CCEW-Tracking

Tracking of convectively-coupled equatorial waves as objects from spatiotemporally filtered data.

Python code to track wave objects and compute forecast statistics for tropical waves -- primarily Convectively Coupled Kelvin Waves (CCKWs), but with support for the "tropical depression (TD)" band and equatorial Rossby waves (n=1), in observational and model data.

These scripts were written in partial support for an in-progress manuscript:

"On the Representation of Kelvin Waves and Easterly Waves in Operational Forecast Models: An Object-Based Approach", by Quinton A. Lawton, Rosimar Rios-Berrios, Falko Judt, Linus Magnusson, and Martin Köhler.

Folder Structure

• example_data/: Example NetCDF precipitation data for testing and demonstration.
• example_shell_scripts/: Example shell scripts for batch processing.
• forecast_metrics/: Scripts for quantifing forecast skill
• tracking_scripts/: Main Python scripts for filtering, preprocessing, and tracking tropical waves.

Main Scripts

• tracking_scripts/preprocess_precipitation_for_filter.py: Preprocesses model and observational precipitation data, slices to desired latitude/time, and pads for filtering.
• tracking_scripts/FFT_filter_imerg_daily_mean.py: Filters precipitation data in wavenumber-frequency space for specified wave types (Kelvin, TD, ER, etc.). Based on Wheeler and Kiladis (1999) and Maria Gehne's Tropical Diagnostics package.
• tracking_scripts/track_filtered_waves.py: Tracks filtered wave systems (Kelvin, TD, ER) in precipitation data and outputs tracked longitude and strength.

Supporting scripts

• tracking_scripts/tropical_diagnostics/spacetime.py: Adapted from Maria Gehne's "Tropical Diagnostics" github package (https://github.com/mgehne/tropical_diagnostics). This contains core functions for space-time spectral analysis and filtering.

Usage

1. Preprocess Data: Use preprocess_precipitation_for_filter.py to prepare input data.
2. Filter Data: Apply FFT_filter_imerg_daily_mean.py to extract desired wave signals.
3. Track Waves: Run track_filtered_waves.py to identify and track wave systems.
4. Forecast Diagnostics: Use functions in forecast_metrics to compute forecast errors.

Requirements

• Python 3.x
• xarray, numpy, pandas, scipy

For more details, see comments in each script.