Classification of Cloud Regimes in Arctic Cold Air Outbreaks using Dropsonde and Satellite Data

Résumé fourni par la source

Arctic cold air outbreaks (CAOs) produce distinct low-level cloud patterns that strongly influence surface energy fluxes. Using more than 500 dropsonde profiles from three aircraft campaigns combined with satellite observations, we present the first large-sample observational validation of the stability parameter (-H/L) as a predictor of cloud regimes in marine CAOs. Two regimes emerge: a shear-driven regime (positive M-Index, small -H/L) and a buoyancy-driven regime (positive M-Index, larger -H/L). The shear-driven regime has horizontal wind speeds about 6 m s-1 higher than in the buoyancy-driven regime. Analysis of three classified cloud patterns (cloud streets, isotropic clouds, and open cells) reveals a systematic transition from shallow, cold, and dry to deep, warm, and moist boundary layers. Cloud streets occur primarily when the M-Index exceeds 3.6, indicating a minimum instability threshold for roll convection and establishing a robust observational link between boundary-layer stability and cloud organization.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.