The model presented extends Charney (1947) model by including Newtonian cooling, Ekman dissipation, linear vertical variation of the stratification parameter and nonlinearity. / The unstable Green modes are similar in many respects to the transient planetary waves: They tilt westward with height in the troposphere and feature a barotopic structure in the stratosphere. They may extend up to 5-6 scale heights before being trapped and exhibit a major peak in the stratosphere. The wavelength (growth rate) of the most unstable Green mode is about three times (1/3 to 2/5) of that of the most unstable Charney mode. Its available potential energy is converted in the lower troposphere, as well as in the stratosphere, and its kinetic energy is generated in both the middle troposphere and the middle stratosphere, with significant destruction near the tropopause. / The vertical increase of the static stability reduces the wavelength of the most unstable modes and affects considerably the growth rate and vertical structure of the Green modes. / The evolutions of the finite amplitude Green modes in the presence of realistic (beta)-effect and moderate internal or Ekman dissipation lead to steady (propagating or stationary) wave states which are always stable to small perturbations. No stable limit cycles or chaotic behaviors are found. The approach to steady wave states may exhibit either a monotonic or a damped oscillatory behavior depending upon the relative magnitudes of the inviscid growth rate and the dissipation. / The Ekman dissipation does not affect wave tilt, while the internal dissipation changes wave tilt by adding a westward component so that the constant phase line, while oscillating, may tilt westward throughout the entire vacillating cycle. As a result, the horizontal heat flux is directed poleward even when the wave decays. The Ekman dissipation may yield a large amplitude, steady wave solution which depends on initial conditions and does not depend on the dissipation and shear supercriticality. In sharp contrast, the internal dissipation may lead to a relatively small amplitude, steady wave solution which does not depend on the initial conditions but depends on the dissipation and the supercriticality. / In a continuous model, the Ekman dissipation never displays a destabilizing effect, while a small amount of Newtonian cooling destabilizes both the wave-free zonal flow near the inviscid critical points and the nonlinear system. / Source: Dissertation Abstracts International, Volume: 45-08, Section: B, page: 2583. / Thesis (Ph.D.)--The Florida State University, 1984.

Since 1950, the West African Sahel has exhibited unusual multi-decadal persistence in rainfall anomalies. Wet conditions were prevalent in the 1950s while drought has existed since the late 1960s. The Kalahari, the southern hemisphere counterpart to the Sahel, has not demonstrated any persistence longer than three or four years. It has been hypothesized that large-scale phenomena initiate drought while land surface-atmosphere feedbacks perpetuate it. / To approach this theory, an updated version of Lettau's three-part climatonomy model is used. Using incoming solar radiation and observed precipitation, the model calculates ground-absorbed solar radiation, evapotranspiration, soil moisture, runoff, all surface radiation and energy balance fluxes, as well as surface and atmospheric temperatures. A typical Sahelian station was used to revise and verify the model. The model was then applied to mean conditions at several stations of various climatic types in West Africa and Southern Africa. Mean hydrologic and surface energy budget parameters between wet and dry years were compared. Finally, model output was used to derive spatial fields of hydrologic and surface energy parameters for both the Sahel and the Kalahari and to approximate the effect of surface energy flux modification upon mid-tropospheric wind dynamics. / Several interesting results emerge from these simulations. Significant modification of latent and sensible heat has occurred over the Sahel since 1950, more so than in the Kalahari. It has also been shown through thermal wind calculations that latent heat flux changes have altered the strength of the Africa Easterly Jet, and hence, possibly the rain bearing systems as well. / Source: Dissertation Abstracts International, Volume: 53-07, Section: B, page: 3541. / Major Professor: Sharon E. Nicholson. / Thesis (Ph.D.)--The Florida State University, 1992.

One of the major limitations of tropical hydrostatic mesoscale models initialized through synoptic and subsynoptic scale data and operating on a grid resolution of 20-50km is that they show limited skill in simulating the spatial and temporal distribution of precipitation despite well-predicted synoptic and subsynoptic-scale flow patterns. In general the models show a precipitation spin-up phase, however once activated, the model tends to become convectively overactive through the synoptic scale-mesoscale feedback mechanism. Our experience suggests that for the tropics where the mesoscale circulations are convectively active, the precipitation spin-up arises from the inability of the initial synoptic-scale analysis to produce dynamic, thermodynamic and moisture fields capable of supporting convection on the mesoscale. In particular, the problem lies in the wrong initial analysis of the velocity divergence and moisture fields. The overactive convection in the model arises when the model fails to initiate convection over some of the areas that are observed to precipitate, hence feeding the available moisture into the model activated regions. / It is shown in this study that this spin-up and overactive convection problem can be overcome by carrying out a dynamic Newtonian assimilation coupled with physical initialization during a preforecast integration phase of the model. In particular it is shown that the Newtonian assimilation of the rotational component of the wind and surface pressure coupled with physical initialization of surface fluxes of moisture, cumulus parameterization and outgoing longwave radiation (OLR) enables the model to build the divergence and moisture fields at the required location. The cumulus initialization is done through a humidity reanalysis via a "Reverse Kuo" algorithm. The surface latent heat flux initialization is done by reanalysis of the model's lowest level humidity fields through a "Reverse similarity algorithm", and the OLR initialization is done through a humidity reanalysis at the upper levels by matching the model OLR with satellite observations. / Source: Dissertation Abstracts International, Volume: 53-07, Section: B, page: 3543. / Major Professor: T. N. Krishnamurti. / Thesis (Ph.D.)--The Florida State University, 1992.

A hypothesis, concerning the spatial scale of the onset of the Asian southwest monsoon of the Northern Hemispheric summer, is put forth. It is implied, from the large scale climatology of the tropospheric motion and temperature fields in May and June, that the monsoon onset is characterized by radical changes in the tropical circulations on a planetary scale. A suitable framework for the quantitative definition of this phenomenon, i.e., the atmospheric energetics in the zonal wavenumber domain, is reviewed. Global tropospheric wind and temperature data for periods surrounding the Indian monsoon onset cases of 1973, 1977 and 1979 are utilized. It is found that the kinetic and available potential energy of the sum of zonal wavenumbers 1, 2 and 3 (defined as the planetary scale waves) increase by about 30 to 50% on the time scale of about 1 week, corresponding to Indian (regional) onset. This increase characterizes the planetary scale onset. From the point of view of scale interactions, the observational calculations show that the planetary scale eddies, in general, supply available potential and kinetic energy to other (zonal mean and sub-planetary) scales during the onset although there are some interesting time variations. It is concluded that additional mechanisms must play the dominant roles in the planetary scale onset. / To determine a more complete energetics for the onset using a dynamically more consistent set of atmospheric observations, an NWP experiment, for the 1979 onset case, is conducted. A global, multi-level, primitive equation spectral model containing a variety of physical effects parameterizations is described in detail. The results of a 96-hour prediction are compared to the observed circulation and rainfall patterns over the Indian Ocean region and the model is seen to reproduce the broad scale synoptic features of the onset fairly well. An analysis of the model diagnosed energetics (for the planetary scale waves) reveals that deep cumulus convection, organized on a planetary scale, is the dominant physical mechanism for the onset. This forcing is most pronounced near the southern Tibetan plateau and over Indochina. The role of this and other heat sources in the monsoon evolution is discussed. / Source: Dissertation Abstracts International, Volume: 44-09, Section: B, page: 2786. / Thesis (Ph.D.)--The Florida State University, 1983.

Radar statistics of convective elements generated in the past decade show lognormal frequency distributions of echo areas, heights and durations. An explanation for the genesis of these distributions, based on the interrelationship between cloud groups and the environment, is proposed. / A closed cumulus ensemble model that makes explicit use of the lognormal distribution function has been developed. In this model, the cloud ensemble is spectrally divided into sub-ensembles, and each of these is characterized by its cloud top pressure. The ensemble-averaged values of cloud characteristics are controlled by the large-scale environment. In return, the cloud ensemble modifies the environment through compensating subsidence, entrainment, downdrafts and lateral and final detrainments. Application of the model to the GATE (Global Atmospheric Research Program's Atlantic Tropical Experiment) data sets predicts rainfall rates and the profiles of large-scale apparent heat source and moisture sink. The results agree reasonably well with the observations under various synoptic situations. / Source: Dissertation Abstracts International, Volume: 47-06, Section: B, page: 2476. / Thesis (Ph.D.)--The Florida State University, 1986.

Radiation data from the Backscatter Ultraviolet (BUV) instrument on Nimbus 4, although designed for retrieval of total ozone and ozone profiles above the ozone maximum, were used in an empirical method to extrapolate ozone profiles to the lower stratosphere. Ozone data and radiation data were first decomposed into eigenvectors and associated coefficients. Since the coefficients are orthogonal to each other, they form linearly independent data sets which were regressed in a least squares manner forming a basis from which retrievals were obtained. Retrieved profiles were found to be stable and well correlated with observed profiles. / After the retrieved profiles were found to correlate with observed profiles, a year of retrieved data were analyzed to yield daily synoptic maps. A synoptic-climatological study was done using the maps, focusing on the winter of 1970-71 for the synoptic study. The climatological study encompassed the full year of analyzed maps. Comparisons were made with other studies of climatological data and numerical models, including transport mechanisms. A figure of 50 metric tons per second of vertically integrated fluxes by the eddies across a latitude circle at high latitudes during the winter corresponds to observational and numerical studies. / Source: Dissertation Abstracts International, Volume: 47-07, Section: B, page: 2964. / Thesis (Ph.D.)--The Florida State University, 1986.

Source: Dissertation Abstracts International, Volume: 30-05, Section: B, page: 2355. / Thesis (Ph.D.)--The Florida State University, 1969.

Two (beta)-plane planetary wave models are used to study ozone transport in the stratosphere. In the first model, ozone transport is calculated for steady, dissipative planetary waves using the Eulerian, Lagrangian-mean, and residual circulations. A Lagrangian model of parcel dynamics is used to interpret planetary wave-photochemistry interaction. In chemically active regions the mean field ozone changes are found to be significant only where there are large gradients in chemical sources and sinks along particle trajectories. The largest changes in the mean field are found in the lower stratosphere and are due to the Lagrangian-mean advection. / In the second model, ozone transport is calculated for the combined diabatic and time dependent planetary wave circulations. Both circulations are instrumental in the formation of the polar spring ozone maximum. The diabatic circulation transports ozone into the lower stratosphere, and planetary waves transport large amounts of ozone northward during sudden and final warmings. Using the transport mechanisms revealed in these models, a scenario is deduced to explain observed large scale ozone transport phenomena. / Source: Dissertation Abstracts International, Volume: 43-07, Section: B, page: 2243. / Thesis (Ph.D.)--The Florida State University, 1982.

200 highly accurate balloon soundings taken at 44(DEGREES)N, 1(DEGREES)W in the Southwest region of France are analysed, using the multiple filtering technique of (Dziewonski et al. 1969). / Inertio-gravity waves having periods between 6 and 17 hours, horizontal wavelengths between 800 and 1250 km and vertical wavelengths between 1200 and 1600 m are isolated from the data. A stability analysis shows that these waves are generated in the Troposphere by a mixed inertia-shear instability and propagate upwards in the Stratosphere. Evidence is presented to prove the existence of inertial waves in the atmosphere as well as the mechanism by which they are generated. / Results obtained from the data are compared to the theory and a fair agreement is found. It is also shown that flux divergence of heat and momentum within this lower range of the inertio-gravity wave spectrum is not capable of transporting momentum upwards into the Mesosphere to bring about the kind of temperature gradient and wind reversals in the context of the Holton-Matsuno theory. / The wave spectrum is found to follow a -5/3 inertial subrange slope with an energy cascade towards high wavenumbers. The universal constant (,(PROPORTIONAL)) is found to lie betwen 1.5 and 11, supporting some findings by (Lilly, 1983) who found a value of 9.8. / Source: Dissertation Abstracts International, Volume: 45-11, Section: B, page: 3534. / Thesis (Ph.D.)--The Florida State University, 1984.

Source: Dissertation Abstracts International, Volume: 41-01, Section: B, page: 0236. / Thesis (Ph.D.)--The Florida State University, 1979.