accumulated winter chill is decreasing in fruit growing regions of california dennis baldocchi...
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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
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
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
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
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16