1. Initial Research Directions for Mapping Chilling Statistics
Christopher Daly
Joseph Smith
PRISM Group
Northwest Alliance for Computational Science and Engineering
Oregon State University
RMA Business Analytics User Group Meeting
13-14 September 2017
Davis, CA
GROUP
PRISM

2. Mapping Chilling Statistics
Background
RMA insures losses from fruit and berry crops, such as peaches and blueberries. Many of these crops have vernalization requirements for proper emergence from dormancy, and subsequent growth, flowering and fruiting. Poor vernalization, in the form of insufficient chilling hours during the dormant season, can result in reduced production and quality.
Objectives of Initial Research
Consider options for chilling calculations
Outline methods for mapping chilling hours nationally
Consider how chilling hours information will be incorporated into existing PRISM/RMA portals
Solicit input from RMA on current procedures and specific needs

3. Chilling Calculations
Chilling Hours (CH) Models
45F and under model
Number of hours at or below 45F
Most commonly used; published chilling hour thresholds available for many species and varieties
32-45F model
Only number of hours between 32 and 45F are counted
Utah Model (chilling units (CU))
Positive or negative accumulations,
depending on temperature

4. Chilling Calculations
Chill Portion (CP) Model
Dynamic model that accounts for “canceling out” of chilling hours when temperatures fluctuate above and below 45F
Originated in Israel, adopted and tested at UC Davis, mostly for California orchard crops
Likely most physiologically accurate
Published chill portion requirements likely not available for as many species and varieties as chill hours ≤ 45F

5. Hourly Temperature Stations

6. Hourly + Daily Tmax/Tmin Stations
Period of Interest:
Sep 2016 – Mar 2017
Red: CPC stations
Green: Additional stations available to PRISM

7. PRISM National Temperature Stations

8. Options for Mapping Chilling Statistics
Option 1 – Hourly Temperature Simulation
Step 1: Estimate hourly temperatures from daily tmax/tmin at each grid cell using a model that simulates the diurnal variation of temperature
Optimum parameters for the hourly temperature simulation vary in space and time; will need to be interpolated to a grid, perhaps monthly
Step 2: Calculate chilling statistic at each grid cell from the hourly temperature grids
Advantage is that any hourly statistic could be calculated on the fly from the hourly grids
Disadvantage is that there will be 24 grids per day, every day

9. Option 1: Create Hourly Temperature Grids from
Daily Tmax/Tmin, then Calculate Chilling Statistic
January, Columbus, GA
Model
Data

10. Options for Mapping Chilling Statistics
Option 2 – Direct Mapping of Chilling Statistics
Step 1: Calculate chilling statistic of interest at each hourly station
Step 2: Interpolate station chilling statistic to a grid using PRISM using tmax/tmin as guidance
PRISM would evaluate a spatially varying relationship between a combination of tmax and tmin and station chilling statistic
Advantage is that each day would not have to be evaluated separately (e.g., every 2-4 weeks)
Disadvantage is that each different chilling statistic would have to be mapped separately with PRISM

11. Daily Chilling Hours <=45F
Option 2: Map Chilling Statistic Directly from Hourly Station Data, Using Daily Tmax/Tmin Grids to Guide Mapping
Columbus, GA
Daily Chilling Hours <=45F
1 Oct 2016 – 30 Apr 2017

12. Option 2: Using Daily Tmax/Tmin Grids to Guide Chilling Statistic Mapping

13. Incorporating Chilling Hours Into PRISM/RMA Adjuster Portal
May need to be a new section, but could be incorporated into Detailed Data
Options for start and end dates, but possibly limited to weekly intervals
Comparisons to previous 10 years and 30-year averages

14. Gather Input From RMA Get perspectives from user group
Which chilling models are currently being used?
How are users currently accessing chilling statistics?
What are they used for?
What standards are the chilling statistics compared to, i.e., what is “normal?”
What is the work flow for evaluating chilling statistics? Reports needed?