V. Kazan

European greenhouse gas emissions estimated from continuous atmospheric measurements and radon 222 at Mace Head, Ireland

Flux estimates of CO2, CH4, N2O, and CFCs over western Europe have been inferred from continuous atmospheric records of these species at the atmospheric research station of Mace Head, Ireland. We use radon (222Rn) which has a fairly uniform source over continents as a reference compound to estimate unknown sources of other species. The correlation between each species and 222Rn is calculated for a suite of synoptic events that have been selected in the Mace Head record over the period 1996/97. In the following, we describe the method and its uncertainties, and we establish data selection criteria that minimize the influence of local sources over Ireland, in the vicinity of the station, in order to select synoptic events originating from western Europe. We estimate western European flux densities of 45–30 103 kg C km−2 month−1 during wintertime for CO2, of 4.8–3.5 103 kg CH4 km−2 yr−1, 475–330 kg N2O km−2 yr−1, 2.5–1.8 kg CFC-11 km−2 yr−1 for CFC-11, and 4.2–2.9 kg CFC-12 km−2 yr−1 for CFC-12. Our estimates are independent, although in good agreement with those produced by inventories, except for CFC-11 where our estimate is much lower than the inventory.

A recent build‐up of atmospheric CO2 over Europe. Part 1: observed signals and possible explanations

We analysed interannual and decadal changes in the atmospheric CO2 concentration gradient (ΔCO2) between Europe and the Atlantic Ocean over the period 1995–2007. Fourteen measurement stations are used, with Mace-Head being used to define background conditions. The variability of ΔCO2 reflects fossil fuel emissions and natural sinks activity over Europe, as well as atmospheric transport variability. The mean ΔCO2 increased by 1–2 ppm at Eastern European stations (∼30% growth), between 1990–1995 and 2000–2005. This built up of CO2 over the continent is predominantly a winter signal. If the observed increase of ΔCO2 is explained by changes in ecosystem fluxes, a loss of about 0.46 Pg C per year would be required during 2000–2005. Even if severe droughts have impacted Western Europe in 2003 and 2005, a sustained CO2 loss of that magnitude is unlikely to be true.We sought alternative explanations for the observed CO2 build-up into transport changes and into regional redistribution of fossil fuel CO2 emissions. Boundary layer heights becoming shallower can only explain 32% of the variance of the signal. Regional changes of emissions may explain up to 27% of the build-up. More insights are given in the Aulagnier et al. companion paper.

A European-wide 222Radon and 222Radon progeny comparison study [Dataset]

Although atmospheric 222Radon (222Rn) activity concentration measurements are currently performed world-wide, they are being made by many different laboratories and with fundamentally different measurement principles, so compatibility issues can limit their utility for regional-to-global applications. Consequently, we conducted a European‐wide 222Rn/222Rn progeny comparison study in order to evaluate the different measurement systems in use, determine potential systematic biases between them, and estimate correction factors that could be applied to harmonize data for their use as a tracer in atmospheric applications. Two compact portable Heidelberg Radon Monitors (HRM) were moved around to run for at least one month at each of the nine European measurement stations included in this comparison. Linear regressions between parallel data sets were calculated, yielding correction factors rela tive to the HRM ranging from 0.68 to 1.45. A calibration bias between ANSTO (Australian Nuclear Science and Technology Organisation) two‐filter radon monitors and the HRM of ANSTO/HRM = 1.11±0.05 was found. Moreover, for the continental stations using one‐filter systems that derive atmospheric 222Rn activity concentrations from measured atmospheric progeny activity concentrations, preliminary 214Po/222Rn disequilibrium values were also estimated. Mean station-specific disequilibrium values between 0.8 at mountain sites (e.g. Schauinsland) and 0.9 at non‐mountain sites for sampling heights around 20 to 30 m above ground level were determined. The respective corrections for calibration biases and disequilibrium derived in this study need to be applied to obtain a compatible European atmospheric 222Rn data set for use in quantitative applications, such as regional model intercomparison and validation, or trace gas flux estimates with the Radon‐Tracer‐Method.