Using a novel experimental technique, based on proton transfer reaction mass spectrometry, from measurements of emissions from laboratory scale biomass burning experiments, we have estimated the ...source strengths of several potential HOx producing gases: formaldehyde, acetaldehyde, methanol and acetone. The derived global average emissions are 5–13; 3.8–10; 1.5‐4; 2.3‐6.1 Tg y−1, respectively. The resulting global average HOx production from photochemical decay of these gases is 3 × 109 molecules cm−2 s−1. Although relatively small in a global context, these emissions are significant for the photochemistry in fresh fire plumes. From our measurements are also estimated global source strengths from biomass burning for CH3CN and HCN of 0.4‐1.0; 0.2‐0.6 Tg y−1 respectively. The biomass burning emissions of CH3CN may well dominate the global source of this compound, which thus might well be a unique tracer for biomass burning. Some discrepancies between experimental studies must, however, be resolved.
Goal of the project CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrumented Container) is to carry out regular and detailed observations of atmospheric ...composition (particles and gases) at cruising altitudes of passenger aircraft, i.e. at 9-12 km. Continuous, fast measurement of CO is indispensable for the chemical characterization of encountered air masses, for the detection of plumes of polluted air and for studying troposphere-stratosphere transport. CO is measured by a commercial resonance fluorescence UV instrument modified for the use onboard passenger aircraft. Modifications were necessary to optimize the instrument reliability allowing unattended operation for several days. The instrument has a precision of 1-2 ppbv at an integration time of 1 s. The response time to reach 63.2% signal strength is 2 s. We describe the modifications of the instrument, the experiences made during its operation since December 2004, the quality control of CO measurements onboard CARIBIC, and suggest a regular service routine that guarantees long-term high-quality data.
An airfreight container with automated instruments for measurement of atmospheric gases and trace compounds was operated on a monthly basis onboard a Boeing 767-300 ER of LTU International Airways ...during long-distance flights from 1997 to 2002 (CARIBIC, Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container, http://www.caribic-atmospheric.com). Subsequently a more advanced system has been developed, using a larger capacity container with additional equipment and an improved inlet system. CARIBIC phase #2 was implemented on a new long-range aircraft type Airbus A340-600 of the Lufthansa German Airlines (Star Alliance) in December 2004, creating a powerful flying observatory. The instrument package comprises detectors for the measurement of O3, total and gaseous H2O, NO and NOy, CO, CO2, O2, Hg, and number concentrations of sub-micrometer particles (>4 nm, >12 nm, and >18 nm diameter). Furthermore, an optical particle counter (OPC) and a proton transfer mass spectrometer (PTR-MS) are incorporated. Aerosol samples are collected for analysis of elemental composition and particle morphology after flight. Air samples are taken in glass containers for laboratory analyses of hydrocarbons, halocarbons and greenhouse gases (including isotopic composition of CO2) in several laboratories. Absorption tubes collect oxygenated volatile organic compounds. Three differential optical absorption spectrometers (DOAS) with their telescopes mounted in the inlet system measure atmospheric trace gases such as BrO, HONO, and NO2. A video camera mounted in the inlet provides information about clouds along the flight track. The flying observatory, its equipment and examples of measurement results are reported.
The Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container (CARIBIC) project investigates physical and chemical processes in the Earth's atmosphere using a ...Lufthansa Airbus long-distance passenger aircraft. After the beginning of the explosive eruption of the Eyjafjallajökull volcano on Iceland on 14 April 2010, the first CARIBIC volcano-specific measurement flight was carried out over the Baltic Sea and Southern Sweden on 20 April. Two more flights followed: one over Ireland and the Irish Sea on 16 May and the other over the Norwegian Sea on 19 May 2010. During these three special mission flights the CARIBIC container proved its merits as a comprehensive flying laboratory. The elemental composition of particles collected over the Baltic Sea during the first flight (20 April) indicated the presence of volcanic ash. Over Northern Ireland and the Irish Sea (16 May), the DOAS system detected SO2 and BrO co-located with volcanic ash particles that increased the aerosol optical depth. Over the Norwegian Sea (19 May), the optical particle counter detected a strong increase of particles larger than 400 nm diameter in a region where ash clouds were predicted by aerosol dispersion models. Aerosol particle samples collected over the Irish Sea and the Norwegian Sea showed large relative enhancements of the elements silicon, iron, titanium and calcium. Non-methane hydrocarbon concentrations in whole air samples collected on 16 and 19 May 2010 showed a pattern of removal of several hydrocarbons that is typical for chlorine chemistry in the volcanic clouds. Comparisons of measured ash concentrations and simulations with the FLEXPART dispersion model demonstrate the difficulty of detailed volcanic ash dispersion modelling due to the large variability of the volcanic cloud sources, extent and patchiness as well as the thin ash layers formed in the volcanic clouds.
The main aspects of an absolute method for measurement of the mixing ratio of atmospheric carbon monoxide (CO) are presented. The method is based on cryogenic extraction of CO from air after ...oxidation to CO2 followed by accurate volumetric determination. Gravimetric measurement is used to determine the quantity of sample air processed. In routine operation the overall error can be kept below 1%. Furthermore, the results of a laboratory intercomparison are analyzed. It is shown how offsets in the commonly applied analytical methods can occur and how these can seriously affect results obtained at the low concentration end (<100 nmole/mole).
The isotopic composition of carbon monoxide (13C, 14C, 18O) and methane (13C, D) was measured on air samples collected between Vladivostok and Moscow using the Trans‐Siberian railroad during August ...1996. Apart from short term fluctuations in the direct vicinity of sources, continuous measurements of CO and CH4 showed sustained, elevated mixing ratios over several hundreds of kilometers indicating the large scale influencing of traversed air masses by significant sources. Persistent, enhanced CH4 levels were found over the west Siberian lowlands concurrent with significantly depleted δ13C and δD values. The derived isotopic signature of the CH4 source (δ13C = −62.5±4.7‰ V‐PDB; δD = −311±14‰ V‐SMOW) clearly indicates the dominance of biogenic CH4, with the west Siberian wetlands being the most likely candidate. A second major feature in the data set is the enormous enhancement of CO (up to 1500 nmol/mol) east of Chita, extending over a 2000 km section along the river Amur. The 14CO measurements and back trajectory analyses identify biomass burning as the origin of the highly elevated CO. This is further supported by the δ18O(CO) and the δ13C/δD signature of the accompanying moderate CH4 enhancement.
Three types of reference simulations, as recommended by the Chemistry–Climate Model Initiative (CCMI), have been performed with version 2.51 of the European Centre for Medium-Range Weather Forecasts ...– Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model: hindcast simulations (1950–2011), hindcast simulations with specified dynamics (1979–2013), i.e. nudged towards ERA-Interim reanalysis data, and combined hindcast and projection simulations (1950–2100). The manuscript summarizes the updates of the model system and details the different model set-ups used, including the on-line calculated diagnostics. Simulations have been performed with two different nudging set-ups, with and without interactive tropospheric aerosol, and with and without a coupled ocean model. Two different vertical resolutions have been applied. The on-line calculated sources and sinks of reactive species are quantified and a first evaluation of the simulation results from a global perspective is provided as a quality check of the data. The focus is on the intercomparison of the different model set-ups. The simulation data will become publicly available via CCMI and the Climate and Environmental Retrieval and Archive (CERA) database of the German Climate Computing Centre (DKRZ). This manuscript is intended to serve as an extensive reference for further analyses of the Earth System Chemistry integrated Modelling (ESCiMo) simulations.
The methyl halides, methyl chloride (CH3Cl), methyl bromide (CH3Br), and methyl iodide (CH3I), were measured in regional air samples and smoke from savanna fires in southern Africa during the ...Southern Africa Fire‐Atmosphere Research Initiative‐92 (SAFARI‐92) experiment (August–October 1992). All three species were significantly enhanced in the smoke plumes relative to the regional background. Good correlations were found between the methyl halides and carbon monoxide, suggesting that emission was predominantly associated with the smoldering phase of the fires. About 90% of the halogen content of the fuel burned was released to the atmosphere, mostly as halide species, but a significant fraction (3–38%) was emitted in methylated form. On the basis of comparison with the composition of the regional background atmosphere, emission ratios to carbon dioxide and carbon monoxide were determined for the methyl halide species. The emission ratios decreased in the sequence CH3Cl > CH3Br > CH3I. Extrapolation of these results in combination with data from other types of biomass burning, e.g. forest fires, suggests that vegetation fires make a significant contribution to the atmospheric budget of CH3Cl and CH3Br. For tropospheric CH3I, on the other hand, fires appear to be a minor source. Our results suggest that pyrogenic emissions of CH3Cl and CH3Br need to be considered as significant contributors to stratospheric ozone destruction.
Using the CARIBIC Boeing 767 aircraft, a suite of trace gases and aerosols was measured between Germany and the Maldives in June 2000 at altitudes between 9.4 and 10 km. In the extratropics, the ...flight track was located in the tropopause region. A large variability of trace gases and ultrafine aerosol concentrations was observed while the aircraft intercepted air masses from the upper troposphere and the lowermost stratosphere, as well as outflow of deep convection. The correlations of alkanes (C2–C5) observed in the nonconvective areas point to relatively rapid mixing across the tropopause within about a day. Unusually high mixing ratios of short‐lived alkanes (C4–C6) in the convective areas indicate rapid transport of boundary layer air masses to cruising altitude. Using the ratios of the mixing ratios of alkanes (C3–C5) observed in the convective and nonconvective areas, we estimate the age of air masses in the tropopause region to be 24(±6) days for this event. This timescale is similar to that of vertical transport within the troposphere. Altogether our observations provide further evidence that the extratropical tropopause is often not a very effective mixing barrier.
Simultaneous measurements of O3, CO, and ultrafine aerosol particles (UFP), conducted on board of a Boeing 767‐ER passenger aircraft flying from Sri Lanka to Germany (project CARIBIC), are used to ...study two‐way cross‐tropopause mixing near a subtropical tropopause fold. On the equatorward side of the fold, downward mixing of stratospheric air into the upper troposphere is identified by enhanced concentrations of O3 and 14CO. Very high UFP number concentrations of up to 1.5×104 cm−3 (STP) were encountered inside the poleward half of the fold. This accumulation of small particles is explained by recent extensive aerosol nucleation, most likely triggered by the mixing of stratospheric air with tropospheric air injected into the fold. Further, nine particle formation events were observed outside the fold which are attributed to isolated cells of deep convection and to rising air parcels under cyclonic conditions that mix with surrounding air. In the upper troposphere O3 and CO were found to be correlated with high ΔO3/ΔCO ratios of 0.6 to 1.5. In the fold the correlation was strongly negative with ΔO3/ΔCO; = −3.5; but the high CO mixing ratios of 100 ppb at O3 mixing ratios of 250 ppb point to earlier injection of tropospheric air, in agreement with the UFP measurements.
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