DOI: 10.5061/dryad.k0p2ngfjk
title: Data from: The role of outflow-layer inertial stability in governing the radial location of secondary eyewall formation in tropical cyclones

description: Secondary eyewall formation (SEF) in tropical cyclones (TCs) emerges from
 a complex interplay of internal dynamics and environmental influences.
 Motivated by observations linking low inertial stability in the TC outflow
 layer to eyewall replacement cycles, we investigate how variations in
 outflow‐layer inertial stability control both the initiation and radial
 position of SEF. Idealized simulations reveal that reduced outflow‐layer
 inertial stability enhances upper‐level divergence and updraft in the TC
 outer core, fostering the growth of stratiform rainbands. By averaging
 secondary circulation over the domain grids featuring stratiform
 precipitation, it is explicitly shown that the strength of the mesoscale
 descending inflow (MDI) is greater within the widespread and more
 developed stratiform clouds. Such stratiform‐induced MDI can dynamically
 and thermodynamically broaden the tangential wind field in the lower
 altitudes. As a result, the ensuing increase in boundary‐layer inertial
 stability and inflow supplies greater absolute vorticity influx in the
 outer‐core region, making the tangential wind tendency peaks and the
 secondary eyewall intensifies at a larger radius. This study highlights
 the role of MDI in the coupling between the upper‐ and lower‐tropospheric
 dynamics.
description: In this study, all the numerical simulations are performed by the
 Weather Research and Forecasting (WRF) model of version 4.3.1 (Skamarock
 et al., 2021). A description of WRF can be found in this website: A Description of the Advanced Research WRF Model Version 4.1 | OpenSky. Due to the great size of raw datafiles produced by the simulation, only namelists and modified source codes that are required to reproduce the results in this paper are elaborated in this repository. More information about this dataset can be found in the README section.
description: # Data from: The role of outflow-layer inertial stability in governing the
 radial location of secondary eyewall formation in tropical cyclones
 [https://doi.org/10.5061/dryad.k0p2ngfjk](https://doi.org/10.5061/dryad.k0p2ngfjk) ## Description of the data and file structure This is the dataset that contains the namelist and modified source code of WRF model (version 4.3.1) needed for the reproduction of results in the manuscript: "**The Role of Outflow-Layer Inertial Stability in Governing the Radial Location of Secondary Eyewall Formation in Tropical Cyclones**". ### Files and variables Five files need to be modified to reproduce simulation results in this study, including: module_initialize_tropical_cyclone.F; module_big_step_utilities_em.F;  module_em.F; namelist.input; input_sounding; #### File: module_initialize_tropical_cyclone.F **Description:** This Fortran file contains the structural parameters of the initial vortex and sea surface temperature.  #### File: module_big_step_utilities_em.F **Description:** This Fortran file is modified from the original source code in the WRF model to conduct sensitivity experiments in which Coriolis parameter at altitudes higher than 10 km are artificially changed. Readers can refer to lines annotated by 'J.,Jiang' to locate modifications in the code. Besides, the subroutine related to the Newtonian relaxation on potential temperature is uncommented to mimic the radiative cooling.  #### File: module_em.F **Description:** Changes made in this source code are necessary to pass values of geopotential height to subroutines that determine whether a mesh grid is above 10 km or not.  Readers can refer to lines annotated by 'J.,Jiang' to locate modifications. #### File: namelist.input **Description:** This text profile lists the parameters regarding the time control, domain, physical parameterizations and etc. #### File: input_sounding **Description:** The basic environmental state (Dunion, 2011) implemented in the simulation. There is one-line header containing: surface pressure (mb), surface potential temperature (K), surface mixing ratio for water vapor (g/kg). Then, the following lines are: height (m), potential temperature (K), mixing ratio for water vapor (g/kg), zonal wind speed (m/s), meridional wind speed (m/s). ## Code/software The data produced by WRF model can be read using Python, NCL, Grads, Fortran, Matlab, and other tools. Here we take Python as an example: To read variables in the datafiles in R80.zip:  `import numpy as np` `import xarray as xr` `filepath = '\\wrfout_d03_2007-09-01_00:00:00.nc'` `rawdata = xr.open_mfdataset(filepath, engine='netcdf4', concat_dim = 'time',combine = 'nested',join = 'inner')` `u = rawdata['u']; v = rawdata['v']; w = rawdata['w']`