ET Data Entry


Calculation of the monthly maximum ET from phreatophytes is accomplished by calculating the crop irrigation requirement from daily minimum and maximum temperatures and precipitation at three stations and then interpolating these values across the model domain.

Creating the input data sets comprises the following steps:

  1. Download and process TD3200 data set;
  2. Run mkttp to extract selected stations and to fill data gaps;
  3. Run mkmonet to calculate monthly maximum ET;
  4. Append new data to data/monet.dbf.

The ET calculations are performed in the all directory. The final result which comprises monthly ET values are stored in the file data/mkonet.dbf.

Daily Meteorological Data

National Climatic Data Center (NCDC) TD3200 Cooperative Summary of the Day (CSOD) data sets are available for download from the NCDC web site at ftp://ftp.ncdc.noaa.gov/pub/data/rcc/final. These data sets contains daily minimum and maximum temperature, precipitation, evaporation, snow depth, and other fields for about 20,000 stations and are quite large. While the mkttp could operate on the full data set, a subset of relevant stations and parameters are provided in the file TD3200 which is the output of the mktd program.

The program mkttp reads the TD3200 file and extracts the daily minimum and maximum temperature and precipitation data for relevant stations. It then performs data filling as necessary and saves the daily minimum and maximum temperature and precipitation for the period of record in TD3200 to files named 050109.txt, 255310.txt and 257070.txt.

Monthly Maximum Phreatophyte ET

In order to update the monthly ET for a year, the program mkmonet is run. The program reads the files 050109.txt, 255310.txt and 257070.txt to extract the daily data for the year specified. It then performs the ET calculations and prints the results to the screen.

These output from mkmonet is then appended to the file monet.txt. This text file is then converted into a dBase file data/monet.dbf using the dat2dbf program.

1918 to 2003 data

For years from 1918 to 2003, the ET calculations were done using several manual steps. This included filling the meteorological data by hand, then running the RefET program to calculate ETo using the Hargreaves 1985 equation, followed by some manual manipulation of the data in spreadsheets and a TR-21 program.

In the process of transferring data from one program to the next using text files, some numerical roundoff occurred. Therefore the results for maximum monthly phreatophyte ET obtained using the mkmonet program is slightly different than that shown in monet.txt.

Example: Prepare ET data for 2004

After downloading TD3200 data to TD3200, mkttp is run to fill the missing data. Then mkmonet is run to calculate the monthly maximum phreatophyte ET and append it to monet.txt. Finally dat2dbf is run to convert the text file to a dBase file. 
mkttp
mkmonet 2004 >> monet.txt
dat2dbf -o ../data/monet.dbf monet.txt
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