This page summarizes the comparison of the Grow Degree Calculator model to available ground weather stations in our scope.
New Mexico State University makes weather data publicly available through the ZiaMet website. Grow Degree units from model and sensed data were compared over nine ZiaMet weather stations throughout New Mexico with dates ranging from 2017-01-01 to 2019-03-31. Not all stations spanned the given range and one station was not used at all due to insufficient data. Results are given in the table below:
| Site | Regression | R^2 | Samples | % Error |
|---|---|---|---|---|
| Artesia ASC | 0.9653x - 0.6367 | 0.97 | 516 | 10.6 |
| Clovis ASB | 0.9494x + 0.4194 | 0.98 | 782 | 0.5 |
| Fabian Garcia SC* | 0.9071x + 0.1435 | 0.96 | 820 | 8.9 |
| Farmington ASC | 0.9400x + 0.0602 | 0.98 | 777 | 5.6 |
| JTH Forestry RC | 0.9594x + 0.2280 | 0.98 | 321 | 0.2 |
| Leyendecker II PSRC | 0.9436x - 0.3348 | 0.96 | 820 | 9.2 |
| Los Lunas ASC | 0.9035x - 0.1963 | 0.97 | 553 | 13.6 |
| NMSU Main* | 0.9021x + 0.7843 | 0.97 | 820 | 3.8 |
| Tucumcari ASC | 0.9450x + 0.4084 | 0.98 | 819 | 1.3 |
You can download the data CSV files here.
Note: The regression equation for each site can be used to calibrate the model values to the sensed values. This functionality will be available in the the next version of the Grow Degree Calculator.
Also note that when the regression offset is negative the adjusted value (negative -> 0) affects the accumulated values, slightly. In practice, it is better to use the calibrated and unadjusted in order to conform to the regression equation. See the "adjusted" column in the data files for numerical details.
You can conduct your own analysis by checking the "Download" box in the SME tool. Look for the "analysis.csv" in the downloaded zip. The crop file used will have the lower and upper parameters specified. The GDC tool will be updated to include the "analysis.csv" file on the next revision.