME, the NEMO ocean circulation model and the wave model WW3, all at a kilometric resolution
Summary
Tropical cyclones (TCs) above all have been known for long to be impacted by the surface cooling of the ocean they generate (e.g., Bender et al, 1993; Bender and Ginis, 2000; Bao et al, 2000). Realistic simulations have shown that the initial state of the ocean, namely, the sea surface temperature (SST) and stratification, may significantly reduce the TC intensity (e.g., Chan et al, 2001). Several large-scale studies have shown that using ocean–atmosphere coupling improves in a statistical way the prediction of TCs with respect to atmosphere-only simulations in every cyclonic basin Sauvage et al.: Towards kilometer-scale ocean–atmosphere–wave coupled forecast
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