DUAL-AIRCRAFT INVESTIGATION OF THE INNER-CORE OF HURRICANE NORBERT .3. WATER-BUDGET

The hydrometeor water budget of Hurricane Norbert on 24 September 1984 is computed using two microphysical retrieval techniques. Three-dimen sional distributions of condensation, evaporation, precipitation, and advection of cloud and precipitation are computed, and a bulk water bu dget is computed as the volume integral of these distributions. The ro le of the microphysical retrievals is to provide the three-dimensional distribution of cloud water content, since it cannot be determined wi th the equipment available. Both retrieval methods use the steady-stat e continuity equation for water. The first method determines precipita tion formation mechanisms from the radar-reflectivity and Doppler wind fields. The cloud water content is determined, through microphysical modeling, to be the amount necessary to explain the rate of precipitat ion formation. The second method (that of Hauser et al.) solves the wa ter continuity equations as a boundary value problem, while also emplo ying microphysical modeling. This method is applied in three dimension s for the first time. Asymmetries in the water budget of Hurricane Nor bert were important, apparently accounting for nearly half the net con densation. The most condensation and heaviest precipitation was to the left of the storm track, while the strongest evaporation was to the r ear of the storm. Many of the downdrafts were unsaturated because they were downwind of the precipitation maximum where little water was ava ilable for evaporation. Since the evaporation in the downdrafts was si gnificantly less than the condensation in their counterpart updrafts, net condensation (bulk condensation-bulk evaporation) was significantl y greater than would be implied by the net upward mass flux. Much of t he vapor required to account for the greater bulk condensation appears to have come from enhanced sea surface evaporation under the dry down draft air to the right of the storm track. The net outflow of condensa te from the storm inner core was quite small, although there were appr eciable outward and inward horizontal fluxes at certain locations. A m aximum of ice outflow to the left of the storm track in the front of t he storm corresponded well to the ice particle trajectories that Houze et al. suggested were feeding the stratiform precipitation found fart her outward from the storm center.