era5_to_int

A simple Python script for converting ERA5 model-level netCDF files to the WPS intermediate format

Overview

The era5_to_int.py script converts ERA5 model-level netCDF files to the WRF Pre-processing System (WPS) intermediate file format, permitting the use of these data with either the Weather Research and Forecasting (WRF) model or the Model for Prediction Across Scales - Atmosphere (MPAS-A).

The only required command-line argument is the date-time, in YYYY-MM-DD_HH format, of ERA5 model-level files to convert. For example:

era5_to_int.py 2024-05-01_00

Conversion of a range of date-times is possible through the use of additional command-line arguments as described in the Usage section.

The following fields from the ds633 datasets are handled by the script:

Field	Dataset	Horiz. grid	Num. levels
Q	d633006	~0.281-deg Gaussian	137
T	d633006	~0.281-deg Gaussian	137
U	d633006	~0.281-deg Gaussian	137
V	d633006	~0.281-deg Gaussian	137
SOILGEO	d633000	~0.281-deg Gaussian	1
SP	d633006	~0.281-deg Gaussian	1
MSL	d633000	0.25-deg Lat-Lon	1
VAR_2T	d633000	0.25-deg Lat-Lon	1
VAR_2D	d633000	0.25-deg Lat-Lon	1
VAR_10U	d633000	0.25-deg Lat-Lon	1
VAR_10V	d633000	0.25-deg Lat-Lon	1
RSN	d633000	0.25-deg Lat-Lon	1
SD	d633000	0.25-deg Lat-Lon	1
LSM	d633000	0.25-deg Lat-Lon	1
SSTK	d633000	0.25-deg Lat-Lon	1
SKT	d633000	0.25-deg Lat-Lon	1
SWVL1	d633000	0.25-deg Lat-Lon	1
SWVL2	d633000	0.25-deg Lat-Lon	1
SWVL3	d633000	0.25-deg Lat-Lon	1
SWVL4	d633000	0.25-deg Lat-Lon	1
STL1	d633000	0.25-deg Lat-Lon	1
STL2	d633000	0.25-deg Lat-Lon	1
STL3	d633000	0.25-deg Lat-Lon	1
STL4	d633000	0.25-deg Lat-Lon	1
CI	d633000	0.25-deg Lat-Lon	1

As fields are converted from netCDF to intermediate format, their names are also converted to match WPS and MPAS-A expectations.

Requirements

The era5_to_int.py script requires:

• Python 3.11+
• netCDF4
• NumPy

Usage

The only required command-line argument is the date-time, in YYYY-MM-DD_HH format, of ERA5 model-level files to convert. For example:

era5_to_int.py 2024-05-01_00

Upon successful completion, an intermediate file with the prefix ERA5 is created in the current working directory; for example, ERA5:2024-05-01_00.

With no optional arguments, the script will search known paths on the NWSC Glade filesystem for ERA5 model-level netCDF files. If the -p/--path option is provided with a local path, the script will instead search that local path for ERA5 files that have been downloaded from the NSF NCAR Research Data Archive (RDA) ds633 datasets. For example:

era5_to_int.py --path /some/data/directory/era5 2024-05-01_00

Processing a range of times is possible by providing as a second positional argument the date-time until which time records should be converted. For example, to converted the entire month of May 2024:

era5_to_int.py 2024-05-01_00 2024-05-31_18

By default, fields are converted at a six-hourly interval, and a different interval may be specified with a third positional argument. For example, to convert data at a three-hourly interval for the month of May 2024:

era5_to_int.py 2024-05-01_00 2024-05-31_21 3

Usage is provided by running the era5_to_int.py script with the -h/--help argument, which prints the following:

usage: era5_to_int.py [-h] [-p PATH] datetime [until_datetime] [interval_hours]

positional arguments:
  datetime              the date-time to convert in YYYY-MM-DD_HH format
  until_datetime        the date-time in YYYY-MM-DD_HH format until which records are converted (Default: datetime)
  interval_hours        the interval in hours between records to be converted (Default: 6)

options:
  -h, --help            show this help message and exit
  -p PATH, --path PATH  the local path to search for ERA5 netCDF files

Supplementary files

Included in this repository is a list of ECMWF vertical level coefficients in the ecmwf_coeffs file. The ecmwf_coeffs file may be used with the WPS calc_ecmwf_p.exe utility program to generate an intermediate file with 3-d pressure, geopotential height, and R.H. fields.