Impact of the Microphysics in HARMONIE-AROME on Fog

• Published in: Atmosphere Vol. 13; no. 12; p. 2127
• Main Authors: Contreras Osorio, Sebastián, Martín Pérez, Daniel, Ivarsson, Karl-Ivar, Nielsen, Kristian Pagh, de Rooy, Wim C., Gleeson, Emily, McAufield, Ewa
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.12.2022
• Subjects: Aerosols; Atmospheric conditions; Atmospheric models; Case studies; Cloud droplet concentration; cloud droplet number concentration; Cloud droplet size; Cloud droplet size distribution; Cloud droplets; cloud microphysics; Clouds; Configurations; Droplets; Environmental aspects; Experiments; Fog; Fog forecasting; HARMONIE-AROME; Ice; Low clouds; Mathematical models; Microphysics; Numerical weather forecasting; numerical weather prediction (NWP); Parameters; R&D; Representations; Research & development; Sedimentation & deposition; Size distribution; Weather forecasting; Spain
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos13122127

This study concerns the impact of microphysics on the HARMONIE-AROME NWP model. In particular, the representation of cloud droplets in the single-moment bulk microphysics scheme is examined in relation to fog forecasting. We focus on the shape parameters of the cloud droplet size distribution and recent changes to the representation of the cloud droplet number concentration (CDNC). Two configurations of CDNC are considered: a profile that varies with height and a constant one. These aspects are examined together since few studies have considered their combined impact during fog situations. We present a set of six experiments performed for two non-idealised three-dimensional case studies over the Iberian Peninsula and the North Sea. One case displays both low clouds and fog, and the other shows a persistent fog field above sea. The experiments highlight the importance of the considered parameters that affect droplet sedimentation, which plays a key role in modelled fog. We show that none of the considered configurations can simultaneously represent all aspects of both cases. Hence, continued efforts are needed to introduce relationships between the governing parameters and the relevant atmospheric conditions.