Life cycle of a flower cloud system during the EUREC⁴A field campaign

Abstract. The organisation of trade-wind cumulus clouds in the vicinity of Barbados can affect the amount and lifetime of the clouds thereby potentially playing an important role in the top of the atmosphere radiation budget. This paper presents a case study of a flower cloud system that occurred on 2 February 2020 near Barbados during the EUREC⁴A field campaign. The evolution of a cluster of clouds that developed into a flower system is investigated from 0000 UTC to 2300 on 2 February using GOES-16 satellite IR and visible images, dropsonde data, and ERA5 reanalysis data. The cloud system began as small clouds ~ 400 km to the north-east of Barbados. Aggregation of clouds continued to occur as the system moved towards Barbados. A striking feature was the development of a large area of rain in the central region of the system in the later stages of development when the area plateaued. Several cloud arcs associated with cold pools became visible as they emerged from the cloud shield. The flower system began to decay about 7 hours after the maximum values of derived effective radius. The environmental conditions determined from ERA5 reanalysis along the trajectory of the flower were examined. The sea surface temperatures were 26.9 ± 0.3 °C along the trajectory. The surface wind speed in the proximity of the flower increased during the first six hours in the early development stage from 7 m s⁻¹ to 9 m s⁻¹ and then decreased gradually to about 5 m s⁻¹ during the next 12 hours. The inversion strength measured with dropsonde was greater in the flower than in its surrounding locations due to the mesoscale variation in temperature field and, probably, the interactions between the flower and the atmosphere. The cloud system was surrounded by high total precipitable water in the early stages and along the trajectory as it developed into the flower. The Barbados region was marked by high aerosol optical depth on the day. The life cycle of the flower cloud system characterized in this paper will help evaluate numerical simulations of shallow convective organisation.