Figures Relevant to the Alberta Agroclimatic Changes 1901-2002
By Samuel Shen
Reference: S.S.P. Shen, H. Yin, K. Cannon, A. Howard, S. Chetner, and T.R. Karl,
Temporal and spatial changes of agroclimate in Alberta during 1901-2002, J. Appl.
Meteo. 44, 1090-1105 (2005).
1
Ecoregions and ecodistrict polygons of Alberta. Alberta is a western province of Canada,
bounded by 49 and 60 degrees North latitude, and 110 and 120 degrees West longitude,
respectively. Alberta is 1,223 kilometers from north to south and between 293 and 660
kilometers in width from west to east. The Canadian Rockies cuts off the southwest
corner.
2
Six Alberta ecoregions with extensive agriculture. Alberta’s area is 0.662 million square
km, and is about the same size as Texas and about 20% larger than France. More than a
third of the area is farmland.
3
400
May-Aug PCPN [mm]
350
300
250
200
150
Year
The May-August precipitation [units: mm] annual time series (thin curve with dots), 11-year
running mean (thick curve), and linear regression line (straight line). The Alberta MayAugust precipitation has increased 14% from 1901 to 2002 and the increment is the largest in
the north and the northwest of Alberta, then diminishes (or even becomes negative over two
small areas) in central and southern Alberta, and finally becomes large again in the southeast
corner of the province. The annual total precipitation follows a similar increasing trend
to that of the May-August precipitation, and the percentile analysis of precipitation
attributes the increase to low-intensity events. The changes of the agroclimatic
parameters imply that Alberta agriculture has benefited from the last century’s climate
change.
4
2001
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
1911
1906
1901
100
175
170
165
LSF [day]
160
155
150
145
140
135
130
Year
The last spring frost (LSF) [units: day] annual time series (thin curve with dots), 11-year
running mean (thick curve), and linear regression line (straight line). The LSF (last spring
frost) day is defined as the last date in a year on or before July 15 when the daily
minimum temperature Tmin  0C. An earlier LSF occurs now all over the province.
5
2001
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
1911
1906
1901
125
280
270
FFF [day]
260
250
240
230
220
Year
The first fall frost (FFF) [units: day] annual time series (thin curve with dots), 11-year
running mean (thick curve), and linear regression line (straight line). The FFF (first fall
frost) day is defined as the first date in a year on or after July 16 when Tmin  0C. A later
FFF occurs now all over the province.
6
2001
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
1911
1906
1901
210
150
140
130
FFP [day]
120
110
100
90
80
70
60
Year
The frost free period [units: day] annual time series (thin curve with dots), 11-year
running mean (thick curve), and linear regression line (straight line). A longer FFF now
than before is all over the province. The FFP (frost-free period) is the number of days
between the LSF and the FFF:
FFP  FFF  LSF  1 .
The means (standard deviations) of the LSF, FFF, and FFP for the Alberta AR region in
1961-1990 are 140 (7.36) [calendar day of a year, i.e., May 20 if not a leap year], 257
(8.66) [calendar day of a year, i.e., September 14 if not a leap year], and 118 (11.39)
[days], respectively.
7
2001
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
1911
1906
1901
50
1800
1700
1600
1500
GDD
1400
1300
1200
1100
1000
900
Year
The accumulated growing degree day (GDD) annual time series (thin curve with dots),
11-year running mean (thick curve), and linear regression line (straight line). Our values
for the GDD are still based on 5C and computed from the mean daily air temperature
(Tmean) by using the formula
 5.0,
T
Daily GDD   mean
,
0
if Tmean  5.0,
otherwise,
where Tmean  (Tmax  Tmin ) / 2.0 . The GDD is accumulated from the SGS to the EGS.
8
2001
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
1911
1906
1901
800
2600
2400
ACHU
2200
2000
1800
1600
Year
The accumulated corn heat unit (ACHU) annual time series (thin curve with dots), 11year running mean (thick curve), and linear regression line (straight line). The daily
CHU is the average of the nighttime CHU and the daytime CHU, calculated by the
formulas below:
CHU  (CHU X  CHU Y ) / 2 ,
where the nighttime CHU is
CHU X  1.8(Tmin  4.4) ,
and the daytime CHU is
CHU Y  3.33(Tmax  10)  0.084(Tmax  10) 2 .
In the above, CHU X  0 if Tmin  4.4  C and CHU Y  0 if Tmax  10.0  C . The
accumulated CHU (i.e., ACHU) is the accumulation of the daily CHU from the last day
of three consecutive days in the spring with mean daily air temperatures greater or equal
to 12.8C, to the first day after July 16, with a minimum temperature less than or equal to
-2C.
9
2001
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
1911
1906
1901
1400
Spatial distribution of the temporal trends of May-August precipitation (units: mm/102yr)
calculated from linear regression. The contour indicates the change of the May-August
precipitation from 1901 to 2002. The change is an increase for almost the entire province.
The increment is the largest in the north and the northwest of Alberta, then diminishes (or
even becomes negative over two small areas) in central and southern Alberta, and finally
becomes large again in the southeast corner of the province. The shaded regions are
where significant trends exist at the 5% significance level. The Rocky Mountain areas are
blacked out because of insufficient station data and large gradients of trends, and hence
possibly very large errors.
10
Spatial distribution of the temporal trends of the frost free period FFP (units: day/102yr)
calculated from linear regression. The contour indicates a FFP increase from 1901 to
2002.The increment is the largest in the north and the northwest of Alberta, then
diminishes (or even becomes negative over two small areas) in central and southern
Alberta, and finally becomes large again in the southeast corner of the province.
The shaded regions are where significant trends exist at the 5% significance level. The
Rocky Mountain areas are blacked out because of insufficient station data and large
gradients of trends, and hence possibly very large errors.
11
The difference of the recent 30-year normal (1973-2002) minus the 1913-1942 normal for
May-August precipitation [units: mm]. The positive difference implies an increase of the
precipitation in 70 years. The Rocky Mountain areas are blacked due to insufficient data.
12
The difference of the recent 30-year normal (1973-2002) minus the 1913-1942 normal for
the start of growing season SGS [units: day]. No significant change has been found for
the SGS. The Rocky Mountain areas are blacked due to insufficient data.
13
The difference of the recent 30-year normal (1973-2002) minus the 1913-1942 normal for
the end of growing season EGS [units: day]. No significant change has been found for
the EGS. The Rocky Mountain areas are blacked due to insufficient data.
14
The difference of the recent 30-year normal (1973-2002) minus the 1913-1942 normal for
the length of growing season LSF [units: day]. No significant change has been found for
the LGS. The Rocky Mountain areas are blacked due to insufficient data.
15
The difference of the recent 30-year normal (1973-2002) minus the 1913-1942 normal for
the first fall frost FFF [units: day]. The Rocky Mountain areas are blacked due to
insufficient data.
16
The difference of the recent 30-year normal (1973-2002) minus the 1913-1942 normal for
the accumulated corn heat units ACHU. The Rocky Mountain areas are blacked due to
insufficient data.
17
The difference of the recent 30-year normal (1973-2002) minus the 1943-1972 normal for
the start of growing season SGS [units: day]. The Rocky Mountain areas are blacked out
due to insufficient data.
18
The difference of the recent 30-year normal (1973-2002) minus the 1943-1972 normal for
the end of growing season EGS [units: day]. The Rocky Mountain areas are blacked out
due to insufficient data.
19
The difference of the recent 30-year normal (1973-2002) minus the 1943-1972 normal for
the growing degree day GDD. The Rocky Mountain areas are blacked out due to
insufficient data.
20
The difference of the recent 30-year normal (1973-2002) minus the 1943-1972 normal for
the accumulated corn heat units ACHU. The Rocky Mountain areas are blacked out due
to insufficient data.
21
The areas with ACHU  2,000 for the 1913-1942 normal, 1943-1972 normal and 19732002 normal. The area with sufficient CHU for corn production, calculated according to
the 1973-2002 normal, has extended to the north by about 200-300 km compared to the
1913-1932 normal, and by about 50-100 km compared to the 1943-1972 normal; this
expansion implies that the potential exists to grow crops and raise livestock in more
regions of Alberta than the past.
22