DOI: 10.5061/dryad.gmsbcc2wj
title: The roles of moat width and outer eyewall contraction in affecting the timescale of eyewall replacement cycle

description: The timescale of the eyewall replacement cycle (ERC) is critical for the
 prediction of intensity and structure changes of tropical cyclones (TCs)
 with concentric eyewall (CE) structures. Previous studies have indicated
 that the moat width can regulate the interaction between the inner and
 outer eyewalls and has a salient relationship with the ERC timescale. In
 this study, a series of sensitivity experiments are carried out to
 investigate the essential mechanisms resulting in the diversity of the
 duration of CEs using both simple and full-physics models. Results reveal
 that a larger moat can induce stronger inflow under the same inner eyewall
 intensity by providing a longer distance for air parcels to accelerate in
 the boundary layer, thus there is greater inward absolute vorticity flux
 to sustain the inner eyewall. Besides, the equivalent potential
 temperature budget indicates that the vertical advection and surface flux
 of moist entropy can overbalance the negative contribution from the
 horizontal advection and lead to an increasing trend of equivalent
 potential temperature in the inner eyewall. This suggests that the
 thermodynamic process in the boundary layer is not indispensable to the
 inner eyewall weakening. It is also found that the contraction rate of the
 secondary eyewall, which directly influences the moat width, is subject to
 the activity of outer spiral rainbands. By directly introducing positive
 wind tendency outside the eyewall and indirectly promoting a vertically
 tilted eyewall structure, active convection in the outer region will
 impede or even suspend the contraction of the outer eyewall hence
 extending the ERC timescale.
description: Two numerical models are implemented in this study. One is the
 improved version of Ooyama-type three-layer model (OM3L) and the other is
 the full-physics Cloud Model 1 (CM1) of version 21.0. The original code of
 OM3L is developed by Prof. Yuqing Wang. If readers are interested in the
 improved OM3L model, please don't hesitate to contact us. The CM1
 model is an open-source mesoscale atmospheric model that allows for
 idealized studies of atmospheric phenomena, whose source code can be
 downloaded from the wewbsite: https://www2.mmm.ucar.edu/people/bryan/cm1/. Model settings in two models can be refered to the detailed description in the paper and corresponding namelists presented here.  Since raw datafiles of the simulation are very large, only the output that is most relavent to the research and is required to reproduce figures in the paper are elaborated in this repository. More information about this dataset can be found in the README section.
description: # The roles of moat width and outer eyewall contraction in affecting the
 timescale of eyewall replacement cycle
 [https://doi.org/10.5061/dryad.gmsbcc2wj](https://doi.org/10.5061/dryad.gmsbcc2wj) This is the dataset that contains the model output needed for the analysis and figure reproduction in the manuscript: "**The Roles of Moat Width and Outer Eyewall Contraction in Affecting the Timescale of Eyewall Replacement Cycle**". ## Description of the data and file structure ***R80.zip, R90,zip, R100.zip, R110.zip, R120.zip*** Reanalyzed NetCDF data files in Polar coordinates from OM3L simulations of experiments R80, R90, R100, R110, and R120, respectively. These variables are three-dimensional. [var(nt,ln,lm), nt=192, ny=361, nx=101] ***structural_params_combined.nc*** This file restores the re-analyzed variables including the decaying rate of the inner eyewall and the moat width based on five hundred sensitivity experiments. Interested readers can find detailed instructions on how to calculate these variables in the paper. [var(np,nt), np=500, nt=289] ***RWM110.zip, RMW180.zip*** These data files are the results of CM1 simulations. Only model output during the time period of concern is provided. [var(nt,nz,ny,nx), nt=49, nz=60, ny=1, nx=700] ***thompson.f*** This Fortran file is modified from the original source code in the CM1 model to conduct sensitivity experiments in which heating rates of outer rainbands are artificially changed. Readers can refer to lines annotated by 'J.,Jiang' to locate modifications in the code. ## Sharing/Access information Python can be obtained by [Distribution | Anaconda](https://www.anaconda.com/download/) ## Code/Software The data 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 = '\\R80\\cm1out_000*.nc'` `rawdata = xr.open_mfdataset(filepath, engine='netcdf4', concat_dim = 'time',combine = 'nested',join = 'inner')` `u = rawdata['u']; v = rawdata['v']; w = rawdata['w']`