J.J. Shinker1 and P.J. Bartlein2
Temperature
Temperature
Jan
Jul
.0125.0250.0375.0500.0625.0750.0875.1000.1125.1250.1375.1500.1625.1750.1875.2000.2125.2250.2375.2500
July/January
July/January Precipitation Ratio
Jul/Jan
10.0
7.5
5.0
2.5
2.0
1.5
1.25
1.0
.800
.667
.500
.400
.200
.133
.100
Temperature
Broadscale
Mesoscale
Local Scale
•Climatologies show control by insolation
through the seasonal cycle, and the
influence of continentality;
•Smallest temperature changes occur from
Jan-->Feb and Jul-->Aug, when insolation is
still slowly changing, while largest changes
occur following the equinoxes;
•Month of min and max precede the month of
least intermonthly change (e.g. Jan min
temperature, Jul max temperature).
•Climatologies show regional differences
between cold interior/northern regions and
warm coastal/southern regions of western
U.S. in winter;
•Intermonthly change maps show a lag in the
timing of the temperature maximum along
the west coast, but an earlier occurrence of
the temperature minimum.
•Local physiography controls heterogeneity of
temperature through the seasonal cycle,
especially in the interior west;
•A lag exists in the timing of maximum
temperature along the west coast and
interior Columbia River Basin region.
-30
-20
-10
0
10
20
30
C
-20
-15
Mesoscale
Local Scale
•Climatologies show a large-scale trade-off
between Pacific (winter) and Gulf of Mexico
moisture sources (summer);
•Intermonthly change maps show timing of
greatest change in precipitation occurs in
transition seasons;
•Spatial heterogeneity in timing of seasonal max
and min.
•Intermonthly change maps show progression
of the North American Monsoon from New
Mexico (May-->Jun) westward (Jun-->Aug),
and north (summer) -south (winter) migration
of the jet stream;
•Month of maximum precipitation highlights
pattern seen in climatology with max
precipitation along the west coast in winter,
northern interior west in late spring and in
the southwest in late summer.
•Climatology of precipitation shows rainshadow
effects;
•Intermonthly change maps emphasize influence
of topography on precipitation;
•Month of Min/Max highlight the variability of
timing of precipitation in the intermountain
west.
Actual Evapotranspiration/Potential Evapotranspiration (AE/PE)
-5
0
5
10
15
20
25 %
-25
Jan
Local Scale
•Southwest U.S. experiences lower AE/PE
throughout most of the seasonal cycle;
•Intermonthly change maps show increase in
moisture stress from winter to summer along
the west coast;
•Intermonthly change maps also show moisture
surplus in northern intermountain west
during transition seasons;
•Influence of North American Monsoon in
summer months reduces moisture stress in
the southwest;
•Month of min/max AE/PE reinforces the month
of min/max for precipitation.
•Climatology of AE/PE show topographic
influence on moisture availability;
•Large plateaus (Colorado/Yellowstone) show
distinct differences in the sign of intermonthly
changes, and timing of the maximum
and minimum when compared with than
surrounding areas.
10
20
30
C
-20
-15
Apr
-40
-30
-20
-10
0
10
20
30
C
-5
0
5
10
15
20
25 %
-25
-20
-15
-30
-20
-10
0
10
20
30
C
-5
0
5
10
15
20
25 %
-25
-20
-30
-20
-10
0
10
20
30
C
-10
-5
0
5
10
15
20
25 %
-25
-20
-15
-30
-20
-10
0
10
20
30
C
-5
0
5
10
15
20
25 %
-25
-20
-15
-30
-20
-10
0
10
20
30
C
ITemperature
-5
0
5
10
15
20
25 %
-25
-20
-30
-20
-10
0
10
20
30
C
ITemperature
-10
-5
0
5
10
15
20
25 %
-25
-20
-30
-20
-10
0
10
20
30
C
ITemperature
-10
-5
0
5
10
15
20
25 %
-25
-20
-15
-30
-20
-10
0
10
20
30
C
I
-5
0
5
10
15
20
25 %
-25
-20
-15
-30
-20
-10
0
10
20
30
C
-40
M
Intermonthly Change
Sep to Oct
-10
Dec
-40
M
Intermonthly Change
Aug to Sep
-15
Nov
-40
M
Intermonthly Change
Jul to Aug
-15
Oct
-40
M
Intermonthly Change
Jun to Jul
-10
Sep
-40
M
Intermonthly Change
May to Jun
-10
Aug
-40
M
Intermonthly Change
Apr to May
-15
Month of Maximum or Minimum
Jul
-40
M
Intermonthly Change
Mar to Apr
-10
Month of Maximum or Minimum
Jun
-40
M
Intermonthly Change
Feb to Mar
-10
May
-40
M
Intermonthly Change
Oct to Nov
-10
-5
0
5
10
15
20
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
May
Jun
Jul
Aug
Sep
Oct
25 %
-25
-20
-15
-30
-20
-10
0
10
20
30
C
M
Intermonthly Change
M
Nov to Dec
-10
-5
0
5
10
15
20
25 %
-25
Month of Maximum or Minimum
-20
-15
-10
-5
0
5
10
15
20
25 %
Month of Maximum or Minimum
Mar
Apr
Nov
Dec
Max
Precipitation
Precipitation
IPrecipitation
IPrecipitation
Feb
Jan
10
20
50
100
200
IPrecipitation
Mar
10
500 mm
Intermonthly Change
20
50
100
200
500 mm
IPrecipitation
Apr
10
M
Intermonthly Change
-10
20
50
100
200
IPrecipitation
May
500 mm
10
M
Intermonthly Change
Jan to Feb
-5
-2
-1
0
1
2
5
10
20 %
-20
-DQ
-IN
IPrecipitation
20
50
100
200
500 mm
Jun
10
M
Intermonthly Change
20
50
100
200
IPrecipitation
Jul
500 mm
10
M
Intermonthly Change
20
50
100
200
IPrecipitation
Aug
500 mm
10
M
Intermonthly Change
20
50
100
200
500 mm
IPrecipitation
Sep
10
M
Intermonthly Change
-10
Feb to Mar
-5
-2
-1
0
1
2
5
10
20 %
-20
-10
Mar to Apr
-5
-2
-1
0
1
2
5
10
20 %
-20
-10
Apr to May
-5
-2
-1
0
1
2
5
10
20 %
-20
-10
May to Jun
-5
-2
-1
0
1
2
5
10
20 %
-20
-10
-5
20
50
100
200
500 mm
IPrecipitation
Oct
10
M
Intermonthly Change
Jun to Jul
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Feb
Mar
Apr
May
Jun
20 %
-20
-10
20
50
100
200
IPrecipitation
Nov
500 mm
10
M
Intermonthly Change
Jul to Aug
-5
-2
-1
0
1
2
5
10
20 %
-20
Month of Maximum or Minimum
I
20
50
100
200
500 mm
Dec
10
M
Intermonthly Change
20
50
100
200
500 mm
10
M
Intermonthly Change
20
50
100
200
500 mm
M
Intermonthly Change
M
-10
Aug to Sep
-5
-2
-1
0
1
2
5
10
20 %
-20
-10
-5
Sep to Oct
-2
-1
0
1
2
5
10
20 %
-20
-10
Oct to Nov
-5
-2
-1
0
1
2
5
10
20 %
-20
-10
Nov to Dec
-5
-2
-1
0
1
2
5
10
20 %
-20
-10
-5
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Aug
Sep
Oct
Nov
Dec
IAE/PE
IAE/PE
IAE/PE
IAE/PE
20 %
Jul
-AX
Actual Evapotranspiration/Potential Evapotranspiration (AE/PE)
AE/PE
IAE/PE
IAE/PE
Feb
Jan
.2
.3
.4
.5
.6
.7
.8
IAE/PE
Mar
.1
.9
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
IAE/PE
Apr
.1
M
Intermonthly Change
Dec to Jan
-.40
-.20
IAE/PE
IAE/PE
IAE/PE
I
.2
.3
.4
.5
.6
.7
.8
.9
May
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
Jun
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
Jul
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
Aug
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
Sep
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
Oct
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
Nov
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
Dec
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
.1
M
Intermonthly Change
.2
.3
.4
.5
.6
.7
.8
.9
M
Intermonthly Change
M
Jan to Feb
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Feb to Mar
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Mar to Apr
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Apr to May
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
May to Jun
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Jun to Jul
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Jul to Aug
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Aug to Sep
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Sep to Oct
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Oct to Nov
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
Nov to Dec
-.10
-.05
.00
.05
.10
.20
.40
-.40
-.20
-.10
-.05
.00
.05
.10
.20
.40
BIOCLI (v. 2.1, Cramer & Prentice 1988; Prentice et al. 1992; BIOCLI pro
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Feb
Mar
Apr
May
Jun
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Month of Maximum or Minimum
Aug
Sep
Oct
Nov
Dec
Month of
Min or Max
ea.ac.uk/]
Jan
Actual Evapotranspiration (AE)
Min
Jul
Max
program code modified by P. J. Bartlein [Univ. of Oregon] and S. L. Shafer [USGS])
Mesoscale
Local Scale
•Increase of AE from winter to spring indicates
onset of growing season;
•Decrease of AE from Oct -->Nov;
•Month of minimum AE shows greater spatial
homogeneity than the month of maximum
AE.
•Climatology of AE show increase in
evapotranspiration occurring in southwest
following onset of monsoon;
•Month of maximum AE is highly variable
across the western U.S. reflecting the
trade-offs between moisture availability and
evaporative demand.
•Intermonthly change maps show high spatial
heterogeneity of AE, particularly on lee side
of mountains.
Actual Evapotranspiration (AE)
Actual Evapotranspiration
IActual Evapotranspiration
Jan
10
Feb
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
This research was funded through NSF grants: ATM-9910638 and ATM-0117160
IActual Evapotranspiration
IActual Evapotranspiration
IActual Evapotranspiration
IActual Evapotranspiration
IActual Evapotranspiration
IActual Evapotranspiration
IActual Evapotranspiration
IActual Evapotranspiration
IActual Evapotranspiration
I
m
10
Dec to Jan
-20
-10
-5
Mar
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Jan to Feb
-2
-1
0
1
2
5
10
20 %
m
-20
-10
-5
Apr
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Feb to Mar
-2
-1
0
1
2
5
10
20 %
m
-20
-10
-5
May
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Mar to Apr
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
Month of Maximum or Minimum
Feb
Mar
20 %
m
-20
-10
-5
20
Jun
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Apr to May
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
20 %
m
-20
-10
-5
Jul
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
May to Jun
-2
-1
0
1
2
5
10
20 %
m
-20
-10
-5
Aug
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Jun to Jul
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
Month of Maximum or Minimum
May
Jun
20 %
m
-20
-10
-5
20
Sep
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Jul to Aug
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
20 %
m
-20
-10
-5
20
Oct
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Aug to Sep
-2
-1
0
1
2
5
10
20 %
m
-20
-10
-5
Nov
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Sep to Oct
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
Month of Maximum or Minimum
Aug
Sep
20 %
m
-20
-10
-5
20
Dec
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
10
Oct to Nov
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
20 %
m
-20
-10
-5
20
30
40
50
60
70
80
90
100 110 120 130 140 mm
M
Intermonthly Change
M
Nov to Dec
-2
-1
0
1
2
5
10
Month of Maximum or Minimum
20 %
m
-20
-10
-5
-2
-1
0
1
2
5
10
20 %
Month of Maximum or Minimum
Month of
Min or Max
References
NCDC U.S. Climate Normals 1971-2000, CLIM81 Climatography of the U.S. NO. 81: Monthly Station
Normals, http://www.ncdc.noaa.gov.
Cramer, W. and I.C. Prentice (1988). Simulation of regional soil moisture deficits on a European scale.
Norsk Geografisk Tidsskrift, 42:149-151.
Mock, C.J. (1996). Climatic controls and spatial variations of precipitation in the western United States.
Journal of Climate, 9(5):1111-1125.
Prentice, I.C., W. Cramer, S.P. Harrison, R. Leemans, R.A. Monserud and A.M. Solomon (1992). A global
biome model based on plant physiology and dominance, soil properties and climate. Journal of
Biogeography, 19:117-134.
Shafer, S., P. Bartlein and R. Thompson (2001). Potential changes in the distributions of western North
America tree and shrub taxa under future climate scenarios. Ecosystems, 4(3):200-215.
Intermonthly
Change
Intermonthly Change
Data and Methods
IActual Evapotranspiration
Climatology
Broadscale
The “normal” seasonal cycle of climate in the western United States can be
illustrated by mapping long-term (1971-2000) averages of climate-station data,
supplemented by gridded climate data that allow the calculation of waterbalance variables. Monthly climate normals (1971-2000 monthly averages) for
temperature and precipitation for 2781 stations in the western United States
were obtained from NOAA’s National Climatic Data Center (NCDC) CLIM81
product. Average monthly percent possible sunshine was interpolated for each
station using the Climate Research Unit (CRU, University of East Anglia) 10-min
CRU CL 2.0 data set (and these 1961-1990 averages were adjusted to 19712000 by applying anomalies calculated using the CR TS 2.0 data set). Actual
evapotranspiration and that ratio of actual-to-potential evapotranspiration (or
the Priestley-Taylor moisture index, alpha) were calculated using the BIOCLI
program (v. 2.1, Cramer & Prentice 1988; Prentice et al. 1992; BIOCLI program
code modified by P. J. Bartlein (Univ. of Oregon) and S. L. Shafer (USGS).
ITemperature
Intermonthly
Change
Mesoscale
•Higher AE/PE occurs along the west coast in
winter, while lower AE/PE occurs in interior
west;
•Nearly all of the western United States has
moisture deficit in summer months;
•Maximum AE/PE generally occurs in late
autumn/early winter and spring months;
•Minimum AE/PE occurs in summer along the
west coast.
0
Feb
Min
.1
Broadscale
-10
Month of Maximum or Minimum
-20
Broadscale
-20
Jan to Feb
-10
Dec to Jan
Precipitation
-30
M
Intermonthly Change
Dec to Jan
-25
Mar
-40
Intermonthly Change
Intermonthly
Change
Maps of several climate variables, their average intermonthly changes, and the timing of the
annual maxima or minima, show three scales of variation: (1) broadscale patterns related
to the seasonal cycle of insolation and the configuration of hemispheric-scale atmospheric
circulation features; (2) mesoscale patterns related to location on the continent and to the
influence of specific circulation features like those involved in the North American monsoon;
and (3) smaller-scale or local spatial variations related to the mediation of the influence of
large-scale circulation by local physiography, and, for the water-balance variables, elevational
variations in the timing of snowmelt. While most stations throughout the western U.S.
have temperature maxima in July, a delay occurs at stations along the coast and interior
Washington, northern Idaho, and Montana. A see-saw pattern of precipitation maximum
is evident between coastal areas and the interior and southwest associated with the
seasonal timing of precipitation and the North American Monsoon. Regions of high spatial
heterogeneity in the timing of precipitation include the northern Rocky Mountains, Utah,
Arizona and north western Montana. The superimposition of these three scales of spatial
variability leads to steep gradients, and in some regions, considerable spatial heterogeneity,
in the seasonal cycles of precipitation and surface water- and energy-balance variables.
ITemperature
Month of
Min or Max
Jan
.0125.0250.0375.0500.0625.0750.0875.1000.1125.1250.1375.1500.1625.1750.1875.2000.2125.2250.2375.2500
July/Annual
ITemperature
Month of
Min or Max
July/Annual Precipitation Ratio
ITemperature
Climatology
January/Annual
ITemperature
Climatology
Precipitation Seasonality
ITemperature
Intermonthly
Change
Introduction
ITemperature
Feb
-40
1Department of Geography, Geology, and Anthropology, Indiana State University (jshinker@indstate.edu), 2Department of Geography, University of Oregon
January/Annual Precipitation Ratio
ITemperature
Climatology
Broadscale Pattern and Spatial Heterogeneity of
Western United States Climate
Jan
Min
Apr
Jul
Oct
Nov
Dec
Max
© J.J. Shinker and P. J. Bartlein
MTNCLIM2005 - Climate & Disturbance Regimes