Articles | Volume 4, issue 3
Atmos. Chem. Phys., 4, 639–647, 2004
Atmos. Chem. Phys., 4, 639–647, 2004

  16 Apr 2004

16 Apr 2004

On the distribution of relative humidity in cirrus clouds

P. Spichtinger1, K. Gierens1, H. G. J. Smit2, J. Ovarlez3, and J.-F. Gayet4 P. Spichtinger et al.
  • 1Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 2Forschungszentrum Jülich, Institut für Chemie und Dynamik der Geosphäre (ICG-II: Troposphäre), Jülich, Germany
  • 3Laboratoire de Météorologie Dynamique du CNRS, Ecole Polytechnique, Palaiseau, France
  • 4Laboratoire de Météorologie Physique, Université Blaise Pascal, Clermont-Ferrand, France

Abstract. We have analysed relative humidity statistics from measurements in cirrus clouds taken unintentionally during the Measurement of OZone by Airbus In-service airCraft project (MOZAIC). The shapes of the in-cloud humidity distributions change from nearly symmetric in relatively warm cirrus (warmer than −40°C) to considerably positively skew (i.e. towards high humidities) in colder clouds. These results are in agreement to findings obtained recently from the INterhemispheric differences in Cirrus properties from Anthropogenic emissions (INCA) campaign (Ovarlez et al., 2002). We interprete the temperature dependence of the shapes of the humidity distributions as an effect of the length of time a cirrus cloud needs from formation to a mature equilibrium stage, where the humidity is close to saturation. The duration of this transitional period increases with decreasing temperature. Hence cold cirrus clouds are more often met in the transitional stage than warm clouds.

Final-revised paper