Velden and Leslie (1991)#

This application diagnoses the tropical cyclone (TC) relative layer mean wind attributes using an application based on Velden and Leslie, (1991).

Configuration#

The following table provides and describes the configurable variables for the application. Note that if a Default Value is missing, the respective variable is mandatory.

Variable	Description	Default
`isolevels`	A list of isobaric levels at which the TC steering flow attributes should be diagnosed.
`distance`	The distance (meters) relative to a TC position about which to filter the respective TC wind field.	1600000.0
`ncoeffs`	The total number of singular values used to reconstruct the filtered TC wind field.	10
`ddist`	The radial distance (meters) interval for the radial interpolation.	100000.0
`output_file`	The netCDF-formatted file path to contain the variables specified in `output_varlist`; only written if `write_output` (below) is `True`.
`output_varlist`	The file path for the YAML-formatted file containing the list of output variables.
`write_output`	Write the variables specified in `output_varlist` to the netCDF-formatted file path described in the TC steering flow configuration file.	`False`

The contents of an example YAML-formatted configuration file for the TC steering flow application follows.

app_module: tcdiags.vl1991_strflw
app_class: VL1991
schema: !ENV ${TCDIAGS_ROOT}/parm/schema/tcdiags.vl1991_strflw.yaml
isolevels:
  - 100000
  - 90000
  - 80000
  - 70000
  - 60000
  - 50000
  - 40000
  - 30000
  - 20000
  - 10000
distance: 1600000.0
ddist: 100000.0
write_output: true
output_file: ./tcdiags.vl1991_strflw.nc
output_varlist: !INC /home/ufs_tcdiags/parm/io/tcdiags.vl1991_strflw.yaml

Note that the application assumes that the environment variable TCDIAGS_ROOT has been defined and points to the top-level directory of the ufs_tcdiags repository clone. Further, the output_varlist points to a YAML-formatted file containing the variables to be written to output_file if write_output is True. A snippet containing some of the contents written to the netCDF-formatted file path follows.

user@host:$ ncdump -h ./tcdiags.vl1991_strflw.nc

dimensions:
        plevs = 10 ;
        lat = 192 ;
        lon = 384 ;
variables:
        int64 plevs(plevs) ;
        double lat(lat) ;
                lat:_FillValue = NaN ;
        double lon(lon) ;
                lon:_FillValue = NaN ;
        double chi(plevs, lat, lon) ;
                chi:_FillValue = 9.96920996838687e+36 ;
                chi:missing_value = 9.96920996838687e+36 ;
                chi:description = "\"The velocity potential field.\"\n" ;
                chi:name = "velocity potential" ;
                chi:units = "meters^2/second" ;
        double divg(plevs, lat, lon) ;
                divg:_FillValue = 9.96920996838687e+36 ;
                divg:missing_value = 9.96920996838687e+36 ;
                divg:description = "\"The total divergence field.\"\n" ;
                divg:name = "divergence" ;
                divg:units = "1/second" ;

Running the Application#

The TC steering flow application can be executed using a variety of methods. Each is described below.

Terminal#

The TC steering flow application may be executed within an supporting environment as follows.

user@host:$ export PYTHONPATH="/path/to/ufs_tcdiags/ush":"${PYTHONPATH}"
user@host:$ cd /path/to/ufs_tcdiags/scripts
user@host:$ ./compute_tcdiags.py --help

Usage: compute_tcdiags.py [-h] [-tcmsi] [-tcpi] [-tcstrflw] yaml

Tropical cyclone diagnostics computation(s) application interface.

Positional Arguments:
  yaml        YAML-formatted tropical cyclone diagnostics configuration file.

Optional Arguments:
  -h, --help  show this help message and exit
  -tcmsi      YAML-formatted file containing the TC multi-scale intensity application configuration.
  -tcpi       YAML-formatted file containing the TC potential intensity application configuration.
  -tcstrflw   YAML-formatted file containing the TC steering application configuration.

user@host:$ ./compute_tcdiags.py /path/to/ufs_tcdiags/parm/tcdiags.demo.yaml -tcstrflw

Jupyter Notebook#

The TC steering flow application can also be executed from within a Jupyter notebook as follows.

user@host:$ export PYTHONPATH="/path/to/ufs_tcdiags/jupyter":"/path/to/ufs_tcdiags/ush":"${PYTHONPATH}"
user@host:$ cd /path/to/ufs_tcdiags/jupyter/notebooks
user@host:$ /path/to/jupyter notebook tcdiags.vl1991_strflw.ipynb

This action behaves as the terminal instance for the application (above) but is executed from within the respective Jupyter notebook.

Docker Container#

The TC steering flow application may be executed within an appropriate Docker container as follows.

user@host:$ /path/to/docker run -v /path/to/ufs_tcdiags:/home/ufs_tcdiags -it ghcr.io/henrywinterbottom-noaa/ubuntu20.04.ufs_tcdiags:latest
user@host:$ export PYTHONPATH="/home/ufs_tcdiags/ush":"${PYTHONPATH}"
user@host:$ cd /home/ufs_tcdiags/scripts
user@host:$ ./compute_tcdiags.py --help

Usage: compute_tcdiags.py [-h] [-tcmsi] [-tcpi] [-tcstrflw] yaml

Tropical cyclone diagnostics computation(s) application interface.

Positional Arguments:
  yaml        YAML-formatted tropical cyclone diagnostics configuration file.

Optional Arguments:
  -h, --help  show this help message and exit
  -tcmsi      YAML-formatted file containing the TC multi-scale intensity application configuration.
  -tcpi       YAML-formatted file containing the TC potential intensity application configuration.
  -tcstrflw   YAML-formatted file containing the TC steering application configuration.

user@host:$ ./compute_tcdiags.py /home/ufs_tcdiags/parm/tcdiags.demo.yaml -tcstrflw

Jupyter Notebook Within a Docker Container#

Similar to the Jupyter notebook and Docker container examples above, the Jupyter notebook can also be launched from within the Docker container. This can be accomplished as follows.

user@host:$ /path/to/docker run -v /path/to/ufs_tcdiags:/home/ufs_tcdiags -p 8888:8888 -it ghcr.io/henrywinterbottom-noaa/ubuntu20.04.ufs_tcdiags:latest
user@host:$ export PYTHONPATH="/home/ufs_tcdiags/ush":"/home/ufs_tcdiags/jupyter":"${PYTHONPATH}"
user@host:$ cd /path/to/ufs_tcdiags/jupyter/notebooks
user@host:$ /path/to/jupyter notebook --ip=0.0.0.0 --port=8888 --no-browser --allow-root tcdiags.vl1991_strflw.ipynb

The above action will provide the user a local HTML path and an associated token as follows.

To access the server, open this file in a browser:
    file:///root/.local/share/jupyter/runtime/jpserver-21362-open.html
Or copy and paste one of these URLs:
    http://5186640b39b0:8889/tree?token=abcdefghijklmnopqrstuvwxwy0123456789ABCDEFGHIJKL
    http://127.0.0.1:8889/tree?token=abcdefghijklmnopqrstuvwxwy0123456789ABCDEFGHIJKL

Copy the paste the token attribute that begins with http://127.0.0.1:8889 into a web browser address bar and execute the respective Jupyter notebook as described above.

Example Results#

The following example is computed from a nominally 1.0-degree ERA5 analysis valid 0000 UTC 01 October 2016.

The layer-mean winds with respect to the intensity ranges illustrated by Figure 2 of Velden and Leslie, (1991) are shown above for the 850- to 500-hPa (top), 850- to 400-hPa (center), and 850- to 300-hPa (bottom). The TC locations, valid for 0000 UTC 01 October 2016, are denoted by the respective red symbols.