A Numerical Model of Deep Moist Convection: Part I. Comparative Experiments for Variable Ambient Moisture and Wind Shear

Abstract This study concerns the influence of ambient conditions upon the behavior of deep moist convection in the atmosphere. By means of a two-dimensional numerical model, an anelastic system of hydrodynamic and thermodynamic equations is integrated in order to simulate convection of the squall-line type. Liquid precipitation and the effect of pressure perturbations upon the buoyancy are included. The joint influence of low-level relative humidity and mid-tropospheric wind shear upon the intensity and persistence of the convection at maturity is investigated. Nine comparative experiments are performed using three values of each parameter, including cases without shear. The various cases are compared with regard to airflow and rainfall patterns. Basic features of the perturbation fields for flow, temperature and pressure are interrelated. It is found that the greater the moisture supply and the weaker the shear, the more intense is the convection in terms of both peak updraft velocity and rainfall rate. ...