Where is the level of neutral buoyancy for deep convection?
Article first published online: 14 AUG 2012
Published in 2012 by the American Geophysical Union
Geophysical Research Letters
Volume 39, Issue 15, August 2012
How to Cite
2012), Where is the level of neutral buoyancy for deep convection?, Geophys. Res. Lett., 39, L15809, doi:10.1029/2012GL052638., and (
- Issue published online: 14 AUG 2012
- Article first published online: 14 AUG 2012
- Manuscript Accepted: 9 JUL 2012
- Manuscript Revised: 6 JUL 2012
- Manuscript Received: 5 JUN 2012
- deep convection;
- level of neutral buoyancy
 This study revisits an old concept in meteorology - level of neutral buoyancy (LNB). The classic definition of LNB is derived from the parcel theory and can be estimated from the ambient sounding (LNB_sounding) without having to observe any actual convective cloud development. In reality, however, convection interacts with the environment in complicated ways; it will eventually manage to find its own effective LNB and manifests it through detraining masses and developing anvils (LNB_observation). This study conducts a near-global survey of LNB_observation for tropical deep convection using CloudSat data and makes comparison with the corresponding LNB_sounding. The principal findings are as follows: First, although LNB_sounding provides a reasonable upper bound for convective development, correlation between LNB_sounding and LNB_observation is low suggesting that ambient sounding contains limited information for accurately predicting the actual LNB. Second, maximum mass outflow is located more than 3 km lower than LNB_sounding. Hence, from convective transport perspective, LNB_sounding is a significant overestimate of the “destination” height level of the detrained mass. Third, LNB_observation is consistently higher over land than over ocean, although LNB_sounding is similar between land and ocean. This difference is likely related to the contrasts in convective strength and environment between land and ocean. Finally, we estimate the bulk entrainment rates associated with the observed deep convection, which can serve as an observational basis for adjusting GCM cumulus parameterization.