bluuebunny/crossref_metadata_2025 huggingface dataset:
The total ozone field separated into meteorological regimes. Part II: Northern Hemisphere mid-latitude total ozone trends
Authors: Hudson R. D. , Andrade M. F. , Follette M. B. , Frolov A. D.
Published: April 2010

Abstract. Previous studies have presented clear evidence that the Northern Hemisphere total ozone field can be separated into distinct regimes (tropical, midlatitude, polar, and arctic) the boundaries of which are associated with the subtropical and polar upper troposphere fronts,and in the winter, the polar vortex. This paper presents a study of total ozone variability within these regimes, from 1979–2003, using data from the TOMS instruments. The change in ozone within each regime for the period January 1979–May 1991, a period of rapid total ozone change, was studied in detail. Previous studies had observed a zonal linear trend of –3.15% per decade for the latitude band 25°–60° N. When the ozone field is separated by regime, smaller linear trends (–2.5%, –2.2%, and –1.9% per decade for the polar, midlatitude, and tropical regimes, respectively) are observed. The trend in the zonal total ozone is larger because the relative areas of the regimes also changed over this time period. The relative area of the polar regime decreased by about 15%; the tropical regime increased by about 10% over this period. The changes in the relative areas can be associated with a change of the mean latitude of the sub-tropical and polar fronts within the latitude interval 25° to 60° N. Over the period from January 1979-May 1991, both fronts moved northward by 1.1±0.2 degrees per decade. Over the entire period of the study the subtropical front moved northward at a rate of 1.1±0.1 degree per decade, while the polar front moved by only 0.5±0.1 degrees per decade.
The contribution of anthropogenic bromine emissions to past stratospheric ozone trends: a modelling study
Authors: Sinnhuber B.-M. , Sheode N. , Sinnhuber M. , Chipperfield M. P. , Feng W.
Published: April 2010

Abstract. Bromine compounds play an important role in the depletion of stratospheric ozone. We have calculated the changes in stratospheric ozone in response to changes in the halogen loading over the past decades, using a two-dimensional (latitude/height) model constrained by source gas mixing ratios at the surface. Model calculations of the decrease of total column ozone since 1980 agree reasonably well with observed ozone trends, in particular when the contribution from very short-lived bromine compounds is included. Model calculations with bromine source gas mixing ratios fixed at 1959 levels, corresponding approximately to a situation with no anthropogenic bromine emissions, show an ozone column reduction between 1980 and 2005 at northern hemisphere mid-latitudes of only ≈55% compared to a model run including all halogen source gases. In this sense anthropogenic bromine emissions are responsible for ≈45% of the model estimated column ozone loss at northern hemisphere mid-latitudes. The chemical efficiency of bromine relative to chlorine for global total ozone depletion from our model calculations, expressed by the so called α-factor, is about 73 on an annual average. This value is much higher than previously published results. Updates in reaction rate constants can explain only part of the differences in α. The inclusion of bromine from very short-lived source gases has only a minor effect on the global mean α-factor.
Mid-latitude ozone changes: studies with a 3-D CTM forced by ERA-40 analyses
Authors: Feng W. , Chipperfield M. P. , Dorf M. , Pfeilsticker K.
Published: April 2010

Abstract. We have used an off-line three-dimensional (3-D) chemical transport model (CTM) to study long-term changes in stratospheric O3. The model was run from 1977–2004 and forced by ECMWF ERA-40 and operational analyses. Model runs were performed to examine the impact of increasing halogens and additional stratospheric bromine from short-lived source gases. The analyses capture much of the observed interannual variability in column ozone, but there are also unrealistic features. In particular the ERA-40 analyses cause a large positive anomaly in northern hemisphere (NH) column O3 in the late 1980s. Also, the change from ERA-40 to operational winds at the start of 2002 introduces abrupt changes in some model fields which affect analysis of trends. The model reproduces the observed column increase in NH mid-latitudes from the mid 1990s. Analysis of a run with fixed halogens shows that this increase is not due to a significant decrease in halogen-induced loss, i.e. is not an indication of recovery. The model predicts only a small decrease in halogen-induced loss after 1999. In the upper stratosphere, despite the modelled turnover of chlorine around 1999, O3 does not increase to the effects of increasing ECMWF temperatures, decreasing modelled CH4 at this altitude, and abrupt changes to the SH temperatures at the end of the ERA-40 period. The impact of an additional 5 pptv stratospheric bromine from short-lived species decreases mid-latitude column O3 by about 10 DU. However, the impact on the modelled relative O3 anomaly is generally small except during periods of large volcanic loading.
Validation of SCIAMACHY top-of-atmosphere reflectance for aerosol remote sensing using MERIS L1 data
Authors: von Hoyningen-Huene W. , Kokhanovsky A. A. , Wuttke M. W. , Buchwitz M. , Noël S. , Gerilowski K. , Burrows J. P. , Latter B. , Siddans R. , Kerridge B. J.
Published: April 2010

Abstract. Aerosol remote sensing is very much dependent on the quite accurate knowledge of the top-of-atmosphere (TOA) reflectance retrieved by a particular instrument. The status of the calibration of such an instrument thus is reflected in the quality of the aerosol retrieval. Currently the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument gives too low values of the TOA reflectance, compared e.g. to data from MERIS (Medium Resolution Imaging Spectrometer), both operating on ENVISAT (ENVIronmental SATellite), but the calibration of the operational L1 product of SCIAMACHY is not yet finished. From an inter-comparison of MERIS and SCIAMACHY TOA reflectance, for collocated scenes correction factors are derived to improve the current SCIAMACHY L1 data for the purpose of aerosol remote sensing. The corrected reflectance has been used for a first remote sensing of the aerosol optical thickness by the BAER (Bremen AErosol Retrieval) approach using SCIAMACHY data.
Mesoscale temperature fluctuations in the stratosphere
Authors: Gary B. L.
Published: April 2010

Abstract. An airborne instrument that measures altitude temperature profiles is ideally suited for the task of characterizing statistical properties of the vertical displacement of isentrope surfaces. Prior measurements of temperature fluctuations during level flight could not be used to infer isentrope altitude variations because lapse rate information was missing. The Microwave Temperature Profiler instrument, which includes lapse rate measurements at flight level as a part of temperature profiles, has been used on hundreds of flights to produce altitude versus ground track cross-sections of potential temperature. These cross-sections show isentrope altitude variations with a horizontal resolution of ~3 km for a >6 km altitude region. An airborne isentrope-altitude cross-section (IAC) can be compared with a counterpart IAC generated from synoptic scale data, based on radiosondes and satellite instruments, in order to assess differences between the altitudes of isentrope surfaces sampled at mesoscale versus synoptic scale. It has been found that the synoptic scale isentropes fail to capture a significant component of vertical displacement of isentrope surfaces, especially in the vicinity of jet streams. Under the assumptions that air parcels flow along isentrope surfaces, and change temperature adiabatically while undergoing altitude displacements, it is possible to compute mesoscale temperature fluctuations that are not present in synoptic scale back trajectory parcel temperature histories. It has been found that the magnitude of the mesoscale component of temperature fluctuations varies with altitude, season, latitude and underlying topography. A model for these dependences is presented, which shows, for example, that mesoscale temperature fluctuations increase with altitude in a systematic way, are greatest over mountainous terrain, and are greater at polar latitudes during winter.
Simulating aerosol microphysics with the ECHAM/MADE GCM – Part II: Results from a first multiannual integration
Authors: Lauer A. , Hendricks J.
Published: April 2010

Abstract. First results of a multiannual integration with the new global aerosol model system ECHAM4/MADE are presented. This model system enables explicit simulations of the particle number concentration and size-distribution, which is a fundamental innovation compared to previous global model studies considering aerosol mass cycles only. The data calculated by the model provide detailed insights into the properties of the global submicrometer aerosol regarding global burden, chemical composition, atmospheric lifetime, particle number concentration and aerosol size-distribution. The model takes into account sulfate (SO4), nitrate (NO3), ammonium (NH4), black carbon (BC), organic matter (OM), mineral dust, sea salt and aerosol water. The simulated climatological annual mean global atmospheric burdens (lifetime) of the dominant submicrometer aerosol components are 2.25 Tg (4.5 d) for SO4, 0.46 Tg (4.5 d) for NH4, 0.26 Tg (5.6 d) for BC, and 1.77 Tg (6.5 d) for OM. The contributions of individual processes such as emission, nucleation, condensation or dry and wet deposition to the global sources and sinks of a specific aerosol component and particle number concentration are quantified. Based on this analysis, the significance of aerosol dynamical processes (nucleation, condensation, coagulation) is evaluated by comparison to the importance of other processes relevant for the submicrometer aerosol on the global scale. The results reveal that aerosol dynamics are essential for the simulation of the particle number concentration and important but not vital for the simulation of particle mass concentration. Hence aerosol dynamics should be taken into account in simulations of atmospheric processes showing a significant dependence on aerosol particle number concentration.
The role of ozone atmosphere-snow gas exchange on polar, boundary-layer tropospheric ozone – a review and sensitivity analysis
Authors: Helmig D. , Ganzeveld L. , Butler T. , Oltmans S. J.
Published: April 2010

Abstract. Recent research on snowpack processes and atmosphere-snow gas exchange has demonstrated that chemical and physical interactions between the snowpack and the overlaying atmosphere have a substantial impact on the composition of the lower troposphere. These observations also imply that ozone deposition to the snowpack possibly depends on parameters including the quantity and composition of deposited trace gases, solar irradiance, snow temperature and the substrate below the snowpack. Current literature spans a remarkably wide range of ozone deposition velocities (vdO3); several studies even reported positive ozone fluxes out of the snow. Overall, published values range from ~−3<vdO3<2 cm s-1, though most data are within ~0<vdO3<0.2 cm s-1. These literature reveal a high uncertainty in the parameterization and the magnitude of ozone fluxes into (and possibly out of) snow-covered landscapes. In this study a chemistry and tracer transport model was applied to investigate the sensitivity of tropospheric ozone towards ozone deposition over Northern Hemisphere snow-covered land and sea-ice. Model calculations using increasing vdO3 of 0.0, 0.01, 0.05 and 0.10 cm s-1 resulted in general ozone sensitivities up to 20–30% in the Arctic surface layer, and of up to 130% local increases in selected Northern Latitude regions. The simulated ozone concentrations were compared with mean January ozone observations from 18 Arctic stations. Best agreement between the model and observations, not only in terms of absolute concentrations but also in the hourly ozone variability, was found by applying an ozone deposition velocity in the range of 0.00–0.01 cm s-1, which is smaller than most literature data and also significantly lower compared to the value of 0.05 cm s-1 that is commonly applied in large-scale atmospheric chemistry models. This sensitivity analysis demonstrates that large errors in the description of the wintertime tropospheric ozone budget stem from the uncertain magnitude of ozone deposition rates and the inability to properly parameterize ozone fluxes to snow-covered landscapes.
Aerosol physical and optical properties in the Eastern Mediterranean Basin, Crete, from Aerosol Robotic Network Data
Authors: Fotiadi A. , Drakakis E. , Hatzianastassiou N. , Matsoukas C. , Pavlakis K. G. , Hatzidimitriou D. , Gerasopoulos E. , Mihalopoulos N. , Vardavas I.
Published: April 2010

Abstract. In this study, we investigate the aerosol optical properties, namely aerosol optical thickness (AOT), Angström parameter (α440–870 and size distribution parameters over the Eastern Mediterranean Basin, using spectral measurements from the recently established FORTH (Foundation for Research and Technology-Hellas) AERONET station in Crete, for the two-year period 2003–2004. The location of the FORTH-AERONET station offers a unique opportunity to monitor aerosols from different sources. The AOT is maximum during spring, because of the high dust load transported mainly from African deserts, and minimum in winter. There are secondary maxima in AOT at 870 and 1020 nm in October, attributed to dust transport events occurring in autumn. Large values of AOT at 340 and 500 nm persisting during summer are associated with transport of fine aerosols of urban/industrial and biomass burning origin. The dust events are characterised by a drastic increase in AOT at all wavelengths accompanied by a drastic decrease in Angström parameter to values below 0.3. The mean annual values of AOT340, AOT500, AOT870 and α440–870, are equal to 0.34±0.14, 0.21±0.11, 0.11±0.09 and 1.17±0.53 respectively. The scatterplots of Angström parameter versus aerosol optical thickness indicate a great variety of aerosol types over the study region including dust, urban-industrial/biomass burning, maritime, as well as mixed aerosol types. This is supported by back-trajectory analyses, and agrees with the measurements of experimental campaigns that took place in Crete during summer. The aerosol volume-size distributions are bimodal over all seasons, with a fine and a coarse mode having effective mean radius of 0.13 μm and 2.12 μm, respectively, and columnar volume concentrations of about 0.038 and 0.061 μm3/μm2. There is a general dominance of coarse to fine mode in terms of aerosol volume, in agreement with other maritime locations persisting through the year except for summer. Our analysis shows that the highest values of AOT are related to wind directions from the east, southeast and south, as well as from northwest. Northwestern winds are associated with maximum fine aerosol loads from industrial areas, while eastern, southeastern and southern winds are related to maximum coarse aerosol loads, namely sea salt and desert dust.
The density of humic acids and humic like substances (HULIS) from fresh and aged wood burning and pollution aerosol particles
Authors: Dinar E. , Mentel T. F. , Rudich Y.
Published: April 2010

Abstract. Atmospheric aerosols play significant roles in climatic related phenomena. The density and shape of particles dominates their fluid-dynamic parameters which in turn dictate their transport and lifecycle. Moreover, density and shape are also related to the particles optical properties, influencing their regional and global radiative effects. In the present study we have measured and compared the densities of humic like substances (HULIS) extracted from smoke and pollution aerosol particles to those of molecular weight-fractionated aquatic and terrestrial Humic Substances (HS). The density was measured by comparing the mobility and aerodynamic diameter of aerosol particles composed of these compounds. Characterization of chemical parameters such as molecular weight, aromaticity and elemental composition allow us to test how they affect the density of these important environmental macromolecules. It is found that atmospheric aging processes increase the density of HULIS due to the oxidation, while packing due to the aromatic moieties plays important role in determining the density of the aquatic HS substances.
Intraseasonal variations of upper tropospheric water vapor in Asian monsoon region
Authors: Zhan R. , Li J. , Gettelman A.
Published: April 2010

Abstract. This study investigates intraseasonal oscillations (ISOs) of upper tropospheric water vapor (UTWV) in the Asian monsoon region in boreal summer by using data with high spatial and temporal resolution from the AIRS instrument. There are robust intraseasonal cycles with periods of 30–60 days and 10–20 days in the UTWV field over both South Asia and East Asia. The 30–60-day oscillation accounts for more than 60 percent of the total variance. For the 30–60-day mode, the source and propagating signature of the UTWV disturbances are distinct in two monsoon sub-systems. Two patterns in the 30–60 day oscillation are seen: a South Asian pattern that originates on the western side of the Arabian Sea and moves eastward, and an East Asian pattern that develops over West Pacific and moves westward. The 10–20-day mode exhibits a uniform westward propagating signature from West Pacific to the Arabian Sea. The Asian summer monsoon region is identified as a main source for UTWV, so another special interest in this study is the relationship between monsoon activity and the 30–60-day oscillation of UTWV. The data show that the upper troposphere is moistened following intense monsoon convection with lags about 5–10 days. An examination of the low level circulation reveals that wet and dry periods in UTWV are closely related to active and break (inactive) periods in monsoon convection, suggesting that the Asian summer monsoon plays an important role in the intraseasonal variations of UTWV. Similar variability is seen in water vapor from European Center for Medium-Range Weather Forecasts (ECMWF) analyses.
Comparisons between ground-based FTIR and MIPAS N2O and HNO3 profiles before and after assimilation in BASCOE
Authors: Vigouroux C. , De Mazière M. , Errera Q. , Mahieu E. , Duchatelet P. , Wood S. , Smale D. , Mikuteit S. , Blumenstock T. , Hase F. , Jones N.
Published: April 2010

Abstract. Within the framework of the Network for Detection of Atmospheric Composition Change (NDACC), regular ground-based Fourier transform infrared (FTIR) measurements of many species are performed at several locations. Inversion schemes provide vertical profile information and characterization of the retrieved products which are therefore relevant for contributing to the validation of MIPAS profiles in the stratosphere and upper troposphere. We have focused on the species HNO3 and N2O at 5 NDACC-sites distributed in both hemispheres, i.e., Jungfraujoch (46.5° N) and Kiruna (68° N) for the northern hemisphere, and Wollongong (34° S), Lauder (45° S) and Arrival Heights (78° S) for the southern hemisphere. These ground-based data have been compared with MIPAS offline profiles (v4.61) for the year 2003, collocated within 1000 km around the stations, in the lower to middle stratosphere. To get around the spatial collocation problem, comparisons have also been made between the same ground-based FTIR data and the corresponding profiles resulting from the stratospheric 4D-VAR data assimilation system BASCOE. This paper discusses the results of the comparisons and the usefullness of using BASCOE profiles as proxies for MIPAS data. It shows good agreement between MIPAS and FTIR N2O partial columns: the biases are below 5% for all the stations and the standard deviations are below 7% for the three mid-latitude stations, and below 10% for the high latitude ones. The comparisons with BASCOE partial columns give standard deviations below 4% for the mid-latitude stations to less than 8% for the high-latitude ones. After making some corrections to take into account the known bias due to the use of different spectroscopic parameters, the comparisons of HNO3 partial columns show biases below 3% and standard deviations below 15% for all the stations except Arrival Heights (bias of 6%, standard deviation of 21%). The results for this species, which has a larger spatial variability, highlight the necessity of defining appropriate collocation criteria and of accounting for the spread of the observed airmasses. BASCOE appears to have more deficiencies in producing proxies of MIPAS HNO3 profiles compared to N2O, but the obtained standard deviation of less than 10% between BASCOE and FTIR is reasonable. Similar results on profiles comparisons are also shown in the paper, in addition to partial column ones.
First Odin sub-mm retrievals in the tropical upper troposphere: humidity and cloud ice signals
Authors: Ekström M. , Eriksson P. , Rydberg B. , Murtagh D. P.
Published: April 2010

Abstract. Odin-SMR is a limb-sounder operating in the 500 region with the capability of performing measurements down to altitudes of about 10 with relatively low influence of ice clouds. Until now spectra from tropospheric tangent altitudes have been disregarded due to inadequate handling of scattering. A first method to extract upper tropospheric quantities has now been developed, yielding the humidity in two layers around 200 and 130 and information on cloud ice content above 200. The main concern for these retrievals is the calibration performance. A careful analysis indicates a systematic calibration error of about 1 K, but also a random component that differs between the two bands. The random calibration uncertainty results in retrieval errors of 10–60% depending on humidity and band. Presently this prohibits use of single retrievals, but averages can be presented with good accuracy. The fixed calibration error can largely be removed, leaving the spectroscopic uncertainties to dominate the humidity retrieval accuracy, estimated to be around 20%. First results are presented that are in agreement with seasonal structure obtained from other satellite measurements. An encouraging comparison between MOZAIC data and measurements for the 200 layer gives further confidence in the capability of Odin-SMR to measure humidity in the upper tropical troposphere.
Source and origin of atmospheric trace elements entrapped in winter snow of the Italian Eastern Alps
Authors: Gabrielli P. , Cozzi G. , Torcini S. , Cescon P. , Barbante C.
Published: April 2010

Abstract. Trace elements concentrations were determined in shallow snow samples from 21 sites in the Italian Eastern Alps in order to identify the sources of the contaminants present in the tropospheric winter boundary layer. The collection of superficial snow layers was carried out weekly at altitudes between 1000 and 3000 m next to meteorological stations, far away from villages, roads and ski slopes. Ultra clean procedures were adopted in order to avoid contamination of the snow during the different experimental phases. Trace elements (Ag, Ba, Bi, Cd, Co, Cr, Cu, Fe, Mo, Mn, Pb, Sb, Ti, U, V and Zn) were determined by Inductively Coupled Plasma Sector Field Mass Spectrometer (ICP-SFMS). Ancillary parameters such as major ions (SO42−, NO3−, Ca2+;, Mg2+, K
Arctic smoke – record high air pollution levels in the European Arctic due to agricultural fires in Eastern Europe
Authors: Stohl A. , Berg T. , Burkhart J. F. , Fjæraa A. M. , Forster C. , Herber A. , Hov Ø. , Lunder C. , McMillan W. W. , Oltmans S. , Shiobara M. , Simpson D. , Solberg S. , Stebel K. , Ström J. , Tørseth K. , Treffeisen R. , Virkkunen K. , Yttri K. E.
Published: April 2010

Abstract. In spring 2006, the European Arctic was abnormally warm, setting new historical temperature records. During this warm period, smoke from agricultural fires in Eastern Europe intruded into the European Arctic and caused the most severe air pollution episodes ever recorded there. This paper confirms that biomass burning (BB) was indeed the source of the observed air pollution, studies the transport of the smoke into the Arctic, and presents an overview of the observations taken during the episode. Fire detections from the MODIS instruments aboard the Aqua and Terra satellites were used to estimate the BB emissions. The FLEXPART particle dispersion model was used to show that the smoke was transported to Spitsbergen and Iceland, which was confirmed by MODIS retrievals of the aerosol optical depth (AOD) and AIRS retrievals of carbon monoxide (CO) total columns. Concentrations of halocarbons, carbon dioxide and CO, as well as levoglucosan and potassium, measured at Zeppelin mountain near Ny Ålesund, were used to further corroborate the BB source of the smoke at Spitsbergen. The ozone (O3) and CO concentrations were the highest ever observed at the Zeppelin station, and gaseous elemental mercury was also enhanced. A new O3 record was also set at a station on Iceland. The smoke was strongly absorbing – black carbon concentrations were the highest ever recorded at Zeppelin –, and strongly perturbed the radiation transmission in the atmosphere: aerosol optical depths were the highest ever measured at Ny Ålesund. We furthermore discuss the aerosol chemical composition, obtained from filter samples, as well as the aerosol size distribution during the smoke event. Photographs show that the snow at a glacier on Spitsbergen became discolored during the episode and, thus, the snow albedo was reduced. Samples of this polluted snow contained strongly enhanced levels of potassium, sulphate, nitrate and ammonium ions, thus relating the discoloration to the deposition of the smoke aerosols. This paper shows that, to date, BB has been underestimated as a source of aerosol and air pollution for the Arctic, relative to emissions from fossil fuel combustion. Given its significant impact on air quality over large spatial scales and on radiative processes, the practice of agricultural waste burning should be banned in the future.
Validation of MIPAS ClONO2 measurements
Authors: Höpfner M. , von Clarmann T. , Fischer H. , Funke B. , Glatthor N. , Grabowski U. , Kellmann S. , Kiefer M. , Linden A. , Milz M. , Steck T. , Stiller G. P. , Bernath P. , Blom C. E. , Blumenstock Th. , Boone C. , Chance K. , Coffey M. T. , Friedl-Vallon F. , Griffith D. , Hannigan J. W. , Hase F. , Jones N. , Jucks K. W. , Keim C. , Kleinert A. , Kouker W. , Liu G. Y. , Mahieu E. , Mellqvist J. , Mikuteit S. , Notholt J. , Oelhaf H. , Piesch C. , Reddmann T. , Ruhnke R. , Schneider M. , Strandberg A. , Toon G. , Walker K. A. , Warneke T. , Wetzel G. , Wood S. , Zander R.
Published: April 2010

Abstract. Altitude profiles of ClONO2 retrieved with the IMK (Institut für Meteorologie und Klimaforschung) science-oriented data processor from MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric Sounding on Envisat) mid-infrared limb emission measurements between July 2002 and March 2004 have been validated by comparison with balloon-borne (Mark IV, FIRS2, MIPAS-B), airborne (MIPAS-STR), ground-based (Spitsbergen, Thule, Kiruna, Harestua, Jungfraujoch, Izaña, Wollongong, Lauder), and spaceborne (ACE-FTS) observations. With few exceptions we found very good agreement between these instruments and MIPAS with no evidence for any bias in most cases and altitude regions. For balloon-borne measurements typical absolute mean differences are below 0.05 ppbv over the whole altitude range from 10 to 39 km. In case of ACE-FTS observations mean differences are below 0.03 ppbv for observations below 26 km. Above this altitude the comparison with ACE-FTS is affected by the photochemically induced diurnal variation of ClONO2. Correction for this by use of a chemical transport model led to an overcompensation of the photochemical effect by up to 0.1 ppbv at altitudes of 30–35 km in case of MIPAS-ACE-FTS comparisons while for the balloon-borne observations no such inconsistency has been detected. The comparison of MIPAS derived total column amounts with ground-based observations revealed no significant bias in the MIPAS data. Mean differences between MIPAS and FTIR column abundances are 0.11±0.12×1014 cm−2 (1.0±1.1%) and −0.09±0.19×1014 cm−2 (−0.8±1.7%), depending on the coincidence criterion applied. χ2 tests have been performed to assess the combined precision estimates of MIPAS and the related instruments. When no exact coincidences were available as in case of MIPAS – FTIR or MIPAS – ACE-FTS comparisons it has been necessary to take into consideration a coincidence error term to account for χ2 deviations. From the resulting χ2 profiles there is no evidence for a systematic over/underestimation of the MIPAS random error analysis.
Air-sea fluxes of methanol, acetone, acetaldehyde, isoprene and DMS from a Norwegian fjord following a phytoplankton bloom in a mesocosm experiment
Authors: Sinha V. , Williams J. , Meyerhöfer M. , Riebesell U. , Paulino A. I. , Larsen A.
Published: April 2010

Abstract. The ocean's influence on volatile organic compounds (VOCs) in the atmosphere is poorly understood. This work characterises the oceanic emission and / or uptake of methanol, acetone, acetaldehyde, isoprene and dimethyl sulphide (DMS) as a function of photosynthetically active radiation (PAR) and a suite of biological parameters. The measurements were taken following a phytoplankton bloom, in May/June 2005 with a proton transfer reaction mass spectrometer (PTR-MS), from mesocosm enclosures anchored in the Raunefjord, Southern Norway. The net flux of methanol was always into the ocean, and was stronger at night. Isoprene and acetaldehyde were emitted from the ocean, correlating strongly with light (ravcorr, isoprene=0.49; ravcorr, acetaldehyde=0.70) and phytoplankton abundance. DMS was also emitted to the air but did not correlate significantly with light (r avcorr, dms= 0.01). Under conditions of high biological activity and a PAR of ~450 µmol photons m−2 s−1, acetone was emitted from the ocean, otherwise it was uptaken. The mean fluxes for methanol, acetone, acetaldehyde, isoprene and DMS were −0.26 ng m−2 s−1, 0.21 ng m−2 s−1, 0.23 ng m −2 s−1, 0.12 ng m−2 s−1 and 0.3 ng m−2 s−1 respectively. This work shows that compound specific PAR and biological dependency should be used for estimating the influence of the global ocean on atmospheric VOC budgets.
A study of polar ozone depletion based on sequential assimilation of satellite data from the ENVISAT/MIPAS and Odin/SMR instruments
Authors: Rösevall J. D. , Murtagh D. P. , Urban J. , Jones A. K.
Published: April 2010

Abstract. A fire storm that occured on 28 May 2001 devastated the town of Chisholm, ~150 km north of Edmonton, Alberta, induced a violent fire-invigorated cumulonimbus cloud. This pyro-cumulonimbus (pyro-Cb) had overshooting tops of 2.5–3 km above the tropopause, and injected massive amounts of smoke into the lower stratosphere. Fortunately, this event occurred under good coverage of radar, rain gauge, lightning and satellite measurements, which allowed in-depth documentation of the event. The combination of heat and smoke created a cloud with extremely small drops, which ascended rapidly in violent updrafts. There appeared to be little freezing up to the homogeneous freezing isotherm level of –38°C. A cloud with such small and short-lived highly supercooled drops is incapable of producing precipitation except for few large graupel and hail, which produced the observed radar echoes and charged the cloud with positive lightning. The small cloud drops froze homogeneously to equally small ice particles, for which there is no mechanism to aggregate into precipitation particles that hence remain in the anvil. The small precipitation efficiency implies that only a small fraction of the smoke is scavenged, so that most of it is exhausted through the anvil to the upper troposphere and lower stratosphere. Comparisons with other cases suggest that a pyro-Cb does not have to be as violent as the Chisholm case to have strongly suppressed precipitation. However, this level of convective vigor is necessary to create the overshooting updraft that injects the smoke into the lower stratosphere.
Mesoscale inversion: first results from the CERES campaign with synthetic data
Authors: Lauvaux T. , Uliasz M. , Sarrat C. , Chevallier F. , Bousquet P. , Lac C. , Davis K. J. , Ciais P. , Denning A. S. , Rayner P.
Published: April 2010

Abstract. We investigate the ability of a mesoscale model to reconstruct CO2 fluxes at regional scale. Formally, we estimate the reduction of error for a CO2 flux inversion at 8 km resolution in the South West of France, during four days of the CarboEurope Regional Experiment (CERES) in spring 2005. Measurements from two towers and two airplanes are available for this campaign. The lagrangian particle dispersion model LPDM was coupled to the non-hydrostatic model Meso-NH and integrated in a matrix inversion framework. Impacts of aircraft and tower measurements are quantified separately and together. We find that the configuration with both towers and aircraft is able to significantly reduce uncertainties on the 4-day averaged CO2 fluxes over about half of the 300×300 km domain. Most of this reduction comes from the tower measurements, even though the impact of aircraft measurements remains noticeable. The noise contributed by imperfect knowledge of boundary inflows does not significantly impair the resolution. We test alternative strategies to improve the impact of aircraft measurements and find that most information comes from measurements inside the boundary layer.
A chemistry-transport model simulation of middle atmospheric ozone from 1980 to 2019 using coupled chemistry GCM winds and temperatures
Authors: Damski J. , Thölix L. , Backman L. , Kaurola J. , Taalas P. , Austin J. , Butchart N. , Kulmala M.
Published: April 2010

Abstract. A Global 40-year simulation from 1980 to 2019 was performed with the FinROSE chemistry-transport model based on the use of coupled chemistry GCM-data. The main focus of our analysis is on climatological-scale processes in high latitudes. The resulting trend estimates for the past period (1980–1999) agree well with observation-based trend estimates. The results for the future period (2000–2019) suggest that the extent of seasonal ozone depletion over both northern and southern high-latitudes has likely reached its maximum. Furthermore, while climate change is expected to cool the stratosphere, this cooling is unlikely to accelerate significantly high latitude ozone depletion. However, the recovery of seasonal high latitude ozone losses will not take place during the next 15 years.
Equatorial wave analysis from SABER and ECMWF temperatures
Authors: Ern M. , Preusse P. , Krebsbach M. , Mlynczak M. G. , Russell III J. M.
Published: April 2010

Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. A case study for the time period of the SCOUT-O3 tropical aircraft measurement campaign in Darwin/Australia (in November and December 2005) is performed and we find that in the lower stratosphere also the longitude-time distribution of the Kelvin waves is correctly reproduced by ECMWF.
Analysis of global water vapour trends from satellite measurements in the visible spectral range
Authors: Mieruch S. , Noël S. , Bovensmann H. , Burrows J. P.
Published: April 2010

Abstract. Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME) flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS) approach has been used. The combination of the data from both instruments provides us with a long-term global data set spanning more than 11 years with the potential of extension up to 2020 by GOME-2 data, on Metop. Using linear and non-linear methods from time series analysis and standard statistics the trends of H2O contents and their errors have been calculated. In this study, factors affecting the trend such as the length of the time series, the magnitude of the variability of the noise, and the autocorrelation of the noise are investigated. Special emphasis has been placed on the calculation of the statistical significance of the observed trends, which reveal significant local changes of water vapour columns distributed over the whole globe.
On the efficiency of rocket-borne particle detection in the mesosphere
Authors: Hedin J. , Gumbel J. , Rapp M.
Published: April 2010

Abstract. Meteoric smoke particles have been proposed as a key player in the formation and evolution of mesospheric phenomena. Despite their apparent importance still very little are known about these particles. Sounding rockets are used to measure smoke in situ, but aerodynamics has remained a major challenge. Basically, smoke particles are so small that they tend to follow the gas flow around the payload rather than reaching the detector if aerodynamics is not considered carefully in the detector design. So far only indirect evidence for the existence of these smoke particles has been available in the form of measurements of heavy charge carriers. Important questions concern the smoke number density and size distribution as a function of altitude as well as the fraction of charged particles. Therefore, quantitative ways are needed that relate the measured particle population to the atmospheric particle population. In particular, we need to determine the size-dependent, altitude-dependent and charge-dependent detection efficiency for a given instrument design. In this paper, we investigate the aerodynamics for a typical electrostatic detector design. We first quantify the flow field of the background gas, then introduce particles in the flow field and determine their trajectories around the payload structure. We use two different models to trace particles in the flow field, a Continuous motion model and a Brownian motion model. Brownian motion is shown to be of basic importance for the smallest particles. By defining an effective relative cross section we compare different model runs and quantitatively investigate the difference between the two particle motion models. Detection efficiencies are determined for three detector designs, two with ventilation holes to allow airflow through the detector, and one without such ventilation holes. Results from this investigation show that rocket-borne smoke detection with conventional detectors is largely limited to altitudes above 75 km. The flow through a ventilated detector has to be relatively large for there to be an increase in the detection efficiency.
An episode of extremely high PM concentrations over Central Europe caused by dust emitted over the southern Ukraine
Authors: Birmili W. , Schepanski K. , Ansmann A. , Spindler G. , Tegen I. , Wehner B. , Nowak A. , Reimer E. , Mattis I. , Müller K. , Brüggemann E. , Gnauk T. , Herrmann H. , Wiedensohler A. , Althausen D. , Schladitz A. , Tuch T. , Löschau G.
Published: April 2010

Abstract. On 24 March 2007, the atmosphere over Central Europe was affected by an episode of exceptionally high mass concentrations of aerosol particles, most likely caused by a dust storm in the Southern Ukraine on the preceding day. At ground-based measurement stations in Slovakia, the Czech Republic, Poland and Germany PM10 mass concentrations rose to values between 200 and 1400 μg m−3. An evaluation of PM10 measurements from 360 monitoring stations showed that the dust cloud advanced along a narrow corridor at speeds of up to 70 km h−1. According to lidar observations over Leipzig, Germany, the high aerosol concentrations were confined to a homogeneous boundary layer of 1800 m height. The wavelength dependence of light extinction using both lidar and sun photometer measurements suggested the dominance of coarse particles during the main event. At a wavelength of 532 nm, relatively high volume extinction coefficients (300–400 Mm−1) and a particle optical depth of 0.65 was observed. In-situ measurements with an aerodynamic particle sizer at Melpitz, Germany, confirmed the presence of a coarse particle mode with a mode diameter >2 μm, whose maximum concentration coincided with that of PM10. A chemical particle analysis confirmed the dominance of non-volatile and insoluble matter in the coarse mode as well as high enrichments of Ti and Fe, which are characteristic of soil dust. A combination of back trajectory calculations and satellite images allowed to identify the dust source with confidence: On 23 March 2007, large amounts of dust were emitted from dried-out farmlands in the southern Ukraine, facilitated by wind gusts up to 100 km h−1. The unusual vertical stability and confined height of this dust layer as well as the rapid transport under dry conditions led to the conservation of high aerosol mass concentrations along the transect and thus to the extraordinary high aerosol concentrations over Central Europe. Our observations demonstrate the capacity of a combined apparatus of in situ and remote sensing measurements to characterise such a dust with a variety of aerosol parameters. As a conclusion, the description of dust emission, transport and transformation processes needs to be improved, especially when facing the possible effects of further anthropogenic desertification and climate change.
Optical particle counter measurement of marine aerosol hygroscopic growth
Authors: Snider J. R. , Petters M. D.
Published: April 2010

Abstract. A technique is developed for the determination of the hygroscopic growth factor of dry particles with diameter between 0.3 and 0.6 µm and is applied to measurements made during the second Dynamics and Chemistry of Marine Stratocumulus experiment. Two optical particle counters are utilized, one measures the aerosol size spectrum at ambient relative humidity and the other simultaneously dries the aerosol prior to light scattering detection. Growth factors are based on measurements made in the region of the Mie scattering curve where scattered light intensity increases monotonically with dry and wet particle diameter, i.e. D<0.9 µm. Factors influencing the accuracy of the measurement are evaluated, including particle drying, refractive index and shape. Growth factors at 90±3% ambient relative humidity in marine airmasses 400 km west of San Diego, California range between 1.5 and 1.8. This suggests that a significant fraction of the particle mass, between 40 and 70%, is either non-hygroscopic or weakly hygroscopic.
A climatology of surface ozone in the extra tropics: cluster analysis of observations and model results
Authors: Tarasova O. A. , Brenninkmeijer C. A. M. , Jöckel P. , Zvyagintsev A. M. , Kuznetsov G. I.
Published: April 2010

Abstract. Important aspects of the seasonal variations of surface ozone are discussed. The underlying analysis is based on the long-term (1990–2004) ozone records of Co-operative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP) and the World Data Center of Greenhouse Gases which do have a strong Northern Hemisphere bias. Seasonal variations are pronounced at most of the 114 locations for any time of the day. Seasonal-diurnal variability classification using hierarchical agglomeration clustering reveals 5 distinct clusters: clean/rural, semi-polluted non-elevated, semi-polluted semi-elevated, elevated and polar/remote marine types. For the cluster "clean/rural" the seasonal maximum is observed in April, both for night and day. For those sites with a double maximum or a wide spring-summer maximum, the one in spring appears both for day and night, while the one in summer is more pronounced for daytime and hence can be attributed to photochemical processes. For the spring maximum photochemistry is a less plausible explanation as no dependence of the maximum timing is observed. More probably the spring maximum is caused by dynamical/transport processes. Using data from the 3-D atmospheric chemistry general circulation model ECHAM5/MESSy1 covering the period of 1998–2005 a comparison has been performed for the identified clusters. For the model data four distinct classes of variability are detected. The majority of cases are covered by the regimes with a spring seasonal maximum or with a broad spring-summer maximum (with prevailing summer). The regime with winter–early spring maximum is reproduced by the model for southern hemispheric locations. Background and semi-polluted sites appear in the model in the same cluster. The seasonality in this model cluster is characterized by a pronounced spring (May) maximum. For the model cluster that covers partly semi-elevated semi-polluted sites the role of the photochemical production/destruction seems to be overestimated. Taking into consideration the differences in the data sampling procedure the carried out comparison demonstrates the ability of the model to reproduce the main regimes of surface ozone variability quite well.