WOA - Python

Reads WORLD OCEAN ATLAS 2018 (WOA18) variables and creates python numpy matrix with climatologies. Also extracts climatological information from a list of coordinate points.

Getting Started

See the World Ocean Atlas for information on the available variables, resolution, etc. To download all variables and resolutions, and convert to numpy arrays run the bash script:

./read_woa_all.sh

Uncomment those varaibles not of your interest.
The compressed numpy files are saved to the output dir (default to woa_np), one file per variable.
WARNING: The files at 0.25 degree resolution are quite large, aprox 1.5 Gb each for the temperature and salinity npz files.

MONTHS are given in a 0 to 11 scale

Utilities

• utils.py contains utility functions to make global maps of specific variables and to extract data from vector of coordinate points for example:

read_and_plot(
		variable='temperature',
	        resolution = '04',
        	woapath='woa_np/',
		month=0,		
		depthlevel=0,	
        	min_val=-5,
        	max_val=35,
        	title= 'Sea surface temperature',
        	filename='sst_jan.png')

would make the plot presented above

extract_woa(
        lons=[-10,-5],
        lats=[42,44], 
        depths=[0,20],
        months= [0,2],
        variable='temperature',
        resolution = '04',
        woapath='woa_np/')

would return 'array([14.12209034, 12.3142004 ])'
this function extracts data from the specificied variable and resolution given lon and lat coordinates, if a depth vector is not provided it will extract the complete profile at each location, if a month vector is not provided it will extract the complete seasonal cycle.

• extract_csv.py is a python script to read coordinates and Month/Depth from a csv file, call extract_woa to extract the given variable at given resolution and save the extracted data into a csv file with the same filename (with suffix of the variable and resolution). For example:

python extract_csv.py --variable "temperature" --resolution "1" --csv "csvs/csvdata.csv"

would write a csv file in csv/csvdata_temperature1.csv with the temperatures at 1 degree resolution for those coordinates, note that many locations close to coast would give no data.

When the csv does not have a column with "Month" the script would extract the data for the 12 months

python extract_csv.py --variable "temperature" --resolution "1" --csv "csvs/csvdata_nomonth.csv"

would write file csv/csvdata_nomonth_temperature1.csv

When the csv does not have a column with "Depth" the script would extract the data for all the depth levels

python extract_csv.py --variable "temperature" --resolution "1" --csv "csvs/csvdata_nodepth.csv"

would write file csv/csvdata_nodepth_temperature1.csv

Other files not used

• read_woa_csv.py: Reads the woa data from csv file format
• read_woa_iris.py: Uses iris and python-oceans packages to extract data from coordinates

Prerequisites

NetCDF4 python library, there is also an (unmaintained) read_woa_csv.py file where you can get ideas on how to read the data from csv files, without the need of NetCDF

Authors

Angel Lopez-Urrutia
This software is a contribution to project Role of membrane DESaturases in the Global Ocean distribution of picoCYAnobacteria (CYADES): RTI2018-100690-B-I00

License

This project is licensed under the MIT License - see the LICENSE.md file for details

Acknowledgments

woa url formatting from python-oceans