Benefits of high-resolution downscaling experiments for assessing strong wind hazard at local scales in complex terrain: a case study of Typhoon Songda (2004)

Abstract

This study investigated the representation of surface winds in complex terrain during the passage of Typhoon Sondga (2004) in downscaling simulations with the horizontal grid spacing of 200 m. The mountainous areas in Hokkaido where forest damages occurred in the typhoon event were chosen for the present analysis. The 200 m grid simulations were compared with the simulations with the grid spacing of 1 km. The 200 m grid simulations clearly indicated more enhanced and more frequent extremes both in the stronger and weaker ranges of surface winds than the 1 km grid case. Both in the 200 m grid and 1 km grid cases, the mean and maximum winds in the analysis areas during the simulated time period increase with the increase in the terrain slope angle, but in the 200 m grid case, the relationships of the mean and maximum winds against the terrain slope angle includes wide scatter. In this way, the response of the wind representations to the grid spacing appears differently between the 200 m and 1 km grid cases. A parameter characterized subgrid-scale orography was used to quantify the influences of the terrain complexity on surface winds, demonstrating that the area-maxima and spatial variance of surface winds are more enhanced with the increase in the subgrid-scale orography in the higher-resolution case. It is suggested that the high-resolution simulations at the 200 m grid highlight the fluctuating nature of surface winds in complex terrain, because of the better representation of the model terrain at 200 m. Benefits of the representation of surface winds in simulations at the resolution on the order of 100 m are due to the better representation of complex terrain, which enables to quantitatively assess the impacts of strong winds on forest and natural vegetation in complex terrain.

Preface for “Projection and impact assessment of global change”

“…Yamada et al (2021) present a study focusing on the survival rate of typhoon "seeds" until they develop into typhoons using global data from High-ResMIP (Haarsma et al 2016), a collection of relatively high-resolution models among the CMIP6 models. Takemi and Ito (2020), on the other hand, perform a case study using a regional model and show that in complex terrain, improvements could be expected with higher resolutions down to the level of several hundred meters.…”

Risk assessment of forest disturbance by typhoons with heavy precipitation in northern Japan

“…Takemi (2018) used a horizontal grid spacing of 167 m to simulate the heavy rainfall event that occurred in the northern part of Kyushu Island in July 2017 and indicated that the 167-m grid simulation quantitatively captured the rainfall amount. Takemi and Ito (2020) examined the ability to represent strong winds due to typhoons in complex terrain with a horizontal grid spacing of 200 m and indicated that the wind speeds simulated with a grid spacing of 200 m were quantitatively estimated better than those simulated with a grid spacing of 1 km. In this way, both studies demonstrated that the grid spacing on the order of 100 m adequately captured the spatial and temporal variability of rainfall and wind in complex terrain.…”

Impact of ocean-atmosphere coupling on present and future Köppen-Geiger climate classification in Europe

“…This technique has a variety of applications (Castro et al, 2005;Rockel, 2015), including local or regional climate change assessment (e.g., Barredo et al, 2020;Komurcu et al, 2018;Mathis et al, 2013;Xue et al, 2014). The finer mesh of the RCMs allows for a better resolved orography or local gradients (e.g., Cabos et al, 2019;Pontoppidan et al, 2017;Rummukainen, 2016;Takemi and Ito, 2020;Tiwari et al, 2014;Xu et al, 2018). Also, the importance of using high-spatial resolution RCMs for regional analyses based on momenta beyond mean values is shown in the literature (e.g., Domínguez et al, 2013;Gómez et al, 2016).…”