Water vapour measurements inside cirrus clouds in Northern and Southern hemispheres during INCA

Ovarlez, J.; Gayet, Jean-François; Gierens, Klaus; Ström, Johan; Ovarlez, H.; Auriol, Frédérique; Busen, R.; Schumann, U.

doi:10.1029/2001gl014440

Cited by 127 publications

(205 citation statements)

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“…This is in good agreement with former findings of about 30 % ice supersaturation within mid-latitude cirrus clouds over the Southern Great Plains from combined Raman lidar measurements (Comstock et al, 2004) and from in situ measurements in the vicinity of Ireland (Ovarlez et al, 2002) during INCA (INter hemispheric difference in Cirrus properties from Anthropogenic emissions), respectively. The small differences in the observed fraction of supersaturated data points may be explained by an absolute error of about 10-15 % in the RHi data, resulting mainly from uncertainties in the used temperature, as well as from differences of the evolution stage of the examined cirrus cloud regimes.…”

Section: Summary and Discussionsupporting

confidence: 92%

“…It has to be kept in mind that we consider only a single case study in our analysis and, as mentioned above, the comparability of this case study with former findings is limited by the evolution state of the observed cloud as well as by ambient conditions. Similar to earlier findings of a positive skewness in cold clouds (Ovarlez et al, 2002), Spichtinger et al (2004) found asymmetric RHi distributions in the upper (and colder) cloud layers based on the MOZAIC (Measurement of Ozone by Airbus In-service aircraft project) data set. They interpret their findings with the influence of vertical motion on the duration of the transition to equilibrium (Gierens, 2003) and therewith on the distribution of (super-)saturation within the cloud.…”

Section: Summary and Discussionsupporting

confidence: 85%

“…The small differences in the observed fraction of supersaturated data points may be explained by an absolute error of about 10-15 % in the RHi data, resulting mainly from uncertainties in the used temperature, as well as from differences of the evolution stage of the examined cirrus cloud regimes. Considering the INCA data set, Ovarlez et al (2002) found that two types of distributions can be fitted to the observations; a Gaussian distribution for warm cirrus clouds (T > −40 • C), and a Rayleigh distribution to cirrus clouds colder than −40 • C. The dependence of the RHi distribution on the temperature is interpreted as an effect of the length of time a cirrus cloud needs from formation to a mature equilibrium state (Spichtinger et al, 2004). Thus, the tail towards higher RHi values might be a signature of clouds that have not yet reached values close to equilibrium.…”

Section: Summary and Discussionmentioning

confidence: 99%

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Potential of airborne lidar measurements for cirrus cloud studies

et al. 2014

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Abstract. Aerosol and water vapour measurements were performed with the lidar system WALES of Deutsches Zentrum für Luft-und Raumfahrt (DLR) in October and November 2010 during the first mission with the new German research aircraft G55-HALO. Curtains composed of lidar profiles beneath the aircraft show the vertical and horizontal distribution and variability of water vapour mixing ratio and backscatter ratio above Germany. Two missions on 3 and 4 November 2010 were selected to derive the water vapour mixing ratio inside cirrus clouds from the lidar instrument. A good agreement was found with in situ observations performed on a second research aircraft flying below HALO. ECMWF analysis temperature data are used to derive relative humidity fields with respect to ice (RHi) inside and outside of cirrus clouds from the lidar water vapour observations. The RHi variability is dominated by small-scale fluctuations in the water vapour fields while the temperature variation has a minor impact. The most frequent in-cloud RHi value from lidar observations is 98 %. The RHi variance is smaller inside the cirrus than outside of the cloud. 2-D histograms of relative humidity and backscatter ratio show significant differences for in-cloud and out-of-cloud situations for two different cirrus cloud regimes. Combined with accurate temperature measurements, the lidar observations have a great potential for detailed statistical cirrus cloud and related humidity studies.

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Section: Summary and Discussionsupporting

confidence: 92%

Section: Summary and Discussionsupporting

confidence: 85%

Section: Summary and Discussionmentioning

confidence: 99%

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Potential of airborne lidar measurements for cirrus cloud studies

et al. 2014

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“…Both distributions are slightly asymmetric with a tail towards higher supersaturation which is more pronounced in the SHARC measurements. This agrees with results from Ovarlez et al (2002), who find similar asymmetric distributions for temperatures below -40°C.…”

Section: Comparison Of Relative Humidity In Clouds 10supporting

confidence: 82%

Intercomparison of mid-latitude tropospheric and lower stratospheric water vapor measurements and comparison to ECMWF humidity data

Kaufmann¹,

Voigt²,

Heller³

et al. 2018

Preprint

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Abstract. Accurate measurement of water vapor in the climate sensitive region near the tropopause turned out to be very challenging. Unexplained systematic discrepancies between measurements at low water vapor mixing ratios made by different instruments on airborne platforms have limited our ability to adequately address a number relevant scientific questions on the humidity distribution, cloud formation and climate impact in that region. Therefore, during the past decade, the scientific community has undertaken substantial efforts to understand these discrepancies and improve the quality of 20 water vapor measurements. This study presents a comprehensive intercomparison of airborne state-of-the-art in situ hygrometers deployed onboard the DLR (German Aerospace Center) research aircraft HALO during the Mid-Latitude CIRRUS (ML-CIRRUS) campaign conducted in 2014 over central Europe. The instrument intercomparison shows that the hygrometer measurements agree within their combined accuracy (±10 to 15%, depending on the humidity regime), total mean values even agree within 2.5%. However, systematic differences on the order of 10% and up to a maximum of 15% are 25 found for mixing ratios below 10 parts per million (ppm) H 2 O. A comparison of relative humidity within cirrus clouds does not indicate a systematic instrument bias in either water vapor or temperature measurements in the upper troposphere.Furthermore, in situ measurements are compared to model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) which are interpolated along the ML-CIRRUS flight tracks. We find a mean agreement within ±10% throughout the troposphere and a significant wet bias in the model on the order of 100% to 150% in the stratosphere close to 30 the tropopause. Consistent with previous studies, this analysis indicates that the model deficit is mainly caused by a blurred humidity gradient at tropopause altitudes.Atmos. Chem. Phys. Discuss., https://doi

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“…160 % (e.g. Ovarlez et al, 2002; The bias of MCH data towards higher values for the period starting in year 2000 could not be explained by physical reasons -see e.g. Lamquin et al (2012) and the discussion therein -but is related to an error in sensor handling during calibration.…”

Section: Description Of Errorsmentioning

confidence: 99%

Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009

et al. 2014

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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 (RH liquid ) and ice (RH ice ).

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Water vapour measurements inside cirrus clouds in Northern and Southern hemispheres during INCA

Cited by 127 publications

References 14 publications

Potential of airborne lidar measurements for cirrus cloud studies

Potential of airborne lidar measurements for cirrus cloud studies

Intercomparison of mid-latitude tropospheric and lower stratospheric water vapor measurements and comparison to ECMWF humidity data

Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009

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