Potential Crop Evapotranspiration Wizard
Using Samani's Equation

Step 1: Getting daily weather data:

User Friendly Choices:


A:
(Get data from the links below and follow steps for choice A or B)
Go to NCDC site and get current daily temperature data or data from past years for a cooperator site
. The data is not in column format. Select the station you desire and the Maximum and Minimum climate variables. The results will be emailed to you. Copy the data without the header into the Wizard and hit the NCDC button to convert the data to column format. Check the data. If the temperature has 9999 values replace these numbers with estimates based on the previous temperature data. The 9999 values means missing data. .

Go to the Western regional climate center and get long term temperature data for a  cooperator site. Fit the data to a polynomial using excel and then generate daily temperature climate data to put in the calculator.


Choice AUtah is a sister climate center that contains weather data for most of the US and some for the whole world.

1..  Paste the data that you selected in the white box  in the Wizard , (to paste go to edit and then paste, you must select the white box before pasting). Now your data is in the white box, make sure that all the lines are complete and uniform.
For Example:
0404,29002202,1995,01,01,-99999,M,0, ,0, ,0, ,-99999,M,-99999,M,-99999,M
.
.
0404,29002202,1995,01,01,-99999,M,0, ,0, ,0, ,-99999,M,-99999,M,-99999,M

Notice the -99999 numbers, this means that data is missing, any invalid data will 
not be processed, make sure that the whole of your submission is not like the line above, 
otherwise you will not get an answer back.

Getting the latitude

2 Now we need to get the latitude for the equation, using the station's name that we took note of earlier or you can get the latitude of any city that publishes climate data .

 


 

Choice B. This is our site's data, we update daily for selected places in NM. Click here to see form and then hit back for instructions

1. Upon selecting the submit button we will retrieve any available information. Another page will then give you an option to download or view your file, simply view it.

2. Now scroll down till you find the date(s) you wish to calculate the PET for . When you have found the data that you wish to use simply copy the selected text to the clip board (To copy to the clip board simply go to edit and select copy.)

3. Ok, we now have the data to be processed. Paste the data that you selected in the following large white box , to get back use the back button. (to paste go to edit and then paste, but you must click on the white box before you can paste in it). Now your data is in the white box, make sure that all the lines are complete and uniform.
For Example:
01 97 01 22 058 29 45 079 32 000 02.6 11.7 01.6 321 10.5 46 03.0 00.0 04 02 029
.
.
.
01 97 01 23 064 39 50 071 27 000 06.5 20.4 05.0 002 10.8 46 03.1 00.0 09 04 030

Getting the latitude

4 Now we need to get the latitude for the equation, using the station's name that we took note of earlier..

5. On the following page select the link corresponding to the station name and make note of the latitude from here.
Note: Value is given as "Latitude: 32 16' 56.0" N" type this in the box below with a colon ':' between the first two and middle two digits,
i.e. 32:16.

Getting the Kt values 

6. Set the value for the Kt , see the link for values at different locations. The default value is low for sites in New Mexico.

Crop Specific Evapotransperation Option and Temperature units.

7. Select the temperature units. F or C

8. Click on the crop box to generate Crop Coefficients and ET. Select the crop from the drop down list. You have to start the climate data from the planting data or for perennials from the first of the year. The crop coefficients can be expanded or compressed for different varieties that have different maturity dates from the varieties used to develop the crop coefficient by changing the ratio number which is the ratio of the growing degree days to maturity for your variety compared to the growing degree days for the current variety. To determine the growing degree days for the current variety see the crop coefficient data base at  http://weather.nmsu.edu/nmcrops/

8. Now you have all the  information that this Wizard requires! Hit the submit button.