Isentropic analysis of convective motions

Olivier M. Pauluis, Agnieszka A. Mrowiec

Research output: Contribution to journalArticlepeer-review

Abstract

This paper analyzes the convective mass transport by sorting air parcels in terms of their equivalent potential temperature to determine an isentropic streamfunction. By averaging the vertical mass flux at a constant value of the equivalent potential temperature, one can compute an isentropic mass transport that filters out reversible oscillatory motions such as gravity waves. This novel approach emphasizes the fact that the vertical energy and entropy transports by convection are due to the combination of ascending air parcels with high energy and entropy and subsiding air parcels with lower energy and entropy. Such conditional averaging can be extended to other dynamic and thermodynamic variables such as vertical velocity, temperature, or relative humidity to obtain a comprehensive description of convective motions. It is also shown how this approach can be used to determine the mean diabatic tendencies from the three-dimensional dynamic and thermodynamic fields. A two-stream approximation that partitions the isentropic circulation into a mean updraft and a mean downdraft is also introduced. This offers a straightforward way to identify the mean properties of rising and subsiding air parcels. The results from the two-stream approximation are compared with two other definitions of the cloud mass flux. It is argued that the isentropic analysis offers a robust definition of the convective mass transport that is not tainted by the need to arbitrarily distinguish between convection and its environment, and that separates the irreversible convective overturning from oscillations associated with gravity waves.

Original languageEnglish (US)
Pages (from-to)3673-3688
Number of pages16
JournalJournal of the Atmospheric Sciences
Volume70
Issue number11
DOIs
StatePublished - Nov 2013

Keywords

  • Convection
  • Convective clouds
  • Deep convection
  • Isentropic analysis
  • Lagrangian circulation/transport

ASJC Scopus subject areas

  • Atmospheric Science

Fingerprint Dive into the research topics of 'Isentropic analysis of convective motions'. Together they form a unique fingerprint.

Cite this