Multiscale interactions in an idealized Walker circulation: Mean circulation and intraseasonal variability

AMS Citation:
Slawinska, J., O. Pauluis, A. J. Majda, and W. W. Grabowski, 2014: Multiscale interactions in an idealized Walker circulation: Mean circulation and intraseasonal variability. Journal of the Atmospheric Sciences, 71, 953-971, doi:10.1175/JAS-D-13-018.1.
Date:2014-03-01
Resource Type:article
Title:Multiscale interactions in an idealized Walker circulation: Mean circulation and intraseasonal variability
Abstract: A high-resolution cloud-resolving model (CRM) simulation is developed here for a two-dimensional Walker circulation over a planetary-scale domain of 40 000 km for an extended period of several hundred days. The Walker cell emerges as the time-averaged statistical steady state with a prescribed sinusoidal sea surface temperature (SST) pattern with a mean temperature of 301.15 K and a horizontal variation of 4 K. The circulation exhibits intraseasonal variability on a time scale of about 20 days with quasi-periodic intensification of the circulation and broadening of the convective regime. This variability is closely tied to synoptic-scale systems associated with expansion and contraction of the Walker circulation. An index for the low-frequency variability is developed using an empirical orthogonal function (EOF) analysis and by regressing various dynamic fields on this index. The low-frequency oscillation has four main stages: a suppressed stage with strengthened midlevel circulation, an intensification phase, an active phase with strong upper-level circulation, and a weakening phase. Various physical processes occurring at these stages are discussed as well as the impact of organized convective systems on the large-scale flow.
Peer Review:Refereed
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OpenSky citable URL: ark:/85065/d7tm7c1f
Publisher's Version: 10.1175/JAS-D-13-018.1
Author(s):
  • Joanna Slawinska
  • Olivier Pauluis
  • Andrew Majda
  • Wojciech Grabowski - NCAR/UCAR
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