A simple, vertically resolved model of tropical disturbances with a humidity closure

• Published in: Tellus. Series A, Dynamic meteorology and oceanography Vol. 59; no. 3; pp. 344 - 354
• Main Authors: Fuchs, željka, Raymond, David J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Taylor & Francis 01.05.2007; Blackwell Publishing Ltd; Blackwell
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; General circulation. Atmospheric waves; Meteorology; Closure model; Air flow; Atmospheric convection; atmospheric precipitation; Marine atmosphere; Gravity wave; Humidity transfer; tropical zone; atmospheric circulation; Modeling; Linearization; Atmospheric wave
• ISSN: 0280-6495; 1600-0870; 1600-0870
• DOI: 10.1111/j.1600-0870.2007.00230.x

A vertically resolved linear model for large-scale motions in an equatorial non-rotating atmosphere is presented. Precipitation is forced by tropospheric precipitable water, cloud-radiation interactions (CRI), and wind-induced surface heat exchange (WISHE). The dynamics of the model are based on the assumption that the vertical heating profile has the shape of the first baroclinic mode. The vertical profiles of vertical velocity, temperature perturbation, etc. are calculated using an upward radiation boundary condition. The modelled modes are of three types: fast gravity waves that resemble adiabatic modes with the vertical wavelength twice the depth of the troposphere; convectively coupled gravity modes that are damped and move with a phase speed of ≈17 m s −1 ; and the unstable moisture mode. The value of the model is that under a single dynamical assumption it yields the observed phase speed for the convectively coupled gravity waves that map to Kelvin waves in the equatorial beta plane case while still producing the unstable moisture mode. However, the model lacks the precipitation physics needed to produce the observed destabilization of the gravity mode.