Carbon dioxide is the most important greenhouse gas and the major factor leading to the global climate change problem. In previous studies, the ocean is considered to be the major storage of anthropogenic carbon dioxide. However, evaluation of the global CO2 flux seldom includes the estuarine and coastal regions. It should be noted that the current estimate is based on a very limited data set. In particular, data from subtropical and tropical river estuaries are scarce. Many researches point out that the estuary is a CO2 source to the atmosphere, but the data is insufficient so one couldn¡¦t obtain the total CO2 flux accurately. In this study, our team sampled 25 estuaries based on field surveys covering four seasons in Taiwan, aiming to better quantify the estimation of CO2 flux in the coastal regions. The dissociation constants of carbonic acid are unavailable to calculate the fCO2 in the low salinity (S<1). Therefore, the difference (%) between measured and calculated is very large but will be reduced with increasing salinity. Furthermore, in the process of measuring total alkalinity and pH, accuracy may reduce because of humic acid and variations of ionic strength. No matter in the western or eastern estuaries, most of fCO2 values is higher than the atmosphere. And they decrease downstream with increasing salinity. The fCO2 is higher in the west than in the east, because of human activities. Neither group of estuaries shows obvious seasonal variability. The fCO2 in the estuaries has a relationship with salinity, because of mixing with sea water. Because fCO2 is controlled by biological activity, it also has a relationship with AOU, pH and nutrients (NO3- and PO43-). In the east, the fCO2 has no correlation with many parameters. It is probably that the slope is steeper and the river length is shorter in the east than in the west resulting in short resident time. So that many reactions are not complete before the water exports to the sea. The average water-to-air CO2 flux is 24.6¡Ó19.2 (mol C m-2 y-1), which is 3.5 times the value of Pearl River (6.9 mol C m-2 y-1) but similar to the world average (23.7¡Ó33.1 mol C m-2 y-1). The CO2 flux is the highest in spring (81.7¡Ó15.8 mmol C m-2 d-1) and the lowest in winter (54.1¡Ó132 mmol C m-2 d-1). Upper/mid/lower estuaries are operationally defined as those areas of estuaries with salinities below 2, between 2 and 25, and above 25, respectively. The trends of fCO2 have good relationships with AOU and PO43- in the upper estuaries. The reason is probably caused by human activities and biological respiration. The phenomenon is more complex in the mid than in the upper estuaries. Consequently, the fCO2 has a good correlation with pH and DIC in the mid estuaries as a result of organic matter decomposition. However, in the lower estuaries, the variation of fCO2 is subjected to biological respiration and mixing with sea water. The fCO2 is the highest in the upper estuaries (2228¡Ó92.0 uatm)¡Athe average water-air CO2 flux is 42.3¡Ó1.54 (mol C m-2 y-1). Measured fCO2 in the mid estuaries is 1302¡Ó353 (uatm) and the average CO2 flux is 25.8¡Ó1.26 (mol C m-2 y-1). The lowest fCO2 (559¡Ó14.9 uatm) is found in the lower estuaries and the CO2 flux is 7.38¡Ó7.45 (mol C m-2 y-1). The 106 estuaries of the globe are divided into three parts by salinity. The fCO2 is 3033¡Ó1078, 2277¡Ó626 and 692¡Ó178 uatm in the upper, mid and lower estuaries, respectively. The average CO2 flux is 68.5¡Ó25.6¡B37.4¡Ó16.5 and 9.92¡Ó15.2 mol C m-2 y-1, respectively. Geographically estuaries in all three latitude bands (¡Õ23.5o, 23.5-50o and ¡Ö50o) are generally sources of CO2. Interestingly, water-to-air fluxes do not significantly, and all fall around 24 mol C m-2 y-1 although the flux is slightly lower at high latitude. The water in estuaries release CO2 in all seasons although the flux seems to be highest in autumn (73.2¡Ó 93.4 mmol C m-2 d-1) and lowest (53.4¡Ó65.1 mmol C m-2 d-1) in winter. The average CO2 flux is 23.9¡Ó33.1 mol C m-2 y-1, and the total CO2 flux is 0.26 Pg C y-1. Next, we estimate the tropical rivers¡¦ carbon fluxes using carbon parameters concerning 175 rivers globally between 30oN and 30oS. The specific DIC yield (flux/area) are 0.63, 3.33, 9.79 and 3.38 g C m-2 y-1 in tropical Africa, the Americas, Asia and Oceania, respectively. The DIC flux in Asia is the highest among the four regions, mainly because the percentage of carbonate rock is highest there and the second highest water discharge there. The PIC fluxes are 7.40¡Ñ1012 g C y-1 in Africa, 2.82¡Ñ1013 g C y-1 in the Americas, 1.53¡Ñ1013 g C y-1 in Asia and 2.49¡Ñ1011 g C y-1 in Oceania. The DOC fluxes are 2.80¡Ñ1013, 5.82¡Ñ1013, 4.50¡Ñ1013 and 4.48¡Ñ1012 g C y-1 in tropical Africa, the Americas, Asia and Oceania, respectively, for a total DOC flux of 0.136 Pg C y-1. Tropical rivers provide 0.53 Pg C y-1 of carbon to the oceans, of which 39.8¢H is DIC, 25.7¢H is DOC, 9.7¢H is PIC and 24.8¢H is POC.

The Wind-Evaporation-Sea Surface Temperature (WES) feedback is believedto play an important role in the tropics, where climate variability is governed byatmosphere-ocean coupled interactions. This dissertation reports on studies to distinctlyisolate the WES feedback mechanism over tropical oceans using a modiedversion of an NCAR-Community Climate Model (CCM3) thermodynamically coupledto a slab ocean model, where the WES feedback is deliberately suppressed inthe bulk aerodynamic formulation for surface heat uxes. A comparison of coupledintegrations using the modified WES-off CCM3 to those carried out using the standardCCM3 conclusively identifies the role of the WES feedback in enhancing theinter-annual variability over deep tropical oceans and the westward propagation ofthe equatorial annual cycle. An important role for near surface humidity in tropicalclimate variability in enhancing inter-annual variability and in sustaining the equatorialannual cycle is also suggested. Statistical analyses over the tropical Atlanticreveal that the free coupled meridional mode of the Atlantic Ocean is amplified in thepresence of the WES feedback. Similar analyses of coupled model integrations, whenforced with an articial El Ni~no Southern Oscillation (ENSO)-like SST cycle in tropicalPacific, reveal that only in the presence of the WES feedback is the meridionalmode the preferred mode of response of the Atlantic to ENSO forcings. It is also foundthat WES feedback reinforces the tendency of the ITCZ to stay north of the equator over the Atlantic during El-Nino events. Comparative studies between Last GlacialMaximum (LGM) equivalent imposed northern hemispheric sea-ice experiments withthe WES-off model and the standard model indicate a dominant role for the WESfeedback in the southward shift of the ITCZ as indicated by paleo-climate records.However, it is found not to be the sole thermodynamic mechanism responsible for thepropagation of high latitude cold SST anomalies to the tropics, suggesting significantroles for other mechanisms in the tropical response to high latitude changes.

An eddy-permitting 2-1/2-layer Reduced Gravity Ocean (RGO) model is developed. Compared with the conventional 2-1/2-layer RGO models, the new model has improvements in subsurface thermodynamics, vertical mixing scheme and open boundary conditions. Using this new 2-1/2-layer RGO model as a dynamical tool, a systematic investigation of the role of oceanic processes in controlling tropical Atlantic sea-surface temperature (SST) response to Atlantic Meridional Overturning Circulation (AMOC) changes is carried out by varying the strength of northward mass transport at the open boundaries. It is found that the North Brazil Undercurrent (NBUC) reverses its direction in response to a shut-down of the AMOC. Such circulation change allows warm waters of the northern subtropical gyre enter the equatorial zone, giving rise to a prominent warming in the Gulf of Guinea and off the coast of Africa. Sensitivity experiments further show that the SST response behaves nonlinearly to AMOC changes. The rate of SST changes increases dramatically when the AMOC strength is below a threshold value. This nonlinear threshold behavior depends on the position of subsurface temperature gradient. The new RGO is coupled to an atmosphere general circulation model (AGCM) (CCM3.6). The coupled model is capable of capturing major features of tropical Atlantic variability. With the aid of this coupled model, a series of experiments with different combinations of oceanic and atmospheric processes are carried out to elucidate the relative importance of the oceanic processes and atmospheric processes in AMOC-induced tropical Atlantic variability/change. It is found that the oceanic processes are a primary factor contributing to the warming at and south of the equator and the precipitation increase over the Gulf of Guinea, while atmospheric processes are responsible for the surface cooling of the tropical north Atlantic and southward displacement of ITCZ. The sensitivity of the coupled system to different strength of the AMOC is further investigated. It is found that equatorial SST and precipitation response also behaves nonlinearly to AMOC changes. The impact of AMOC changes on Tropical Instability Waves (TIWs) is assessed. It is found that the activity of TIWs is reduced in response to the AMOC-induced equatorial SST warming. Correlation analysis suggests that AMOC may affect TIW activities by modifying SST gradient north of the equator.

To investigate the tropical Atlantic response to the remote El Nino-Southern Oscillation (ENSO) forcing, a Reduced Physics – Coupled Global Circulation Model (RP-CGCM) is developed, and four experiments are carried out. The results show that the RP-CGCM is capable of capturing the major features of Tropical Atlantic Variability (TAV) and its response to ENSO forcing. The SST response to the remote influence of ENSO may be divided into two stages. In stage one, the ENSO influences the tropical Atlantic SST primarily through the Troposphere Temperature (TT) mechanism, which predicts a uniform warming in the tropical Atlantic following the mature phase of El Nino. In the north tropical Atlantic (NTA), the Walker mechanism and the Pacific-North-American (PNA) mechanism work in concert with the TT-induced warming, giving rise to a robust SST response during the boreal spring in this region. In the south tropical Atlantic (STA), the southeasterly wind anomaly and increased stratus clouds work against the TT-induced warming, resulting in a much weaker SST response in this region. At this stage, the response can be largely explained by the ocean mixed layer response to changes in surface heat fluxes induced by ENSO. In stage two, ocean dynamics play a more active role in determining the evolution of SST. The cross-equatorial wind anomaly in the western to central equatorial Atlantic can change the SST in the eastern equatorial Atlantic through Bjerknes feedback and the SST in the central equatorial Atlantic through Ekman feedback. These feedback result in a cooling of SST in the equatorial south Atlantic (ESA) region which is so overwhelming that it cancels the warming effect induced by the TT mechanism and reverses the sign of the warm SST anomaly that is formed during stage one in this region. In general, the horizontal advection of heat plays a secondary role in the SST response to the remote influence of ENSO, except in the regions where the North Equatorial Countercurrent (NECC) dominates and the SST variability is strong. Entrainment is particularly important in maintaining the correct SST structure during boreal summer.

In the first part of this dissertation we use an Intermediate Coupled Model to develop a quantitative test to validate the null hypothesis that low-frequency varia- tion of ENSO predictability may be caused by stochastic processes. Three "perfect model scenario" prediction experiments are carried out, where the model is forced ei- ther solely by stochastic forcing or additionally by decadal-varying backgrounds with different amplitudes. These experiments indicate that one can not simply reject the null hypothesis unless the decadal-varying backgrounds are unrealistically strong. The second part of this dissertation investigates the extent to which internal atmospheric variability (IAV) can influence ENSO variation, and examines the un- derlying physical mechanisms linking IAV to ENSO variability with the aid of a newly developed coupled model consisting of an atmospheric general circulation model and a Zebiak-Cane type of reduced gravity ocean model. A novel noise filter algorithm is developed to suppress IAV in the coupled model. A long control coupled simulation, where the filter is not employed, demonstrates that the coupled model captures many statistical properties of the observed ENSO behavior. It further shows that the development of El Ni~no is linked to a boreal spring phenomenon referred to as the Pacific Meridional Model (MM). The MM, character- ized by an anomalous north-south SST gradient and anomalous surface circulation in the northeasterly trade regime with maximum variance in boreal spring, is inherent to thermodynamic ocean-atmosphere coupling in the Intertropical Convergence Zone latitude. The Northern Pacific Oscillation provides one source of external forcing to excite it. This result supports the hypothesis that the MM works as a conduit for extratropical atmospheric influence on ENSO. A set of coupled simulations, where the filter is used to suppress IAV, indicate that reducing IAV in both wind stress and heat flux substantially weakens ENSO variance. Furthermore, the resultant ENSO cycle becomes more regular and no longer shows strong seasonal phase locking. The seasonal phase locking of ENSO is strongly tied to the IAV in surface heat flux. The ENSO cycle is strongly tied to IAV in surface wind stress.

Spatial variability of rainfall is a significant factor in hydrologic and water quality modeling. In recent years, characterizing and analyzing the effect of spatial variability of rainfall in hydrologic applications has become vital with the advent of remotely sensed precipitation estimates that have high spatial resolution. In this study, the effect of spatial variability of rainfall in hourly runoff generation was analyzed using the Soil and Water Assessment Tool (SWAT) for Big Sandy Creek and Walnut Creek Watersheds in North Central Texas. The area of the study catchments was 808 km2 and 196 km2 for Big Sandy Creek and Walnut Creek Watersheds respectively. Hourly rainfall measurements obtained from raingauges and weather radars were used to estimate runoff for the years 1999 to 2003. Results from the study indicated that generated runoff from SWAT showed enormous volume bias when compared against observed runoff. The magnitude of bias increased as the area of the watershed increased and the spatial variability of rainfall diminished. Regardless of high spatial variability, rainfall estimates from weather radars resulted in increased volume of simulated runoff. Therefore, weather radar estimates were corrected for various systematic, range-dependent biases using three different interpolation methods: Inverse Distance Weighting (IDW), Spline, and Thiessen polygon. Runoff simulated using these bias adjusted radar rainfall estimates showed less volume bias compared to simulations using uncorrected radar rainfall. In addition to spatial variability of rainfall, SWAT model structures, such as overland flow, groundwater flow routing, and hourly evapotranspiration distribution, played vital roles in the accuracy of simulated runoff.

<p>This paper is based on the XAP system (eXtended Application Provisioning) and serves for the modeling of application family. The importance of modeling application family is increasing rapidly. To improve a mechanism to express the structure, properties of concepts, features and implementations within an application family becomes necessary and important. Feature tree is a well accepted means for the product line. We can use and improve it to suit our requirements in the following way</p><p>In the degree project, we create a tool to model application family with reusability, commonality and variability. The hierarchy, feature properties and dependencies are graphically represented.</p>

Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 170-178). Also available for download via the World Wide Web; free to University of Oregon users.

The West Florida Shelf (WFS), typically characterized as being oligotrophic, is one of the most productive continental shelves in the United States. In addition to supporting a large fishing industry, the WFS also supports high biomass blooms of the toxic dinoflagellate Karenia brevis. Because of the large ecological and economic impacts these blooms have on the area, the ECOHAB: Florida program was developed to gain a better understanding of red tides and their initiation, maintenance, and dispersal. This interdisciplinary program consisted of monthly cruises from June 1998 through December 2001, with a hiatus from January through March of 2001. Hydrography, nutrients, chlorophyll a, phaeopigments, and a wide variety of other factors were measured during the cruises. In this paper chlorophyll a and phaeopigment concentration, nutrients, and hydrographic data were examined to explain the temporal and spatial distribution of chlorophyll on the shelf. Average surface chlorophyll values were 0.55 mg/m 3 with near bottom values averaging 0.85 mg/m 3. Chlorophyll was found to be highest near the estuaries of Tampa Bay and Charlotte Harbor with a decreasing gradient seaward. Near bottom chlorophyll values were generally two to fourfold greater than surface values. Midshelf stations (35- 50 m) were characterized by high near bottom chlorophyll, whereas the offshore stations (86-200 m) were characterized by a subsurface chlorophyll maximum ranging between 40 to 80 m deep. Nutrients were generally low across the shelf except for 1998 when a subsurface intrusion of nutrient rich slope water reached to the 20 m isobath. Temperatures ranged from 14.00 ° C to 31.47° C. Salinity ranged from 30.5 to 37.50 in the study area. Four blooms of Karenia brevis, lasting several months, contributed to the high chlorophyll concentrations along the inner shelf. Maximum chlorophyll concentrations of 27.10 mg/m 3 were a result of the October 1999 to March 2000 red tide. Blooms of Trichodesmium and diatoms also were contributors to patterns seen on the shelf. Maximum chlorophyll values were generally highest in the late summer and fall except for offshore values which showed little to no seasonality. Inshore of the 50 m isobath, average phaeopigments comprised from 43 to 68 percent of the measured Chl a, while offshore values were from 68 to over 100 percent. Inshore chlorophyll distributions were attributed to riverine and estuarine flux of nutrients, localized upwelling, and recycling of nutrients aided by salinity and temperature fronts. Midshelf distributions were attributed to the movement of biologically important material through the bottom Ekman layer from offshore to the inshore regions of the shelf. Offshore distributions were attributed to Loop Current upwelling and synoptic scale processes associated with seasonal meteorological forcing.

As the world moves towards a more sustainable development, the energy coming from fossil fuels still produces the greenhouse gases that threaten the world’s climate. The UK government has established targets for the penetration of renewable energy generation and low-carbon alternatives for the electricity production. One of these technologies is microgeneration. In 2006, the UK government launched the Microgeneration Strategy pushing forward micro and small-scale generation as a supplementary source of energy for the country’s growing electricity demand. The proposal is focused on several technologies, including micro-wind and micro-PV, among others. These microgeneration technologies are now a reality and widespread across the distribution networks. Therefore, the analysis of the impact of these systems connected to distribution grids and the benefits of these technologies, alongside with their negative effects on the network is an important research area. Correct modelling of micro and small-scale renewablebased generation technologies implemented in urban areas, however, is not a simple task, as it requires an adequate representation of highly dispersed and uncontrolled generation systems. These systems are small in size, but high in numbers and usually experience large variations in available renewable energy inputs. This thesis presents aggregate models of urban micro and small-scale PV and wind generation systems, which are connected to low-voltage networks. The thesis analyses impact of urban PV and wind generation on the steady-state network performance (power flows and voltage profiles), taking into account variability of energy inputs. The presented analysis is of particular importance for the analysis of the future of power system supplies, which will have significantly higher penetration levels of renewable-based distributed generation technologies, resulting in a much wider range of interactions between microgeneration systems, loads and transmission/distribution networks. In order to perform this analysis, the resource assessment for urban areas has to be carried out to both quantify the potential for each technology and help in their modelling. This has been a challenge since the aggregation of microgeneration systems is far from simple, as the parameters, performance and size varies between different technologies. A solution presented in this thesis is an approach for simple yet accurate aggregation of microgeneration technologies. This approach allows to quantify and analyse their impact and effect on the power supply systems directly in terms of penetration levels and general technology characteristics.