Abstract
The linear boundary layer solution which includes the effect of temporal acceleration is used to parameterize the CISK (Conditional Instability of the Second Kind) mechanism of tropical waves. By simplifying the first law to a statement of balance between adiabatic cooling and diabatic heating, which is usually valid for weak tropical motions, the model is formulated as a one-level primitive equation expressed at the top of the boundary layer and is solved numerically for its eigenvalues. The growth rates are generally scale-independent and are fairly small. The presence of a quasi-Stokes boundary layer near the equator and a transition zone between this layer and a quasi-Ekman layer poleward seems important only in the wave structures but not the growth rates.
