TMY3_to_ET0 by Andy Sturges

A Ruby program to read weather (TMY3) and crop data (USDA) and produce evapotranspiration data (ET₀).

This project comes from the Environmental Energy Technologies division of Lawrence Berkeley National Laboratory in Berkeley, CA.

Background Information

Currently the project is divided into three steps.

tmy3.rb -- This is a Ruby program that reads TMY3 data files and outputs a .csv file with monthly average weather data by state. The columns it produces are inputs to step 2.
eto_calculation.xlsx -- This Excel file takes the .csv file output from step 1 as its input, and performs the ET₀ calculation. The final result is a list of ET₀ values by month and by state.
water_requirements/water_requirements_by_region.rb -- This is a Ruby program that takes as inputs ET₀ values from step 2, as well as crop data gathered from USDA and FAO sources, and outputs a table showing specific crop irrigation requirements by state and month.

ET₀: The reference evapotranspiration--a coefficient based on geography and weather--but not crop characteristics--representing how much crops need to be irrigated in a particular location at a particular time (i.e. under certain weather characteristics).
k_C: The crop coefficient-- this is specific to a particular crop, and when multplied by the reference ET₀, yields that particular crop's irrigation needs in that particular location, usually measured in millimeters per day.
TMY3: Typical Meteorological Year 3 -- A dataset produced by the National Renewable Energy Lab (NREL) that represents "typical" meteorological conditions.
USDA: The United States Agricultural Assocation. This project uses USDA crop data.
FAO: The United Nations' Food and Agriculture Organization. This project uses FAO crop data.

Ruby (tested on version 1.9.2)
TMY3 Weather data should be placed in a folder called "tmy3_data_files" outside (i.e. next to) the TMY3_to_ET0 project folder. USDA crop information is already included.

You can download this project in either zip or tar formats.

You can also clone the project with Git by running:

$ git clone git://github.com/arsturges/TMY3_to_ET0

There is no installation required. Simply download the project directory and run the file tmy3.rb.

$ git clone git://github.com/arsturges/TMY3_to_ET0
$ cd TMY3_to_ET0
$ ruby tmy3.rb

This project code is free and open source.

Andy Sturges (arsturges@lbl.gov)