- DiGangi, J. P;
- Boyle, E. S;
- Karl, T.;
- Harley, P.;
- Turnipseed, A.;
- Kim, S.;
- Cantrell, C.;
- Maudlin III, R. L;
- Zheng, W.;
- Flocke, F.;
- Hall, S. R;
- Ullmann, K.;
- Nakashima, Y.;
- Paul, J. B;
- Wolfe, G. M;
- Desai, A. R;
- Kajii, Y.;
- Guenther, A.;
- Keutsch, F. N
We report the first observations of formaldehyde (HCHO) flux measured via eddy covariance, as well as HCHO concentrations and gradients, as observed by the Madison Fiber Laser-Induced Fluorescence Instrument during the BEACHON-ROCS 2010 campaign in a rural, Ponderosa Pine forest northwest of Colorado Springs, CO. A median noon upward flux of ~80 μg m−2 h−1 (~24 pptv m s−1) was observed with a noon range of 37 to 131 μg m−2 h−1. Enclosure experiments were performed to determine the HCHO branch (3.5 μg m-2 h−1) and soil (7.3 μg m−2 h−1) direct emission rates in the canopy. A zero-dimensional canopy box model, used to determine the apportionment of HCHO source and sink contributions to the flux, underpredicted the observed HCHO flux by a factor of 6. Simulated increases in concentrations of species similar to monoterpenes resulted in poor agreement with measurements, while simulated increases in direct HCHO emissions and/or concentrations of species similar to 2-methyl-3-buten-2-ol best improved model/measurement agreement. Given the typical diurnal variability of these BVOC emissions and direct HCHO emissions, this suggests that the source of the missing flux is a process with both a strong temperature and radiation dependence.