The process by which tropical cyclones evolve from loosely organized convective clusters into well organized systems is still poorly understood. Due to the data sparse regions in which tropical cyclones form, observational studies of tropical cyclogenesis are often more difficult than similar studies of land-based phenomena. As a result, many studies of tropical cyclogenesis are limited to either a few case studies or are forced to rely on simulations to examine the genesis process. The recent PREDICT and GRIP field experiments have provided a new opportunity to gain insight into these processes using unusually dense observations in both time and space. The present study aims at using this new data to perform a detailed analysis of the three-dimensional evolution of both kinematic (e.g. vorticity and divergence) and thermodynamic (i.e. temperature and moisture) in both developing and non-developing tropical convective systems in the western Atlantic. By examining these structures relative to one another, the nature of the system evolution can be better understood. In order to better capture the true state of the atmosphere in these systems, a new method of calculating vorticity, divergence, and deformation from non-gridded observations using Green's theorem is also presented. Previous approaches using Green's theorem on a non-uniform data distribution have either used triangular regions, which are easily implemented in computer code, or hand-selected polygonal regions, which are more robust. The method presented here combines both convenience and robustness and is shown to be significantly more accurate than triangle-based methods on a random distribution of observations as well as on flight-path-based distributions. Using this new data and analysis method, five tropical convective systems are analyzed: three non-developing and two developing. Although the analysis includes only a limited number of cases, the results suggest that there is little kinematic difference between the developing and non-developing systems. In most cases, the only significant difference between developing and non-developing systems is in the distribution of humidity. In the developing cases the vorticity maxima are encased in high relative humidity values at all levels. In the non-developing cases the vorticity maximum either extends into regions of dry air or mid-level vorticity generation non-existent, likely due to an excessively dry middle troposphere. Additionally, many of the cases, both developing and non-developing, exhibit evidence of vorticity generation associated, at mid-levels, with a mesoscale convective system and, at low-levels, with deep convective activity. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2012. / June 29, 2012. / Atlantic, cyclogenesis, dropsonde, hurricane, tropical / Includes bibliographical references. / Robert E. Hart, Professor Directing Thesis; Mark Bourassa, Committee Member; Vasu Misra, Committee Member.

Emission of mercury from the burning of coal is considered one of the important anthropogenic sources of atmospheric mercury. Along with current measurements of the isotopic composition of atmospheric mercury being conducted in our laboratory, we have analyzed mercury emitted from a coal fired power plant. Biswas and others (2008) previously reported variations in the isotopic composition of mercury in samples of coal deposits. Since the combustion of coal is expected to release virtually all its mercury, we expect similar isotopic patterns in coal and total emitted mercury. The emitted mercury exists in various physical and chemical forms, each possessing distinct properties that affect atmospheric transport. Flue gases have been sampled in the stacks of a coal-fired electric power plant. The Ontario Hydro method was used to collect mercury of the flue gases. The method, a modification of EPA method 29 uses oxidant solutions (KCl, H2O2-HNO3 and KMnO4-H2SO4) in its sampling train. In addition gaseous reactive mercury was sampled downwind in large volume rain samples. The measurements shows a similar mass independent fractionation with coal samples. But, displays a wide range of mass dependent fractionation (δ198Hg -1.239 to 2.294). We found that samples in Hg2+ are light isotope enriched, while in Hg0 these are reverse. Plant specimens collected from an altitudinal range of 3700 to 4500m above sea level in the Zhada Basin in southwesten Tibet were identified into species and analyzed for their stable carbon isotopic compositions. These plants represent 35 species and 11 families. Their stable carbon isotope ratios (δ13C) show that although C3 plants are the dominant vegetation in local ecosystems a few C4 plants also exist in the study area in the warmest months. The C4 grasses found in the Zhada Basin are Achnatherum splendens and Pennisetum flaccidum of the family Graminaea, Atriplex centralasiatica and Salsola ruthenica of the family Chenopodiaceae and Poa lahulensis of Poaceae . The δ13C data indicate that among the 35 plant species found in the Zhada basin, 30 are C3 plants (31 samples representing 30 different species) and have δ13C values ranging from -30.3 / to -21.1 /, with a mean of -25.1+2 / (n=31). C4 grasses (6 samples representing 5 different species) from the basin yielded δ13C values ranging from -15.6 / to -13.6 /, with a mean of -14.3+0.7 / (n=5), and account for ~14% of all species collected. The discovery of C4 species in the Zhada Basin shows that C4 plants can exist at high elevations though they are few in number as cold conditions do not favor C4 grasses. The stable carbon isotope (δ13C) analysis of tooth enamel from modern herbivores show that C4 grasses do not contribute significantly to the diets of modern herbivores in the Zhada Basin and thus confirm the current dominance of C3 vegetation in the area. Stable isotope analyses of tooth enamel from both fossil and modern herbivores were used to reconstruct the modern and ancient diets and paleoenvironment of the Zhada Basin, southwestern Tibetan Plateau. The δ13C values of enamel samples from wild Tibetan ass (Equus kiang) and domestic cows (Bos primigeniuss) from the Zhada Basin are -9.4 /, which indicate a diet comprising predominantly of C3 plants and are consistent with the current dominance of C3 vegetation in the area. However, some of the serial samples from the Bos primigenius show δ13C values higher than -8 /, which suggests the consumption of small amounts of C4 grasses and/or CAM plants by the Bos primigenius. The bulk enamel-δ13C values of fossil herbivores including Hipparion, Rhinocerotidaes, Bovidaes, Elephantidaes and Cervidae are -9.2 ±0.1 /, indicating that these ancient mammals, like modern herbivores in the area, fed primarily on C3 vegetation and lived in an environment dominated by C3 plants. The δ18O values of serial tooth enamel samples from modern herbivores show intra-tooth variations of ~2-5 /. The oxygen isotope ratios (δ18O) of fossil herbivores are more negative relative to those of modern Bos primigenius and Tibetan asses. There is no inverse correlation between δ13C and δ18O values within individual fossil teeth from 5.3 to 3.5Ma, confirming that little or no C4 grasses were consumed in the basin from 5.3 to 3.1 Ma is consistent with the bulk enamel isotope data. The intra-tooth δ18O variations of fossil herbivores ranged from ~ 1 to ~5 /, similar to those observed in modern teeth. The present day climate in the Zhada Basin is cold and does not favor the growth of C4 grasses. Although C4 plants have been found in the Zhada Basin, they do not contribute significantly to local biomass as well as herbivores' diets as indicated by the enamel δ13C values. The bulk and serial isotope data suggest that cold and C3-dominated environments have been a feature of the Zhada Basin since at least 5.3 Ma. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2012. / February 8, 2012. / CARBON ISOTOPES, FLUE GASES, LATE CENOZOIC MAMMALS, MERCURY ISOTOPES, OXYGEN ISOTOPES, TIBETAN PLATEAU / Includes bibliographical references. / A Leroy Odom, Professor Co-Directing Dissertation; Yang Wang, Professor Co-Directing Dissertation; Gregory M. Erickson, University Representative; Vincent Salters, Committee Member; Lynn Dudley, Committee Member.

ABSTRACT High-resolution biostratigraphic data were collected from two cores drilled in 2007 and 2009 by the United States Geological Survey at the South Dover Bridge (SDB) and the Cambridge-Dorchester (Cam-Dor) Airport in eastern Maryland. The objectives of this study are to assess the down-core diatom abundances in order to build on a biostratigraphic framework that has been established for the Miocene Calvert Formation (Chesapeake Group) of the Atlantic Coastal Plain. Samples were prepared using a strewn mounting method and examined via light microscopy for relative abundances. The Shannon diversity index was used to measure the species richness throughout the cores, and hierarchical cluster analysis was used to group the diatoms to determine the degree of similarity between species and to determine whether other relationships between species and depths could be measured. The biostratigraphy was used to infer paleoecology, climatic trends, and sea-level fluctuations as well as to correlate between the two cores. Existing calcareous nannofossil zonations were used to provide age control for the South Dover Bridge core based on a modified version of the East Coast Diatom Zonation (ECDZ) of Andrews (1976). Using this zonal scheme, both cores were assigned relative ages throughout the sampled section. Five zones were identified in the SDB core (ranging from Middle Burdigalian to Middle Serravalian) and four at the Cam-Dor site (Upper Burdigalian to Middle Serravalian). The Cam-Dor core penetrated a thicker section. The first occurrences of marker diatom species and the presence of an unconformity at both sites were used to correlate between the two sections. The diatom assemblages present are indicative a shallow-marine shelf environment that experienced fluctuations in sea level and were influenced by high energy events. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2012. / March 13, 2012. / biostratigraphy, Calvert, diatom, paleoecology / Includes bibliographical references. / Sherwood Wise, Professor Directing Thesis; James Tull, Committee Member; William Burnett, Committee Member.

Accurate forecasting of seasonal rainfall is important for many areas of commerce, including, but not limited to, agriculture, manufacturing, and power generation. There have been several studies addressing the predictability of rainfall variations over South America and the Amazon basin. The use of coupled atmospheric-ocean numerical models to predict these anomalies has had mixed results. A primary factor leading to model inaccuracy in precipitation forecasts is the coarse resolution data utilized by coupled models during the initialization phase. By using MERRA reanalysis and statistical downscaling along with the superensemble methodology, it is possible to obtain more precise forecasts of rainfall anomalies over tropical South America during austral fall. Selective inclusion (and exclusion) of superensemble member models also allows for increased accuracy. Improvement in individual member models is also possible on smaller spatial scales and in regions where substantial topographical changes were not handled well under original model initial conditions. The combination of downscaling and superensemble methodologies with other research methods presents the potential opportunity for increased accuracy not only in seasonal forecasts but on shorter temporal scales as well. / A Thesis submitted to the Department of Earth, Ocean & Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2012. / June 15, 2012. / Amazon, downscaling, monsoon, precipitation, South America, superensemble / Includes bibliographical references. / Paul Ruscher, Professor Directing Dissertation; Guosheng Liu, Committee Member; Vasu Misra, Committee Member.

Offshore resource assessment relies on estimating wind speeds at turbine hub height using observations typically made at substantially lower height. The methods used to adjust from observed wind speeds to hub height can impact resource estimation. The importance of directional sea state is examined, both as seasonal averages and as a function of the diurnal cycle. A General Electric 3.6 MW offshore turbine is used as a model for a power production. Including sea state increases or decreases seasonally averaged power production by roughly 1%, which is found to be an economically significant change. These changes occur because the sea state modifies the wind shear (vector wind difference between the buoy height and the moving surface) and therefore the extrapolation from the observation to hub height is affected. These seemingly small differences in capacity can alter profits by millions of dollars depending upon the size of the farm and fluctuations in price per kWh throughout the year. A 2% change in capacity factor can lead to a 10 million dollar difference from total kWh produced from a wind farm of 100 3.6MW turbines. These economic impacts can be a deciding factor in determining whether a resource is viable for development. Modification of power output due to sea states are shown for seasonal and diurnal time scales. Three regions are examined herein: West Florida, East Florida, and Nantucket Sound. The average capacity after sea state is included suggests areas around Florida could provide substantial amounts of wind power throughout three-fourths of the calendar year. At certain times of day winter average produced capacity factors in West Florida can be up to 45% more than in summer when sea state is included. Nantucket Sound capacity factors are calculated for comparison to a region near a planned United States offshore wind farm. This study provides evidence to suggest including sea state in offshore wind resource assessment causes economically significant differences for offshore wind power siting. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2012. / May 29, 2012. / Florida, sea state, weather patterns, wind power / Includes bibliographical references. / Mark Bourassa, Professor Directing Thesis; Robert Hart, Committee Member; Mark Powell, Committee Member; Philip Sura, Committee Member.

Validation of satellite-based precipitation products to gauge networks in new locations is key to furthering our understanding of current satellite datasets and developing better datasets in the future. In this study, the Tropical Rainfall Measuring Mission (TRMM) 3B43 monthly average product is compared to gauge data from Cameroon, Gabon, and Malawi. The product is validated using the 2.5° x 2.5° method laid out by Xie and Arkin (1995) in conjunction with locally collected gauge data. It is shown to be reliable even though it struggles with local geography. Further validation of TRMM 3B43 at a 1° x 1° resolution shows there is insufficient data in this study to make an accurate statement on its validity, but the results are relatively positive. / A Thesis submitted to the Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2012. / June 27, 2012. / TRMM, Validation / Includes bibliographical references. / Sharon Nicholson, Professor Directing Thesis; Mark Bourassa, Committee Member; Vasubandhu Misra, Committee Member.

The Great Smokey Group and the Mineral Bluff Group of the southern Appalachians Blue Ridge contain units of metaconglomerate that contain stretched quartz pebbles. Quartz pebbles have been widely used as strain markers in conglomerates. Metaconglomerate strain results of both groups (obtained by using Rf/Ø and Fry methods on two principle strain planes XZ, YZ),show that there are no significant differences between the strain in the Great Smokey Group and the Mineral Bluff Group. The consistent strain results, the unstrained status of the strain markers, the χ2 and Isym tests of Lisle (1985), the symmetrical distribution of the Rf and Ø data along the line of maximum stretching orientation, and the same oblate to almost plane deformation in both Groups (obtained by plotting k values on Flinn diagrams), support that Great Smoky Group and the Mineral Bluff Group were deformed by the same deformation and probably at the same time. This deformation had to be younger than Middle Ordovician (the minimum age of the Mineral Bluff Group); indicating the deformation has to be associated with the Acadian orogeny or younger (neo-Acadian). Therefore, there was no deformation between the Great Smokey Group depositional time (Late Neoproterozoic) and the Mineral Bluff Group depositional time (< Middle Ordovician). During the neo-Acadian deformation the Murphy belt was shortened about 32% in the minimum strain axis direction, Z (N67W 65NW), extended about 6% in the direction of the intermediate strain axis direction, Y (S89E 25SE), and extended about 44% in the direction of the maximum stretching axis, X (S7W 9SW). This study also concluded that the easiest relief for the rocks as a response to the compression (during the neo-Acadian event) in the Z direction was mainly in the direction of X with less flow and extension in the Y direction as the crustal load above the rocks prevented more extension in that direction. There is no difference in the strain values between the northern and middle parts of the Murphy syncline, therefore, the Jasper fold (a later event after Murphy syncline development) was too weak to change or to overprint the earlier deformation that x produced the Murphy syncline and the mineral elongation. The strain results were also correlated across the Murphy syncline (E-W). The two limbs strain results are also consistent with no considerable difference in the results. A component of this study was to correlate the results of the essentially different computational methods used for strain analysis. All the software produces almost the same results for the same sample, indicating that all software used in this study are suitable to be used for similar strain study. The two methods also show no significant difference between their results on two different scales(thin section and bulk sample); indicating that ductility contrast does not significantly affecting the strain values. Therefore, the pebbles represent the whole rock strain. It is concluded by this study that Rf/Ø and Fry methods are suitable to be used for strain analysis on quartz pebbles of conglomerates, if the quartz is abundant on both scales (hand specimens, and thin sections). / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall, 2011. / August 3, 2011. / Fry, Murphy Syncline, Rf/Phi, Strain Analysis / Includes bibliographical references. / James F. Tull, Professor Directing Dissertation; Kamal Tawfiq, University Representative; A. Leroy Odom, Committee Member; Stephen A. Kish, Committee Member.

Heat fluxes at the air-sea interface are an important component of the Earth's heat budget. In addition, they are an integral factor in determining the sea surface temperature (SST) evolution of the oceans. Different representations of these fluxes are used in both the atmospheric and oceanic communities for the purpose of heat budget studies and, in particular, for forcing oceanic models. It is currently difficult to quantify the potential impact varying heat flux representations have on the ocean response. In this study, a diagnostic tool is presented that allows for a straightforward comparison of surface heat flux formulations and atmospheric data sets. Two variables, relaxation time (RT) and the apparent temperature (T*), are derived from the linearization of the bulk formulas. They are then calculated to compare three bulk formulae and five atmospheric datasets. Additionally, the linearization is expanded to the second order to compare the amount of residual flux present. It is found that the use of a bulk formula employing a constant heat transfer coefficient produces longer relaxation times and contains a greater amount of residual flux in the higher order terms of the linearization. Depending on the temperature difference, the residual flux remaining in the second order and above terms can reach as much as 40-50% of the total residual on a monthly time scale. This is certainly a non-negligible residual flux. In contrast, a bulk formula using a stability and wind dependent transfer coefficient retains much of the total flux in the first order term, as only a few percent remain in the residual flux. Most of the difference displayed among the bulk formulas stems from the sensitivity to wind speed and the choice of a constant or spatially varying transfer coefficient. Comparing the representation of RT and T* provides insight into the differences among various atmospheric datasets. In particular, the representations of the western boundary current, upwelling, and the Indian monsoon regions of the oceans have distinct characteristics within each dataset. Localized regions, such as the eastern Mexican and Central American coasts, are also shown to have variability among the datasets. The use of this technique for the evaluation of bulk formulae and datasets is an efficient method for identifying the unique characteristics of each. Furthermore, insight into the heat fluxes produced by particular bulk formula or dataset can be gained. / A Thesis submitted to the Department of Earth Ocean and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2012. / December 5, 2011. / Comparison, Data Sets, Heat Flux, Linearization / Includes bibliographical references. / Eric Chassignet, Professor Co-Directing Thesis; Mark Bourassa, Professor Co-Directing Thesis; Philip Sura, Committee Member.

A large fraction of the continental shelf is covered by permeable sediments that are flushed by wave, wind, and tide generated bottom currents. Elevated dissolved organic carbon (DOC) concentrations in coastal zones, a diverse and abundant sediment microbial community, and advective filtration of seawater through the surface layers of permeable sediments, make these environments important zones for the cycling of organic matter. This research investigates the role of permeable sediments in the dynamics of two central components of the carbon cycle: DOC and oxygen. In Chapter 2, published in Limnology & Oceanography, I investigate decomposition rates and compositional changes of DOC when filtered through permeable sediments contained in laboratory column reactors. Substantial amounts of DOC were mineralized in the sediments and could be linked to incorporation by aerobic and anaerobic microbes. In DOC pore-water profiles measured at two study sites with permeable sediment, we observed a concave shape of the profiles in the upper 10 cm of permeable sediment resulting from transport of DOC with advective pore water flows into the sand, and DOC decomposition in the subsurface layers. We found that the flushed sand layer between the water column and deeper anoxic sediment layers acts as an effective DOC filter, with subsurface horizontal pore-water flows promoting decomposition of DOC, suggesting that permeable sediments play a key role in the cycling of organic matter. In Chapter 3, submitted to Continental Shelf Research, I use the findings of Chapter 2 for the interpretation of field time series data of DOC, DIC, and TN concentrations in the water column and coastal sediment pore waters. We use these time series to investigate the spatial and temporal dynamics of dissolved organic matter and how benthic pelagic coupling influences DOC concentrations in the permeable sediments. Our results reveal that DOC in the upper layer (0-12 cm) of the shallow sands is controlled by benthic-pelagic coupling facilitated by advective pore water filtration modulated by the regional wave climate. For the quantification of oxygen fluxes in the permeable coastal sands resulting from the benthic organic matter production and consumption and the current-induced sediment flushing, I deployed the eddy correlation technique. In order to make this technique more suitable for our shallow coastal zone with relatively rough hydrodynamic conditions (as compared to deeper marine environments), we adapted existing eddy correlation instruments for use with more durable and repairable oxygen optodes. This development is described in detail in Chapter 4 that has been submitted for publication in Limnology and Oceanography Methods. Our results show that optodes have a comparable response time to electrodes, produce similar fluxes in field deployments, and are a viable alternative for use with the eddy correlation measurement in coastal environments with strong currents and wave action. These hydrodynamic conditions are an important factor controlling production and decomposition processes at the sediment-water interface and within the sediment because they can largely control the availability of DOC and oxygen to microbial communities in the sediments. In Chapter 5, which is presently is being prepared for submission to Marine Ecology - Progress Series, we investigate the relationship between flow, wave height, DOC concentration, temperature, light, and the benthic oxygen fluxes. The results reveal a large range of production and consumption rates in the permeable coastal sediments with distinct seasonal changes. The latter are caused by the availability of degradable organic matter and the magnitude of the pore water flushing process that carries these organic substrates and oxygen into the permeable coastal sands. We conclude that the highly degradable DOC produced by pelagic and benthic primary producers enhances water column - sediment biogeochemical coupling in the coastal zone thereby increasing the contribution of the sediment surface layer in the cycling of carbon and nutrients. / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2011. / November 3, 2011. / Benthic flux, Carbon degradation, DOC, Oxygen, Permeable sediment / Includes bibliographical references. / Markus Huettel, Professor Directing Dissertation; William Cooper, University Representative; Peter Berg, Committee Member; William Dewar, Committee Member; Joel Kostka, Committee Member; Ian MacDonald, Committee Member.

Climatologists have been paying much attention to the question of how the climate of the northern hemisphere would change if the Atlantic Meridional Overturning Cell (AMOC) were to slow down. Since less heat would be released to the atmosphere, it has been suggested that a slow down of the AMOC would cause the northern hemisphere to cool. There are large international observational programs focusing on the question of how much the AMOC will slow down and how much the atmosphere will cool. Our research uses a sequence of nonlinear analytical models to show that the northward heat transport by the AMOC is very large compared to the heat released from the AMOC to the atmosphere and due to the non-linearity of the system even changes of 50% in the AMOC transport hardly change the atmospheric temperature. Our most realistic atmospheric convection model involves a warm oceanic current losing heat to an otherwise motionless and colder atmosphere. As a result of this heat exchange, the atmosphere convects and the generated air flow ultimately penetrates horizontally into the surrounding air in a way similar to the airflow in the familiar heat-island problem. The heat exchange near the air-sea interface follows the familiar bulk formulae and the compressible, convective atmosphere penetrates into a stably stratified atmosphere with a constant lapse rate (outside the convective region). This research illuminates the critical importance of the four key aspects of the heat exchange process: (i) the non-linear dependence of the atmospheric mass transport on the ocean mass transport, (ii) the dependence of the atmospheric transport on the ocean heat capacity and the large heat capacity ratio of water to air (~4) (iii) the proportionality of the heat-flux to the temperature difference between the ocean and the air (for our simplest conceptual models where saturation specific humidity, Bowen ratio, relative humidity are assumed to be constant), and (iv) the fact that the ocean is warmer (by 10-20 degrees) than the air above it. These four aspects of the problem combine in the non-linear system and lead the system to a saturation state where even significant changes in the AMOC have almost no effect on both the ocean/air heat-flux and the resulting outgoing atmospheric temperature. In the hypothetical limit of infinitesimally large specific heat capacity of water, there is no change in the atmospheric transport or the temperatures of the ocean and the atmosphere, regardless of the reduction in the AMOC transport. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2012. / April 2, 2012. / air, convection, heat-flux, ocean, overturning / Includes bibliographical references. / Doron Nof, Professor Directing Dissertation; Mark Bourassa, University Representative; Allan Clarke, Committee Member; Georges Weatherly, Committee Member; William Burnett, Committee Member.