Shift-Data-Plane

Shift-Data-Plane griggs Thu, 04/25/2019 - 16:06

This tool may be run to perform a rigged shift of the entire grid based on user-defined specifications and write the field(s) out in NetCDF format. This tool was originally designed to account for track error when comparing fields associated with tropical cyclones. The user specifies the latitude and longitude of the source and destination points to define the shift. Both points must fall within the domain and are used to define the X and Y direction grid unit shift. The rigid is then applied to all grid points. The user may specify the method of interpolation and the field to be shifted. The effects of topography and land/water masks are ignored.

Shift-Data-Plane Usage

View the usage statement for Shift-Data-Plane by simply typing the following:

shift_data_plane

At a minimum, the following five arguments must be passed: the gridded data file (input_filename), the output NetCDF file (output_filename), the data to be shifted from the input file (field_string), the starting location to define the shift (-from lat lon), and the ending location to define the shift (-to lat lon).

Run

Run griggs Thu, 04/25/2019 - 16:10

Next, we'll run Shift-Data-Plane on the command line using the following command:

shift_data_plane \

$MET_TUTORIAL_DATA/input/sample_fcst/2005080700/wrfprs_ruc13_12.tm00_G212 \

$MET_TUTORIAL_DATA/output/shift_data_plane/shift_pres.nc \

'name="PRES"; level="Z0";' \

-from 39.74 -105.00 \

-to 41.88 -87.63

This command shifts the surface pressure field from Denver, CO to Chicago, IL and is meant to simply illustrate the functionality of this tool. On the next page we'll plot the result.

Output

Output griggs Thu, 04/25/2019 - 16:11

Run the following commands to plot the input and output of Shift-Data-Plane:

plot_data_plane \

$MET_TUTORIAL_DATA/input/sample_fcst/2005080700/wrfprs_ruc13_12.tm00_G212 \

$MET_TUTORIAL_DATA/output/shift_data_plane/shift_input.ps \

'name="PRES"; level="Z0";'

plot_data_plane \
$MET_TUTORIAL_DATA/output/shift_data_plane/shift_pres.nc \
$MET_TUTORIAL_DATA/output/shift_data_plane/shift_output.ps \
'name="PRES_Z0"; level="(*,*)";'

Display the output images by running the following commands:

gv $MET_TUTORIAL_DATA/output/shift_data_plane/shift_input.ps &

gv $MET_TUTORIAL_DATA/output/shift_data_plane/shift_output.ps &

Notice the rigid shift that has been applied. Why would anyone want to shift data in this way? This tool has been applied when doing feature-relative verification. For example when evaluating hurricane forecasts, select the forecast storm track location and the corresponding location of the BEST track. Prior to computing grid-to-grid statistics, first shift the data from the forecast track location to the BEST track location. Then compute statistics near the storm. This is a simple way of removing the effect of track error when evaluating hurricane forecasts.