A contribution on the thermodynamic structure of the atmosphere over continental West Africa: static stability measure

Jegede, Olugbemiro J.; Balogun, E. E.

doi:10.1016/0169-8095(91)90052-x

Cited by 3 publications

(2 citation statements)

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“…In this layer, its gradient is northwards with low values near the equatorial zone and high values in the North over the Sahara. These results are consistent with the stability measure for 1000-850 hPa layer shown by Jegede and Balogun (1991) and based on mean tropospheric soundings from eight upper-air stations in West Africa, for an 11-year period (1960)(1961)(1962)(1963)(1964)(1965)(1966)(1967)(1968)(1969)(1970). In the 700-500 hPa layer, which is characteristic of free atmosphere, the gradient reverses sign (Fig.…”

Section: Measures Of Static Stability Parametersupporting

confidence: 76%

“…We note that, contrary to what is usually assumed (Kwon, 1989), static stability is not vertically constant. As already noted by Jegede and Balogun (1991), it varies spatially and seasonally. In the boundary layer (1000-850 hPa), this parameter presents a maximum around 15 • N near the coasts of Senegal with high values over the continental region (Fig.…”

Section: Measures Of Static Stability Parametermentioning

confidence: 86%

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Sensitivity of African easterly waves to boundary layer conditions

Lenouo

Kamga

2008

Ann. Geophys.

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Abstract.A linearized version of the quasi-geostrophic model (QGM) with an explicit Ekman layer and observed static stability parameter and profile of the African easterly jet (AEJ), is used to study the instability properties of the environment of the West African wave disturbances. It is found that the growth rate, the propagation velocity and the structure of the African easterly waves (AEW) can be well simulated. Two different lower boundary conditions are applied. One assumes a lack of vertical gradient of perturbation stream function and the other assumes zero wind perturbation at the surface. The first case gives more realistic results since in the absence of horizontal diffusion, growth rate, phase speed and period have values of 0.5 day −1 , 10.83 m s −1 and 3.1 day, respectively. The zero wind perturbation at the surface case leads to values of these parameters that are 50 percent lower. The analysis of the sensitivity to diffusion shows that the magnitude of the growth rate decreases with this parameter. Modelled total relative vorticity has its low level maximum around 900 hPa under no-slip, and 700 hPa under free slip condition.

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Section: Measures Of Static Stability Parametersupporting

confidence: 76%

Section: Measures Of Static Stability Parametermentioning

confidence: 86%