Multiscale interactions in an idealized Walker cell: Analysis with isentropic streamfunctions

AMS Citation:
Slawinska, J., O. Pauluis, A. J. Majda, and W. W. Grabowski, 2016: Multiscale interactions in an idealized Walker cell: Analysis with isentropic streamfunctions. Journal of the Atmospheric Sciences, 73, 1187-1203, doi:10.1175/JAS-D-15-0070.1.
Date:2016-03-01
Resource Type:article
Title:Multiscale interactions in an idealized Walker cell: Analysis with isentropic streamfunctions
Abstract: A new approach for analyzing multiscale properties of the atmospheric flow is proposed in this study. For that, the recently introduced isentropic streamfunctions are employed here for scale decomposition with Haar wavelets. This method is applied subsequently to a cloud-resolving simulation of a planetary Walker cell characterized by pronounced multiscale flow. The resulting set of isentropic streamfunctions--obtained at the convective, meso-, synoptic, and planetary scales--capture many important features of the across-scale interactions within an idealized Walker circulation. The convective scale is associated with the shallow, congestus, and deep clouds, which jointly dominate the upward mass flux in the lower troposphere. The synoptic and planetary scales play important roles in extending mass transport to the upper troposphere, where the corresponding streamfunctions mainly capture the first baroclinic mode associated with large-scale overturning circulation. The intermediate-scale features of the flow, such as anvil clouds associated with organized convective systems, are extracted with the mesoscale and synoptic-scale isentropic streamfunctions. Multiscale isentropic streamfunctions are also used to extract salient mechanisms that underlie the low-frequency variability of the Walker cell. In particular, the lag of a few days of the planetary scale behind the convective scale indicates the importance of the convective scale in moistening the atmosphere and strengthening the planetary-scale overturning circulation. Furthermore, the mesoscale and synoptic scale lags behind the planetary scale reflect the strong dependence of convective organization on the background shear.
Peer Review:Refereed
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OpenSky citable URL: ark:/85065/d7zg6ttm
Publisher's Version: 10.1175/JAS-D-15-0070.1
Author(s):
  • Joanna Slawinska
  • Olivier Pauluis
  • Andrew Majda
  • Wojciech Grabowski - NCAR/UCAR
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