Daily carbon surface fluxes in the West Ebre (Ebro) watershed from aircraft profiling on late June 2007

Abstract

A B S T R A C T An intensive aircraft campaign measuring atmospheric CO 2 mixing ratios was carried out in the central part of the Ebre watershed on late June 2007 to characterize the CO 2 dynamics in the Ebre basin and to calculate the regional cumulative carbon surface flux. CO 2 concentrations were obtained from vertical profiles over La Muela (LMU; 41.60 • N, 1.1 • W) from 900 to 4000 m above the sea level (masl), horizontal transects at ∼2000 m 100 km west from LMU, and continuous measurements at ∼650 masl. Different estimates of surface flux from changes in the convective boundary layer (CBL) CO 2 concentration were obtained following the Integral CBL budgeting equation (ICBL) and the carbon content integration (CCI) method. Values of the mean surface flux calculated from the different approaches range from −2.4 to −7.9 μmolCO 2 /m 2 s. Regional surface flux calculated from vertical profiling appears to be consistent in a distance of 70 km away from the measurement site. The ICBL method is very sensitive to the accurate determination of the concentration in the entrainment zone. The overall uncertainty from fluxes calculated from the ICBL method rises to a value of 70%, whereas the uncertainty linked to the CCI method is 55%.

Scalar arguments of the mathematical functions defining molecular and turbulent transport of heat and mass in compressible fluids

“…For trace gas transport, the scalar ζ in might be substituted by constituent density (ρ c ; e.g. Businger, 1986; Stull, 1988) or by a dimensionless proportion (Baldocchi et al, 1988; Stull, 1988; Struthers et al, 2007; Font et al, 2010) such as the specific humidity ( q ) or mixing ratio ( c ). Even Fick's law might define molecular diffusion as proportional to dimensional (Sutton, 1953; Arya, 1988; Oke, 1990; Wyngaard, 1990) or dimensionless (Batchelor, 1967; Wyngaard, 1984; Holton, 1992; Bird et al, 2002) ‘concentration’ gradients.…”

Assessing the regional surface influence through Backward Lagrangian Dispersion Models for aircraft CO<sub>2</sub> vertical profiles observations in NE Spain

“…However, global inversions do not provide much spatial resolution nor do they have the potential to increase the current understanding of the terrestrial processes at the regional scale responsible for the future control of fluxes (Canadell et al, 2000). The CO 2 concentration over continents shows large variability resulting from surface fluxes which vary both spatially across the landscape in close relation to vegetation types and conditions (Gerbig et al, 2003a;Sarrat et al, 2007a;Choi et al, 2008); and temporally due to signal reversal of biospheric fluxes between night (respiration) and day (photosynthesis) combined with strong daily mixing within the planetary boundary layer (Gloor et al, 2001;Lafont et al, 2002;Gerbig et al, 2008;Denning et al, 2008). In addition, CO 2 variability over continents is also linked to synoptic and mesoscale changes in meteorological conditions (Sidorov et al, 2002;Shashkov et al, 2007;Ahmadov et al, 2009).…”

“…Bakwin et al, 2003), from aircraft vertical sampling (Wofsy et al, 1988;Lloyd et al, 2001;Font et al, 2010) or by performing Lagrangian boundary layer budget campaigns (Schmitgen et al, 2004;Martins et al, 2009;Sarrat et al, 2009). The estimation of the regional surface fluxes based on a single tall tower is restrained by the influence of local fluxes (of up to 50 km distance) .…”