Joint analyses of carbon dioxide mixing ratio and flux by steepslope9876

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									 Joint analyses of carbon dioxide
mixing ratio and flux measurements
     Kenneth J. Davis, Martha P. Butler,
   Michael D. Hurwitz, Daniel M. Ricciuto,
              and Chuixiang Yi
     The Pennsylvania State University

       Peter S. Bakwin, NOAA CMDL

  Michael L. Jensen, Kristen Schulz, Ben B.
        Balsley and John W. Birks
           University of Colorado
Interannual
variability
in the rate of
accumulation
of atmospheric
CO2
                          Outline
• Problem: Flux vs. mixing ratio observations
• Method: CO2 mixing ratios from flux towers
• Application: What can we learn from a single site?
   – Advection matters
   – CO2 advection occurs with weather
   – ABL budget method is promising for regional fluxes
• Application: How can we integrate multiple sites?
   – Continental and regional network ideas
      • Sketch. Resolve budget equation.
   – Spatial coherence across many sites – spring anomaly
      • Upscale fluxes – absolute value of fluxes cannot be
        extrapolated, but temporal variability can. Linked to climate.
        Linked to CO2. Continental budgets, interannual variability.
        Data is lacking.
Atmospheric approaches to observing the terrestrial
                 carbon cycle
     C      C    U i'C '
        U i                SC
     t      xi    xi
  Time rate of         Mean         Turbulent       Source in the
change (e.g. CO2)    transport   transport (flux)    atmosphere

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

      C                 C                F0C  FzC
                     Ui                 
      t                 xi                   z
  F0C encompasses all surface exchange: Oceans, deforestation,
            terrestrial uptake, fossil fuel emissions.
     Inversion study: Observe C, model U, derive F
             Flux study: Observe F directly
             Methods for determining NEE of CO2
                Methods for bridging the gap
                         Forest inventory                                               Inverse study
              decade

                                                       Tower flux
              year                                     Upscale via ecosystem models
                              Chamber flux


                                                       and networks of towers.
Time Scale




              month
                                                                        ABL budget     Move towards
                                                   Airborne flux                       regional inverse
                                                                                       modeling
              day


              hour

                        (1m)2                (1km)2         (10km)2       (100km)2    (1000km)2 Rearth
                       = 10-4ha              = 102ha        = 104ha       = 106ha     = 108ha

                                                        Spatial Scale
           Methodology:
  How can we use flux towers to
  gather worthwhile CO2 mixing
       ratio measurements?
• Calibrate! Bakwin et al, 1995. Zhao et al,
  1997.
• Use midday data - very small vertical
  gradients.
• Midday surface layer CO2 data resolves
  synoptic, seasonal and annual spatial and
  temporal trends.
Chequamegon Ecosystem-Atmosphere
 Study (ChEAS) http://cheas.psu.edu
WLEF tall tower (447m)              Forest stand towers:
CO2 flux measurements at:             Mature upland deciduous
 30, 122 and 396 m                    Deciduous wetland
CO2 mixing ratio measurements at:     Mixed old growth
 11, 30, 76, 122, 244 and 396 m     All have both CO2 flux and
                                      high precision mixing
                                      ratio measurements.
                                       Upland, wetland, and
          
                                       very tall flux tower. Old
North
        WISCONSIN
                                       growth tower to the NE.

                                       High-precision CO2
                                       profile at each site.

                                       Mini-mesonet, 15-20km
                                      spacing between towers.
                          Lost Creek
                                          Landcover key
                                              Open water
          WLEF                               Wetland
                                              Coniferous
                                              Mixed deciduous/coniferous

                                              Shrubland
                    
                                              General Agriculture
                    Willow Creek
View from 396m above Wisconsin: WLEF TV tower
Diurnal cycle of CO2 in the ABL
      Surface layer flux towers can be
      used to monitor continental CO2!
1997 monthly mean CO2 mixing ratios from the WLEF tower.

        CO2 (ppm)     CO2 (ppm)      CO2 (ppm)    CO2 (ppm)   CO2 (ppm)
          at 11m,      at 396m,      11m – 396m,    at 396m, 396m pm – 396m
Month early pm only early pm only early pm only    entire day   entire day,
  1        371.4         370.3            1.1         369.7         0.6
  2        371.4         371.2            0.2         371.1         0.1
  3        371.4         371.0            0.4         371.0         0.0
  4        370.4         370.4            0.0         370.4         0.0
  5        368.1         368.2           -0.1         368.3        -0.1
  6        355.5         357.3           -1.8         359.4        -2.1
  7        348.0         350.2           -2.2         351.1        -0.9
  8        346.1         348.1           -2.0         349.3        -1.2
  9        354.9         356.2           -1.3         358.0        -1.8
  10       365.8         365.6            0.2         366.0        -0.4
  11       370.3         369.9            0.3         369.6         0.3
  12       371.5         370.6            0.9         370.2         0.4
Annual
 mean      363.7         364.1           -0.4         364.5       -0.4
Annual mean at Mauna Loa, 1997, was 366.7 ppm.
Synoptic variability in CO2
The seasonal amplitude
of the gradient in CO2
between the continental
ABL and the marine
boundary layer is large.

Surface layer - mid-ABL
difference (1 to 2 ppmv)
does not overwhelm
this signal.
      CO2 gradients vs. the surface-
       layer - ABL bias at WLEF
                   Synoptic        Seasonal           Annual
  (all values in   (days, within   (across time and   (marine-
   ppm CO2)        continent)      the marine-        continental
                                   continental        gradient)
                                   boundary)
Gradient           5-20            4-15               2
(can be used as
input to derive
fluxes)
Bias (midday       1-4             1-4                0.4/0.8
surface layer to   (night-time     (both peak in      (about half
24-hour mid-       data hard to    summer)            day-night, half
ABL)               interpret?)                        vertical)
  Results: What can be learned
about regional fluxes from single
 site flux-mixing ratio analyses?
• Advection and local fluxes are both
  important in the ABL CO2 budget.
• Relative importance changes across the
  continent.
• Advection can be huge with synoptic
  events.
• In between synoptic events, even 1-D ABL
  budgets do a fair job for flux estimates.
           ABL budget
(why? Flux „fetch‟ of ~100‟s of km!)

   C        C                F0C  FzC
         Ui                 
   t        xi                   z
                           0?
           To estimate surface flux:
              Observe first term,
        observe or neglect second term,
              observe or avoid Fz,
                  solve for F0.
Net ecosystem-atmosphere exchange
   of CO2 in northern Wisconsin
                            Monthly average
                            ABL budgets
                            from three towers.

                            HForest is the
                            least “1-D”.

                            BOREAS NSA
                            is the most “1-D”.

                            Advection is
                            related to the
                            continent – marine
                            CO2 gradient.

Credits to Harvard group.
Cold frontal passage and CO2
 advection (14 July, 1998)
ABL budgets - regional inverse studies
                                                                   Fluxes at WLEF on May 18, 2001

                                  0.30
                                  0.20
                                  0.10


           CO2 Flux (ppm m s-1)
                                  0.00
                                  -0.10
                                  -0.20
                                  -0.30
                                                          Flux 1
                                  -0.40
                                                          Flux 2
                                  -0.50
                                                          Flux 3
                                  -0.60
                                  -0.70
                                          0                   5                10                15                20           25
                                                                                    Hour (UTC)

                                              Flux 1: surface flux using vertical advection, storage flux, and turbulent flux
                                              Flux 2: surface flux using storage flux and turbulent flux
                                              Flux 3: surface flux using an ABL budget based on PPC data
                                1-D ABL budget vs eddy
                         0.2
                                   covariance fluxes
                         0.1
                                                                 Oct 9
                                                                               Credit:
Surface Flux (ppm*m/s)




                           0
                                                                               Marc Fischer,
                                  Mar 26   Mar 30 May 18 Oct 7                 LBNL
                         -0.1

                         -0.2

                         -0.3
                                                             Predicted Tower Based
                         -0.4                                Surface Flux
                                                             Predicted Aircraft
                         -0.5                                based surface flux


                         -0.6
North American Carbon Plan
        (NACP)
    http://www.carboncyclescience.gov
      Multiple-site syntheses
• Interannual variability in NEE of CO2 is
  driven by climate(?).
• Multiple flux towers experience the same
  climatic anomalies.(?)
• Large flux anomalies can be detected by
  atmospheric CO2 data.(?)
• Flux tower network and CO2 measurements,
  therefore, observe the same phenomenon!
  (The gap is bridged!)
Early leaf-out, 1998, Wisconsin
Impact on atmospheric [CO2]
       Spatial coherence of seasonal flux anomalies
                                      A similar pattern is
                                      seen at several flux
Temp




                                      towers in N. America
                                      and Europe.

                                      Three sites have
                                      high-quality [CO2]
CO2




                                      measurements + data
                                      at Fluxnet (NOBS,
                                      HF, WLEF).

                                      The spring 98 warm
NEE




                                      period and a later
                                      cloudy period appear
                                      at all 3 sites.
       80       Day of year     200
Detection of the spring 98 anomaly via oceanic flasks?
                                    2 Alaskan flask
                                    sites have slightly
                                    higher [CO2] in
                                    the spring of 98.

                                    Mace Head, Ireland
                                    shows a depression
                                    of [CO2] in the
                                    spring of 98.

                                    Potential exists to link
                                    flux towers with
                                    seasonal inverse
                                    studies.
             Acknowledgements
• Funding and personnel support:
   –   DoE – NIGEC – Midwest and Great Plains
   –   NOAA CMDL
   –   NASA – EOS Validation
   –   DoE – TCP/TECO
   –   NSF/NCAR
   –   USDA-FS
• Data and analyses
   – Harvard Forest group
   – Marc Fischer, LBNL
Courtesy D. Hollinger
 CO2 advection in the continental ABL
Day      NEE of                     dCO2/dt                      zi
of        CO2       observed     Predicted = F0C.t.zmixing    (km)
Year      = F0C      (ppm         zmixing =     zmixing = zi
       (gC m-2 d-1)  mo-1)         10km
                                (ppm mo-1)      (ppm d-1)
330-   0.39        -0.68       4.04           0.94             1.0
120

120-   0.20        -4.68       2.07            0.24            2.0
150
150-   -2.35       -6.96       -24.3           -2.83           2.0
220
220-   -0.66       6.80        -6.83           -1.06           1.5
255
255-   0.96        5.36        9.88            1.54            1.5
330
Radar ABL depth




WLEF fluxes




CO2 profile

								
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