The record-breaking flood of 1993 provides an excellent opportunity to address many issues to the interest of GCIP-Mississippi: the large-scale characteristics of the hydrometeorology, the predictability of ECMWF model, and the sensitivity of mesoscale simulation. The effects of meridional and zonal vapor transport on precipitation production have been examined in the observation as well as in the ECMWF/TOGA and ERA data. Components of atmospheric and terrestrial water balance were compared. Cloud water change/flux activity, convection feature, diurnal variation, and land-atmospheric interaction were investigated, and intercompared among the three data sets. The intercomparison has demonstrated partial improvement from TOGA to ERA. It also indicates possible internal inconsistencies in the ERA, the ability and inability of simulating large-scale or mean fields and fine-scale extremes. It reveals the impacts of the new soil hydrology and boundary layer schemes in ERA in warmer and winter times, and the possible influence on surface hydrology. A 9.5-day (28 June to 7 July 1993) simulation study by the Penn State/NCAR MM5 mesoscale model, with the help of enhanced IR images from GOES satellite data was carried out. The sensitivity of MCS simulations to different cumulus parameterization schemes and explicit moisture schemes was investigated. The model is considerably skillful in the environmental steering wind direction, but greatly limited in the orthogonal direction. The model could not reproduce the "last-hour" rain--an extraordinary MCC, indicating that the model lacks representation of the mechanisms responsible for modifying the environmental controls on the evolution of long-lived MCSs, particularly after the system reaches its maximum extent.

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A coupled 3D atmosphere-ocean model is developed to study the effect of the oceanic mixed layer depth (OMLD) on the intensification and the motion of the tropical cyclones. We first study the baroclinic response of the ocean with uniform and nonuniform initial OMLD to the steady forcing of an axisymmetric TC moving at a prescribed translating speed. Emphases are placed on the TC-ocean interactions in the coupled model simulations. Results from 96-hour integrations show TC that move into deeper (shallower) OMLD regions experience rates of increase (decrease) in their intensities once the OMLD is 10 m deeper (2.5 m shallower) than that of the TC's origin. The rightward bias of the sea surface temperature (SST) response appears in every numerical experiment and the maximum SST cooling is about 1-2$\sp\circ$C, depending on the initial OMLD distribution and the TC's translating speed. Wind induced near inertial oscillation of the mixed layer current and subinertial oscillation of the mixed layer depth are found in the wake of the storm. The TC in the atmosphere-only model tends to displace toward the north further than the TC in the coupled model does. The deviation of the two tracks begins to occur after 36 hours. The maximum difference between the tracks is about 89 km occurring at 93 hours. A good correlation is found between the maximum wind speed and the northward deflection of the TC. Results of this study compare favorably with the statistics of the TC's track in the western North Pacific and the North Atlantic. / Source: Dissertation Abstracts International, Volume: 55-04, Section: B, page: 1480. / Major Professor: Richard L. Pfeffer. / Thesis (Ph.D.)--The Florida State University, 1994.

A method is developed for thermodynamic and kinematic analysis by partitioning boundary layer data by parcel vertical velocity and the conservative forms of temperature and moisture using a Lagrangian parcel approach. Large Eddy Simulation (LES) derived data fields were used to develop the partitioning method. The LES model provides sufficiently dense and thermodynamically consistent data, which are not yet available from observational datasets. LES Model data fields are three velocity components, potential temperature, total water mixing ratio, cloud liquid water, turbulent kinetic energy (TKE), and buoyancy. The procedure calculates vertical mixing, vertical transports, and the joint frequency histograms of the turbulent data fields with respect to potential temperature and total water mixing ratio, with a Lagrangian partitioning into strong rising, strong sinking, and weakly moving subsets. / An analysis of boundary layer thermodynamics using datasets from the large eddy simulation (LES) model is used to test the partitioning and analysis method. Observed datasets from the Frontal Air Sea Interaction Experiment (FASINEX) are used for comparative analysis of marine boundary layers and LES results. Results indicate the method is useful in further understanding the diurnal boundary layer entrainment hysteresis cycle, vertical transport, and similar features which develop from the non-Gaussian properties of turbulent boundary layer data. Potential applications of these results in boundary layer modeling are discussed. / Source: Dissertation Abstracts International, Volume: 55-01, Section: B, page: 0131. / Major Professor: Eric A. Smith. / Thesis (Ph.D.)--The Florida State University, 1993.