Global in situ evidence of narrow droplet size distributions in low, non-precipitating marine boundary layer clouds

Résumé fourni par la source

Accurate cloud particle size distributions (PSDs) are essential for bulk microphysics parameterizations (BMPs) in weather and climate models. This study evaluated 11 spectral shape formulations for estimating marine boundary layer cloud PSDs using in situ observations from 15 aircraft field campaigns spanning subtropical to near-polar regions. Marine cloud PSDs are consistently narrower than the broad distributions assumed in many BMPs, with narrowing particularly strong in mixed-phase clouds and persistent at 1–30 km horizontal scales typical of regional models. Exponential PSDs produced the largest overestimations of cloud effective radius and cloud-to-rain mass autoconversion rate. Diagnostic formulations based on cloud number concentration (Nt) or liquid water content (LWC) provided more accurate estimates for use in BMPs, but combining Nt and LWC did not necessarily improve performance. These results provide new global-scale observational constraints on cloud PSD shapes that can help reduce biases in marine cloud properties in next-generation models.

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