Sensitivity of tropical west pacific oceanic squall lines to tropospheric wind and moisture profiles

Two-dimensional experiments using the Goddard Cumulus Ensemble model ore pe rformed in order to examine the influence of environmental profiles of wind and humidity on the dynamical and microphysical structure of mesoscale con vective systems (MCSs) over the tropical oceans. The initial environments u sed in this study are derived from the results of a cluster analysis of the TOGA COARE sounding data. The model data are analyzed with methods and mea surements similar to those used in observational studies. Experiments to test the sensitivity of MCSs to the thermodynamic profile fo cus on the role of humidity in the free troposphere. In the experiments, a constant amount of relative humidity is added to every level above the boun dary layer. As humidity is increased, model storms transition from weak, un steady systems with little precipitation to strong, upshear-tilted systems with copious rainfall. This behavior is hypothesized to be the result of th e entrainment of environmental air into the updraft cores. Experiments to test the sensitivity of MCSs to the kinematic profile focus on the amount of vertical wind shear in the midlevels, between approximatel y 2 and 10 km. Five kinematic profiles are used. The dynamical and microphy sical characteristics of the runs changed dramatically in different shear e nvironments. Shear in the midlevels affects the convective systems by alter ing the perturbation pressure field. Stronger sheer results in a broader an d deeper mesolow below the updraft and a more intense dynamic high above th e lending edge.