accumulated winter chill is decreasing in fruit growing regions of california dennis baldocchi...

Accumulated Winter Chill is Decreasing in Fruit Growing Regions of California

Dennis BaldocchiUniversity of California, Berkeley

Ag and Food BoardModesto, CA

November 29, 2012

ESPM 111 Ecosystem Ecology

ESPM 111 Ecosystem Ecology

Berkeley Earth Temperature Project Re-Confirms Global Warming

http://berkeleyearth.org/

ESPM 111 Ecosystem Ecology

What is Happening in the Central Valley?

Modesto

Year

1920 1940 1960 1980 2000 2020

Mea

n A

nnua

l Air

Tem

pera

ture

, C

14

15

16

17

18

19

Mean Annual Air Temperature at Modesto is Warming

Impacts of Warmer Temperature on Agriculture?

• More Evaporation and Water Use• Earlier Growing Season

– Faster phenology– Risk of frost– Asynchrony between flowering and pollinators

• Less Winter Chill and Dormancy– Reductions in Yield

Distribution of Orchards

Luedeling et al 2009 PLOS

Deciduous Fruit Trees Need Dormancy and Rest during the Winter

Tmin

Tmax

Tref

a

d

b

c

TaveNoon

chillhours d TT T

refref

2

2( )min

dchillhours

T Tref 2

tan ( )min tanmin

a

b

hr

T Tave

6

Estimating Winter Chill

C hill H ours 2004 2005

-124 -123 -122 -121 -120 -119 -118 -117 -116 -115

33

34

35

36

37

38

39

40

41

42

0

500

1000

2000

3000

4000

5000

6000

Map of Chill-Degree Hours

Year

1985 1990 1995 2000 2005 2010Ch

ill D

egre

e-H

our

s, b

elo

w 7

.22

oC

Nov

1 th

roug

h F

eb 2

9

1000

1500

2000

2500

3000

3500

4000

Brentwood, CA

Year

1985 1990 1995 2000 2005 2010

Ch

ill H

ours

, bel

ow 7

.22

o C N

ov1

thro

ugh

Feb

29

400

600

800

1000

1200

1400

1600

Downward Trend in Chill Hours near Brentwood, East Contra Costa

20 year record, CIMIS Data

Orland, Ca

Year

1940 1950 1960 1970 1980 1990 2000 2010

Ch

ill H

ou

rs, b

elo

w 7

.22

oC

400

600

800

1000

1200

1400

1600

1800

Coefficients:b[0] 14228b[1] -6.711r ² 0.234

Year

1940 1950 1960 1970 1980 1990 2000 2010

Ch

ill D

egre

e-H

ou

rs, b

elo

w 7

.22

oC

0

1000

2000

3000

4000

5000

Coefficients:b[0]: 47974b[1]: -23.01r ²: 0.248

Downward Trend in Chill Hours near Orland, northern Sac Valley

50+ year Record, Coop Data

-124 -123 -122 -121 -120 -119 -118 -117 -116 -115

33

34

35

36

37

38

39

40

41

42

-40 to -20 -20 to -15 -15 to -10 -10 to -5 -5 to 0 0 to 10

Trends in W inter Chill Hour Accum ulation (hours per year)Nov-M ar, 0 to 7.22 C

Trends in Chill Hours

-124 -123 -122 -121 -120 -119 -118 -117 -116 -115

33

34

35

36

37

38

39

40

41

42

-100 to -75 -75 to -50 -50 to -25 -25 to -10 -10 to 0 0 to 10

Trends in W inter Chill Degree Hours Accum ulation (degree-hours per year)N ov-M ar, 0 to 7.22 C

Trends in Chill Degree hours

Red Bluff, CA, B1

Years

1940 1960 1980 2000 2020 2040 2060 2080 2100 2120

Ch

ill H

ou

rs, b

elo

w 7

.22

o C

200

400

600

800

1000

1200

1400

1600

Davis, CA, B1

Years

1940 1960 1980 2000 2020 2040 2060 2080 2100 2120

Ch

ill H

ou

rs, b

elo

w 7

.22

o C

0

200

400

600

800

1000

1200

1400

1600

1800

Fresno, CA, B1

Years

1940 1960 1980 2000 2020 2040 2060 2080 2100 2120

Ch

ill H

ou

rs,

be

low

7.2

2

o C

200

400

600

800

1000

1200

1400

1600

Potential Trends, based on Climate Scenarios

Winter Chill Models

Darbyshire et al 2011. AgForMet

Luedeling et al 2009 PLOS

Safe Chill, 10th Quintile of the Chill Probability Distribution,A Conservative Measure of Potential Chill

Reductions in Winter Chill are Predicted, but Less Severe with Dynamic Model

Luedeling et al 2009 PLOS

Map with Classic Chill Model

Map with Dynamic Model

Proposed Hypotheses as to Why Winter Chill Accumulation is Declining

• Are Downward Trends in Winter Tule Fog Occurring?

• Are they amplifying effects of global warming, by causing a switch in the surface energy balance?

Detecting Trends in Fog

• Remote Sensing, AVHRR and MODIS– Time Series extends back to 1981– Gives good spatial coverage– Two samples per day; does not detect night fog– Can’t see through Clouds

• Automated Weather Stations, CIMIS– Time series extends back to 1982– Poor spatial Coverage

• Coop Weather Stations– Time Series extends back to 1920s– Few Stations– Fog must be inferred from rain and temperature

Central Valley Tule Fog, Iconic Case

Clear

Fog

Fog and Clouds

Clouds and Fog

Science and Art in Detecting Fog and Fog Area

Presence and Absence of Fog has Marked Influence on Temperature and Solar Radiation

mm d-1 MJ m-2 d-1 oC oC oC

ppt Rg Tave Tmax Tmin RH Tdew

Brentwood 0.10 3.77 7.38 10.27 4.34 92.30 6.23

Davis 0.30 4.18 6.42 9.78 3.53 91.77 5.13

Firebaugh 0.09 3.63 7.63 10.20 4.85 95.32 6.92

Five Points 0.54 3.44 5.39 8.97 4.05 93.27 4.39

Gerber 0.26 5.74 7.69 13.15 3.51 85.08 5.20

Kettleman City 0.27 4.67 8.21 11.22 5.37 86.86 6.06

Modesto 0.13 3.76 7.04 9.90 4.13 92.93 5.95

Parlier 0.14 3.78 7.71 10.57 5.30 93.25 6.67

Twitchell Island 0.19 3.45 4.75 7.68 2.15 94.55 3.92

Westlands 0.09 3.59 7.61 10.21 4.90 91.70 6.40

ave 0.21 4.00 6.98 10.19 4.21 91.70 5.69

std 0.14 0.71 1.12 1.41 0.98 3.25 0.99

Weather under Tule Fog

MJ m-2 d-1

Rg Tave Tmax Tmin RH

Brentwood 11.52 9.55 17.12 2.53 60.43

Davis 11.28 8.88 16.80 2.05 58.74

Firebaugh 11.22 8.65 17.37 0.89 63.37

Five Points 12.35 8.33 17.56 0.64 61.22

Gerber

Kettleman City 11.92 10.22 17.89 2.67 56.89

Modesto 11.26 7.47 16.89 -0.18 70.03

Parlier 11.53 8.51 17.62 1.33 71.03

Twitchell Island 11.77 8.74 17.07 1.26 66.90

Westlands 12.04 8.12 17.84 -0.36 59.89

mean 11.65 8.72 17.35 1.20 63.17

stddev 0.39 0.80 0.40 1.09 5.05

Weather Clear Days during the Fog Season

0 100 200 300 400 500 600 700 800 9000

1

2

3

4

5

6

7

Tle

af -

Tai

r, K

Rnet, W m-2

Temperature Difference, Bud-Air

0 5 10 15 2080

82

84

86

88

90

92

94

96

98

100

Tmax-Tmin

RH

0

0.005

0.01

0.015

0.02

0.025

0.03

Weather Conditions on Fog Days

0 5 10 15 20 2540

50

60

70

80

90

100

Tmax-Tmin

RH

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

Weather Conditions on Clear Days, during Fog Season

20 40 60 80 100 120

20

40

60

80

100

120

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Fraction of Fog, AVHRR 1981-1999

Central Valley

Year

1980 1990 2000 2010

Spa

tial-T

em

po

ral F

og

Fra

ctio

n, N

ov-F

eb

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

AVHRRMODIS

Downward Trend in the Fraction of Fog Days-Area in the Central Valley

Year

1980 1985 1990 1995 2000 2005 2010 2015

Fog

-Fra

ctio

n

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

NovemberNovember RegressionDecemberDecember RegressionJanuaryJanuary RegressionFebruaryFebruary Regression

AVHRR

Year

1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

Spa

tial-T

empo

ral F

og

Fra

ctio

n

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

Central ValleyUpper Sacramento Valley:Lower San Joaquin ValleyPlot 1 Regr

Conclusions Downward Trends in Winter Chill are Being computed with the Simple Classical Model and the Better Dynamic Model

Downward Trends in Winter Fog are Occurring

Trends in Fog are Contributing to Downward Trend in Winter Chill

More Clear and Warm Days will have a Negative Effect on Accumulated Winter Chill, Amplifying Reductions in Winter Chill

Fog is not Explicitly Modeled in the Climate Scenarios Used so Far

CIMIS Stations on Fog Days

RH

50 60 70 80 90 100

pdf

0.00

0.05

0.10

0.15

0.20

0.25

CIMIS Stations on Fog Days

Tmin

-4 -2 0 2 4 6 8 10 12

pdf

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

CIMIS Stations on Fog Days

Tmax

0 5 10 15 20

pdf

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

CIMIS Stations on Fog Days

Tdew (C)

-4 -2 0 2 4 6 8 10 12

pdf

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16