Conditionally unstable flow past two-dimensional topography
Abstract
Properties of orographic precipitation are strongly dependent on the stability and moisture content of the impinging airflow. In the present study consideration is given to quasi-steady stratified flow over a mountain ridge with an upstream profile of uniform wind speed, constant dry stability and constant relative humidity. The temperature (and implied specific humidity) of the impinging flow is used as a control parameter for the upstream conditional instability. Numerical experiments are undertaken with a non-hydrostatic mesoscale model using explicit warm-rain Kessler-type microphysics and a TKE-based turbulence scheme. Two-dimensional as well as fully three-dimensional model domains are employed. Simulations within the stratiform, slightly convective and strongly convective precipitation regime are presented. The results confirm that convective dynamics have a substantial impact on the efficiency and distribution of orographic precipitation. For the slightly convective experiments, embedded cellular convection is observed. The sensitivity of these flow features to the control parameter, the dimensionality of the model domain and the turbulence parametrization is investigated.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....6888F