M. Hermann

Meridional distributions of aerosol particle number concentrations in the upper troposphere and lower stratosphere obtained by Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container (CARIBIC) flights

[1]xa0Number concentrations of submicrometer aerosol particles at altitudes of 8.5–11.3 km were measured along a single flight route between Germany (∼50°N, ∼10°E) and the Indic (∼5°N, ∼80°E) over 3 years using a commercial aircraft platform (project Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container (CARIBIC)). During 41 intercontinental flights (∼380 flight hours), more than one million individual particle concentration measurements were made, yielding a comprehensive and unique aerosol data set. Using these data, the first meridional and seasonal probability distributions for ultrafine particles and for Aitken mode plus accumulation mode particles in the upper troposphere (UT) and lower stratosphere (LS) were derived. High particle number concentrations were observed in summer at tropical latitudes over the Arabian Sea and at midlatitudes over Europe, in contrast to lower values in the subtropics over the Middle East. This distribution primarily reflects the vertical transport pattern of the atmosphere. In winter, number concentrations were generally lower. The Intertropical Convergence Zone (ITCZ) was identified as a region of pronounced particle formation, but particle nucleation also occurred in the upper troposphere at midlatitudes. At tropical latitudes, convective transport and photochemistry appear to be the main driving forces for particle formation in the free troposphere. Consistent with these observations, integral length scales calculated from the aerosol data ranged from 6 to 12 km. Compared to particle concentrations in the midlatitudinal upper troposphere, those in the lowermost stratosphere were lower in winter, but equal or higher in summer. This seasonality is likely caused by stronger in-mixing of upper tropospheric air in summer.

Identification of extratropical two‐way troposphere‐stratosphere mixing based on CARIBIC measurements of O3, CO, and ultrafine particles

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.

Emissions of gaseous mercury from biomass burning in South America in 2005 observed during CARIBIC flights

[1]xa0Plumes of biomass burning effluents were observed during CARIBIC flights between Sao Paulo and Santiago de Chile on August 31 and October 5, 2005, as well as during the last part of the flight from Frankfurt to Sao Paulo on October 4, 2005. Total gaseous mercury (TGM) correlated with CO on August 31 and October 4 yielding a TGM/CO emission ratio of (1.2 ± 0.2) × 10−7 and (2.4 ± 1.0) × 10−7 mol/mol, respectively. No significant TGM/CO correlation was observed on October 5 probably because of variable background concentrations of both gases. The TGM/CO emission ratios observed here over South America fall within the rather narrow range of (0.67–2.4) × 10−7 mol/mol reported hitherto for sites geographically as different as South Africa, Canada, and the U.S.A. A total average emission of 437 Tg CO/yr from biomass burning over the years 1996–2000 implies an average TGM emission of 210–750 t/yr from biomass burning, representing 3–11% of all mercury emissions. TGM emissions from biomass burning are likely to be larger than anthropogenic emissions in the southern hemisphere during the burning season in August–October.

Influence of the 2008 Kasatochi volcanic eruption on sulfurous and carbonaceous aerosol constituents in the lower stratosphere

Influences on stratospheric aerosol during the first four months following the eruption of Kasatochi volcano (Alaska) were studied using observations at 10700 +/- 600 m altitude from the CARIBIC platform. Collected aerosol samples were analyzed for elemental constituents. Particle number concentrations were recorded in three size intervals together with ozone mixing ratios and slant column densities of SO2. The eruption increased particulate sulfur concentrations by a factor of up to 10 compared to periods before the eruption (1999-2002 and 2005-August 2008). Three to four months later, the concentration was still elevated by a factor of 3 in the lowermost stratosphere at northern midlatitudes. Besides sulfur, the Kasatochi aerosol contained a significant carbonaceous component and ash that declined in time after the eruption. The carbon-to-sulfur mass concentration ratio of the volcanic aerosol was 2.6 seven days after the eruption and reached 1.2 after 3 - 4 months. Citation: Martinsson, B. G., C. A. M. Brenninkmeijer, S. A. Carn, M. Hermann, K.-P. Heue, P. F. J. van Velthoven, and A. Zahn (2009), Influence of the 2008 Kasatochi volcanic eruption on sulfurous and carbonaceous aerosol constituents in the lower stratosphere, Geophys. Res. Lett., 36, L12813, doi: 10.1029/2009GL038735. (Less)

Chemical composition and morphology of individual aerosol particles from a CARIBIC flight at 10 km altitude between 50°N and 30°S

Analysis of individual particles by analytical electron microscopy as well as quantitative analysis using particle-induced X-ray emission (PIXE) and particle elastic scattering analysis (PESA) were carried out on samples collected from a flight at 10 km altitude between 50 degrees N and 30 degrees S as part of the Civil Aircraft for Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) project (http://www.caribic-atmospheric.com). Particle morphology showed large variability with sampling latitude. Complicated branched structures dominated the large particles of the extratropical northern and southern hemisphere and the northern tropics. Particles in the tropics of the southern hemisphere were small in size and large in number concentration, whereas particles in or close to the intertropical convergence zone were few and small in size. Particles in the lowermost stratosphere were found to have similar structures but more branched than the ones found in the upper troposphere of the extratropics. Quantitative analysis revealed that the sulfur concentration varied by a factor of 50 in the nine samples analyzed in this study. The carbon-to-sulfur mass concentration ratio was lowest in the lowermost stratosphere (0.5) and highest in the tropics of the southern hemisphere (3.5). The elemental distribution of carbon and sulfur in individual particles was mapped by energy-filtered transmission electron microscopy (EFTEM). Almost all particles analyzed contained a mixture of carbonaceous and sulfurous matter. Particles with satellites were found by EFTEM to contain both carbon and sulfur in the central particle, whereas in the satellite particles only carbonaceous material was detected. (Less)

Influence of clouds on aerosol particle number concentrations in the upper troposphere

Atmospheric Chemistry Dep., Max Planck Institute for Chemistry, 55128, Mainz, Germany Keywords: aerosol-cloud interaction, particle formation From 1997 to 2001, 47 flights between Colombo (Sri Lanka) or Male (Maldives) and Germany were conducted as part of the CARIBIC project (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrumentation Container, Brenninkmeijer et al., 1999, http://www.caribic- atmospheric.com). During these flights several trace gas and aerosol parameters were measured. Aerosol number concentrations for three different size ranges were obtained using three condensation particle counters (CPCs), i.e., ultrafine particles (4 to 12 nm, N

Electrical discharge source for tropospheric ''ozone-rich transients''

[1] In situ trace gas (O3, NO, NO2 ,N Oy) and ultrafine aerosol particle data from a passenger aircraft (project CARIBIC) and the NOAA WP-3D research aircraft are used to identify the origin of ‘‘ozone-rich transients’’ that occasionally appear in aircraft ozone data sets along flight distances of 5–80 km. Evidence of ozone import from the stratosphere, once suggested as the most likely cause, cannot be found. Our data rather reveal that the majority of the recorded ozone transients are artifacts caused by electrical discharges on the aircraft fuselage and the sample air inlet system. These discharges produce not solely O3 but also nitric oxide (NO) which rapidly reacts with O3 to form nitrogen dioxide (NO2). Further evidence is, however, provided showing that some of the less pronounced and broader O3-NO-NO2-rich transients are of atmospheric origin. We hypothesize that they are formed in an early (i.e., prelightning) phase of thunderstorms due to cold electrical discharges on the surface of charged hydrometeors. Simple considerations suggest that the amount of O3 and NO produced through these mechanisms is negligible with regard to the global tropospheric budget for the two gases. INDEX TERMS: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 3362 Meteorology and Atmospheric Dynamics: Stratosphere/troposphere interactions; KEYWORDS: Tropospheric ozone budget, electricity induced trace gas production, stratosphere-to-troposphere ozone

Submicrometer aerosol particle distributions in the upper troposphere over the mid‐latitude North Atlantic—results from the third route of ‘CARIBIC’

Particle number and mass concentrations of submicrometer aerosol particles were determined for the upper troposphere over the mid-latitude North Atlantic within the Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container project (CARIBIC, http://www.caribic-atmospheric.com). Between May 2001 and April 2002, 22 flights from Germany to the Caribbean were conducted using an automated measurement container on a B767 passenger aircraft. Spatial and seasonal probability distributions for ultrafine and Aitken mode particles as well as mass concentrations of particulate sulphur in 8–12 km altitude are presented. High particle number concentrations (mostly 2500–15 000 particles cm-3 STP) are particularly found in summer over the western North Atlantic Ocean close to the North American continent. The distributions together with an analysis of particle source processes show that deep vertical transport is the dominant process leading to most of the events with high particle number concentrations (8000 particles cm-3 STP) for ultrafine particles as well as for Aitken mode particles. This study emphasizes the importance of deep vertical transport and cloud processing for the concentration of aerosol particles in the upper troposphere.

Analyzing atmospheric trace gases and aerosols using passenger aircraft

CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container) resumed regular measurement flights with an extended scientific payload in December 2004. After an automated measurement container was successfully deployed on intercontinental flights using a Boeing 767 from 1997 to 2002, a far more powerful package is deployed using a new Airbus A340-600 made available by Lufthansa German Airlines (Star Alliance). The new CARIBIC system will help address a range of current atmospheric science questions during its projected lifetime of 10 years. European and Japanese scientists are developing a variety of atmospheric chemistry research and monitoring projects based on the use of passenger aircraft. This is a logical approach with a main advantage being that near-global coverage is obtained, in contrast to limited coverage through research aircraft-based expeditions. Moreover, highly detailed and consistent data sets can be acquired, as compared to satellite observations in general. In addition, even compared to land-based observatories, operational costs are moderate.

CARIBIC aircraft measurements of Eyjafjallajökull volcanic plumes in April/May 2010

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 Eyjafjallaj ökull 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 SO 2 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.