Posters

Abstract

Tropical cyclones are associated with extreme wind conditions. Particularly, enhanced low-level wind shear and veer can result in strong loads acting on wind turbines. However, measurements in tropical cyclones are scarce and it remains difficult to quantify relevant properties for turbine load calculations, such as wind shear and veer. This study uses the Weather Research and Forecasting model (WRF V4.4) to obtain vertical wind sheer and veer distributions in the eyewall, the inner and the outer rainbands of typhoon Megi (2016). WRF depends on the parametrization of boundary layer processes. To assess related uncertainties in veer and shear distributions, WRF simulations with the following boundary layer schemes are compared: 1.) the Yonsei University scheme (YSU), 2.) the Mellor-Yamada Nakanishi and Niino level 2.5 scheme and 3.) the Mellor-Yamada-Janjic scheme (MYJ). All three simulations can reproduce the typhoon track and structure. However, the simulated cyclone intensity and low-level (26-211 m) wind shear and veer differ. While simulations using the YSU and the MYJ parametrizations show similar cyclone intensities, the low-level shear and veer is clearly smaller for the YSU simulation. The simulation using the MYNN boundary layer results in the least intense cyclone, with the largest low-level shear and veer of the three simulations. The study indicates, that model realizations resulting in intense cyclones are not necessary describing the wind field associated with the strongest load case.