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

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

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

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

Hourly Temperature Stations

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

PRISM National Temperature Stations

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

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

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

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

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

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

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?