Selected Presentation from the INSTAAR Monday Noon Seminar Series.
Institute of Arctic and Alpine Research, University of Colorado at Boulder.http://instaar.colorado.edu
http://instaar.colorado.edu/other/seminar_mon_presentations
This seminar presentation has been posted to the internet to foster communication with the science community and thepublic.
Most of the INSTAAR presentations were originally given in PowerPoint format; they were converted to Adobe PDF forposting. You may need to install the free Adobe Acrobat Reader to view these files.
These presentations are "works in progress". They are not peer reviewed. They should not be referenced for any kind ofpublication. Contact the author for proper references and additional information before any use, even for unpublishedworks such as your own presentations.
LICENSING AGREEMENT.Free use of these presentations is limited to a nonprofit educational or private non-commercial context and requires thatyou contact the author, give credit to the author, and display the copyright notice. All rights to reproduce thesepresentations are retained by the copyright owner. Images remain the property of the copyright holder. By accessingthese presentations, you are consenting to our licensing agreement.
07 Oct. 2002 Tim Kittel et al., National Center for Atmospheric Research, INSTAAR affiliate, Email: [email protected]"Historical and Future Climates of the Rocky Mountains".Seminar given at INSTAAR, University of Colorado. Copyright 2002 Tim Kittel. All Rights Reserved.Kittel presentation (0.5 Mb PDF).
T. Kittel INSTAAR Seminar 7 Oct
2002
HISTORICAL AND FUTURE CLIMATESHISTORICAL AND FUTURE CLIMATES
OF THE US ROCKY MOUNTAINSOF THE US ROCKY MOUNTAINS
Timothy Kittel
INSTAAR Affiliate
University of Colorado, Boulder
with: J. Andy Royle, USFWS
Peter Thornton, Nan Rosenbloom, & Steve Aulenbach, NCAR
Tom Chase, CIRES and Dept of Geography, CU
T. Kittel INSTAAR Seminar 7 Oct 2002
+ Citations for presented research are:
• Kittel, T.G.F., P.E. Thornton, J.A. Royle, and T.N. Chase. 2002.Climates of the Rocky Mountains: Historical and Future Patterns.Pages 59-82 (Chapter 4), in: J.S. Baron (ed.). Rocky MountainFutures: An Ecological Perspective. Island Press, Covelo, CA. 325 p.
• Kittel, T.G.F. and J.A. Royle. 100-year climate history of the U.S.Rocky Mountains. J. Climate, in preparation.
+ Contact information:
• [email protected] 303 258-0908
+ Original graphics and tables not published in Baron 2002 are copyright © 2002 T. Kittel.
All rights reserved.
T. Kittel INSTAAR Seminar 7 Oct 2002
THE ROCKY MOUNTAINS
+ Geographic context• Societal• Hydrological• Ecological
+ Spatially extensive –• 35-65°N
• warm temperate ‡ boreal
+ Source for great river systems
D. Cairns in Baron 2002
T. Kittel INSTAAR Seminar 7 Oct 2002
GEOGRAPHY OF BIOGEOCHEMICAL PROCESSES
The Mountain West:
+ Positive net ecosystemexchange (C sequestration)
+ Net exchange sensitive toclimate variability anddirectional change
Schimel et al. 2002. Eos
ANNUAL NET ECOSYSTEM EXCHANGE (NEE)
Biome-BGC simulated NEE draped over topography
VEMAP Climate 1980-1989
T. Kittel INSTAAR Seminar 7 Oct 2002
OBJECTIVES
+ Are there significant historical temporal patterns in climate –trends and interannual variability – across the US Rockies?
+ Are there lessons from a retrospective – and from climatemodels – that can be applied to understanding effects ofcontinued altered forcing on high elevation climates?
T. Kittel INSTAAR Seminar 7 Oct 2002
HISTORICAL ANALYSIS
+ US Rockies
• 3 regions
+ 1895-1993
• 79 long-record stations
• US HCN and coop stns (NCDC)
• Statistical in-filling
• Moving-window kriging model(Kittel et al. in review)
+ Variables
• Tmin Tmax
• Diurnal temperature range (DTR)
• Precipitation
NORTHERN
CENTRAL
SOUTHERN
Long-Record Climate Station
500m contours
US ROCKY MOUNTAINS
T. Kittel INSTAAR Seminar 7 Oct 2002
SPECIFIC QUESTIONS
+ What is the character of climate variability in the Rockies?
• Does this variability (and its teleconnections) depend on:• Region
• Elevation
+ Are there significant trends in temperature and precipitation inthe historical record?
• Do these trends depend on:• Region
• Elevation
T. Kittel INSTAAR Seminar 7 Oct 2002
ARE THERE 20th CENTURY TRENDS?
+ Temperature
• Significant T trendstend to be >0
• Tmin (+0.5 - +1.0°C/100y)
> Tmax
• Diurnal T Rangetrends <0
+ Precipitation
• Significant trendstend to be >0
PPT Trend = 30%/100y (p<0.05)
DTR Trend = -0.6°C/100y (p<0.05)
T. Kittel INSTAAR Seminar 7 Oct 2002
DO TRENDS DIFFER BY REGION? – PPT
+ Regional differences vary withseason
Precipitation Trend (%/100y)
5%-5%SOUTH
30%*3%NORTH
*p<0.05
33%*2%CENTRAL
SUMMERWINTER
T. Kittel INSTAAR Seminar 7 Oct 2002
DO TRENDS DIFFER BY REGION? – DTR
+ Regional differences followcontinental pattern
• Strongest DTR decreases in mid-latitudeNAmer, weakening poleward(Easterling et al. 1997)
• Due to increased cloud cover(Dai et al. 1999)
• Consistent with increasing ppt
Diurnal T Range Trend (°C/100y)
+0.2-0.2SOUTH
-0.6*-0.6*NORTH
*p<0.05 **p<0.005
-1.2**-0.5CENTRAL
SUMMERWINTER
T. Kittel INSTAAR Seminar 7 Oct 2002
+ PPT trends f (elevation)
• Reduction or amplificationof lowland signal
> Strong trends at oneelevation zone
• Trend sign switching withelevation
> Decoupling
+ Seasonal dependence
• Elevation effect switchingwith season
DO TRENDS VARY WITH ELEVATION? – PPT
NORTHERN
0
1000
2000
3000
4000
-5 -4 -3 -2 -1 0 1 2 3 4 5
Precipitation Trend (cm/100y)
Ele
va
tio
n (
m)
Fall
Winter Summer
Spring
,, ::
p<0.01
n.s.
T. Kittel INSTAAR Seminar 7 Oct 2002
+ Significant changes in trends with elevation> trends in lapse rate
+ Sign switching with elevation
+ Diurnal dependence
Tmax NORTHERN
0
1000
2000
3000
4000
-5 -4 -3 -2 -1 0 1 2 3 4 5
Temperature Trend (C/100y)E
lev
ati
on
(m
)
Tmin NORTHERN
0
1000
2000
3000
4000
-5 -4 -3 -2 -1 0 1 2 3 4 5
Temperature Trend (C/100y)
Ele
va
tio
n (
m) Winter
Spring
Summer
Fall
p<0.05
n.s.
TRENDS vs. ELEVATIONTmin and Tmax
T. Kittel INSTAAR Seminar 7 Oct 2002
TRENDS vs. ELEVATION? –
Diurnal Temperature Range
+ Diurnal T Range trend elevation dependent
NORTHERN
0
1000
2000
3000
4000
-5 -4 -3 -2 -1 0 1 2 3 4 5
DTR Trend (C/100y)
Ele
va
tio
n (
m) Winter
Spring
Summer
Fall
SOUTHERN
0
1000
2000
3000
4000
-5 -4 -3 -2 -1 0 1 2 3 4 5
DTR Trend (C/100y)
+
+ Region dependent
p<0.05
n.s.
T. Kittel INSTAAR Seminar 7 Oct 2002
AN ELEVATION EFFECT?
+ Higher reaches of mountain systems in closer contact with free troposphere
• Respond rapidly to upper-air changes (Greenland and Losleben 2001)
• Less affected by ameliorating surface processes (Giorgi et al. 1997)
+ Upper air overrides lower air in presence of inversions
• Widely differing air mass sources
• Decoupled from lower-level convective mixing, valley fogs (Beniston and Rebetez 1996, Diaz and Bradley 1997)
+ Snow-albedo feedback
• Amplification of regional temperature signal –
• Years with regionally higher temperatures have less snowcover at elevation
>more absorption of solar radiation
>greater high elevation warming (Giorgi et al. 1997)
T. Kittel INSTAAR Seminar 7 Oct 2002
INTERANNUAL VARIABILITY
– SIMILAR ACROSS REGIONS? –
+ Adjacent regions more strongly correlated
+ Cross-correlations similar by season
CROSS-CORRELATION
-
0.8*
0.6*
SOUTH
Annual PPT Annual Tmin
0.4*0.2SOUTH
0.9* -NORTH
*p<0.01
-0.6*CENTRAL
CENTRALNORTH
T. Kittel INSTAAR Seminar 7 Oct 2002
TELECONNECTIONS?
+ Teleconnections with:
• North Pacific SST and Lows (NPI)
• El Niño/Southern Oscillation (SOI)
modified from Mitchell 1976
Bash, in Benedict 1991
GENERAL ATMOSPHERIC CIRCULATION
+ Drivers of regional patterns in meanclimate
+ Indicators of sources ofinterannual climate variability
T. Kittel INSTAAR Seminar 7 Oct 2002
TELECONNECTIONS
+ Southern Oscillation Index (SOI)
• Associated with El Niño
• Negative SOI = Warm SST phase(El Niño)
• Positive SOI = Cold phase
SOI
NPI+ Northern Pacific Index (NPI)
• Aleutian Low Pressure System
• Negative NPI = Deep Low ‡Blocking, meridional flow
• Positive NPI = Weak Low ‡ Zonalflow
• Pacific Decadal Oscillation
Trenberth and Hurrell
T. Kittel INSTAAR Seminar 7 Oct 2002
ARE THERE TELECONNECTIONS?
+ Negative NPI corresponds todeeper Aleutian Low
• Negative coefficient > warmerwinter with deeper Low
• Stronger circulation around Low> more southerly flow (warmerair) into the US Rockies inwinter
+ Gradient in teleconnectionstrength: S ‡ N
WINTER Tmin
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Circulation Index
Re
gre
ss
ion
Co
eff
icie
nt
NPI
SOI
North
Central
South
* p<0.05
**p<0.005
*
** **
T. Kittel INSTAAR Seminar 7 Oct 2002
SUMMER PPT
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
NPI SOI
Circulation Index
** ** **
SUMMER
+ Negative NPI > Stronger Low
• More ppt in North
+ Negative SOI > Warm phase
• More ppt in the South & Central
TELECONNECTIONS– Vary along N-S Gradient and by Season –
WINTER
+ Positive NPI > Zonal flow
• More storm tracks into mid-lats
+ Negative SOI > Warm phase
• More ppt in the South
WINTER PPT
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
NPI SOI
Circulation Index
Reg
ressio
n C
oeff
icie
nt
North
Central
South
* p<0.05
**p<0.005
*
**
T. Kittel INSTAAR Seminar 7 Oct 2002
DO TELECONNECTIONS
VARY WITH ELEVATION?
+ Relative importance ofcirculation index changes withelevation
+ Behavior dependent on regionand season
SOUTHERN ROCKIES
SOI
ELEVATION (m)
CO
RR
ELA
TIO
N
0
NPI
JULY PPT- Circ Correlation
CO
RR
ELA
TIO
N
0
p<0.01
p<0.05
T. Kittel INSTAAR Seminar 7 Oct 2002
THE FUTURE?
+ Multiple Forcings
• Increasing greenhouse gases
• Landuse change, regional andglobal
+ Regional sensitivity to alteredGHGs and sulfate aerosols
• Comparable for landuse change(Chase et al. 2001)
Annual PPT
Summer PDSI
Winter DTR
HAD
CCC
NORTH
CENTRAL
SOUTH
Palmer Drought Severity Index
Palmer Drought Severity Index
Palmer Drought Se i t Index
Historical Future Simulated
T. Kittel INSTAAR Seminar 7 Oct 2002
SURFACE RESPONSES TO REGIONAL FORCING
Coupled Climate Model Experiment – Increasing GHG+Sulfate Aerosols
Snowfree period calculated with Biome-BGC (P. Thornton, in Kittel et al. 2002)
+ Broad extraregionally forced changes result in finer scaled responses
CCC Climate
T. Kittel INSTAAR Seminar 7 Oct 2002
+ Elevation effect
+ Region dependent
+ Climate model experiment dependent
SURFACE RESPONSES TO REGIONAL FORCING –
ELEVATIONAL DEPENDENT?
NORTH
D SNOW-FREE PERIOD D SUMMER PDSI
Change in PDSI Change in Snow-free Period (months)
ELE
VATIO
N (
m)
ELE
VATIO
N (
m)
p<0.005p<0.001
p<0.001p<0.001
CENTRAL
T. Kittel INSTAAR Seminar 7 Oct 2002
SUMMARY
HISTORICAL TRENDS
+ Significant, generally positive 20th century regional trends in PPT, Tmin,and Tmax
• Tmin trends > Tmax trends – Diurnal T Range narrowed
• Differed by region – larger in North and Central
+ Trends varied with elevation
• High elevation trends were amplified, reduced, or opposite from lowerelevation
• No consistent pattern with season or region
T. Kittel INSTAAR Seminar 7 Oct 2002
SUMMARY
INTERANNUAL VARIABILITY
+ Interannual variability in PPT, Tmin, and Tmax was regional in nature
• Adjacent regions more strongly correlated
+ Significant teleconnections with global atmospheric circulation patterns
• Regional dependence: NPI influence stronger in north, SOI in South
• Strength and/or sign of relationship can depend on season
• Depend elevation
T. Kittel INSTAAR Seminar 7 Oct 2002
SUMMARY
FUTURE PATTERNS?
+ Extraregional forcing from altered atmospheric composition, land coverchange
+ Strong, complex regional and elevation dependent reworking of thisforcing by mountain climatic processes – atmospheric, hydrological, andecological
• Amplification or reduction of lowland signal, or decoupling
T. Kittel INSTAAR Seminar 7 Oct 2002
Further reading:
Kittel, T.G.F., P.E. Thornton, J.A. Royle, and T.N.Chase. 2002. Climates of the Rocky Mountains:Historical and Future Patterns. Pages 59-82(Chapter 4), in: J.S. Baron (ed.). Rocky MountainFutures: An Ecological Perspective. Island Press,Covelo, CA. http://www.islandpress.com