1. Frost Forecasting for Lettuce Fields in Yuma, Arizona
Nick Dawson
Soil, Water, and Environmental Sciences Department
Advisor: Dr. Paul Brown

2. Outline Background Model description Test cases Experimental model
Results
Future work

3. Why Do We Care? > 90% winter production 450 million dollars
Consumer prices
1000% price hike

4. Weather Research and Forecasting Model
WRF
1.8 km resolution
27 hour forecasts
5am – 8am
Winter 2010/11
~4 C too warm

5. Resolution Comparison

6. Case Study Days for Trials
Above freezing/humid
Above/dry
Below/humid
Below/dry
Cold advective
5 weather station sites

7. Default Land Use Classification
Urban (Yuma)
Crop Fields
Orange - urban
3 – irrigated crops
14 – evergreen needleleaf forest
15 – mixed forest
19 – baren/sparsely vegetated
Forest

8. Default
Revised

9. Trial Setup Input Files Look-up Tables VF = vegetation fraction
SMC = soil moisture content
Trial Setup
Trial #
Adjustment 1
LAI min= 1.56; LAI max = 5.68
z 𝑜 min = 0.01; z 𝑜 max = 0.1 2
Input file soil changes: Sand changed to loamy sand, sandy loam to clay loam.
Table file changes: minimum SMC = 0.36 3
Trial 2 + Top two soil layers SMC = 0.36 for all crop/pasture land, VF = 85%
(all changes made to input files) 4
Trial 2 + VF = 85% (input file changes)

10. Trial Results 2 3 4 Trial Change 1 Table Soil Change SMC = 0.36 and
VF = 80% 4
Trial Results

11. 60% VF
0.32 SMC
Updated Land Use
Experimental Model

12. Results

13. Coldest 15-minute Temperature Scatter Plots
1 December 2011 – 15 January 2012

15. Statistic Control Model Experimental Model
RMSE
2.95
1.79
MAE
2.51
2.35
Bias
2.39
-0.42

16. Results in Action 7am temperatures GFS and NAM 51 hr forecast movie

17. Future Work Post forecast products Bi-weekly VF updates
Lettuce leaf temperature forecast

18. Review Big/important business Identified model issues
Improved ~ 3 degrees Celsius

19. Frost Forecasting for Lettuce Fields In Yuma, Arizona
Questions?
Selected references:
Deardorff, J. W., Efficient Prediction of Ground Surface Temperature and Moisture, With Inclusion of a Layer of Vegetation. J. Geo Research, 83,
Ek, M. B., K. E. Mitchell, Y. Lin, E. Rogers, P. Grunmann, V. Koren, G. Gayno, and J. D. Tarpley, Implementation of Noah land surface model advances in the National centers for Environmental Prediction operational mesoscale Eta model. J. Geophys. Res., 108, 22 PP, doi: /2002JD
Hogue, T.S., L. Bastidas, H Gupta, S. Sorooshian, K. Mitchell, W. Emmerich, Evaluation and Transferability of the Noah Land Surface Mode in Semiarid Environments. J. Hydrometeor, 6,
Prabhakaran, T., G. Hoogenboom, S. G. Gopalakrishnan, Evaluation of WRF for frost warning and consequences of cold air pooling. J. Compute. Electron. Agric., 64,
Wilks, D. S., Statistical methods in the atmospheric sciences. Burlington, MA [etc.]: Academic Press.