The size characteristics and physical explanation for the radius of maximum wind of hurricanes
Introduction
Destructiveness caused by hurricanes are increasing rapidly in recent years (Webster et al., 2005; Emanuel, 2005; Hallegatte, 2012; Bass et al., 2017; Yang et al., 2021). At first, for the wind damage induced by a hurricane, it only considered a single factor, such as maximum wind speed (Saffir, 1975), accumulated cyclone energy (Bell et al., 2000), power (Emanuel, 2005), and turbulence kinetic energy dissipation (Businger and Businger, 2001), and so on. However, for the hurricane damage potential estimation, some researchers found that a single factor alone is insufficient, as the maximum wind speed. Hurricane wind damage is dependent on the hurricane intensity and its size (Powell and Reinhold, 2007; Ren et al., 2020). Especially in Ren et al. (2020), they found that the low-intensity case has much higher wind damage than the high-intensity case, which claimed the importance of the hurricane spatial extent information.
The most damaging area of a hurricane is the eyewall region, which relates to the radius of maximum wind (RMW) that defined as the distance between the location of the maximum wind speed of a tropical cyclone and the center of the cyclone in the Glossary of NHC terms, as shown at the website of http://www.nhc.noaa.gov/aboutgloss.shtml#l. Even though the RMW is a critical parameter in determining the size of a hurricane, there is still no universal law describing its size characteristics (He et al., 2016; Montgomery and Smith, 2017; Zhou et al., 2018; Zhu et al., 2022). Hsu and Yan (1998) found an average RMW is 47 km for hurricanes with a minimum pressure of 909–993 hPa; Fujii (1998) found an average RMW is 84–98 km for hurricanes with minimum pressure smaller than 980 hPa; this issue also discussed in Ku et al. (2019). These indicate the RMW depends on the characteristics of the selected hurricane. Holland (1983) and Merrill (1984) emphasized that the observed hurricane size difference was predominantly related to the large-scale weather system environment accompanying the angular momentum transport. Wang (2009) found that the release of latent heat from the outer spiral rainbands could increase the size of the inner core of the hurricane; this should relate to the relative environmental humidity (Xu and Wang, 2010a; Hill and Lackmann, 2009). Also, Xu and Wang (2010b) studied the sensitivity of the simulated tropical cyclone inner-core size to the initial vortex size. Meanwhile, the physics mechanism that different hurricanes have different RMWs is still unclear nowadays. Thus, in the present study, we performed four different intensity level cases to find out the possible mechanism for the different RMW characteristics of different hurricanes. The numerical weather prediction model that considers the multi-physics process was carried out to simulate the natural hurricane structure. Specifically, the WRF model (Skamarock et al., 2008) was adopted.
The structure of the current study is as follows. In section 2, simulation settings are introduced. In section 3, the RMW characteristics of different intensity level hurricanes are analyzed. In section 4, the physics mechanism of why the different RMW for different cases is discussed. Finally, the conclusion is given in section 5.
Section snippets
Simulation settings
In this study, six nested domains are performed for four hurricane numerical simulation cases with sea surface temperatures (SSTs) of 26 °C, 27 °C, 28 °C, 29 °C, namely, SST-26, SST-27, SST-28, and SST-29 cases, respectively, which includes different hurricane intensity levels. And Table 1 shows the details of each case. Since the horizontal and vertical grid-scale ratios of each nested domain are quite different, different algorithms need to be used to solve the wind field of each nested
The characteristics for RMW of different intensity hurricanes
To analyze the difference of the essential wind characteristics among each domain, without nesting cases of each parent domain are also conducted; thus, the results for different domains are independent of nests in the current study, each of which can represent a hurricane structure. And by increasing the number of samples that can be analyzed in this paper in this way, the credibility of the analysis of the results is increased and the degree of robustness and convergence of the conclusions is
The physical mechanism for RMW of different intensity hurricanes
Studies have shown that areas of heavy rainfall are generally located near the eyewall of a hurricane (Black et al., 1994; Raveh-Rubin and Wernli, 2016). And the rainfall area contains a lot of diabatic heating, which could affect the hurricane structure due to its warm core structure (Stern and Zhang, 2016). Meanwhile, the radial inflow layer plays an important role in warming, since the warm core is attributable to the strength of the inflow (Ge et al., 2015).Therefore, the relationship
Conclusions
In the present study, four idealized hurricane simulation cases were performed in six nested domains with the largest and smallest grid size of 15 km and 62 m, which represent different intensity levels. The difference for the RMW of different intensity hurricanes was analyzed, and we finally explained this by the physical mechanism of absolute angular momentum considerations. Specifically, for a weak hurricane of SST-26 case, the absolute angular momentum at the location of RMW decreases from
Data availability
The data that supports the findings of this study are available from the corresponding author upon reasonable request.
Author contributions
Conceptualization, H. R. and J. D.; Methodology, H. R. and J. D.; Software, H. R. and J. D.; Validation, H. R.; Formal Analysis, H. R.; Investigation, H. R. and J. D.; Resources, J. D. and H. L.; Data Curation, H. R.; Writing-Original Draft Preparation, H. R.; Writing-Review & Editing, J. D.; Visualization, H. R.; Supervision, J. D. and H. L.; Project Administration, H. L.; Funding Acquisition, H. R. and H. L. All authors have read and agreed to the published version of the manuscript.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work is financially supported by the National Natural Science Foundation of China (52108456), the Natural Science Foundation of Jiangsu Province (BK20210309). NCAR is sponsored by the National Science Foundation. We also acknowledge high-performance computing support from Cheyenne (doi: https://doi.org/10.5065/D6RX99HX) provided by the NCAR's CISL.
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2022, Journal of Wind Engineering and Industrial AerodynamicsCitation Excerpt :These variables include variables related to wind speed, such as the maximum sustained wind speed in 1, 2, or 10 min (Saffir, 1973; Simpson, 1974), gust wind speed (Saffir, 1975), and turbulence kinetic energy dissipation (Businger and Businger, 2001), as well as those not related to wind speed, such as minimum surface pressure (Bakkensen and Mendelsohn, 2016; Klotzbach et al., 2020) and typhoon outer and inner-core strengths (Weatherford and Gray, 1988; Croxford and Barnes, 2002). Other possible related variables characteristics can be found in Ren et al. (2022a), especially for the most hazardous eyewall region in a typhoon for engineering structures (Ren et al., 2022b). This characterization method can be easily used in actual typhoon forecasting and in predicting the extent of engineering hazards (Saffir, 1973; Emanuel, 2005).