German Weather Service
agrometeorological department
Determine the vegetation period and
regional trends in Germany
Wolfgang Janssen
wolfgang.janssen@dwd.de
Phenology 2010, June
German Weather Service
agrometeorological department
Background:
- different crops have different growth periods
- some issues need a general definition of the vegetation period
- impacts of climate change
 how
to define?
 good reproduction in past years?
 any trends?
Phenology 2010, June
German Weather Service
agrometeorological department
How to define?
 many different approaches with different results
 use only temperature as meteorological input
 link to definition of the phenological year
vegetation starts in early spring
with plant stages:
forsythia, flowering (25.3.)
gooseberry, leaf unfolding (27.3.)
vegetation stops at beginning of winter
with plant stages:
oak, leaf fall
beech, leaf fall (27.10.)
Phenology 2010, June
German Weather Service
agrometeorological department
58 stations with meterological and phenelogical observations
large variation of phenological observations in small areas
most probable values by interpolation
many different relations where tested
not the best but simplest relation with good results was taken
Tsum =
Phenology 2010, June
(Tmean day temperature – Treference temperature)
start day
German Weather Service
agrometeorological department
Tsum =
(Tmean day temperature – Treference temperature)
start date
a simple methode to find the optimal start date and reference temperature
60 different start dates
30 different ref. temp.
(1800 cases)
observed phenological
dates of 58 stations in
18 years
for each case optimal
temp. sum for 58
stations in 18 years
for each case date reaching
opt. temp. sum at 58
stations in 18 years
difference between observed
and calculated dates =>
dispersion for each case
Phenology 2010, June
German Weather Service
agrometeorological department
dispersion matrix for gooseberry (leaf unfolding)
3
2
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
reference temperature
1
-11
61
58
55
52
49
46
43
40
37
34
31
28
25
22
19
16
13
10
7
4
1
-12
day of the year (start date)
start date = 49. day of year, reference temperature = 0 °C, sum = 164 °C
4,4-4,6
4,6-4,8
4,8-5
5-5,2
5,2-5,4
5,4-5,6
5,6-5,8
5,8-6
6-6,2
6,2-6,4
6,4-6,6
6,6-6,8
7-7,2
7,2-7,4
7,4-7,6
7,6-7,8
7,8-8
8-8,2
8,2-8,4
8,4-8,6
8,6-8,8
8,8-9
9-9,2
9,2-9,4
Phenology 2010, June
6,8-7
German Weather Service
agrometeorological department
a fixed start date or end of dormancy can‘t be correct !
 start date must depend from weather situation
 made a test with the both coldest and warmest years
2
2
1
1
0
-1
-1
-2
-2
-3
-4
-5
-6
-7
same ref. temp. -2.5 °C
different start days
reference temperature
7,2-7,4
7-7,2
6,8-7
6,6-6,8
6,4-6,6
6,2-6,4
6-6,2
5,8-6
5,6-5,8
5,4-5,6
5,2-5,4
5-5,2
4,8-5
4,6-4,8
4,4-4,6
warm years
-3
-4
-5
-6
-7
-8
-8
-9
-9
-10
-10
-11
cold years
-11
-12
-12
15
20
25
30
Phenology 2010, June
35 40 45
start date
50
55
60
15
20
25
30
35 40 45
start date
50
55
60
reference temperature
0
4,7-4,9
4,5-4,7
4,3-4,5
4,1-4,3
3,9-4,1
3,7-3,9
3,5-3,7
3,3-3,5
3,1-3,3
2,9-3,1
2,7-2,9
2,5-2,7
2,3-2,5
2,1-2,3
1,9-2,1
German Weather Service
agrometeorological department
determing for every year with a fixed reference temperature of -2.5 °C
optimal start date and optimum temperature sum (TScrop)
350
observed
300
optimal temperature sum
fitted dependence
250
200
correlation 0.87
150
100
50
0
36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
start date
TScrop  65  534e0.01962*startday
Phenology 2010, June
German Weather Service
agrometeorological department
TS  startdayTM  Tref .temp.
TScrop  65  534e0.01962*startday
as start date is earlier, a higher temperatur sum is required (small chilling)
as start date is later, a lower temperatur sum is required (large chilling)
110
Calculation cheme:
TS limit  min TS  TS crop , TS limit 
100
90
observed
• starting at 1.1.
• for every following day
• calculating TScrop
• calculate TSlimit
80
no
TS > TSlimit ?
correlation of 0,90
dispersion of 4.3 days
70
yes
60
plant state reached
60
70
80
90
calculated
Phenology 2010, June
100
110
German Weather Service
agrometeorological department
observed phenological
plant state in 2009
calculated phenological
plant state in 2009
in mean +0,8 days difference
Phenology 2010, June
German Weather Service
agrometeorological department
dispersion matrix for beech (leaf fall, 300. day of year)
40
37
36
34
33
31
30
28
27
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
235
25
240
day of the year (start date)
start date = 214. day of year, reference temperature = 30 °C, sum = -1383 °C
5,5-5,7
7,7-7,9
5,7-5,9
7,9-8,1
Phenology 2010, June
5,9-6,1
8,1-8,3
6,1-6,3
8,3-8,5
6,3-6,5
8,5-8,7
6,5-6,7
8,7-8,9
6,7-6,9
8,9-9,1
6,9-7,1
9,1-9,3
7,1-7,3
9,3-9,5
7,3-7,5
9,5-9,7
7,5-7,7
9,7-9,9
reference temperature
39
German Weather Service
agrometeorological department
determing for every year with a fixed reference temperature of 30 °C
optimal start date and optimum temperature sum (TScrop)
0
observed
-200
fitted dependence
-400
optimal temperature sum
-600
-800
correlation 0.99
-1000
-1200
-1400
-1600
-1800
-2000
170
180
190
200
210
220
230
start date
Phenology 2010, June
240
250
260
270
280
TS crop  4265  13,25 * startdate
German Weather Service
agrometeorological department
TS  startdayTM  Tref .temp.
TS crop  4265  13,25 * startdate
with high temperatures end of vegetation is later
latest possible end is 18.11. (322. day of year)
Calculation cheme:
TS limit  max( TS  TS crop , TS limit )
no
TS < TSlimit ?
yes
correlation of 0,60
dispersion of 5,1 days
315
observed
• starting at 180. day
• for every following day
• calculating TScrop
• calculate TSlimit
325
305
295
285
275
275
plant state reached
Phenology 2010, June
285
305
295
calculated
315
325
German Weather Service
agrometeorological department
observed phenological
plant state in 2007
calculated phenological
plant state in 2007
in mean +0,4 days difference
Phenology 2010, June
German Weather Service
agrometeorological department
290
85
285
80
280
75
275
70
270
years
calculated begin
Phenology 2010, June
observed begin
calculatetd end
observed end
2006
90
2001
295
1996
95
1991
300
1986
100
1981
305
1976
105
1971
310
1966
110
1961
day of the year
Comparison between observed and calculated mean values for Germany
German Weather Service
agrometeorological department
time series for mean vegetation period in Germany
230
1980
1991
8 days longer
period 1
225
period 2
220
period in days
215
210
205
200
195
190
years
Phenology 2010, June
calculated period
observed period
running average
2006
2001
1996
1991
1986
1981
1976
1971
1966
1961
185
German Weather Service
agrometeorological department
calculated vegetation
period 1991 - 2009
calculated vegetation
period 1961 - 1980
trend
Phenology 2010, June
German Weather Service
agrometeorological department
optimal parameter for other plant stages
phenological plant stage
ref. temp.
correlation
dispersion
grasland, start of greening (19.3.)
-2.5
0.89
4.5
dandelion, flowering (14.4.)
-2.5
0.89
4.1
apple, flowering (28.4.)
1.0
0.90
3.7
Phenology 2010, June
German Weather Service
agrometeorological department
begin greening of grasland
5
4
3
2
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
5
3
1
-10
day of the year
6-6,2
8-8,2
6,2-6,4
8,2-8,4
Phenology 2010, June
6,4-6,6
8,4-8,6
6,6-6,8
8,6-8,8
6,8-7
8,8-9
7-7,2
9-9,2
7,2-7,4
9,2-9,4
7,4-7,6
9,4-9,6
7,6-7,8
9,6-9,8
7,8-8
9,8-10
reference temperature in °C
1
German Weather Service
agrometeorological department
500
450
400
350
ref. Temp. = -2,5 °C
300
250
TScrop  35  600e0.01962*startday
200
correlation 0,84
150
100
50
0
20
25
30
35
40
45
50
55
60
65
115
110
correlation 0,89
mean dispersion 4,5 days
105
100
observed
95
90
85
80
75
70
65
60
55
55
60
65
70
75
80
85
calculated
Phenology 2010, June
90
95
100
105
110
115
German Weather Service
agrometeorological department
flowering of dandelion
5
4
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
81
78
75
72
69
66
63
60
57
54
51
48
45
42
39
36
33
30
27
24
21
-10
start day
4,8-5
6,8-7
8,8-9
Phenology 2010, June
5-5,2
7-7,2
9-9,2
5,2-5,4
7,2-7,4
9,2-9,4
5,4-5,6
7,4-7,6
9,4-9,6
5,6-5,8
7,6-7,8
9,6-9,8
5,8-6
7,8-8
6-6,2
8-8,2
6,2-6,4
8,2-8,4
6,4-6,6
8,4-8,6
6,6-6,8
8,6-8,8
reference temperature in °C
3
German Weather Service
agrometeorological department
700
600
500
ref. Temp. = -2,5 °C
400
TScrop  15  715e0.01*startday
300
correlation 0,81
200
100
0
20
25
30
35
40
45
50
55
60
130
observed
120
correlation 0,89
mean dispersion 4,1 days
110
100
90
80
70
70
80
90
100
calculated
Phenology 2010, June
110
120
130
German Weather Service
agrometeorological department
apple, flowering
correlation of 0,90 and 3,7 days deviation
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
10
9
8
7
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
100
always 24.2. for start day, ref. temp. of 1 °C, temp. sum of 361 °C
3,8-4
4-4,2
4,2-4,4
4,4-4,6
4,6-4,8
4,8-5
5-5,2
5,2-5,4
5,4-5,6
5,6-5,8
6,2-6,4
6,4-6,6
6,6-6,8
6,8-7
7-7,2
7,2-7,4
7,4-7,6
7,6-7,8
7,8-8
8-8,2
Phenology 2010, June
5,8-6
6-6,2
German Weather Service
agrometeorological department
Thank you for your attention!
Phenology 2010, June