Large-scale effects on the regulation of tropical sea surface temperature

Journal Article · Mon Nov 01 04:00:00 EST 1993 · Journal of Climate; (United States)

DOI:https://doi.org/10.1175/1520-0442(1993)006<2049:LSEOTR>2.0.CO;2· OSTI ID:5297239

Hartmann, D L; Michelsen, M L ^[1]

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1. Univ. of Washington, Seattle, WA (United States)

The dominant terms in the surface energy budget of the tropical oceans are absorption of solar radiation and evaporative cooling. If it is assumed that relative humidity in the boundary layer remains constant, evaporate cooling will increase rapidly with sea surface temperature (SST) because of the strong temperature dependence of saturation water vapor pressure. The resulting stabilization of SST provided by evaporate cooling is sufficient to overcome positive feedback contributed by the decrease of surface net longwave cooling with increasing SST. Evaporate cooling is sensitive to small changes in boundary-layer relative humidity. Large and negative shortwave cloud forcing in the regions of highest SST are supported by the moisture convergence associated with large-scale circulations. In the descending portions of these circulations the shortwave cloud forcing is suppressed. When the effect of these circulations is taken into account by spatial averaging, the area-averaged cloud forcing shows no sensitivity to area-averaged SST changes associated with the 1987 warming event in the tropical Pacific. While the shortwave cloud forcing is large and important in the convective regions, the importance of its role in regulating the average temperature of the tropics and in modulating temperature gradients within the tropics is less clear. A heuristic model of SST is used to illustrate the possible role of large-scale atmospheric circulations on SST in the tropics and the coupling between SST gradients and mean tropical SST. The intensity of largescale circulations responds sensitively to SST gradients and affects the mean tropical SST by supplying dry air to the planetary boundary layer. Large SST gradients generate vigorous circulations that increase evaporation and reduce the mean SST. 37 refs., 14 figs., 1 tab.

• OSTI ID: 5297239
• Journal Information: Journal of Climate; (United States), Journal Name: Journal of Climate; (United States) Vol. 6:11; ISSN JLCLEL; ISSN 0894-8755
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540310* -- Environment
Aquatic-- Basic Studies-- (1990-)
ATMOSPHERIC CIRCULATION
ENERGY BALANCE
MATHEMATICAL MODELS
SEAS
SURFACE WATERS
TEMPERATURE MEASUREMENT
TROPICAL REGIONS