Forecasting Chilling Accumulation, Rest Completion,
and Crop Development in the Southeastern U.S.
John G. BellowAgrometeorologist – Extension
Specialist
Center for Ocean-Atmospheric Prediction StudiesThe Florida State University
Tallahassee, FL
Meetings withstakeholders and advisorsindicated a need for additional climate variablesemphasizingdevelopment andphenology
Methods NWS Coop Data Data cleaning Calculation of hourly temp Calculation of daily, monthly,
and seasonal thermal units ANOVA and Tukey in 293
counties
• Hourly temperature estimation from: Lat., Long., Max T, Min T•Non-linear fit using FAWN hourly data for 9 sites (3 coastal 6 inland)•Tested on independent FAWN sites: R2 =0.92 (n = 6)
Hourly temperature estimation from daily Tmax and Tmin
A.M. Time of Day P.M.0 3 6 9 12 3 6 9 12
Tem
per
atu
re °
F
60
65
70
75
80
85
Observed TemperaturePredicted Temperature
ROJAS AND MARTINEZ, 1990
0 3 6 9 12 15 18 21 24 27 30
2
1
1
Temperature
CU
Coeff
icie
nt
1
2
f 9 t( )
300 t
Chill units accumulated a 1 CU per hour at optimal temperatureand 0.0 CU per hour at Tmax and Tmin
The loss of chill units with diurnal warming was not included in the present analysis
ANDERSON AND SEELEY , 1992
Derived forecast productsChilling accumulation
Blueberries Chill hours Chill Units
T < 7.2 °C Tmax:15.0 °C; Topt:7.2 °C; Tmin: -2.5 °CSHINE AND BUCHANAN 1982
Strawberries Tmax:20.0 °C; Topt:7.2 °C; Tmin: 0 °CBIGEY 2002
Peaches T < 7.2 °C Tmax:14.0 °C; Topt:6.0 °C; Tmin: -2.0 °C
Growing degree days
GDD Hourly GDD Daily Mean EREZ ET AL 1990
Wheat THour > 0 °C Tmean > 0 °C (T-Tbase)
Rest Completion
Subtropicals Rest hours
Avocado -1.1 < T < 15.0 °C
Mango 4.4 < T < 15.0 °C
Lychee 10 < T < 15.0 °C
CRANE AND SHAFFER 2004
Blueberries Range of chill required 150 – 800 hrs Anthesis Feb-Mar; Harvest Apr-Jun Integration from Oct through Feb. Role of cool temperatures on floral bud
initiation and maturation.
El Niño CU Oct-Apr method 3
bb_ensomeans_oct_apr.no3
421 - 500
501 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
2501 - 3000
El Niño CU Oct-Apr method 5
bb_ensomeans_oct_apr.no5
60 - 500
501 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
2501 - 3000
Chill units estimation Chill hours estimation
CU provide a higher estimation of chilling than chill hours.
La Niña CU Oct-Apr method 5
bb_ensomeans_oct_apr.na5
52 - 500
501 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
2501 - 3000
La Niña CU Oct-Apr method 3
bb_ensomeans_oct_apr.na3
292 - 500
501 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
Chill units estimation Chill hours estimation
El Niño Chill Units Anomolies
nino_3
-109.6780 - -100.0000
-99.9999 - 0.0000
0.0001 - 100.0000
100.0001 - 200.0000
200.0001 - 300.0000
300.0001 - 400.0000
El Niño Chilling hour anom.
nino_5
-114.4531 - -100.0000
-99.9999 - 0.0000
0.0001 - 100.0000
100.0001 - 200.0000
200.0001 - 300.0000
300.0001 - 400.0000
Chill units anomalies Chill hours anomalies
El Niño signal is an increase in chill
La Niña Chill Units Anomolies
nina_3
-193.2572 - -100.0000
-99.9999 - 0.0000
0.0001 - 100.0000
100.0001 - 200.0000
200.0001 - 300.0000
La Niña Chilling hour anom.
nina_5
-331.7363 - -300.0000
-299.9999 - -200.0000
-199.9999 - -100.0000
-99.9999 - 0.0000
0.0001 - 100.0000
100.0001 - 200.0000
200.0001 - 300.0000
Chill units anomalies Chill hours anomalies
La Niña brings reduced chilling
Strawberry
•Chill requirements from 700 to 1300 hours•Responses to inadequate chilling include artificial chilling and photoperiod treatments
El Niño chill
nino
606 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
La Niña Chill
nina
540 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
Movement of chill isotherms south in C Fl during El Niño.
La Niña Anomolies
ninaanom
-306 - -300
-299 - -200
-199 - -100
-99 - 0
1 - 100
101 - 200
El Niño Anomolies
ninoanom
-78 - 0
1 - 100
101 - 200
201 - 300
Signals weak or non-existent in N GA & AL.
Increase in chill with El Niño and decrease in chill with La Niña.
Peach Alabama peach growers are facing a serious crisis as a result of the 1998-99 winter weather
pattern that has resulted in what may prove to be a record shortage of chilling. Georgia, South Carolina and Alabama have made application for state labels (24C) for application of Dormex on peaches, nectarines and blueberries to help overcome the shortage of chilling hours being experienced this winter. It is hoped the Alabama label will be issued by January 21, 1999. Georgia and South Carolina have already issued their state labels.
Chill requirements 150 – 1050 hours Anthesis Jan – Feb; Harvest May -July
El Niño Means
snhr_no
191 - 500
501 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
El Niño Means
_45mn_no
7 - 500
501 - 1000
1001 - 1500
1501 - 2000
2001 - 2500
2501 - 3000
CU methods estimates greater chill accumulation compared with Chill hours using daily mean values.
El Niño Anomolies
noan_snhr
-42 - 0
1 - 100
101 - 200
201 - 300
301 - 400
El Niño Anomolies
noan_45mn
-46 - 0
1 - 100
101 - 200
201 - 300
Clear increase in chill for peaches with El Niño
La Niña Anomolies
naan_snhr
-226 - -200
-199 - -100
-99 - 0
1 - 100
101 - 200
201 - 300
La Niña Anomolies
naan_45mn
-409 - -400
-399 - -300
-299 - -200
-199 - -100
-99 - 0
1 - 100
Wheat
Winter forage grass October establishment – Jan – Mar use. Biomass development and timing are
principal concerns.
El Niño anomolies Mean
noan_1
-370 - -250
-249 - 0
1 - 200
La Niña anomolies Mean
naan_1
-78 - 0
1 - 250
251 - 500
501 - 750
GDD anomalies for wheat consistent with known ENSO signals, El Niño cooler and La Niña warmer.
Anomalies broadly significant across tri-state region.
Wheat La Niña GDD Hourly
na_2
3004 - 4000
4001 - 5000
5001 - 6000
6001 - 7000
7001 - 8000
8001 - 9000
Wheat La Niña GDD Daily Mean
na_1
3205 - 4000
4001 - 5000
5001 - 6000
6001 - 7000
7001 - 8000
8001 - 9000
Little impact of hourly vs. daily estimation, both appear satisfactory.
Subtropicals
180 to 400 hours of rest
Rest hours for subtropicals reduced during La Niña and increased during El Niño.
Enso anomalies small within S FL Differences not significant in region
Avocado La Niña anomolies_N_M
naan_avoc
100.1 - 200.0
0.1 - 100.0
-99.9 - 0.0
-199.9 - -100.0
-299.9 - -200.0
-314.5 - -300.0
Avocado El Niño anomolies_N_M
noan_avoc
3 - 100
101 - 200
201 - 300
301 - 400
Mango El Niño anomolies_N_M
noan_mang
22.9 - 100.0
100.1 - 200.0
200.1 - 300.0
Mango La Niña anomolies_N_M
naan_mang
-278.1 - -200.0
-199.9 - -100.0
-99.9 - 0.0
0.1 - 100.0
Lychee El Niño anomolies_N_M
noan_lych
-54 - -50
-49 - 0
1 - 50
51 - 100
101 - 150
151 - 200
Lychee La Niña anomolies_N_M
naan_lych
-148 - -100
-99 - -50
-49 - 0
1 - 50
Conclusions
Prediction of thermal units for development and phenology based on ENSO climatology seems robust for deciduous fruits and wheat, however results were somewhat weaker for subtropical rest completion.
Signal is consistent with previous knowledge
All forecasts will be enhanced by the integration of ‘season to date’ data.
Weakness from the integration dates range
Further directions
Reanalysis for ‘days to completion’ for threshold accumulations for specific cultivars or varietals?
Phenology models for budbreak and anthesis incorporating CU to dormancy and HU to budbreak?
Deployment as probabilistic forecast through agclimate