In situ observations of supercooled liquid water clouds over Dome C, Antarctica, by balloon-borne sondes
Year: 2024
Authors: Ricaud P., Durand P., Grigioni P., Del Guasta M., Camporeale G., Roy A., Attiy J.L., Bognar J.
Autors Affiliation: Univ Toulouse, CNRM, Meteo France, CNRS, 42 Ave G Coriolis, F-31057 Toulouse, France; Univ Toulouse, Lab Aerol, CNRS, UPS, 14 Ave Edouard Belin, F-31400 Toulouse, France; ENEA, Lab Observat & Measurements Environm & Climate, Via Anguillarese 301, I-00123 Rome, Italy; INO CNR, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy; CNR, IREA, Via G Amendola n 122 D-O, I-70126 Bari, Italy; Anasphere Inc, 5400 Frontage Rd, Manhattan, MT 59741 USA.
Abstract: Clouds in Antarctica are key elements that affect radiative forcing and thus Antarctic climate evolution. Although the vast majority of clouds are composed of ice crystals, a non-negligible fraction constitutes supercooled liquid water (SLW; water held in liquid form below 0 degrees C). Numerical weather prediction models have great difficulty in forecasting SLW clouds over Antarctica, favouring ice at the expense of liquid water and therefore incorrectly estimating the cloud radiative forcing. Remote-sensing observations of SLW clouds have been carried out for several years at Concordia Station (75 degrees S, 123 degrees E; 3233 m above mean sea level), combining active lidar measurements (SLW cloud detection) and passive HAMSTRAD microwave measurements (liquid water path, LWP). The present project aimed at in situ observations of SLW clouds using sondes developed by the company Anasphere, specifically designed for SLW content (SLWC) measurements. These SLWC sondes were coupled to standard meteorological pressure-temperature-humidity sondes from Vaisala and released under meteorological balloons. During the 2021-2022 summer campaign, 15 launches were made, of which 7 were scientifically exploitable above a height of 400 m above ground level, a threshold height imposed by the time the SLWC sonde takes to stabilize after launch. The three main outcomes from our analyses are as follows: (a) the first in situ observations so far of SLW clouds in Antarctica with SLWC sondes; (b) on average, the consistency of SLW cloud heights as observed by in situ sondes and remote-sensing lidar; and (c) the liquid water path (vertically integrated SLWC) deduced by the sondes being generally equal to or greater than the LWP remotely sensed by HAMSTRAD. In general, the SLW clouds were observed in a layer close to saturation (U > 80 %) or saturated (U similar to 100 %-105 %) just below or at the lowermost part of the entrainment zone, or capping inversion zone, which exists at the top of the planetary boundary layer and is characterized by an inflection point in the potential temperature vertical profile. Our results are consistent with the theoretical view that SLW clouds form and remain at the top of the planetary boundary layer.
Journal/Review: ATMOSPHERIC MEASUREMENT TECHNIQUES
Volume: 17 (17) Pages from: 5071 to: 5089
More Information: The HAMSTRAD programme 910 and the SLW-CLOUDS programme 1247 were supported by IPEV, the Institut National des Sciences de l’Univers (INSU)/Centre National de la Recherche Scientifique (CNRS), Meteo-France, and the Centre national d’etudes spatiales (CNES)KeyWords: Mixed-phase; Boundary-layer; Ice; Microphysics; Peninsula; Aerosol; ImpactDOI: 10.5194/amt-17-5071-2024