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Mary Alice Rennick

Abstract

The relationship between the lapse rate of temperature and the surface temperature is investigated by comparing the zonally averaged temperature structure of the atmosphere to that which is generated by several assumptions concerning the lapse rate.

It is found that the value of ∂θ/∂p for any given temperature sounding is essentially constant, but that this value varies with both latitude and season. The ratio of ∂θ/∂p to the value of ∂θ/∂p along a moist adiabat at the surface is found empirically to have a cubic dependence on the surface temperature. This dependence is used to define a relationship between the surface temperature and the lapse rate which can be used to generate a zonally averaged temperature structure for the troposphere which is in good agreement with that which is observed.

The parameterization is suitable for use in a climate model based either on radiative equilibrium or zonally averaged energy balance calculations.

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Mary Alice Rennick

Abstract

A linearized, pseudo-spectral, primitive equation model is used to simulate the response of the low-level easterly jet over northern Africa to perturbations on the scale of African waves. The model results show that the jet is unstable due to both its horizontal and vertical shears. The most unstable wave supported by the jet has a wavelength of 3O00 km and a period of 2.0–2.5 days. It attains its maximum intensity at the 700 mb level, near 14°N. This compares favorably with the characteristics of the observed waves.

The kinetic energy of the waves grows at the expense of the kinetic energy of the mean jet. Energy is transferred at approximately equal rates by the horizontal and vertical Reynolds stresses. Energy conversions involving available potential energy are nearly an order of magnitude smaller, reflecting the fact that the kinetic energy of the wave accounts for about 90% of the total wave energy.

The characteristics of the most unstable wave are virtually unchanged when a crude parameterization of latent heat release is included in the model.

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Robert L. Haney and Mary Alice Rennick

Abstract

Abstract not available.

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