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Through semi-structured interviews with Mexican climatologists and farmers and others in the agricultural sector in Tlaxcala, Mexico, this study explored how uncertainties posed by both variable climatic and changing political-economic conditions affect the vulnerability of small-scale maize producers. The objective of my research was to assess whether and how small-scale Tlaxcaltecan farmers could use long-lead forecasts to mitigate climatic uncertainty. The potential effectiveness of the climate forecasts was evaluated within the context of cultural, political, social and economic factors that influence the decision-making of smallholder farmers. This research determined that the vulnerability of small-scale producers in Tlaxcala is more a function of political-economic uncertainty than of physical circumstances. While farmers employ complex methods for anticipating climatic events based on religious beliefs and local knowledge, their ability to adapt is constrained by lack of resources. As a result, the success of the forecasts in mitigating small-farmer vulnerability will be limited.

The development of a system capable of continuously monitoring atmospheric brightness temperatures at H₂O and O₂ absorption/emission windows is discussed. Designed for remote (unattended) operation, the system employs radiometric technology and operates at microwave frequencies, thereby achieving essentially all-weather operation. The design, construction and calibration of the radiometer system are described. In addition, some of the physics and mathematics on which the theory of atmospheric radiative transfer is based is presented. Examples of measurements made during the system's first operational performance study is presented along with preliminary calibration calculations. Future work required to refine the measurement and calibration techniques is discussed.

A spectral Chebyshev-collocation method is devised for the 1-1/2 layer non-linear reduced-gravity equations. Following a general description of spectral methods with their application to meteorological and oceanographic problems the implementation of the numerical technique is described. A bicharacteristic scheme is applied to solve the equations at the boundaries incorporating the boundary conditions. This treatment enables stable time integrations (spectral methods in general are very sensitive to boundary errors). A simple transfinite grid generation method is used to construct grids over irregular (non-rectangular) simply-connected domains. / The model is used in a study of the dynamics of Yanai (or mixed Rossby-gravity) wave packets. These are of interest because of the observations of equatorial instability waves (which have the characteristics of Yanai waves) and their role in the momentum and heat budgets in the tropics. A series of experiments is performed to investigate the generation of the waves by simple cross-equatorial wind stress forcings in various configurations and the influence of a western boundary on them. They may be generated in the interior ocean as well as from a western boundary. The observations from all the oceans indicate that the waves have a preferential period and wavelength of around 26 days and 1000 km respectively. This is seen in the model results too and a plausible explanation is provided as being due to the dispersive properties of Yanai waves. / Source: Dissertation Abstracts International, Volume: 53-10, Section: B, page: 5132. / Major Professor: James J. O'Brien. / Thesis (Ph.D.)--The Florida State University, 1992.

Dry deposition of nitrate, estimated from a box model based on NO$\rm\sb{x}$ emissions and rain chemistry monitoring data over the contiguous 48 states, accounts for about half of the total US NO$\rm\sb{x}$ emissions, a deposition flux twice that of measured wet deposition. Thus, total atmospheric nitrate deposition is roughly three times wet only deposition. Ten subregions of wet only nitrate depositions were delineated by EOF analysis from the entire U.S.A., in which each has a narrow range of annual deposition flux and exhibits unique seasonal variation. The study was based on statistical analysis of chemical concentrations measured for more than 10 years in weekly rainfall samples of the National Atmospheric Deposition Program, NADP, and more than 20 years of river water samples of the U.S. Geological Survey, USGS. NO$\rm\sb{x}$ emissions appear to regulate the annual average total deposition fluxes while in the subregions rainfall characterizes the seasonal and shorter term variations in wet only depositions. Atmospheric wet and dry deposition ("acid rain") appears to be the principal source of nitrogen in twelve northern Florida watersheds that range from Pensacola to Gainesville (Escambia to Alachua Counties). River fluxes of total dissolved nitrogen average close to the atmospheric deposition fluxes of nitrate and ammonium ions. Factor analysis was applied to the data sets to resolve principal components: (1) in atmospheric data, that distinguish air pollution nitrate and sulfate from sea salt sodium and chloride, and (2) in surface water data, that distinguish ground water calcium, magnesium, and silica from meteoric water nitrate and sulfate. River concentration ratios N/P in the watersheds are high, averaging twice the Redfield mole ratio N/P = 16 for aquatic plant nutrients. The results indicate that excess dissolved nitrogen could be / temporarily recycled in the watersheds but not retained, so that it could eventually flow to the coastal zone where N may be a limiting nutrient for marine plants. Hydrologic conditions, which exhibit variations on seasonal and longer time scales, play an important role in the transport of nutrients and other species in the rivers. / Source: Dissertation Abstracts International, Volume: 57-04, Section: B, page: 2448. / Major Professor: John W. Winchester. / Thesis (Ph.D.)--The Florida State University, 1996.

Arctic aerosols at Barrow AK from 16 March to 7 May 1986 were sampled and studied for natural aerosols or natural aerosol components as well as pollutants using ion chromatography and proton induced X-ray emission analyses, and a modified principal component analysis receptor model, absolute principal component analysis (APCA). Natural organic acids were found in the aerosols at high concentrations and were likely due to low temperature condensation of acid vapors. By APCA, 20% of non-sea salt sulfate was found to come from oxidation of marine emitted organo-sulfur compounds by means of the tracer methanesulfonate. 80% of sulfate was found in the form of NH$\sb4$HSO$\sb4$. Pollutant coal combustion aerosols, determined from their chemical composition as condensate from gaseous precursors, were found and were traced back to northern Europe during a major haze event by synoptic meteorological studies. Similarly, sea salt aerosols were present and were traced back to either the Beaufort Sea or the remote North Pacific. Dust particles were present in the Arctic throughout the sampling period. Bromine was found to exist in aerosol particles not related to these aerosol components. The size distributions of these aerosol components were obtained by applying APCA to 8 cascade impactor stages, and indicated (1) the sea salt particles were aged and were consistently enriched in chlorine; (2) the dust particles were probably due to long range transport of eolian dust and had absorbed sulfur gases; (3) the coal combustion pollutants were due to gaseous phase condensation; and (4) bromine on particles was due to absorption of bromine gases. Aerosol bromine was found to vary inversely with ozone concentration changes during both day and night time, but only when very low aerosol nitrate was present. When nitrate levels were high, ozone followed the variation in nitrate, / indicating a pollution origin. Movements of ozone-depleted air and ozone-rich air apparently caused very large in situ ozone concentration fluctuations, but the excess bromine-ozone anticorrelation argues for a chemical interaction between them. / Source: Dissertation Abstracts International, Volume: 50-12, Section: B, page: 5681. / Major Professor: John Widmer Winchester. / Thesis (Ph.D.)--The Florida State University, 1989.

The two-dimensional 5 year mean energy transport potential function, based on the Nimbus-7 ERB measurements, shows an east-west coupled dipole structure in which North Africa is the major energy sink and the western Pacific is the major energy source. In conjunction with the dipole, the cross-meridional transports are up to 30% of the tropical north-south transports. This is the main justification for the importance of the east-west energy transport. The separation of the required energy transport into oceanic and atmospheric components based on the maximum entropy production reveals that cross-meridional energy transports in the oceanic areas are mainly achieved by the ocean fluid. / Cloud-radiation feedback shows that cloud-induced longwave warming (cloud greenhouse influence) is dominant over the tropics whereas cloud-induced shortwave cooling (cloud albedo influence) is dominant in the mid- and high-latitudes. These differential distributions result in a global net cloud cooling effect of $-$2.1 Wm$\sp{-2}$. There are three distinct regimes in terms of cloud warming or cooling, i.e. warming in the tropics and in the high latitudes, and cooling in the extratropical latitudes between 20$\sp\circ$ and 55$\sp\circ$. These are in direct correspondence to the meridional three cell circulations, and are consistent with the kinetic energy generation within these cells. Furthermore, cloud-radiation feedback generates zonal available potential energy between 40$\sp\circ$N and 35$\sp\circ$S and destroys it poleward of these latitudes. The cloud-radiation feedback behavior in the three regimes results largely from strong warming due to high-level clouds in the tropics and strong cooling due to middle and low-level clouds at mid-latitudes. / Source: Dissertation Abstracts International, Volume: 51-05, Section: B, page: 2253. / Major Professor: Eric A. Smith. / Thesis (Ph.D.)--The Florida State University, 1990.