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- Title
The Role of Passive Cloud Volumes in the Transition From Shallow to Deep Atmospheric Convection.
- Authors
Vraciu, Cristian V.; Kruse, Irene L.; Haerter, Jan O.
- Abstract
Properly capturing the transition from shallow to deep convection remains a major shortcoming of numerical weather and climate models due to poor understanding of the physical processes controlling this transition. Although recent studies suggest shallow preconditioning and cold pool feedbacks to be important, these studies are unable to explain the initial phase of the transition. We identify an additional mechanism, namely the interaction between passive cloud volumes (PCV)—old cumulus cloud volumes in the decaying stage—and updrafts, and discuss the potential role of this mechanism in the transition from shallow to deep convection. We show that the number of updrafts interacting with PCV is very large during the transition and the updrafts better preserve their buoyancy due to entrainment of much moister air. We argue that PCV might play an important role in the transition and cumulus parameterizations could therefore benefit from including them. Plain Language Summary: Cumulonimbus clouds are responsible for many severe weather events and control the water cycle in the atmosphere. Although they are of great importance for both weather forecasting and climate projections, the initiation of these clouds is poorly represented by the numerical models, partially due to our lack of understanding the complex mechanisms controlling the transition from shallow to deep convection. Two possible mechanisms have been proposed to explain the initiation of deep convection: the moistening of the mid–troposphere by the non–precipitating clouds, and the positive feedback of the cold pools induced by the precipitating shallow cumuli. However, recent studies showed that the former is too slow of a process to fully explain the deep initiation, while the later is not able to explain the first phase of the transition. Here, we identify another mechanism, namely the interaction between the passive cloud volumes and the convective updrafts, and argue based on theoretical arguments and numerical experiments why it might play an important role in the rapid transition from shallow to deep convection. Key Points: The interaction between active and passive cloud volumes (PCV) may lead to higher cloud topsThe organization of the passive cumuli is beneficial for the transition to deep convectionThe PCV help the new updraft plumes to reach the level of free convection
- Subjects
FRONTS (Meteorology); WEATHER control; WEATHER forecasting; CUMULUS clouds; ATMOSPHERIC models; PHASE transitions
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 23, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL105996