The influence of Microphysics in the Formation of Intense Wake Lows: A Numerical Modeling Study

Abstract

A two-dimensional cloud model is used to investigate whether microphysical processes alone within the stratiform rain regions of mesoscale convection systems can induce strong descent and intense surface wake lows accompanying such systems. Idealized simulations are run with a domain that captures the back edge of the stratiform rain region. A simplified microphysical field, representing snow alone, is prescribed within the stratiform cloud to produce radar reflectivities similar to observations. When the prescribed snow field is assumed time-independent, strong subsidence develops but does not induce an intense wake low since microphysical cooling strongly opposes adiabatic warming. Simply increasing snow quantities, although resulting in heavier rain rates and stronger subsidence, does not produce significant pressure falls. However, when precipitation rates are prescribed to decrease with time as might occur with collapsing precipitation cores, subsidence induces greater pressure falls, and a tighter pressure gradient near the wake low, in better agreement with observations.