Effects of hurricane forward speed and approach angle on storm surges: an idealized numerical experiment
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Effects of hurricane forward speed and approach angle on storm surges: an idealized numerical experiment Chenguang Zhang1, Chunyan Li1* 1 Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge LA 70803, USA
Received 19 November 2018; accepted 24 December 2018 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
The effects of hurricane forward speed (V) and approach angle (θ) on storm surge are important and a systematic investigation covering possible and continuous ranges of these parameters has not been done before. Here we present such a study with a numerical experiment using the Finite Volume Community Ocean Model (FVCOM). The hurricane track is simplified as a straight line, such that V and θ fully define the motion of the hurricane. The maximum surge is contributed by both free waves and a forced storm surge wave moving with the hurricane. Among the free waves, Kelvin-type waves can only propagate in the down-coast direction. Simulations show that those waves can only have a significant positive storm surge when the hurricane velocity has a down-coast component. The optimal values of V and θ that maximize the storm surge in an idealized semi-circular ocean basin are functions of the bathymetry. For a constant bathymetry, the maximum surge occurs when the hurricane approaches the coast from the normal direction when the free wave generation is minimal; for a stepped bathymetry, the maximum surge occurs at a certain acute approach angle which maximizes the duration of persistent wind forcing; a step-like bathymetry with a sloped shelf is similar to the stepped bathymetry, with the added possibility of landfall resonance when the free and forced waves are moving at about the same velocity. For other cases, the storm surge is smaller, given other parameters (hurricane size, maximum wind speed, etc.) unchanged. Key words: storm surge experiments, FVCOM, hurricane forward speed, approach angle, Kelvin waves, forced and free surge interactions Citation: Zhang Chenguang, Li Chunyan. 2019. Effects of hurricane forward speed and approach angle on storm surges: an idealized numerical experiment. Acta Oceanologica Sinica, 38(7): 48–56, doi: 10.1007/s13131-018-1081-z
1 Introduction Storm surge is sea surface variation produced by severe weather such as hurricanes (Proudman, 1955; Gill, 1982). It can occur in coastal areas with severe damages. In the United States, both the costliest (e.g., Hurricanes Katrina and Harvey) and deadliest (the 1900 Galveston Hurricane) natural disasters were from storm surges (Blake et al. 2007). Ocean surface provides hurricanes with thermal energy originally from solar radiation. Thus, the thermal condition of ocean surface greatly affects hurricane’s intensity (Emanuel, 1987). With the global warming caused by the increased CO2 emission, hurricane activity is predicted to increase significantly, as has been shown by idealized theoretical analysis (Emanuel, 1987), observations and advanced climate mo
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