J.-I. Yano ⁽¹⁾, J.-P. Chaboureau ⁽²⁾ and F. Guichard ⁽¹⁾

(1) CNRM–GAME (CNRS and Météo-France), France
(2) Laboratoire d’Aérologie, Observatoire Midi-Pyrénées, France

Q. J. R. Meteorol. Soc., 2005, vol 131, pp. 861-875        [doi: 10.1256/qj.03.188]

Summary : The concept of the potential-energy convertibility (PEC) is proposed as a generalization of convective available potential energy (CAPE). It is defined as a vertical integral of buoyancy weighted by a non-dimensional normalized vertical momentum. This is a measure of convertibility of potential energy into kinetic energy in the sense that the actual conversion rate is recovered when PEC evaluated by the convective-scale local buoyancy and vertical momentum, as available from cloud-resolving model (CRM) simulations, is multiplied by the normalization factor for the vertical momentum. It reduces to CAPE, when the standard parcel-lifted buoyancy and a unit value for the normalized vertical momentum are used. It is equivalent to Arakawas–Schubert’s cloud work function, when the buoyancy and the vertical momentum profile for an entraining plume are used. PEC evaluated from locally defined buoyancy and vertical momentum in CRM simulations correlates better with the convective precipitation than CAPE. The evaluation of PEC within a convective parametrization may be possible with an
appropriate definition of the effective entrainment rate, for example, which is expected to improve CAPE-based convective parametrizations.

keywords : convective parametrization - energy cycle - PEC