Tower - Region - Continent - Globe: Bridging the gap between flux

towers and flasksGoals

Merge our mechanistic understanding of terrestrial C dynamics at the tower scale with our understanding

of the global CO2 budget obtained from the flask network.

Understand the mechanisms that govern changes in the atmospheric CO2 budget at seasonal to annual time scales, and regional to continental spatial scales.

ContributorsM.P. Butler, K.J. Davis, M. Hurwitz, D. Ricciuto, W. Wang, and C. Yi, The

Pennsylvania State University

B.D. Cook, University of Minnesota

P.S. Bakwin, NOAA/CMDL

A.S. Denning and colleagues, Colorado State

J. Berry, B. Helliker, Carnegie Institute

B. Balsley, J. Birks, M. Jensen, and K. Schultz,

University of Colorado

Support: NIGEC, DoE-TCP, NASA, NSF

Related talks: Schmid, Wofsy, Hollinger, Denning, Keeling

Methods for determining NEE of CO2 Methods for bridging the gap

Cha

mbe

r fl

uxTower flux

ABL budgetAirborne flux

Forest inventory Inverse study

decade

year

month

hour

day

Tim

e S

cale

Spatial Scale

(1m)2

= 10-4ha (1000km)2

= 108ha (100km)2

= 106ha (10km)2

= 104ha (1km)2

= 102haRearth

Upscale via ecosystem modelsand networks of towers.

Move towardsregional inversemodeling

Atmospheric approaches to determining NEE of CO2

Ci

i

i

i Sx

CU

x

CU

t

C

''

Time rate ofchange of CO2

Mean transport

Turbulenttransport (flux)

Source in theatmosphere

Average over the depth of the atmosphere (or the ABL):

0C

zi

i

CC C

t x

FU

z

F

F0C encompasses all surface exchange: Oceans, deforestation,

terrestrial uptake, fossil fuel emissions.

Inverse study: Observe C, model U, derive FFlux study: Observe F directly

Progress

• AmeriFlux towers can be used to monitor continental boundary layer [CO2]! Downscale inversions. dC/dt, dC/dx

Future: Create this network. Complement tall towers, airborne profiles, satellite [CO2].

Surface layer towers can (should!) be used to monitor continental CO2

1997 monthly mean CO2 mixing ratios from the WLEF tower.

Month

CO2 (ppm)at 11m,

early pm only

CO2 (ppm)at 396m,

early pm only

CO2 (ppm)11m – 396m,early pm only

CO2 (ppm)at 396m,entire day

CO2 (ppm)396m pm – 396m

entire day,1 371.4 370.3 1.1 369.7 0.62 371.4 371.2 0.2 371.1 0.13 371.4 371.0 0.4 371.0 0.04 370.4 370.4 0.0 370.4 0.05 368.1 368.2 -0.1 368.3 -0.16 355.5 357.3 -1.8 359.4 -2.17 348.0 350.2 -2.2 351.1 -0.98 346.1 348.1 -2.0 349.3 -1.29 354.9 356.2 -1.3 358.0 -1.8

10 365.8 365.6 0.2 366.0 -0.411 370.3 369.9 0.3 369.6 0.312 371.5 370.6 0.9 370.2 0.4

Annualmean 363.7 364.1 -0.4 364.5 -0.4

Annual mean at Mauna Loa, 1997, was 366.7 ppm.

The seasonal amplitudeof the gradient in CO2

between the continental ABLand the marine boundary layer is large.

Surface layer - mid-ABLdifference (1 to 2 ppmv)does not overwhelmthis signal.

Progress

• Coherence among continental-scale, annual and seasonal flux anomalies exists and is reflected in the atmospheric CO2 network. Upscale fluxes. F0

C Downscale inversions (in time).

Future: Continue analyses. Incorporate flux data into inversion models. Explain 1998 anomalous increase in atmospheric CO2?

Spatial coherence of seasonal flux anomalies

A similar pattern isseen at several fluxtowers in N. Americaand Europe.

Three sites have high-quality [CO2] measurements + dataat Fluxnet (NOBS,HF, WLEF).

The spring 98 warm period and a later cloudy period appear at all 3 sites.

Detection of the spring 98 anomaly via oceanic flasks?

2 Alaskan flasksites have slightlyhigher [CO2] inthe spring of 98.

Mace Head, Irelandshows a depression of [CO2] in thespring of 98.

Potential exists to link flux towers with seasonal inverse studies.

Progress• ABL budgets are being used to derive regional, daily NEE of CO2.

Downscale inversions. COBRA, Powered parachute, tower-based.– Lagrangian budgets. COBRA.

– Advection in the continental ABL [CO2] cannot be neglected on monthly time scales. U dC/dx.

– Synoptic events drive advection of CO2. U dC/dx.

– Promising results using H2O - CO2 similarity. Helliker and Berry.

Future: Continental [CO2(x,y,z)] network is required. Critical method for model validation at large time and space scales.

Fluxes at WLEF on May 18, 2001

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0 5 10 15 20 25

Hour (UTC)

CO2

Flux

(ppm

m s

-1)

Flux 1

Flux 2

Flux 3

Flux 1: surface flux using vertical advection, storage flux, and turbulent fluxFlux 2: surface flux using storage flux and turbulent fluxFlux 3: surface flux using an ABL budget based on PPC data

ABL budgets - regional inverse studies

CO2 advection in the continental ABL

CO2

i (F0C.t)i

CO2 advection in the continental ABLdCO2/dt

Predicted = F0C.t.zmixing

zmixing =10km

zmixing = zi

DayofYear

NEE ofCO2

= F0C

(gC m-2 d-1)

observed(ppmmo-1)

(ppm mo-1) (ppm d-1)

zi

(km)

330-120

0.39 -0.68 4.04 0.94 1.0

120-150

0.20 -4.68 2.07 0.24 2.0

150-220

-2.35 -6.96 -24.3 -2.83 2.0

220-255

-0.66 6.80 -6.83 -1.06 1.5

255-330

0.96 5.36 9.88 1.54 1.5

Synoptic variability in CO2

Regional fluxes from H2O - CO2 similarity

FromHellikerand Berry,poster.

Progress• The rectifier effect - a major source of uncertainty in

transport models - is being quantified via observations. COBRA. Powered parachute. WLEF ABL radar deployment. Improve inversions. Fz

C and z.

Future: Examine conclusions with more continental profile data, including airborne data and additional AmeriFlux/Fluxnet sites. Validate tower-based assessment with airborne profiles. Quantify transport between the continental ABL and the marine boundary layer.

Rectifier is underestimated in the day?

WLEFtower +ABL radar vs.Denning1995model.

Rectifier is overestimated seasonally?

WLEFtower +ABL radar vs.Denning1995model.

Research needed• Construct a continental [CO2] network. Make AmeriFlux

towers part of this network. Move towards regional inversions and assimilation of flux and mixing ratio data into coupled ecosystem-atmosphere models.

• Increase the AmeriFlux/Fluxnet database. Include [CO2]. Report data! Common formats/QC!

• Continue to analyze spatial patterns in flux measurements to link to the mechanisms of global CO2 variability.

• Airborne flux - modeled flux - ABL budget/regional inversion joint projects.

• Conduct the North American Carbon Program.