Remote sensing ice supersaturation inside and near cirrusclouds: a case study in the subtropics

Christophe Hoareau (1) , Vincent Noël (2) , Hélène Chepfer (1) , Jérôme Vidot (3) , Marjolaine Chiriaco (4) , Sophie Bastin (4) , Mathieu Reverdy (1) , Gregory Cesana (5)

1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
2 LAERO - Laboratoire d'aérologie
3 Centre de Météorologie Spatiale
4 SPACE - LATMOS
5 JPL - Jet Propulsion Laboratory

Combining vertically resolved lidar retrievals of water vapor and cloud detection, we document a 2-day subtropical cirrus case study over La Réunion (20.9∘S–55.5∘E) in March 2005, focusing on the conditions of ice supersaturation inside and near the observed cloud. Using satellite observations, we describe the synoptic conditions leading to cloud formation. Supersaturation occurs 25% of the time within the cirrus, up to 35% in its middle segment, where relative humidity goes beyond 150%. In clear-sky areas, relative humidity stays consistentlylow, especially in profiles without clouds. High-troposphere atmospheric waves could initiate the formation of supersaturation conditions, especially on 16 March.

Keywords: water vapor; subtropics; supersaturation; Raman lidar; cirrus

Domains: Meteorology

Christophe Hoareau, Vincent Noël, Hélène Chepfer, Jérôme Vidot, Marjolaine Chiriaco, et al.. Remote sensing ice supersaturation inside and near cirrusclouds: a case study in the subtropics. Atmospheric Science Letters, 2016, 17, pp.639-645. ⟨10.1002/asl.714⟩. ⟨insu-01408828⟩