Wavelet-Stat Tool: General

Wavelet-Stat Functionality

The Wavelet-Stat tool provides a wavelet-based intensity-scale decomposition for comparing gridded forecasts to gridded observations. Wavelet-Stat may be used in a generalized way to compare any two fields but has been most commonly applied to precipitation. The steps performed in Wavelet-Stat consist of:

• Preprocess the input forecast and observation fields to select one or more tiles of dimension 2^n by 2^n. The wavelet decomposition may only be performed on such fields.
• Threshold the forecast and observation fields to create a 0/1 binary field.
• Use a wavelet decomposition approach to decompose the thresholded forecast and observation tiles into separate scales.
• Compare the forecast and observation tiles at each scale and compute statistics, such as the mean-squared error and intensity skill score.
• If multiple tiles were used, aggregate the results across all of the tiles and write out the aggregated statistics as well as the statistics for each tile.

Wavelet-Stat may be configured to use several different types of wavelet decompositions, all of those that are supported by the GNU Scientific Library. Here we'll use the Haar wavelet which is employed in the Intensity-Scale method by Casati et al. See the MET User's Guide for a more thorough description of how to configure the Wavelet-Stat tool.

Wavelet-Stat Usage

View the usage statement for Wavelet-Stat by simply typing the following:

bin/wavelet_stat

At a minimum, the input fcst_file in GRIB or NetCDF format (from PCP-Combine), the input obs_file in GRIB or NetCDF format (from PCP-Combine), and the configuration config_file must be passed in on the command line. Just as with Grid-Stat, the forecast and observation fields must be interpolated to a common grid prior to running Wavelet-Stat. The copygb utility is recommended for regridding files in GRIB format.