4.8: Accessing Climatic Information
- Page ID
- 44382
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The rate plants use water determines irrigation schedules and ultimately the depth of irrigation water to apply. Without this information it is difficult to efficiently manage irrigation systems. The methods in this chapter rely on data for reference crop conditions with the Penman-Monteith equation. This involves accurate measurement of several climatic variables. Most irrigators will not measure these variables at their field. Fortunately, weather data networks have been established across the United States to provide data for the Penman-Monteith method. In most situations, networks also compute the reference crop ET. Care must be taken to ensure that the reference ET provided by the service is for a short reference crop (i.e., grass clipped to a height of 5 inches). Providers of the climatic data may also compute water use rates for crops grown in the local vicinity. While these calculations should be carefully monitored for accuracy and reliability, the computed values can often be used directly for managing irrigation. Readers should refer to the local Extension Service at their university for assistance in locating climatic data for their location. An example of data provided from the High Plains Regional Climate Center is provided in Table 4.8. These data can be used in irrigation scheduling and other applications. Smith (1992) developed a decision support program to estimate crop water requirements for a wide range of crops. The program can utilize local weather data or historical climatic information to develop average water requirements for planning purposes. The program can be used for irrigation scheduling and is useful for managing whole-farm irrigation systems. Data are also becoming available from analysis of Landsat and other remote sensing systems. Techniques have been developed to predict ET and crop coefficients. There are several current and emerging techniques along with new satellite capabilities that promise future opportunities for irrigation planning and management. The example from Barker, et al. (2018) shows that remote sensing can accurately predict crop coefficients periodically throughout the growing season. Methods like that by Barker et al. (2018) also provide methods to estimate ET and crop coefficients between the days that satellites pass over the specific locations. Currently, these methods are still being developed but promise substantial opportunity for real-time irrigation management in the future.
| Month | Day | Air Temperature, °FMax. | Air Temperature, °F Min. | Air Temperature, °F Avg. | Air Temperature, °F Dew Point | Wind Speed (mi/hr) | Solar Radiation (Lang/d) | Rain (in) | ETo (in/d) | Growing Degree Units |
|---|---|---|---|---|---|---|---|---|---|---|
| 7 | 2 | 85.5 | 63.9 | 76.7 | 70.4 | 8.2 | 559 | 0.16 | 0.26 | 25 |
| 7 | 3 | 87.5 | 63.1 | 75.3 | 65.9 | 5.4 | 951 | 0 | 0.27 | 25 |
| 7 | 4 | 88.4 | 64.6 | 76.5 | 68.3 | 4.1 | 668 | 0 | 0.26 | 25 |
| 7 | 5 | 86.7 | 64.3 | 75.5 | 67.8 | 3.0 | 542 | 0 | 0.21 | 25 |
| 7 | 6 | 91.1 | 65.6 | 78.4 | 70.2 | 4.5 | 600 | 0 | 0.25 | 26 |
| 7 | 7 | 91.3 | 67.4 | 79.4 | 69.6 | 9.5 | 659 | 0 | 0.34 | 27 |
| 7 | 8 | 92.2 | 62.6 | 77.4 | 66.0 | 11.4 | 643 | 0.62 | 0.38 | 24 |
| 7 | 9 | 83.8 | 59.9 | 71.9 | 65.6 | 5.0 | 638 | 0 | 0.24 | 22 |
| 7 | 10 | 88.7 | 62.5 | 75.6 | 68.8 | 6.7 | 597 | 0.01 | 0.26 | 24 |
| 7 | 11 | 85.0 | 62.0 | 73.5 | 66.0 | 5.8 | 647 | 0 | 0.26 | 24 |
| 7 | 12 | 85.1 | 58.1 | 71.6 | 64.0 | 4.5 | 548 | 0 | 0.22 | 22 |
| 7 | 13 | 91.8 | 63.1 | 77.5 | 68.0 | 8.7 | 636 | 0.14 | 0.33 | 25 |
| 7 | 14 | 77.8 | 63.4 | 70.6 | 65.3 | 6.4 | 407 | 0.01 | 0.16 | 21 |
| 7 | 15 | 81.4 | 60.8 | 71.1 | 63.3 | 4.2 | 584 | 0 | 0.22 | 21 |