Storm‐Scale and Fine‐Scale Boundary Layer Structures of Tropical Cyclones Simulated With the WRF‐LES Framework

Abstract

The main energy source for tropical cyclones (TCs) is from the warm ocean through their boundary layer (BL) processes. Understanding the TC boundary layer (TCBL) structure has become increasingly important in the effort toward developing high-resolution numerical models and improving TC intensity forecasts (

Wind Gusts Associated with Tornado-Scale Vortices in the Tropical Cyclone Boundary Layer: A Numerical Simulation

“…Significant variability in the wind field at 10-m height can be seen in Figure 1A. The variabilities in the surface winds are caused by the fine-scale coherent structures, which have been studied in many observational and numerical studies (Wurman and Winslow, 1998;Morrison et al, 2005;Marks et al, 2008;Rotunno et al, 2009;Lorsolo et al, 2010;Foster, 2013;Gao and Ginis, 2014;Green and Zhang, 2015;Wu et al, 2018;Wurman and Kosiba, 2018;Wu et al, 2019;Liu et al, 2021). 1-min mean wind fields at 10-m height are shown in Figure 1B.…”

“…The TC center is determined with the algorithm from previous studies (Wu et al, 2006;Yang et al, 2020), in which the TC center is located until the maximum azimuthally-averaged tangential wind is found. The identification algorithm of TSVs in the numerical experiment is based on the specific threshold of vertical velocity and vorticity similar to that used in the previous studies (Wu et al, 2018;Wu et al, 2019;Feng et al, 2021;Liu et al, 2021). Since the innermost domain moves with the TC, the variables are all projected into a fixed reference framework (overlapped domains within the 22-min) during the 22-min period.…”

“…Our understanding of the TCBL process in TC intensity change and structure evolution has been improved with the advances in observational technology, computational power, and numerical models (Willoughby, 1990;Smith, 2003;Bell and Montgomery, 2008;Smith and Montgomery, 2010;Zhang and Montgomery, 2012;Ma and Fei, 2022;Li et al, 2022). The fine-scale (less than 1000 m) features have been explicitly simulated over the past decade (Zhu, 2008;Rotunno et al, 2009;Zhu et al, 2013;Green and Zhang, 2015;Qin and Zhang, 2018;Stern and Bryan, 2018;Wu et al, 2018;Wu et al, 2019;Zheng et al, 2020;Feng et al, 2021;Liu et al, 2021;Qin et al, 2021;. The TSVs occurring inside the TC eyewall can be resolved with the grid spacing of 37 m in the Weather Research and Forecast (WRF) model with the LES (Wu et al, 2018;Wu et al, 2019;Feng et al, 2021;Liu et al, 2021).…”

“…The fine-scale (less than 1000 m) features have been explicitly simulated over the past decade (Zhu, 2008;Rotunno et al, 2009;Zhu et al, 2013;Green and Zhang, 2015;Qin and Zhang, 2018;Stern and Bryan, 2018;Wu et al, 2018;Wu et al, 2019;Zheng et al, 2020;Feng et al, 2021;Liu et al, 2021;Qin et al, 2021;. The TSVs occurring inside the TC eyewall can be resolved with the grid spacing of 37 m in the Weather Research and Forecast (WRF) model with the LES (Wu et al, 2018;Wu et al, 2019;Feng et al, 2021;Liu et al, 2021). The three-dimensional structures of TSVs can also be represented in their numerical studies.…”

“…The simulated TSVs often contain strong updraft/downdraft couplets and may cause strong localized surface winds. However, the characteristics of TSV-induced gusts and gust factors are still unclear since the model output is stored at one-hour intervals in previous numerical experiments (Wu et al, 2018;Wu et al, 2019;Feng et al, 2021;Liu et al, 2021). In this study, a numerical experiment with a horizontal grid spacing of 37 m is conducted using the WRF-LES framework.…”