Kinetic Energy Budgets of a Subtropical Squall Line Determined from TAMEX Dual-Doppler Measurements

Abstract

Dual-Doppler data collected during the Taiwan Area Mesoscale Experiment (TAMEX) are used to study the kinetic energy balance of a subtropical squall line over the Taiwan Straits. Values of each term in the kinetic energy budget equation are assessed from the Doppler-derived winds and retrieved thermodynamic variables using 1-km grid spacing in all three directions. The budget domain has horizontal dimensions of 23 ? 40 km2,/, covering the convective region of the squall line. Results show that vertical totals of the horizontal generation and total buoyancy production terms act as a source of kinetic energy, while vertical totals of dissipation and vertical generation provide the main sinks. The horizontal flux divergence (convergence) of kinetic energy is nearly balanced by the vertical flux convergence (divergence) at most levels. The computed tendencies agree well with the observed tendencies in the lower and upper layers. The vertical total of kinetic energy change is negative for both the observed and computed values, showing the decrease of total kinetic energy of the squall system as it approached the west coast of Taiwan.