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CyMeP (Cyclone Metrics Package)

DOI

Zarzycki, C. M., Ullrich, P. A., and Reed, K. A. (2021). Metrics for evaluating tropical cyclones in climate data. Journal of Applied Meteorology and Climatology. doi: 10.1175/JAMC-D-20-0149.1. Preprint PDF. Supplemental PDF.

This directory (the root) is defined as ${CYMEP}. The released version of CyMeP is stored in ${CYMEP}/cymep/.

General workflow

  1. Add TempestExtremes ASCII trajectories to ./traj/
  2. Create a configuration .csv file in ./config-lists/
  3. Edit user settings in cymep.py
  4. Run cymep.py
  5. Run graphics-cymep.sh

0. Install dependencies

The actual statistics package is all written in Python3 and requires several libraries. The easiest way to install relevant things is via conda install. pip or the full Anaconda package may also be an option. Required Python packages are:

numpy
pandas
scipy
netCDF4

Or you can use the configuration file included in this repository:

conda env create -n cymep --file configuration.yaml 
conda activate cymep

Also required for graphic generation (graphics-cymep) is NCL. NCL can either be installed from source or binary, MacPorts, or via conda. The latter is preferred.

1. Add trajectory files to ./traj/ folder.

Currently these files must be in "Tempest" ASCII format (a derivative of the old "GFDL" format, for those who understand what that means!):

start   31      1980    1       6       6
        482     303     120.500000      -14.250000      9.987638e+04    1.464815e+01    0.000000e+00    1980    1       6       6
        476     301     119.000000      -14.750000      9.981100e+04    1.398848e+01    0.000000e+00    1980    1       6       12
        476     300     119.000000      -15.000000      9.953694e+04    1.369575e+01    0.000000e+00    1980    1       6       18
       
        ...

where each trajectory has a header line beginning with start followed by the number of points in the trajectory (ex: 31) and the start date of the trajectory in YYYY MM DD HH.

Each subsequent line (31 lines) contains a point along the trajectory. Currently, this is hardcoded such that the columns are defined thusly:

index label description
1 ix i-index (currently ignored)
2 jx j-index (currently ignored)
3 lon longitude (degrees east)
4 lat longitude (degrees north)
5 slp sea level pressure (Pa)
6 wind wind speed (m/s)
7 phis surface geopotential (m2/s2)
8 yyyy year integer
9 mm month integer
10 dd day integer
11 hh hour integer (GMT)

There are two folders within the package that may be helpful:

  1. An example of generating a TempestExtremes trajectory file from reanalysis is found in ${CYMEP}/tempest-tc/. This script reads in MERRA2 data and generates a track file on NCAR Cheyenne.
  2. Sample scripts for creating alternative formats can be found in ${CYMEP}/convert-traj/. For example, one could use ibtracs_to_tempest.ncl to generate a text-based file compatibile with the software package from an IBTrACS NetCDF file.

2. Create a CSV file describing model configurations

Example for rean_configs.csv

ibtracs-1980-2019-GLOB.v4.txt,OBS,False,1,40,1.0
trajectories.txt.ERAI,ERAI,False,1,39,1.0
trajectories.txt.CR20,20CRv3,False,1,36,1.0
trajectories.txt.MERRA,MERRA,False,1,36,0.85
trajectories.txt.MERRA2,MERRA2,False,1,39,0.85
trajectories.txt.JRA,JRA,False,1,39,0.98
trajectories.txt.CFSR,CFSR,False,1,39,0.883
trajectories.txt.ERA5,ERA5,False,1,39,1.0

Using the first line as an example...

Variable Description
ibtracs-1980-2019-GLOB.v4.txt Trajectory file name in traj dir
OBS "Shortname" used for plotting, data output
False Is the traj file unstructured? (1-D column indices instead of 2-D)
1 Number of ensemble members included in trajectory file
40 Number of years per ensemble member in trajectory file
1.0 Wind speed correction factor

NOTE: The first line will be defined as the reference, so this should always be either observations or some sort of model/configuration control.

NOTE: The wind speed correction factor is a multiplier on the "wind" variable in the trajectory file to normalized from lowest model level to some reference height (e.g., lowest model level to 10m winds for TCs).

3. Edit cymep.py

Variable Description
gridsize Length of side of each square gridbox used for spatial analysis in degrees (e.g., 8.0)
basin Set to negative to turn off filtering, otherwise specify particular ocean basin/hemisphere based on mask functions
csvfilename The name of the file stored in config_files that contains the list of files to be analyzed
styr Start year for overlapping interannual correlation analysis
enyr End year for overlapping interannual correlation analysis
truncate_years If True then filter out years external to styr and enyr. If False keep all data
do_defineMIbypres Define maximum intensity location by PSL instead of wind? (default: False = wind)
do_fill_missing_pw Fill missing data with observed pressure-wind curve? (False leaves data as missing)
do_special_filter_obs Do we have special observational filtering? (if true, code modifications needed)
THRESHOLD_ACE_WIND Select threshold wind (in m/s) for ACE calculations (negative value means no threshold)
THRESHOLD_PACE_PRES Select threshold SLP (in hPa) for PACE calculations (negative value means no threshold)

NOTE: if you have a non-TempestExtremes-TC configuration, you need to modify the array extraction found by grepping for USER_MODIFY in cymep.py.

4. Run cymep.py

Finally, run cymep.

$> python cymep.py

This will produce two sets of files. One, a handful of CSV files in ${CYMEP}/cymep/csv-files/. Two, a NetCDF file in ${CYMEP}/cymep/netcdf-files/.

NOTE: Eventually, the csv-files folder will become obsolete and all output from the suite will be packaged via NetCDF.

5. Run graphics-cymep.sh

$> ./graphics-cymep.sh netcdf-files/netcdf_GLOB_rean_configs.nc

This will produce a suite of figures in various subfolders within ./fig/.