Influence of Topography and the Underlying Surface of the Bohai Sea on Wind and Gust Forecasts. Issue 1 (29th December 2022)

• Record Type: Journal Article
• Authors: Wang, Ke; Lyu, Xinyu; Huang, Jing; Luo, Meng; Xu, Fei
• Is Part Of: Earth and space science. Volume 10:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-29
• Subjects: topography -- underlying surface -- meteorologically stratified gust factor -- gust forecasts; Space sciences -- Periodicals; Geophysics -- Periodicals; 500.5
• DOI: 10.1029/2022EA002705
• Languages: English
• ISSNs: 2333-5084

Abstract

Abstract: Accurate gust forecasts can reduce potential threats to people's lives and properties, but we need more reliable forecasting methods and models. A recent development is the meteorologically stratified gust factor (MSGF) model, which is more accurate in forecasting gusts than the previous gust factor model. The regional terrain and underlying surface both have crucial effects on the gust factor. We therefore combined observations from the China Meteorological Administration over the ocean surface and along the coast with the MSGF model to explore the influence of topography and the underlying surface on wind and gust forecasts. The regional terrain and underlying surface affected the peak gust climatologies, the mean wind speed, the mean prevailing wind direction and the gust factors. The topography and the underlying surface had different impacts in different ranges of the mean wind speed. The strong turbulence that causes changes in the gust factor under light winds is not initiated over rough underlying surfaces. When the mean wind speed is >2.5 m s −1, the underlying surface influences both the wind speed and the gust factor. A rough underlying surface stimulates stronger turbulence and increases the gust speed and gust factor, whereas a smooth underlying surface directly increases the mean wind speed and the gust speed by different magnitudes to reduce the difference between them, thus decreasing the gust factor. We evaluated the ability of the MSGF model to forecast gusts and verified a method combining the products of a numerical model and the MSGF model in gust forecasts. Plain Language Summary: Wind gusts are defined as a sudden increase in wind speed caused by air parcels with high kinetic energies. The regional terrain and the properties of the underlying surface are crucial factors affecting gusts and their forecasts. In October 2017, the China Meteorological Administration set up 15 observational stations over the Bohai Sea, making it possible to study gusts over the ocean surface. We studied the influence of the topography and the properties of the underlying surface on wind and gust forecasts using observations from the China Meteorological Administration over the ocean surface and along the coast combined with the meteorologically stratified gust factor (MSGF) model and the European Centre for Medium‐Range Weather Forecasts model to verify a method that can combine both numerical model products and the MSGF model in gust forecasts. The regional terrain and the underlying surface affected the peak gust climatology, the mean wind speed, the mean direction of the prevailing wind and the gust factors in a particular region. We suggest that a combination of the MSGF model and the mean wind speed output by numerical models after correction could lead to more accurate forecasts of wind gusts. Key Points: Different definitions of the mean wind and gust speed affect the calculations of the gust factors The topography and the underlying surface had different impacts in different ranges of the mean wind speed A combination of the MSGF model and the mean wind speed after correction could lead to more accurate forecasts of wind gusts