The Mutual Variation of Wind , Shear , and Baroclinicity in the Cumulus Convective Atmosphere of the Hurricane

The enhanced cumulus convection in tropical disturbances acts in two opposing ways. In one sense the condensation heat from the cumulus acts to warm the inner portions of the disturbance and induce vertical shear of the horizontal wind through the thermal wind relationship. In the opposite sense the cumulus also act to suppress vertical wind shear by transfer of horizontal momentum within their upand downdrafts. The operation of this dual or "paradox" role of the cumulus cloud is of fundamental importance for understanding the steady-state dynamics of the hurricane's inner core region and is also hypothesized to be of basic importance in the development of tropical storms and generation of easterly waves. Observational information and calculations on the radial distribution of baroclinicity and vertical shear collected on 102 incHvidual flight legs (on 19 flight levels) into hurricanes Hown by the Research Flight Facility of the U. S. Weather Bureau are presented. The measured baroclinicity in the lowe r half of the troposphere at the inner 50-70 km radii is two to three times larger than cylindrical thermal wind balance would require. This baroclinicity may be 50 to 100 times larger in the inner areas of the hurricane than in the easterly wave, yet vertical wind shear in the hurricane may be but one to three times as large.