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Atmospheric Tracers and the Great Lakes. Ankur R Desai University of Wisconsin. Questions. Can we “see” Lake Superior in the atmosphere? Lake effect. Lake Effect. Source: Wikimedia Commons. Lake Effect. Source: S.Spak, UW SAGE. Questions. Can we “see” Lake Superior in the atmosphere? - PowerPoint PPT Presentation
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Atmospheric Tracers and the Great Lakes
Ankur R DesaiUniversity of Wisconsin
Questions
• Can we “see” Lake Superior in the atmosphere?– Lake effect
Lake Effect
• Source: Wikimedia Commons
Lake Effect
• Source: S.Spak, UW SAGE
Questions
• Can we “see” Lake Superior in the atmosphere?– Lake effect– Carbon effect?
• If so, can we constrain air-lake exchange by atmospheric observations?
• If that, can we compare terrestrial and aquatic regional fluxes?
Carbon Effect?
• Is the NOAA/UW/PSU WLEF tall tower greenhouse gas observatory adequate for sampling Lake Superior air?
First
• A little bit about atmospheric tracers and inversions…
Classic Inversion
• Source: S. Denning, CSU
• Source: NOAA ESRL
Flask Analysis
Gurney et al (2002) Nature
Regional Sources/Sinks
• Global cooperative sampling network not sufficient to detail processes at sub-seasonal, sub-continental, and sub-biome scale– Weekly/monthly sampling– Low spatial density– Poorly constrained inversion
Regional Sources/Sinks
• Global cooperative sampling network not sufficient to detail processes at sub-seasonal, sub-continental, and sub-biome scale– Weekly/monthly sampling– Low spatial density– Poorly constrained inversion
A Tall Tower
In Situ Sampling
What We See
Continental Sources/SinksWLEF Park Falls, WI 396m
330
340
350
360
370
380
390
400
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
CO
2 (p
pm
)
Daily 10am-2pm Tower (NOAA Globalview) Marine Background
Where We See
• Surface footprint influence function for tracer concentrations can be computed with LaGrangian ensemble back trajectories– transport model wind fields, mixing depths (WRF)– particle model (STILT)
Where We See
Where We See
• Source: A. Andrews, NOAA ESRL
Regional Sources/Sinks
• Global cooperative sampling network not sufficient to detail processes at sub-seasonal, sub-continental, and sub-biome scale– Weekly/monthly sampling– Low spatial density– Poorly constrained inversion
NOAA Tall Tower Network
Tower Sensitivities
Regional Sources/Sinks
• Global cooperative sampling network not sufficient to detail processes at sub-seasonal, sub-continental, and sub-biome scale– Weekly/monthly sampling– Low spatial density– Poorly constrained inversion
Bayesian Regional Inversions
CarbonTracker (NOAA)
Terrestrial Flux
• Annual NEE (gC m-2 yr-1) -160 (-60 – -320)– Buffam et al (submitted) -200
CarbonTracker (NOAA)
Problems With Regional Inversions• It is still an under-constrained problem!• Assumptions about surface forcing can skew
results• Great Lakes are usually ignored
• Sensitive to assumptions about “inflow” fluxes• Sensitive to error covariance structure in
Bayesian optimization• Transport models have more error at higher
resolution• Great Lakes have complex meteorology
Simpler Techniques
• Boundary Layer Budgeting– Compare [CO2] of lake and non-lake trajectory air
• WRF-STILT nested grid tracer transport model
– Estimate boundary layer depth and advection timescale to yield flux
• Equilibrium Boundary Layer– Compare [CO2] of free troposphere and boundary
layer air averaged over synoptic cycles– Estimate subsidence rate to yield flux
There Is a Lake Signal
• Source: N. Urban (MTU)
We Might See It at WLEF
• Source: M. Uliasz, CSU
5 6 7 8 9 10 11m onths
-8
-6
-4
-2
0
2
4
6
!CO2 [ppm]
5 6 7 8 9 10 11m onths
-8
-6
-4
-2
0
2
4
6
!CO2 [ppm]
EBL method (Helliker et al, 2004)
Mixed layer
Surface flux
Free troposphere
Onward
• Trajectory analysis and simple budgets – see next talk by Victoria Vasys
• Attempting regional flux inversions with lakes explicitly considered – in progress (A. Schuh, CSU)
• Direct eddy flux measurements over the lake – in progress (P. Blanken, CU; N. Urban, MTU)
I See Eddies
Fluxnet
Flux Mesonet
Lost Creek Shrub “Wetland”
Trout Lake NEE (preliminary)
• Source: M. Balliett, UW
Thanks!• CyCLeS project: G. Mckinley, N. Urban, C. Wu, V.
Bennington, N. Atilla, C. Mouw, and others, NSF• NSF REU: Victoria Vasys• WLEF: A. Andrews, NOAA ESRL, R. Strand, WI ECB; J.
Thom, UW; R. Teclaw, D. Baumann, USFS NRS• WRF-STILT: A. Michalak, D. Huntzinger, S. Gourdji, U.
Michigan; J. Eluszkiewicz, AER• Regional Inversions: M. Uliasz, S. Denning, A. Schuh,
CSU• EBL: B. Helliker, U. Penn• Eddy flux: P. Blanken, CU
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