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

Outline Background Model description Test cases Experimental model Results Future work

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

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

Resolution Comparison

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

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

Default Revised

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)

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

60% VF 0.32 SMC Updated Land Use Experimental Model

Results

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

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

Results in Action 7am temperatures GFS and NAM 51 hr forecast movie http://ag.arizona.edu/azmet/LIF.htm

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

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

Frost Forecasting for Lettuce Fields In Yuma, Arizona Questions? Selected references: Deardorff, J. W., 1978. Efficient Prediction of Ground Surface Temperature and Moisture, With Inclusion of a Layer of Vegetation. J. Geo Research, 83, 1889-1903. Ek, M. B., K. E. Mitchell, Y. Lin, E. Rogers, P. Grunmann, V. Koren, G. Gayno, and J. D. Tarpley, 2003. 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:10.1029/2002JD003296. Hogue, T.S., L. Bastidas, H Gupta, S. Sorooshian, K. Mitchell, W. Emmerich, 2005. Evaluation and Transferability of the Noah Land Surface Mode in Semiarid Environments. J. Hydrometeor, 6, 68-84. Prabhakaran, T., G. Hoogenboom, S. G. Gopalakrishnan, 2008. Evaluation of WRF for frost warning and consequences of cold air pooling. J. Compute. Electron. Agric., 64, 234-347. Wilks, D. S., 2006. Statistical methods in the atmospheric sciences. Burlington, MA [etc.]: Academic Press.