Precipitation and kinematic structure of an oceanic mesoscale convective system. Part II: momentum transport and generation

The momentum budget reveals some behavior that differs from that of earliest systems studied. For example, above 7 km the momentum transport and pressure gradient reinforce to produce substantial acceleration of air exiting the band at high levels toward the front (east), although the vertical transport contributes only a small amount to the observed acceleration. The u positive acceleration at higher levels, being larger than the Doppler estimates of dŪ/dt at lower levels, increases the overall u shear within the convective band. Estimation of the vertical momentum-flux divergence and pressure-gradient term at low levels from the in situ data supports this result. In previously observed tropical systems, u shear was increased by convective bands only when the u shear was negative. At midlevels, the vertical transport of line-parallel wind (v) by the line acts to increase and slightly elevate the southerly jet maximum in the environmental wind profile usually seen in this region. As in previously documented systems, dV̄/dv decreases with time within the band. -from Authors