Repository: Freie Universität Berlin, Math Department

Analysis of latent heat effects in the cloud-top mixing layer

Mellado, J.- P. and Stevens, B. and Schmidt, H. and Peters, N. (2009) Analysis of latent heat effects in the cloud-top mixing layer. Quarterly Journal of the Royal Meteorological Society, 135 (641). pp. 963-978.

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A theoretical and numerical small-scale study of the evaporative cooling phenomenon that might appear in the stratocumulus-topped boundary layers is presented. An ideal configuration of a cloud-top mixing layer is considered as defined by two non-turbulent horizontal layers, stably stratified and with buoyancy reversal within a certain range of mixture fractions due to the evaporative cooling. Linear stability analysis of the shear-free configuration is employed to provide a new interpretation of the buoyancy reversal parameter, namely in terms of a time-scale ratio between the stable and the unstable modes of the system. An incompressible high-order numerical algorithm to perform direct numerical simulation of the configuration is described and two-dimensional simulations of single-mode perturbations are presented. These simulations confirm the role of the different parameters identified in the linear stability analysis and show that convoluted flow patterns can be generated by the evaporative cooling even for the low levels of buoyancy reversal found in stratocumulus clouds. They also show that there is no enhancement of turbulent entrainment of upper-layer fluid in the shear-free configuration, and turbulent mixing enhancement by the evaporative cooling is restricted to the lower layer.

Item Type:Article
Uncontrolled Keywords:buoyancy reversal instability • stratocumulus • free convection • free turbulent flows
Subjects:Mathematical and Computer Sciences > Mathematics > Applied Mathematics
Divisions:Department of Mathematics and Computer Science > Institute of Mathematics > Geophysical Fluid Dynamics Group
ID Code:713
Deposited By: Ulrike Eickers
Deposited On:11 Aug 2009 07:37
Last Modified:20 Aug 2009 11:56

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