Duvel, J. P., S. Bony, H. Le Treut and R. Kandel, 1995: Results
of the AMIP diagnostic subproject on the clear-sky greenhouse effect sensitivity
to seasurface temperature changes (Diagnostic Subproject 4). Abstracts
of the First International AMIP Scientific Conference, Monterey, California,
19.
We test the ability of ten atmospheric General Circulation Models (GCMs)
participating in AMIP to reproduce the observed seasonal and interannualvariability
of precipitable water (W) and the clear-sky greenhouse effect (G). Using
satellite data (SSM-I, ISCCP/TOVS and ERBE), we first develop simplestatistical
analyses to quantify the rate of variation of W and G as a function of
the local variation in the sea surface temperature (SST). The same analysisprocedure
is then applied to the GCM output in order to evaluate their representation
of these seasonal and interannual sensitivities. This evaluation revealsthat
certain biases are common to most models. For example, most GCMs tend to
underestimate mean values of both W and G in the tropics compared toobservations.
Also in the tropics, the modelled interannual (seasonal) sensitivity of
the clear-sky greenhouse effect to a local SST change tends to be toolarge
(small). However, there are also differences between the models themselves
that are not clearly related to the various parametizations. To trace thesource
of these differences, we need more information about the variability of
the vertical structure (temperature and water vapor) of the atmosphere.
Theinfluence of the variability of the atmospheric vertical structure is
investigated using ECMWF meteorological analyses. The results are used
to analyse the origin of the seasonal variation of precipitable water and
the clear-sky greenhouse effect for a few models.