M. Krämer

Forschungszentrum Jülich, Jülich, North Rhine-Westphalia, Germany

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Publications (118)264.53 Total impact

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    ABSTRACT: he Fast In-situ Stratospheric Hygrometer (FISH) is an airborne Lyman-α photofragment fluorescence hygrometer for accurate and precise measurement of total water mixing ratios (WMR) (gas phase + evaporated ice) in the upper troposphere and lower stratosphere (UT/LS) since almost two decades. Here, we present a comprehensive review of the measurement technique, calibration procedure, accuracy and reliability of FISH. A crucial part for the FISH measurement quality is the regular calibration to a water vapor reference, namely the commercial frostpoint hygrometer DP30. In the frame of this work this frostpoint hygrometer is compared to German and British traceable metrological water standards and its accuracy is found to be 2–4%. Overall, in the range from 4–1000 ppmv, the total accuracy of FISH was found to be 6–8% as stated also in previous publications. For lower mixing ratios down to 1 ppmv, the uncertainty reaches a lower limit of 0.3 ppmv. For specific, non-atmospheric conditions, as set in experiments at the AIDA chamber – namely mixing ratios below 10 and above 100 ppmv in combination with high and low pressure conditions – the need to apply a modified FISH calibration evaluation has been identified. The new evaluation improves the agreement of FISH with other hygrometers to ± 10% accuracy in the respective mixing ratio ranges. Further, a quality check procedure for high total water measurements in cirrus clouds at high pressures (400–500 hPa) is introduced. The performance of FISH in the field is assessed by reviewing intercomparisons of FISH water vapor data with other in-situ and remote sensing hygrometers over the last two decades. We find that the agreement of FISH with the other hygrometers has improved over that time span from overall up to ±30% or more to about ±5–20% @ < 10 ppmv and to ±0–15% @ > 10 ppmv. As presented here, the robust and continuous calibration and operation procedures of the FISH instrument over the last two decades, establish the position of FISH as one of the core instruments for in-situ observations of water vapor in the UT/LS.
    Atmospheric Chemistry and Physics 03/2015; 15(5):7735-7782. DOI:10.5194/acp-15-8521-2015 · 5.51 Impact Factor
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    ABSTRACT: In situ observational data on the relative humidity (RH) in the upper troposphere and lowermost stratosphere (UT/LS), or tropopause region, collected aboard civil passenger aircraft in the MOZAIC (Measurements of OZone, water vapour, carbon monoxide and nitrogen oxides by in-service AIrbus airCraft) programme were reanalysed for the period 2000 to 2009. Previous analyses of probability distribution functions (PDFs) of upper troposphere humidity (UTH) data from MOZAIC observations from year 2000 and later indicated a bias of UTH data towards higher RH values compared to data of the period 1994 to 1999. As a result, the PDF of UTH data show a substantial fraction of observations above 100% relative humidity with respect to liquid water. Such supersaturations, however, do not occur in the atmosphere because there is always a sufficient number of condensation nuclei available, that trigger condensation as soon as liquid saturation is slightly exceeded. An in-depth reanalysis of the data set identified a coding error in the calibration procedure from year 2000 on. The error did not affect earlier data from 1994 to 1999. The full data set for 2000–2009 was reanalysed applying the corrected calibration procedure. Applied correction schemes and a revised error analysis are presented along with the reanalysed PDF of relative humidity with respect to liquid water (RHliquid) and ice (RHice).
    Atmospheric Chemistry and Physics 12/2014; 14(13):18905-18942. DOI:10.5194/acpd-14-18905-2014 · 4.88 Impact Factor
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    ABSTRACT: Enhanced tropospheric trace gases such as CO, CH4 and H2O and reduced stratospheric O-3 were measured in situ in the lowermost stratosphere over northern Europe on 26 September 2012 during the TACTS aircraft campaign. The measurements indicate that these air masses clearly differ from the stratospheric background. The calculation of 40-day backward trajectories with the trajectory module of the CLaMS model shows that these air masses are affected by the Asian monsoon anticyclone. Some air masses originate from the boundary layer in Southeast Asia/West Pacific and are rapidly lifted (1-2 days) within a typhoon up to the outer edge of the Asian monsoon anticyclone. Afterwards, the air parcels are entrained by the anticyclonic circulation of the Asian monsoon. The subsequent long-range transport (8-14 days) of enhanced water vapour and pollutants to the lowermost stratosphere in northern Europe is driven by eastward transport of tropospheric air from the Asian monsoon anticyclone caused by an eddy shedding event. We found that the combination of rapid uplift by a typhoon and eastward eddy shedding from the Asian monsoon anticyclone is a novel fast transport pathway that may carry boundary emissions from Southeast Asia/West Pacific within approximately 5 weeks to the lowermost stratosphere in northern Europe.
    Atmospheric Chemistry and Physics 12/2014; 14(12):18461-18497. DOI:10.5194/acpd-14-18461-2014 · 4.88 Impact Factor
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    ABSTRACT: In January 2010 and December 2011, synopticscale polar stratospheric cloud (PSC) fields were probed during seven flights of the high-altitude research aircraft M- 55 Geophysica within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interaction) and the ESSenCe (ESSenCe: ESA Sounder Campaign) projects. Particle size distributions in a diameter range between 0.46 and 40 μm were recorded by four different optical in situ instruments. Three of these particle instruments are based on the detection of forward-scattered light by single particles. The fourth instrument is a grayscale optical array imaging probe. Optical particle diameters of up to 35 μm were detected with particle number densities and total particle volumes exceeding previous Arctic measurements. Also, gas-phase and particle-bound NOy was measured, as well as water vapor concentrations.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 10/2014; 14(19):12071-12120. DOI:10.5194/acpd-14-12071-2014 · 5.30 Impact Factor
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    ABSTRACT: The AquaVIT-1 Intercomparison of Atmospheric Water Vapor Measurement Techniques was conducted at the aerosol and cloud simulation chamber AIDA at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m3, multiple instruments analyzed air with a common water vapor mixing ratio, either by extracting air into instrument flow systems, locating instruments inside the chamber, or sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. These results indicate that the core instruments, in general, have intrinsic skill to determine unknown water vapor mixing ratios with an accuracy of at least ±20%. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms. eISSN 1867-8610 = AMTD
    Atmospheric Measurement Techniques 04/2014; 7:3159-3251. DOI:10.5194/amtd-7-3159-2014 · 3.21 Impact Factor
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    ABSTRACT: accurate measurements of water vapor at the low mixing ratios (< 10 ppm) encountered in the upper troposphere and lower stratosphere (UT/LS) has proven to be a significant analytical challenge evidenced by persistent disagreements between high-precision hygrometers. These disagreements have caused uncertainties in the description of the physical processes controlling dehydration of air in the tropical tropopause layer and entry of water into the stratosphere and have hindered validation of satellite water vapor retrievals. A 2011 airborne intercomparison of a large group of in situ hygrometers onboard the NASA WB-57F high-altitude research aircraft and balloons has provided an excellent opportunity to evaluate progress in the scientific community toward improved measurement agreement. In this work we intercompare the measurements from the Midlatitude Airborne Cirrus Properties Experiment (MACPEX) and discuss the quality of agreement. Differences between values reported by the instruments were reduced in comparison to some prior campaigns but were nonnegligible and on the order of 20% (0.8 ppm). Our analysis suggests that unrecognized errors in the quantification of instrumental background for some or all of the hygrometers are a likely cause. Until these errors are understood, differences at this level will continue to somewhat limit our understanding of cirrus microphysical processes and dehydration in the tropical tropopause layer.
    02/2014; 119(4). DOI:10.1002/2013JD020817
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    ABSTRACT: We present high-resolution measurements of water vapour, aerosols and clouds in the Arctic stratosphere in January and February 2010 carried out by in-situ instrumentation on balloon-sondes and high-altitude aircraft combined with satellite observations. The measurements provide unparalleled evidence of dehydration and rehydration due to gravitational settling of ice particles. An extreme cooling of the Arctic stratospheric vortex during the second half of January 2010 resulted in a rare synoptic-scale outbreak of ice PSCs (polar stratospheric clouds) detected remotely by the lidar aboard the CALIPSO satellite. The widespread occurrence of ice clouds was followed by sedimentation and consequent sublimation of ice particles, leading to vertical redistribution of water inside the vortex. A sequence of balloon and aircraft soundings with chilled mirror and Lyman-α hygrometers (CFH, FISH, FLASH) and backscatter sondes (COBALD) conducted in January 2010 within the LAPBIAT and RECONCILE campaigns captured various phases of this phenomenon: ice formation, irreversible dehydration and rehydration. Consistent observations of water vapour by these independent measurement techniques show clear signatures of irreversible dehydration of the vortex air by up to 1.6 ppmv in the 20-24 km altitude range and rehydration by up to 0.9 ppmv in a 1 km-thick layer below. Comparison with space-borne Aura MLS water vapour observations allow the spatiotemporal evolution of dehydrated air masses within the Arctic vortex to be derived and upscaled.
    Atmospheric Chemistry and Physics 11/2013; 13(5-5):14249-14295. DOI:10.5194/acpd-13-14249-2013 · 4.88 Impact Factor
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    ABSTRACT: Bei chemischen Analysatoren auf Basis optischer Absorptionsmessungen stellt sich häufig die Problematik, dass die optische Messstelle von der Lichtquelle räumlich getrennt werden muss, um Störeinflüsse auf diese zu minimieren, Platzrestriktionen zu umgehen, Gefahrenbereiche zu meiden und eine Gasanalyse ohne Probennahme zu ermöglichen. Für die hochspezifische Wasserdampfmessung auf dem neuen deutschen Forschungsflugzeug HALO wurde das Konzept der direkt fasergekoppelten White-Zelle auf den simultanen Einsatz zweier optischer Wellenlängen (1.4 µm und 2.6 µm) erweitert. Ziel ist dabei, trotz einer bis zu 1000 km/h schnellen Durchströmung der offenen Messzelle, Gastemperaturen von -70 °C bis +50 °C und einem Außendruck von 100-1000 hPa die absolute Bestimmung des Wasserdampfgehaltes der Luft (1 bis 30000 ppmv) mit hoher Zeitauflösung auf der Außenhaut zu ermöglichen. Hierfür werden beiden Wellenlängen über zwei single mode-Lichtwellenleiter in eine gemeinsame White-Zelle ohne weitere Transferoptiken eingekoppelt. Auf der Tagung werden wir den Aufbau und erste Messdaten zur Beurteilung der optischen Qualität sowie deren Eignung für den Nachweis weitere Spezies wie z.B. CO2.diskutieren.
    114. Jahrestagung der Deutsche Gesellschaft für angewandte Optik e. V. (DGaO); 05/2013
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    ABSTRACT: EGU General Assembly 2013, Geophysical Research Abstracts, Vol. 15, EGU2013-9191, 2013
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    ABSTRACT: EGU General Assembly 2013, Geophysical Research Abstracts, Vol. 15, EGU2013-7311-3, 2013
    Euopean Geosciences Uninon General Assembly, 7-12. April 2013; 04/2013
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    ABSTRACT: EGU General Assembly 2013, Geophysical Research Abstracts, Vol. 15, EGU2013-9191, 2013
    Euopean Geosciences Uninon General Assembly, 7-12. April 2013; 04/2013
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    ABSTRACT: The MACPEX mission permitted observation of aerosol size distributions in the 4 to 1000 nm diameter range, cloud particles and water vapor in and around clouds in the mid-latitude upper troposphere. The NMASS consists of 5 condensation particle counters (cpcs) operating in parallel. The 5 cpcs have lower detection limits of approximately 4 nm, 8 nm, 16 nm, 32 nm and 50 nm. The FCAS measures the optical size of particles in the 100 nm to 1000 nm range. The data from these instruments are combined to provide size distributions from 4 to 1000 nm. Size distributions that show a local maximum in the smallest size range are evidence for recent new particle formation since the lifetime of particles in this size range is short due to coagulation. Size distributions showing evidence of new particle formation were observed inside and near clouds in the altitude range from 10 to 14 km. The cloud particles in these high clouds are expected to be ice. Care was taken to avoid interpreting shattering of ice on the aerosol inlets as new particles. The size distributions showing new particle formation are contrasted with size distributions that do not show new particle formation in and out of the clouds. Temperature, relative humidity and trace gas abundances in air parcels exhibiting new particle formation are contrasted with those in air parcels not showing new particle formation.
    AGU Annu. Mtg., San Francisco, CA; 12/2012
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    ABSTRACT: Ice clouds are known to be major contributors to radiative forcing in the Earth's atmosphere, yet describing their microphysical properties in climate models remains challenging. Among these properties, the ice water content (IWC) of cirrus clouds is of particular interest both because it is measurable and because it can be directly related to a number of other radiatively important variables such as extinction and effective radius. This study expands upon the work of Schiller et al. (2008), extending a climatology of IWC by combining datasets from several European and US airborne campaigns and ground-based lidar measurements over Jülich, Germany. The relationship between IWC and temperature is further investigated using the new merged dataset and probability distribution functions (PDFs). A PDF-based formulation allows for representation of not only the mean values of IWC, but also the variability of IWC within a temperature band. The IWC-PDFs are found to be bimodal over the whole cirrus temperature range, which might be attributed to different cirrus formation mechanisms such as heterogeneous and homogeneous freezing. The PDFs of IWC are further compared to distributions of cirrus ice crystal number and mass mean radius, which show that the general relationship between IWC and temperature appears to be influenced much more by particle number than by particle size.
    Atmospheric Chemistry and Physics 11/2012; 12(11):29443-29474. DOI:10.5194/acpd-12-29443-2012 · 4.88 Impact Factor
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    P. Spichtinger · M. Krämer
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    ABSTRACT: The occurrence of high, persistent ice supersaturation inside and outside cold cirrus in the tropical tropopause layer (TTL) remains an enigma that is intensely debated as the "ice supersaturation puzzle". However, it was recently confirmed that observed supersaturations are consistent with very low ice crystal concentrations, which is incompatible with the idea that homogeneous freezing is the major method of ice formation in the TTL. Thus, the tropical tropopause "ice supersaturation puzzle" has become an "ice nucleation puzzle". To explain the low ice crystal concentrations, a number of mainly heterogeneous freezing methods have been proposed. Here, we reproduce in situ measurements of frequencies of occurrence of ice crystal concentrations by extensive model simulations, driven by the special dynamic conditions in the TTL, namely the superposition of slow large-scale updraughts with high-frequency short waves. From the simulations, it follows that the full range of observed ice crystal concentrations can be explained when the model results of the scenarios are mixed for both heterogeneous/homogeneous and pure homogeneous ice formation occurring in very slow (<1 cm s-1) and faster (>1 cm s-1) large-scale updraughts. This statistical analysis shows that about 80% of TTL cirrus can be explained by "classical" homogeneous ice nucleation, while the remaining 20% stem from heterogeneous and homogeneous freezing occurring within the same environment. The mechanism limiting ice crystal production via homogeneous freezing in an environment full of gravity waves is the shortness of the gravity waves, which stalls freezing events before a higher ice crystal concentration can be formed.
    Atmospheric Chemistry and Physics 10/2012; 12(10):28109-28153. DOI:10.5194/acpd-12-28109-2012 · 4.88 Impact Factor
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    ABSTRACT: Contrails and especially their evolution into cirrus-like clouds are thought to have very important effects on local and global radiation budgets, though are generally not well represented in global climate models. Lack of contrail parameterisations is due to the limited availability of in situ contrail measurements which are difficult to obtain. Here we present a methodology for successful sampling and interpretation of contrail microphysical and radiative data using both in situ and remote sensing instrumentation on board the FAAM BAe146 UK research aircraft as part of the COntrails Spreading Into Cirrus (COSIC) study. Forecast models were utilised to determine flight regions suitable for contrail formation and sampling; regions that were both free of cloud but showed a high probability of occurrence of air mass being supersaturated with respect to ice. The FAAM research aircraft, fitted with cloud microphysics probes and remote sensing instruments, formed a distinctive spiral-shaped contrail in the predicted area by flying in an orbit over the same ground position as the wind advected the contrails to the east. Parts of these contrails were sampled during the completion of four orbits, with sampled contrail regions being between 7 and 30 min old. Lidar measurements were useful for in-flight determination of the location and spatial extent of the contrails, and also to report extinction values that agreed well with those calculated from the microphysical data. A shortwave spectrometer was also able to detect the contrails, though the signal was weak due to the dispersion and evaporation of the contrails. Post-flight the UK Met Office NAME III dispersion model was successfully used as a tool for modelling the dispersion of the persistent contrail; determining its location and age, and determining when there was interference from other measured aircraft contrails or when cirrus encroached on the area later in the flight. The persistent contrails were found to consist of small (~10 μm) plate-like crystals where growth of ice crystals to larger sizes (~100 μm) was typically detected when higher water vapour levels were present. Using the cloud microphysics data, extinction co-efficient values were calculated and found to be 0.01-1 km-1. The contrails formed during the flight (referred to as B587) were found to have a visible lifetime of ~40 min, and limited water vapour supply was thought to have suppressed ice crystal growth.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 09/2012; 12(17):8157-8175. DOI:10.5194/acp-12-8157-2012 · 5.30 Impact Factor
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    ABSTRACT: FISH, a Lyman Alpha Fluorescence Hygrometer used on aircraft and balloons since 1990, participated in recent field and laboratory comparison experiments including the airborne campaign MACPEX out of Houston, USA, with the high altitude aircraft WB-57 and the extensive laboratory intercomparison campaign AQUAVIT at the AIDA chamber. The aim was to investigate the reasons for discrepancies of water measurements between different hygrometers in recent field experiments, which exceeded the stated uncertainties of these advanced hygrometers. Recent studies have shown that even 0.5 ppmv of uncertainty in those measurements matter in terms of radiative forcing and microphysics. However, the absolute discrepancies during campaigns in the 2010ies was up to 1 ppmv. During AquaVIT the discrepancies below 10 ppmv have shown the same tendency with lower magnitude. The relative discrepancies between the different hygrometers during MACPEX was the same as for previous experiments. Nevertheless, the absolute discrepancies may vary between individual instruments for different campaigns. In total they were in the range of 0.8 ppmv.
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    ABSTRACT: Contrails and especially their evolution into cirrus-like clouds are thought to have very important effects on local and global radiation budgets, though are generally not well represented in global climate models. Lack of contrail parameterisations is due to the limited availability of in situ contrail measurements which are difficult to obtain. Here we present a methodology for successful sampling and interpretation of contrail microphysical and radiative data using both in situ and remote sensing instrumentation on board the FAAM BAe146 UK research aircraft as part of the COntrails Spreading Into Cirrus (COSIC) study. Forecast models were utilised to determine flight regions suitable for contrail formation and sampling; regions that were both free of cloud but showed a high probability of occurrence of air mass being supersaturated with respect to ice. The FAAM research aircraft, fitted with cloud microphysics probes and remote sensing instruments, formed a distinctive spiral-shaped contrail in the predicted area by flying in an orbit over the same ground position as the wind advected the contrails to the east. Parts of these contrails were sampled during the completion of four orbits, with sampled contrail regions being between 7 and 30 min old. Lidar measurements were useful for in-flight determination of the location and spatial extent of the contrails, and also to report extinction values that agreed well with those calculated from the microphysical data. A shortwave spectrometer was also able to detect the contrails, though the signal was weak due to the dispersion and evaporation of the contrails. Post-flight the UK Met Office NAME III dispersion model was successfully used as a tool for modelling the dispersion of the persistent contrail; determining its location and age, and determining when there was interference from other measured other aircraft contrails or when cirrus encroached on the area later in the flight. The persistent contrails were found to consist of small (~10 μm) plate-like crystals where growth of ice crystals to larger sizes (~100 μm) was detected when higher water vapour levels were present. Using the cloud microphysics data, extinction co-efficient values were calculated and found to be 0.01-1 km-1. The contrails formed during the flight (referred to as B587) were found to have a visible lifetime of ~40 min, and limited water vapour supply was thought to have suppressed ice crystal growth.
    Atmospheric Chemistry and Physics 03/2012; 12(3):7829-7877. DOI:10.5194/acpd-12-7829-2012 · 4.88 Impact Factor
  • Bulletin of the American Meteorological Society 02/2012; 93(2):Bulletin of the American Meteorological Society. DOI:10.1175/BAMS-D-11-00123.1 · 11.57 Impact Factor
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    ABSTRACT: An overview is presented of airborne systems for in situ measurements of aerosol particles, clouds and radiation that are currently in use on research aircraft around the world. Description of the technology is at a level sufficient for introducing the basic principles of operation and an extensive list of references for further reading is given. A number of newer instruments that implement emerging technology are described and the review concludes with a description of some of the most important measurement challenges that remain. This overview is a synthesis of material from a reference book that is currently in preparation and that will be published in 2012 by Wiley.
    Atmospheric Research 10/2011; 102(2011):10-29. DOI:10.1016/j.atmosres.2011.06.021 · 2.42 Impact Factor
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    ABSTRACT: In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign overWest Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3±1.6) cm−3 and rimed ice particles with maximum dimensions exceeding 1.5mm were found. A maximum ice water content of 0.05 gm−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3×10−4 gm−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4×10−4 gm−3. All known in situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established for modelling purposes. A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles may result from activation of the present aerosol, yielded low ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 06/2011; 11(2011):5569-5590. DOI:10.5194/acpd-11-745-2011 · 5.30 Impact Factor

Publication Stats

1k Citations
264.53 Total Impact Points

Institutions

  • 2000–2014
    • Forschungszentrum Jülich
      • Institute of Energy and Climate Research (IEK)
      Jülich, North Rhine-Westphalia, Germany
  • 2009
    • Droplet Measurement Technologies
      Boulder, Colorado, United States
  • 2006
    • Central Aerological Observatory
      Moskva, Moscow, Russia
  • 1996–2003
    • University of Wuerzburg
      • Department of Neurosurgery
      Würzburg, Bavaria, Germany
  • 2002
    • Deutsche Klinik für Diagnostik, Wiesbaden
      Wiesbaden, Hesse, Germany
    • Heinrich-Heine-Universität Düsseldorf
      • Koordinierungszentrum für Klinische Studien (KKS)
      Düsseldorf, North Rhine-Westphalia, Germany
  • 2000–2002
    • Singapore General Hospital
      • Department of Colorectal Surgery
      Tumasik, Singapore
  • 1992–2002
    • Johannes Gutenberg-Universität Mainz
      • Institute for Atmospheric Physics
      Mayence, Rheinland-Pfalz, Germany