Open AccessEstimates of net CO 2 flux by application of equilibrium boundary layer concepts to CO 2 and water vapor measurements from a tall tower
Author(s) -
Helliker Brent R.,
Berry Joseph A.,
Betts Alan K.,
Bakwin Peter S.,
Davis Kenneth J.,
Denning A. Scott,
Ehleringer James R.,
Miller John B.,
Butler Martha P.,
Ricciuto Daniel M.
Publication year - 2004
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jd004532
Subject(s) - troposphere , water vapor , eddy covariance , flux (metallurgy) , atmospheric sciences , planetary boundary layer , environmental science , boundary layer , convective boundary layer , atmosphere (unit) , mixing ratio , turbulence , meteorology , mechanics , chemistry , geology , physics , ecology , ecosystem , biology , organic chemistry
Convective turbulence within the atmospheric boundary layer (ABL) and movement of the ABL over the surface results in a large spatial (10 4 –10 5 km 2 ) integration of surface fluxes that affects the CO 2 and water vapor mixing ratios. We apply quasi‐equilibrium concepts for the terrestrial ABL to measurements of CO 2 and water vapor made within the ABL from a tall tower (396 m) in Wisconsin. We suppose that CO 2 and water vapor mixing ratios in the ABL approach an equilibrium on timescales longer than a day: a balance between the surface fluxes and the exchange with the free troposphere above. By using monthly averaged ABL‐to‐free‐tropospheric water vapor differences and surface water vapor flux, realistic estimates of vertical velocity exchange with the free troposphere can be obtained. We then estimated the net surface flux of CO 2 on a monthly basis for the year of 2000, using ABL‐to‐free‐tropospheric CO 2 differences, and our flux difference estimate of the vertical exchange. These ABL‐scale estimates of net CO 2 flux gave close agreement with eddy covariance measurements. Considering the large surface area which affects scalars in the ABL over synoptic timescales, the flux difference approach presented here could potentially provide regional‐scale estimates of net CO 2 flux.