Turbulence parameters in the tropical troposphere and lower stratosphere

Abstract

Using the mesosphere-stratosphere-troposphere (MST) radar observations in the troposphere and lower stratosphere at a tropical station, Gadanki, the rate of turbulent kinetic energy dissipation ε, as estimated by the spectral width method, the power method, and the variance method, has been compared. It is found that ε from the spectral width method and variance method agree quite well under low background wind conditions, whereas under high background wind conditions, ε from the spectral width method appears to be an underestimate. The ε from the power method is generally lower than that from the other two methods. Adopting the variance method, the turbulence parameters ε and the eddy diffusivity for momentum Km have been estimated for tropospheric and lower stratospheric regions over Gadanki for the period 18 January 1999 to 5 March 1999, making use of the vertical wind observations from MST radar on each night for ~2 hours. Average altitude profiles of ε and Km for the winter season are presented. The turbulence parameter profiles reveal a prominent peak in the upper troposphere. From Richardson number considerations the observed turbulence is attributed mainly to wind shear.