Impact of dynamical downscaling of surface winds on surface waves around Japan coast
Abstract
In this study we investigate impacts of dynamical downscaling of surface wind fields on surface wave fields around Japan. To achieve this, we compare wave fields predicted by high-resolution wind fields and those predicted by low-resolution wind fields. The high-resolution wind fields are predicted by 3 different regional atmospheric models; Regional Atmospheric Model (RAMS), Non-Hydrostatic Model (NHM), and Weather Research and Forecasting (WRF) model. These atmospheric models are configured at a spacing of 20 km for latitude and longitude with the lateral boundary condition of the JRA25 reanalysis at 6-hour intervals during 2002-2004. Ocean surface wave fields are predicted by WaveWATCH III (WW3) configured at a spacing of 0.1 degree for latitude and longitude. On the other hand, wave fields are also predicted by low-resolution wind fields (1.125 deg.) obtained from the JRA25 reanalysis. We compare the wave parameters predicted by models with those measured by the Nationwide Ocean Wave Information network for Ports and HArbourS (NOWPHAS). It is found that climatological annual mean of significant wave height (Hs) around Japan are successfully simulated as observed. However, Hs predicted by low-resolution wind fields are negatively biased by about 10-50 cm at most of the observation points. In contrast, Hs predicted by high-resolution wind fields show better agreement with measured Hs. This result suggests that surface wind fields predicted by regional atmospheric models have higher skill than low-resolution reanalysis wind fields with respect to predicting wave fields, even if the reanalysis data are corrected by assimilation scheme. The main reason of the higher skill of high-resolution wind fields would be the fact that regional atmospheric models can simulate surface winds intensified by the convergence of winds attributable to high-resolution model topography. A higher temporal resolution of the regional models also would help to decrease the bias. The bias of climatological annual mean of significant wave heights predicted by WW3 against those observed. Surface winds for WW3 come from RAMS, NHM, WRF, and JRA25.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.A33A0227S
- Keywords:
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- 3355 ATMOSPHERIC PROCESSES / Regional modeling