Publication Abstracts

Fu et al. 1994

Fu, R., A.D. Del Genio, and W.B. Rossow, 1994: Influence of ocean surface conditions on atmospheric vertical thermodynamic structure and deep convection. J. Climate, 7, 1092-1108, doi:10.1175/1520-0442(1994)007<1092:IOOSCO>2.0.CO;2.

The authors analyze the influence of sea surface temperature (SST) and surface wind divergence on atmospheric thermodynamic structure and the resulting effects on the occurrence of deep convection using National Meteorological Center radiosonde data and International Satellite Cloud Climatology Project data for July 1983-July 1985. The onset of deep convection requires not only the existence of positive convective available potential energy (CAPE), but also an unstable planetary boundary layer (PBL). A stable PBL is observed to suppress deep convection even when CAPE is positive. Variations of SST have a major effect on CAPE, but surface wind divergence can also affect deep convection by changing the lapse rate in the lower troposphere and humidity in the PBL. Specifically, when SST ≥ 28°C, CAPE is always positive, and surface wind divergence does not qualitatively change the buoyancy profile above the PBL. Strong surface wind divergence, however, stabilizes the PBL so as to suppress the initiation of convection. In warm SST regions, CAPE > 0 regardless of assumptions about condensate loading, although the pseudoadiabatic limit is more consistent with the observed deep convection than the reversible moist-adiabatic limit under these circumstance. When SST < 27°C, CAPE is usually negative and inhibits convection, but strong surface wind convergence can destabilize the inversion layer and moisten the PBL enough to make the atmosphere neutrally stable in the mean. As a result, deep convection is generally enhanced either when SST ≥ 28°C in the absence of strong surface wind divergence or when strong surface wind divergence occurs even if SST < 27°C. The anomalous suppression of deep convection in the warm area of the equatorial west Pacific lying between ITCZ and SPCZ is probably caused by dryness in the PBL and inversion in that area.

The seasonal cycles of deep convection and surface wind divergence are in phase with the maximum solar radiation and lead SST for one to three months in the central Pacific. The change of PBL relative humidity plays a critical role in the changeover to convective instability in this case. The seasonal change of deep convection and associated clouds seems not to have important effects on the seasonal change of local SST in the central Pacific.

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BibTeX Citation

  author={Fu, R. and Del Genio, A. D. and Rossow, W. B.},
  title={Influence of ocean surface conditions on atmospheric vertical thermodynamic structure and deep convection},
  journal={Journal of Climate},

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RIS Citation

ID  - fu02100q
AU  - Fu, R.
AU  - Del Genio, A. D.
AU  - Rossow, W. B.
PY  - 1994
TI  - Influence of ocean surface conditions on atmospheric vertical thermodynamic structure and deep convection
JA  - J. Climate
JO  - Journal of Climate
VL  - 7
SP  - 1092
EP  - 1108
DO  - 10.1175/1520-0442(1994)007%3C1092%3AIOOSCO%3E2.0.CO;2
ER  -

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