Fractured Landscapes:
How Fine-Scale Factors Can Complicate
the Effect of Elevation on Warming
Christopher Daly
PRISM Climate Group
Oregon State University
Corvallis, Oregon, USA
Effects of Elevation are Hard to Isolate
As we move upwards in elevation, other factors that affect the local
temperature regime change as well. These include:
Topographic position
Slope and aspect
Canopy cover
Snow cover
Proximity to riparian zones
Case study: Topographic position
HJ Andrews Experimental Forest
1278 m
442 m
Daily Temp Gradient (C/km), VANMET-PRIMET
1995-2000
Tmax
Tmin
Average
Environmental
Lapse Rate
(-6.5C/km)
Anticyclonic
700-mb Flow
Curvature Types
Zonal
•
•
•
•
High Pressure
Clear
Light Winds
Warm air aloft
•
•
•
•
Low Pressure
Cloudy
Strong winds
Cool air aloft
Cyclonic
HJA VANMET-PRIMET Daily Minimum Temperature Gradient
Vs
700-mb Flow Strength and Curvature, 1987-2005
4
Mean Daily Tmin Gradient (C / km)
3
2
1
0
L
M
H
L
M
H
L
M
-1
-2
-3
-4
-5
-6
Anti-cyclonic
Zonal
Cyclonic
H
HJA December Tmax Change
+2.5C Regional Warming and
5 Days Moving From Cyclonic to Anti-cyclonic Flow Pattern
Main Points
• Elevation gradients in warming are hard to identify because of
complicating factors
• Topographic position is an example of one such factor
• The effect of topographic position on temperature can be
modulated by synoptic features (e.g., upper-air flow patterns)
• Synoptic features have varied in the past, and may be altered
by climate change
• Such changes could create landscape-scale gradients in
temperature responses greater than regional GHG
temperature change itself
Comparison of December Tmax Anomalies
VANMET-PRIMET Estimated Tmin Difference
Given A-C Increases
VANMET-PRIMET Tmin Difference
(C)
5
VAN-PRI tmin+5A-C
VAN-PRI tmin+10A-C
4
3
2
1
0
-1
-2
Jan
Feb
Mar
Apr May Jun
Jul
Aug Sep
Month of Year
Oct
Nov Dec
VANMET-PRIMET Estimated Tmax Difference
Given A-C Increases
5
VAN-PRI tmax+5A-C
VAN-PRI tmax+10A-C
VANMET-PRIMET Tmax
Difference (C)
4
3
2
1
0
-1
-2
Jan
Feb Mar
Apr May Jun
Jul
Aug Sep
Month of Year
Oct Nov Dec
USDA Plant Hardiness Zone Map
Northeastern Utah
Standard Deviation
1976-2005
Difference
1991-2005 minus 1976-1990
Annual Extreme Minimum Temperature
Northeastern Utah
Ouray (valley)
High Variability
High Trend
Altamont (slope)
Moderate Variability
Moderate Trend
Lakefork Basin (mtns)
Low Variability
Low Trend
Complex Temperature Landscape
•
Not just spatially complex, but temporally complex as well
•
If future climate changes result in changes in the frequency
distribution of synoptic flow patterns, actual temperature
responses could diverge widely between very closely-spaced
locations.
•
The magnitude of this divergence might equal or exceed that
of the projected temperature change itself.