Chapter 3 | | SCIENTIFIC OBJECTIVES |
In order to test the thermostat hypothesis discussed in the previous chapter, all radiative and
heating terms and state parameters of the ocean-atmosphere system that enter into the hypothesis
must be measured as a function of SST over the equatorial ocean. The CEPEX domain spans a
region of significant SST gradients, from the western Pacific with its very warm SSTs to the
relatively cooler central Pacific.
The primary experiment objectives of CEPEX are to:
- measure, by direct atmospheric observations, the vertical structure of the water-vapor
greenhouse effect (the difference between the long-wave flux emitted by the sea surface
and the outgoing long-wave radiation flux at any given level in the atmosphere)
- measure the effect of widespread cirrus layers on radiation fluxes over the equatorial
Pacific
- measure the east-west gradients of SST and the evaporative and sensible heat-fluxes from
the sea surface along the equatorial Pacific
- measure the east-west gradients of the vertical distribution of water-vapor along the
equatorial Pacific
- explore the microphysical factors contributing to the high albedo of widespread tropical
cirrus layers
As will be discussed in Chapter 4, a complete examination of the thermostat mechanism must
include studies with coupled ocean-atmosphere radiative-convective equilibrium models. Carrying
out these studies will require additional information, which is encompassed by the following
supporting objectives:
- measure vertical profiles of water-vapor distribution from 15 to 25 km from west to east
across the central equatorial Pacific, to examine the role of thin cirrus outside the warm
pool
- study the radiative heating due to thin cirrus outside the warm pool
- through a combination of direct observations and radiation models, to characterize
radiative cooling profiles under clear skies to develop radiative-convective equilibrium
models
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