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NEW MEXICO CLIMATE CENTER |
Eto = reference evapotranspiration or potential evapotranspiration referenced to grass.
The reference for this work is Sammis, T.W., E.G. Hanson, C.E. Barnes, H.D. Fuehring, E.J. Gregory, R.F. Hooks, T.A. Howell, and M.D. Finkner. 1979. Consumptive use and yield of crops in New Mexico. New Mexico State University, Las Cruces. WRRI Report No. 115.
Crop Coefficient uses growing degree days (GDD) accumulated from planting based on the averaging method of calculating GDD with a maximum temperature cutoff of 81 F and a minimum cutoff temperature of 40 F. The Base Temperature is 40 F. Data fits two 3 ordor polynomals. Use the firt polynomal up to 1300 GDD and then use the second polynomal.
| intercept | x | x^2 | x^3 |
-1.74E-02 |
8.94E-04 |
-5.10E-07 |
0.00E+00 |
-1.93E+00 |
2.28E-03 |
-4.47E-07 |
0.00E+00 |
The data can be fit to one polynomal which is kc=2.70E-1 -4.8E-4 Gdd +6.27E-7 GDD^2-1.3E-10 GDD^3 When the data is expressed in heat units the drop in the crop coefficient during the winter months is small because little heat units are generated during December and January.
| If you have any questions please contact webmaster@weather.nmsu.edu Updated: Dec 18 1996 Copyright © 1996 New Mexico State University |
Department of Agronomy and Horticulture Box 30001 / Dept.3Q / Las Cruces, N M 88003-8003 Telephone: (505)646-3405 FAX: (505)646-6041 |