Run Track and Circle Types

Run Track and Circle Types

On this page, we provide examples for using the "track" masking type using BEST track hurricane data and "circle" masking type.

Start by extracting the lat/lon locations for Hurricane Dorian:

echo "DORIAN" > ${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/dorian.poly
cat ${METPLUS_DATA}/model_applications/medium_range/dorian_data/track_data/bal052019.dat | awk '{printf "%d %d\n", $7, $8}' | awk '{printf "%.1f %.1f\n", $1/(10), $2/(-10)}' | uniq >> ${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/dorian.poly

Inspect the dorian.poly file that begins with "DORIAN" and has the lat/lon storm locations on subsequent lines.

cat ${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/dorian.poly

Compute a mask for all grid points within 200 km of the Hurricane Dorian track. Run Gen-Vx-Mask using the following command:

gen_vx_mask \
G003 \
${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/dorian.poly \
${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/Dorian_Track.nc \
-type track -name Dorain_Track -thresh le200

Extract the first track point for Dorian and use the circle masking option to select all grid points within 500 km:

head -2 ${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/dorian.poly > ${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/dorian_first.poly

Run Gen-Vx-Mask on the command line using the following command:

gen_vx_mask \
G003 \
${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/dorian_first.poly \
${METPLUS_TUTORIAL_DIR}/output/met_output/gen_vx_mask/Dorian_Origin.nc \
-type circle -name Dorain_Track -thresh le500

The "circle" mask type draws a circle around each of the lat/lon points in the input poly file. The "circle" option may be useful when verifying within a certain radius of known radar locations. If you rerun without the "-thresh" command line option, Gen-Vx-Mask still runs but prints a warning message:

WARNING: apply_circle_mask() -> since "-thresh" was not used to specify a threshold in kilometers for circle masking, the minimum distance to the points will be written.

Can you figure out what this output file now contains? Run ncview or plot_data_plane to visualize it.

The "-thresh" option can also be omitted from the "track", "data", "solar_alt", and "solar_azi" masking types. If no threshold is specified, a warning message is printed, and the raw, un-thresholded values are written to the output NetCDF file.

Gen-Vx-Mask also supports the "box", "solar_azi", and "shape" masking types, not covered in these exercises. Interested users can download Natural Earth shapefiles and run Gen-Vx-Mask using the "-type shape" option.

Next, we'll take a look at using the "shape" masking type with Gen-Vx-Mask.

jpresto Fri, 12/10/2021 - 15:14