Séminaire
Cumuli congestus, with their sprouting shape and sharp outline, are abundant in the tropics. They constitute the third dominant cloud population beside shallow cumulus and cumulonimbus. Recent studies have pushed forward the idea that congestus clouds are important for the development of cumulonimbi, in the sense that through their moistening of the atmosphere, they could promote deep convection. This idea is investigated here by combining ship observations, large-eddy simulations and brightness temperature measurements. Focus is set on the tropical Atlantic and adjacent land areas. The analysis is based on a time-scale analysis. It involves a comparison of the time scales that characterize the transition from congetsus to cumulonimbus on the one hand and processes thought to be driving this transition on the other hand (especially congestus clouds versus large-scale forcing). Implications of the results for the representation of deep convection in global climate models are discussed.
MP Lefebvre (0144272799)