[show abstract][hide abstract] ABSTRACT: 1] This paper presents a Lagrangian budgeting approach to quantify the uptake of CO 2 by vegetation at horizontal scales of several tens of kilometers. For this purpose, CO 2 and meteorological parameters were measured from a small aircraft during four flights in June 2001 over a flat homogeneous and productive temperate forest in the Landes region (southwestern France). Additional CO measurements were made in order to identify and quantify the potential influence of anthropogenic emissions on the net CO 2 flux derived from the measurements. For one of four flights, Lagrangian conditions were nearly perfectly fulfilled. On average, the CO 2 mixing ratio in the boundary layer decreased at a rate of 0.11 ppm km À1 , yielding an average CO 2 uptake by the forest of 16 ± 2.5 mmol m À2 s À1 between 1230 and 1430 UT. Our result is about 15% smaller than the local net ecosystem exchange measured by eddy covariance at a tower north of the flight domain and about 12% higher than a regional estimate based on remote sensing data for the whole experimental area. The contribution of anthropogenic emissions to the regional CO 2 budget was estimated from the CO measurements to be to <0.5 mmol m À2 s À1 . (2004), Carbon dioxide uptake of a forested region in southwest France derived from airborne CO 2 and CO measurements in a quasi-Lagrangian experiment, J. Geophys. Res., 109, D14302, doi:10.1029/2003JD004335.
Journal of Geophysical Research-Atmospheres. 01/2004; 109(D14).
[show abstract][hide abstract] ABSTRACT: This paper presents strong experimental evidence for a major perturbation in ozone concentrations over large parts of the North Atlantic Ocean from the surface to 8 km associated with continental pollutants. The evidence was gathered in the course of 7 flights by the UK Meteorological Office C-130 aircraft based on the Azores, and 4 ferry flights between the UK to the Azores in spring and summer 1997 as a component of the NERC-funded ACSOE project. The total latitude range covered was approximately 55°N?25°N, and the longitude range was approximately 0° to 40°W. Many profiles were made between the sea surface and altitudes up to 9 km to survey the composition of the marine atmosphere.
The C-130 aircraft was comprehensively equipped to measure many chemical and physical parameters along with standard meteorological instrumentation. Thus it was able to measure ozone and speciated NO<sub>y</sub>, along with tracers including water vapour, carbon monoxide and condensation nuclei, in near real time. The overall "picture" of the troposphere over large parts of the North Atlantic is of layers of pollution from the continents of different ages interspersed with layers of air uplifted from the marine boundary layer. The lowest ozone concentrations were recorded in the marine boundary layer where there is evidence for extensive ozone destruction in summer.
Flights were made to penetrate the outflow of hurricane Erica, to determine the southerly extent of polluted air in summer, to examine the impact of frontal systems on the composition of remote marine air, and to trace long-range pollution from the west coast of the USA interspersed with air with a stratospheric origin. In one of the spring flights it is possible that a plume of polluted air with high ozone and NO<sub>y</sub>, and with an origin in southeast Asia, was intercepted off the coast of Portugal. The concentrations of NO<sub>x</sub>, in this plume were sufficient for ozone formation to be continuing along its track from west to east.
The instrument to measure NO<sub>y</sub> almost certainly was only measuring the sum of organic nitrates (mostly in the form of PAN) plus NO<sub>x</sub>. The high correlation between NO<sub>y</sub> and ozone under these conditions strongly suggests a non-stratospheric source for most of the ozone encountered over large parts of the atmosphere upwind of Europe. There was a marked seasonal variation in the NO<sub>y</sub> with about twice as much present in the spring flights than in the summer flights. The overall ozone levels in both spring and summer were somewhat similar although the highest ozone concentration encountered (~100 ppbv) was observed in summer in some polluted layers in mid Atlantic with an origin in the boundary layer over the southeastern USA. The bulk of the pollutants, ozone, CO, and NO<sub>y</sub>, were in the free troposphere at altitudes between 3 and 8 km. The only instances of pollution at lower levels were in the form of ship plumes, which were encountered several times. The data therefore strongly support the need for more in-situ aircraft experiments to quantify and understand the phenomenon of long-range transport of pollution from continent to continent. Observations at ground-based stations are inadequate for this purpose and satellite data is incomplete both in terms of its altitude detail and in the extent of chemical speciation, particularly for ascertaining whether chemical production and destruction processes for ozone are occurring.
[show abstract][hide abstract] ABSTRACT: In this paper, ozone (O3), water vapor (H2O), carbon monoxide (CO), and peroxide concentrations and photolysis rates measured in the troposphere over the North Atlantic during two Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) aircraft field campaigns are used to calculate the concentration of nitric oxide (NO) required for net photochemical O3 production (nPO3) to be positive (NOcomp). NOcomp tended to show a decrease with altitude, although it was sometimes found to be low in the marine boundary layer (MBL) where H2O concentrations were high and O3 concentrations were low. nPO3 was calculated for the spring when NO data were available and was found to be mostly negative and generally increased from about −0.5 to −0.2 ppbv hr−1 in the MBL to +0.04 ppbv hr−1 at about 7–8 km altitude. The results suggest that much of the lower and middle troposphere over the eastern North Atlantic during spring is in a state of slow net photochemical O3 destruction. However, in the upper troposphere, the system changes to one of net photochemical production, which results from the drier environment and higher NO concentrations. Furthermore, examples of net O3 production were also observed in the lower and middle troposphere associated with either in situ sources of NO or long-range transport of pollution. The paper also illustrates the sensitivity of this O3 production/loss state to H2O and NO concentrations, photolysis rates, and temperatures.
Journal of Geophysical Research-Atmospheres. 01/2002; 107(D23).
[show abstract][hide abstract] ABSTRACT: A mesoscale meteorological model with passive tracers is applied in order to analyze transport from the atmospheric boundary layer to the free troposphere. The validation of the model against aircraft measurements indicates that the model adequately simulates the tracer distributions in the free troposphere as well as in the boundary layer. Budget calculations of passive tracers are performed in order to estimate the amount of transport in the area of a frontal system. The results show a very effective uplift associated in particular with a WCB transporting up to ∼70% of a passive tracer initialized in the boundary layer to the free troposphere within 3 days.
Geophysical Research Letters - GEOPHYS RES LETT. 01/2001; 28(15):2907-2910.
[show abstract][hide abstract] ABSTRACT: The fast-response resonance fluorescence instrument for the airborne measurement of carbon monoxide described by Gerbig et al.  was modified by implementing an improved optical filter with more efficient optics and an optimized resonance lamp. Besides reductions in size and weight, the new instrument achieves a sensitivity 10 times higher, a lower background (65 ppb compared with 250 ppb), and a faster time response (
Journal of Geophysical Research 01/1999; 104:1699-1704. · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: Over the 10 past years, the global monitoring network of atmospheric CO2 has been largely used to retrieve the large scale distribution of sources and sinks at the surface. The most recent studies have demonstrated the need for more data over continental regions, to make feasible robust estimations of the biospheric contribution to the re- gional carbon budget. Consequently, several programs are emerging to develop regular vertical profiles of atmospheric CO2 over selected areas. However, to assess the rep- resentativeness of the selected sites we need to complete these frames with intensive survey flights. The Co-ordinated Access to Aircraft for Transnational Environmental Research (CAATER), an European initiative, has given us the opportunity to perform two large scale transects over Western Europe in May 2001 and February 2002. In this presentation we will show the results of these survey flights which took place over Europe aboard the Falcon 20 of the Deutsches Zentrum für Luft und Raumfahrt (Oberpfaffenhofen Germany). The flights were designed to cover background (North Atlantic) and polluted (Ruhr valley, Hungary) regions in the low troposphere (500- 5000m). During this experiment the aircraft was equipped with two new instruments designed for airborne applications: the first, CONDOR, to measure CO2, the sec- ond, AVIRAD, to sample and analyse Radon-222 which is used as a tracer of vertical mixing. A continuous CO analyser and an aethalometer were also installed on board during february flight. In addition to the in-situ measurements, flasks were sampled regularly for subsequent analysis of CO, CO2, SF6, N2O, CH4, and NMHCs.
[show abstract][hide abstract] ABSTRACT: A crucial challenge in measuring the partitioning of sources and sinks of atmospheric CO2 is the separation of regional anthropogenic CO2 sources from biogenic activity. The aim of the COCA project is to quantify the fossil fuel and biogenic CO2 fractions using continuous airborne CO2 and CO measurements, where CO acts as a tracer for anthropogenic CO2. At first part of the project COCA an attempt was made to measure daytime biogenic CO2 fluxes over a forest area (about 15 by 30 km size). The campaign took place around the CARBOEUROFLUX site ``Le Bray'' (Pinus pinaster) close to Bordeaux in France end of June 2001 Based on continuous airborne CO2, H2O and CO flux and concentration measurements a Lagrangian budgeting approach was chosen to measure regional CO2 deposition fluxes. The objective is to determine the CO2 uptake of the extended forest area from the CO2/CO gradients up- and downwind of the ecosystem, using CO as air mass tracer and such estimating the influence of anthropogenic CO2 advected into the area First results of the summer flight on June 23rd will be shown, where fair wind speeds (~5 m/s) and a low CBL height led to the observation of a clear decrease in CO2 at the downwind flight stacks with basically constant CO concentrations. For other summer flights with very low wind speeds, local effects dominate the observations leading to a larger variability in the observations. Both, correlations and anti-correlations of CO2 with the anthropogenic tracer CO have been observed. Positive correlations indicate fresh plumes of anthropogenic CO2. Negative correlations are indicative of entrainment of free tropospheric air, that was marked by relatively higher CO2 and lower CO concentrations than the average CBL concentrations. During a second campaign the variance of anthropogenic CO and CO2 emissions of a large city unaffected by biogenic processes has been studied. This campaign was carried out on February 16 and 17, 2002 over the Paris metropolitan area (Ile de France, about 100 by 100 km size). Correlation plots of the measurements in the Paris plume on February 16th show a clear correlation between CO and CO2. This confirms the suitability of CO as a tracer for anthropogenic emissions at regional scales where the inputs of primary CO and CO2 with different ratios have blended to define regional mean CO/CO2 ratios.
[show abstract][hide abstract] ABSTRACT: As part of the project COCA an attempt was made to measure the daytime biogenic CO2 fluxes over a forest area (about 15 by 30 km). This campaign took place around the CARBOEUROFLUX site "Le Bray" (Pinus pinaster) close to Bordeaux in France end of June 2001. Based on continuous airborne CO2, H2O and CO flux and concen- tration measurements a Lagrangian budgeting approach was chosen for the determi- nation of the regional CO2 fluxes. The objective is to determine the CO2 uptake of the extended forest area from the CO2/CO gradients up- and downwind of the ecosystem, using CO as air mass tracer and such eliminating the influence of anthropogenic CO2 advected into the area. First results will be shown of a flight on June 23rd, where fair wind speeds (about 5 m/s) and a low CBL height led to the observation of a clear decrease in CO2 at the downwind flight stacks with basically constant CO concentrations. For other flights with very low wind speeds, local effects dominate the observa- tions leading to a larger variability in the observations. Both, correlations and anti- correlations of CO2 with the anthropogenic tracer CO have been observed. Positive correlations indicate fresh plumes of anthropogenic CO2. Negative correlations are indicative of entrainment of free tropospheric air, that was marked by relatively higher CO2 and lower CO concentrations than the average CBL concentrations.
[show abstract][hide abstract] ABSTRACT: 1] The passage of two cold front systems over the United Kingdom are compared and contrasted, using the results of a detailed aircraft and ground-based study. The measurements are interpreted by means of three-dimensional, reverse-domain-filling trajectories using both global models and limited-area mesoscale models. This method provides a three-dimensional picture of the interleaving air-masses in the frontal zone as defined by their Lagrangian histories. The two systems studied differ in that the first is associated with an intense surface low in January and the second is associated with a relatively weak surface low in April. In the intense surface low case the trajectory study suggests that a dry intrusion with stratospheric characteristics penetrated deep into the troposphere along the upper level front. Measurements indeed revealed an unsaturated layer with anomalously high ozone. This layer was intersected at four levels in the troposphere (at 8.5, 7.1, 5.2 and 3.7 km), and the lower the intersection, the lower the measured anomalous ozone and the higher the water vapor content. It is argued that this is best explained by the dry-intrusion layer becoming mixed with background air by three-dimensional turbulence, also encountered by the aircraft, along the upper level front. Evidence for this mixing is apparent on tracer-tracer scatterplots. In the weak surface low case, by contrast, the dry intrusion has a more complex structure, with up to three separate layers of enhanced ozone and low humidity. Strong evidence for mixing was apparent only in the lowest layer. The weaker system may therefore be much more efficient at transporting upper tropospheric/stratospheric ozone to the lower troposphere. The transport of boundary layer air to the upper troposphere in the warm conveyor belt (WCB), however, was found to be around 8 times stronger in the intense system. Sonde measurements suggested that the WCB was ventilated by convection from the surface front in some regions to about 5–6 km, while it was stably stratified in other regions, suggesting layerwise long-range transport.