Frictional Dissipation in a Precipitating Atmosphere

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Abstract
The frictional dissipation in the shear zone surrounding falling hydrometeors is estimated to be 2–4 W m−2 in the Tropics. A numerical model of radiative–convective equilibrium with resolved three-dimensional moist convection confirms this estimate and shows that the precipitation-related dissipation is much larger than the dissipation associated with the turbulent energy cascade from the convective scale. Equivalently, the work performed by moist convection is used primarily to lift water rather than generate kinetic energy of the convective airflow. This fact complicates attempts to use the entropy budget to derive convective velocity scales. Abstract The frictional dissipation in the shear zone surrounding falling hydrometeors is estimated to be 2–4 W m−2 in the Tropics. A numerical model of radiative–convective equilibrium with resolved three-dimensional moist convection confirms this estimate and shows that the precipitation-related dissipation is much larger than the dissipation associated with the turbulent energy cascade from the convective scale. Equivalently, the work performed by moist convection is used primarily to lift water rather than generate kinetic energy of the convective airflow. This fact complicates attempts to use the entropy budget to derive convective velocity scales.

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