19 Oct 2022
19 Oct 2022
Status: this preprint is currently under review for the journal ACP.

Characteristics of supersaturation in mid-latitude cirrus clouds and their adjacent cloud-free air

Georgios Dekoutsidis1, Silke Groß1, Martin Wirth1, Martina Krämer2,3, and Christian Rolf2 Georgios Dekoutsidis et al.
  • 1Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, 82234 Wessling, Germany
  • 2Institute for Energy and Climate Research (IEK-7), Research Center Jülich, 52425 Jülich, Germany
  • 3Institute for Atmospheric Physics (IPA), Johannes Gutenberg University, Mainz, Germany

Abstract. Water vapor measurements of mid-latitude cirrus clouds, obtained by the WALES (WAter vapor Lidar Experiment in Space) lidar system during the Mid-Latitude Cirrus (ML-Cirrus) airborne campaign, that took place in spring of 2014 over central Europe and the NE Atlantic Ocean, are combined with model temperatures from the European Centre for Medium-Range Weather Forecasts (ECMWF) and analysed. Our main focus is to derive the distribution and temporal evolution of humidity with respect to ice within cirrus clouds and in their adjacent cloud-free air. We find that 34.1 % of in-cloud data points are supersaturated with respect to ice. Supersaturation is also detected in 6.8 % of the cloud-free data points. When the probability density of the Relative Humidity over ice (RHi) is calculated with respect to temperature for the in-cloud data points from the ML-Cirrus data-set there are two peaks. One around 225 K and close to saturation, RHi = 100 % and a second one at colder temperatures around 215 K in subsaturation, RHi = 90 %. These two regions seem to represent two cirrus cloud categories: in-situ formed and liquid-origin. Regarding their vertical structure, most clouds have higher supersaturations close to the cloud-top and become subsaturated near the cloud bottom. Finally, we find that the vertical structure of RHi within the clouds is also indicative of their life stage. RHi skewness tends to go from positive to negative values as the cloud ages. RHi modes are close to saturation in young clouds, supersaturated in mature clouds and subsaturated in dissipating clouds.

Georgios Dekoutsidis et al.

Status: open (until 02 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-717', Anonymous Referee #1, 06 Nov 2022 reply

Georgios Dekoutsidis et al.

Georgios Dekoutsidis et al.


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Short summary
Cirrus clouds affect the earth’s atmosphere deeming their study important. Here we use water vapor measurements by lidar and study the Relative Humidity (RHi) within and around mid-latitude cirrus clouds. We find high supersaturations in the cloud-free air and within the clouds, especially near cloud-top. We study two cloud types with different formation processes. Finally, we conclude that the shape of the distribution of RHi can be used as an indicator of different cloud evolutionary stages.