Grow Degree Calculator

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Grow Degree Calculator application.

The Grow Degree Calculator (GDC) project is based on the WRF Hindcast project and calculates the Grow Degree values for either crops or insects. Users can enter the temperature parameters, location, and start and end dates for the organism of interest. Output includes an image of the total accumulated values over the target sector, a plot of accumulated values over time, and a text report.

Accumulated grow degree values are important for agriculture because it can accurately predict organism behavior. For example, knowing the accumulated grow degree values throughout a season, farmers can say when orchard trees will blossom, or when insects will hatch, and more. Click here to use the GDC application.

This is an educational platform disseminating research ideas and applications. We hope that the user can benefit from the software and hardware sources provided but we do not take any responsibility for the consequences of decisions based on data released or on the results given in our applications. See the footer disclaimer for more information.


The GDC application calculates a location's accumulated grow degree value from historical WRF Hindcast data stored on our server. The user customizes the calculation request by entering temperature parameters, location, and run dates. The application determines which sector and data pixel to use, gets historical daily minimum and maximum temperatures, calculates and accumulates the grow degree units over the run dates given for the pixel location.

Calculation of Grow Degree

The Grow Degree Calculator (GDC) package implements a simple daily calculation:

                     (Daily Max Air Temp + Daily Min Air Temp)
   Daily Degree Day = ----------------------------------------  - Base Temp


        "Daily Max Air Temp" is capped by the "Upper" temperature threshold.


        if "Daily Degree Day" < 0 then set "Daily Degree Day" = 0.

"Daily Degree Day" values are accumulated over the period of specified run days.

Links of Interest

GDC application with numbered sections

Guide to GDC application.

Input section

Temps (celsius)

 yellow #1 in the above image

Organisms (plants and insects) have a range of temperatures in which they can grow. Example: 5, 30

    base  5
      The base input value (celsius) is the lowest temperature at which the organism can grow.
    upper  30
      The upper input value (celsius) is the highest temp at which the organism can grow.

Location (decimal degrees)

 yellow #2 in the above image

Note: currently about 1/3 of the geographical area of the contiguous 48 states is available for processing. See WRF Hindcast for current operational sectors. If the provided latitude and longitude values are not within the active sectors an error message will appear stating 'Cannot find given location in active sectors'.

The latitude and longitude values of the area of interest, in decimal form. Example: 32.25049, -106.74516

    latitude  32.25049
    longitude  -106.74516

Rundates (yyyymmdd)

 yellow #3 in the above image

The start and end date specify when to accumulate the grow degree values. Dates are given in the YYYYMMDD format, eg. March 5, 2017 would be 20170305. Example: January 1, 2017; April 6, 2017

    start  20170101
    end  20170406


 yellow #4 in the above image

Run the application with the provided values of Temps, Location, and Rundates.

Output section

Three images: 3.3km, 10km, 30km

 yellow #5 in the above image

Clicking on a tab will display the processed accumulated Grow Degree image of the area of interest. All 3 images are 171 x 171 pixels in size but the resolution of each pixel varies in each of the 3.

    3.3km  each pixel in this image represents an area approximately 3.3 km by 3.3 km.
    10km   each pixel in this image represents an area approximately 10 km by 10 km.
    30km   each pixel in this image represents an area approximately 30 km by 30 km.

Clicking on the '+' in the image will 'zoom-in' the image.

Clicking on the '-' in the image will 'zoom-out' the image.

If your mouse has a wheel you can use it to zoom in and out.

Clicking and holding down the left button on the mouse enables moving the image.

Clicking on the 'house' in the image will restore the image to its initial display size and position.

In the 3.3km image you should see a small blinking black square in the image. Your latitude and longitude of interest will be inside this square. Use the '+' sign or the wheel on your mouse to zoom in. Move the mouse around inside the square until the latitude and longitude values shown in #6 approximate the values you entered in #2 for latitude and longitude. It is unlikely they will match exactly, a small disappointing aspect of the display software. Note that the 'Text report' (yellow #8) has the exact latitude and longitude.

If you don't see the small blinking black square it's because the underlying or surrounding area is also black or blackish. In this case move the mouse around in the image and look at the latitude and longitude values displayed in #6 until you have homed in on the desired area, then zoom in, etc.

Latitude, Longitude, GDC value

 yellow #6 in the above image

Each pixel of the displayed image (171 x 171 pixels = 29,241 total pixels per image) has values representing the pixel's latitude, longitude, and the calculated Grow Degrees. Move your mouse over the image and watch #6 to see the results.

Plot of Grow Degrees during Rundates for the area of interest and temperatures

 yellow #7 in the above image

Text report

 yellow #8 in the above image

Text description of the GDC run and its results.