Abstract
Abstract. Eight years of occasional flask air sampling and 3 years of frequent in situ measurements of carbon dioxide (CO2) vertical profiles on board of a small aircraft, over a tall tower greenhouse gases monitoring site in Hungary are used for the analysis of the variations of vertical profile of CO2 mole fraction. Using the airborne vertical profiles and the measurements along the 115 m tall tower it is shown that the measurements at the top of the tower estimate the mean boundary layer CO2 mole fraction during the mid-afternoon fairly well, with an underestimation of 0.27–0.85 μmol mol−1 in summer, and an overestimation of 0.66–1.83 μmol mol−1 in winter. The seasonal cycle of CO2 mole fraction is damped with elevation. While the amplitude of the seasonal cycle is 28.5 μmol mol−1 at 10 m above the ground, it is only 10.7 μmol mol−1 in the layer of 2500–3000 m corresponding to the lower free atmosphere above the well-mixed boundary layer. The maximum mole fraction in the layer of 2500–3000 m can be observed around 25 March on average, two weeks ahead of that of the marine boundary layer reference (GLOBALVIEW). By contrast, close to the ground, the maximum CO2 mole fraction is observed late December, early January. The specific seasonal behavior is attributed to the climatology of vertical mixing of the atmosphere in the Carpathian Basin.
Highlights
The present paper evaluates the temporal variation of CO2 mole fraction in the lower free troposphere, in the boundary layer and at the surface using the measurements carried out on and above the tall tower at Hegyhatsal, Hungary, between 2001 and 2008
One of the major sources of uncertainty in the representation of CO2 mole fractions by atmospheric transport models lies in the imperfect parametrisation of the vertical mixing through the planetary boundary layer
On the basis of aircraft and tall tower measurements at and above Hegyhatsal, Hungary, we estimated how accurately the mean CO2 mole fraction in the planetary boundary layer (PBL) can be estimated from tall tower measurements and what are the differences in the seasonal cycles in the CO2 mole fraction at different elevations from the ground, through the PBL and up to the lower free troposphere
Summary
Development and increasing use of high-resolution 3dimensional carbon dioxide (CO2) transport models require detailed information on the spatial distribution of carbon dioxide in the atmosphere and its temporal variation as both input information and data for validation (Bakwin et al, 2004; Geels et al, 2007; Peters et al, 2007; Stephens et al, 2007; Yang et al, 2007; Engelen et al, 2009; Feng et al, 2011; Patra et al, 2011; Pickett-Heaps et al, 2011). Calibration/validation of satellite-borne measurements, ground based remote sensing instruments require detailed mole fraction data from the lower troposphere (Engelen and McNally, 2005; Wunch et al, 2010).
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