published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

A simple atmosphere and ocean model of relevance to El Nino and Southern Oscillation (ENSO) is discussed. Both the atmosphere and ocean models are two layer, three dimensional, linear and baroclinic, and generally follow the Oregon State University coupled general circulation model. However, the parameterization differs considerably from previous work in the treatment of the atmospheric latent heat release. This new parameterization follows the formula used in the theory of conditional instability of the second kind (CISK). In this the latent heat release is proportional to the low level convergence. Utilizing the "Comprehensive Ocean Atmosphere Data Set" (COADS), which contains all oceanic and atmospheric surface variables over the global ocean from 1946-1979, experimental model results are discussed for determination of the validity of the parameterizations. In particular, the years 1957, 1965 and 1972 in which El Nino events occurred are examined. The parameterization is deemed to be realistic, and should permit simulation of the El Nino upon coupling the two models. / Graduation date: 1988

For the purpose of investigating the fundamental nature of the interannual oscillation observed in the tropical Pacific in conjunction with El Nino/Southern Oscillation (ENSO), the Comprehensive Ocean Atmosphere Data Set was analyzed. Based upon this analysis, an "intermediate" tropical atmosphere-ocean coupled model was developed. For reason of their particular importance to atmosphere-ocean interactions, moisture processes such as condensation-convergence, evaporation-sea surface temperature and evaporation-wind feedbacks were given special emphasis in both the data analysis and modeling processes. The atmospheric component of the model is based on the first baroclinic mode, which is driven by the atmospheric internal heating. The oceanic model consists of two layers with an imbedded oceanic mixed-layer, by which SST is predicted. The present study has demonstrated that despite the structural simplicity of the oceanic model, it is capable of simulating mean oceanic circulation. In preparation for coupling, individual models were first tested with the use of appropriate time-dependent boundary conditions specified from the composite ENSO data. Both model simulations reproduced the major features associated with the ENSO events. Coupling was performed following the imposition of wind stress anomalies over the western Pacific for a given time period and the removal of all external forcing for a period of eight years thereafter. The coupled responses simulated during the the first two-year period provided reasonable simulations of the following ENSO-like features: the appearance of warm sea-surface temperature anomalies in the central Pacific, deepening/shallowing of mixed-layers in the eastern/western Pacific, weakening of the trades in the central Pacific, strengthening/weakening of the North Equatorial Counter Current/South Equatorial Currents, and enhanced convective activities around the dateline. The long-term coupled integration showed a pattern of interannual oscillation over a period of approximately three years. The results obtained from this coupling study have illustrated (1) that the necessary condition for the interannual oscillation is the interaction between the atmosphere and the ocean and (2) that it is likely that oceanic wave dynamics plays a crucial role in the determination of the growth and decay of ENSO events. / Graduation date: 1991

Graduation date: 1988

PhD. (Environmental Management) / This research investigates associations between El Niño Southern Oscillation (ENSO) phases and the occurrence of an unusual atmospheric transport patterns over southern Africa, observed during the SAFARI 2000 field campaign. This transport pattern manifested itself as a smoke and hazeladen flow, originating from the sub-equatorial tropical regions over northern Angola and western Zambia, and traversing the subcontinent with exit off the south-east coast over southern Mozambique and northern KwaZulu-Natal into the Indian Ocean. This pattern has been dubbed The River of Smoke. This pattern is distinctly different from the continental re-circulation pattern associated with continental high-pressure systems over the subtropical sub-region, which is the prevalent system according to current literature. The period during which the SAFARI 2000 campaign was conducted happened to be at the height of the strong 1999/2000 La Niña episode, associated with excessively wet conditions over the sub-continent. In contrast, during an earlier field campaign, SAFARI’92, the continental re-circulation transport mode, termed the gyre, was observed to prevail over the subtropical sub-region. SAFARI’92 coincided with the 1991/1992 El Niño episode that resulted in drought conditions over much of southern Africa. These observations triggered the current investigation of the causal associations and frequencies of the River of Smoke flow with phases of the ENSO. This study has employed conventional and modeled methods of meteorological analysis to investigate the influence of ENSO on atmospheric transport and synoptic coupling mechanisms, Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) forward trajectory computations supported by an enhanced method of cluster analysis were used to determine and characterize the mean atmospheric transport modes over the subcontinent. Trajectories were calculated originating at two source points, representative of the tropical and subtropical subregions respectively (Mongu, Zambia; and Tshane, Botswana). Three study years were selected, corresponding to three distinct phases of ENSO: an El Niño episode during 1991/1992, a neutral ENSO episode during 1996/1997, and a La Niña episode during 1999/2000. The National Center for Environmental Prediction (NCEP)/ National Center for Atmospheric Research (NCAR) Reanalysis model is employed to reproduce mean composite synoptic circulation fields over southern Africa during the three periods. Findings show that for airflows originating over tropical southern Africa, the Indian Ocean fast exit pathway is unique to the neutral ENSO phase, while the continental re-circulation transport mode exhibits zero occurrences during the neutral phase. A continental re-circulation transport mode in the lower troposphere was observed during the El Niño and La Niña extremes, but with low annual frequencies (less than 30%). The direct Atlantic Ocean, the north-west and the Indian Ocean slow exit pathways are common to all three ENSO phases. For airflows originating over the subtropical sub-region, the continental re-circulation transport mode has the highest vi frequencies during all three ENSO phases, more especially during the El Niño episode, with more than 50% annual frequency, as observed during SAFARI’92. The north-west, Indian Ocean slow and Indian Ocean fast pathways are observed during all the three ENSO phases, with lower overall frequencies. The anticyclonic circulation flows are driven by the strengthened high-pressure systems over southern Africa: the semi-permanent subtropical high-pressure systems over the adjacent oceans (Atlantic Ocean High and Indian Ocean High) and the transient cut-off continental high-pressure systems. Airflows exiting toward the Indian Ocean have been described previously. In this work, a novel distinction is made between the Indian Ocean fast and the Indian Ocean slow exit pathways. The Indian Ocean slow corresponds to the conventional off-coast flow, such as observed during SAFARI’92. The Indian Ocean fast exit pathway is a newly described transport mode, which results from strong coupling between the subtropical circulation systems and the mid-latitude westerly flows. This strong-coupling induced transport mechanism provides favourable conditions for transport of mass fluxes, such as fire emissions originating from the tropical sub-region, towards the Indian Ocean. The Indian Ocean fast exit transport mode is characterized by higher speeds while exiting off the south-east coast, and extends further into the temperate latitudes towards Australia. When coupled with tropical sub-region, this flow mode is responsible for the occurrence of the River of Smoke phenomenon identified during SAFARI 2000. This Indian Ocean fast transport mode is intermittent in nature, and couples to the tropical sub-region only during the neutral ENSO episode, during which it exhibits low monthly frequencies, mainly during the dry season July through October. The intermittent nature, dependent on ENSO phases, and the associated low frequencies, may explain why it was observed in SAFARI 2000, but escaped observation and comment during previous studies, such as SAFARI’92.

by Yeung Wai Lung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 120-122). / Text in English; abstracts in English and Chinese. / by Yeung Wai Lung. / Abstract --- p.i / Abstract (Chinese version) --- p.ii / Acknowledgements --- p.iii / Contents --- p.iv / List of figures --- p.vii / List of tables --- p.xi / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- The El Nino ´ؤ Southern Oscillation Phenomenon --- p.3 / Chapter 2.1 --- Introduction to El Nino - Southern Oscillation --- p.3 / Chapter 2.2 --- The mean conditions of the Tropical Ocean --- p.4 / Chapter 2.3 --- Life Cycle of ENSO --- p.8 / Chapter 2.4 --- Understanding ENSO --- p.12 / Chapter 3 --- ENSO prediction schemes --- p.18 / Chapter 3.1 --- Introduction --- p.18 / Chapter 3.2 --- Statistical prediction models --- p.19 / Chapter 3.2.1 --- Introduction --- p.19 / Chapter 3.2.2 --- Atmospheric models --- p.19 / Chapter 3.2.3 --- Oceanic models --- p.22 / Chapter 3.3 --- Coupled ocean-atmosphere models --- p.24 / Chapter 3.3.1 --- Introduction --- p.24 / Chapter 3.3.2 --- Intermediate coupled models --- p.25 / Chapter 3.3.3 --- Hybrid coupled models --- p.28 / Chapter 3.3.4 --- Coupled general circulation models --- p.30 / Chapter 3.4 --- Skill sensitivities --- p.36 / Chapter 3.4.1 --- Introduction --- p.36 / Chapter 3.4.2 --- Dependence of skill on season --- p.36 / Chapter 3.4.3 --- Dependence of skill on decade --- p.37 / Chapter 3.4.4 --- Dependence of skill on the Phase of the ENSO cycle --- p.38 / Chapter 4 --- The ENSO model --- p.40 / Chapter 4.1 --- Introduction --- p.40 / Chapter 4.2 --- Models formalism --- p.40 / Chapter 4.2.1 --- Oceanic model --- p.40 / Chapter 4.2.2 --- Atmospheric model --- p.43 / Chapter 4.2.3 --- Coupling of atmospheric and oceanic models --- p.44 / Chapter 4.3 --- Numerical implementation --- p.45 / Chapter 4.3.1 --- Oceanic model --- p.45 / Chapter 4.3.2 --- Atmospheric model --- p.49 / Chapter 4.3.3 --- Averaging and interpolation during coupling --- p.52 / Chapter 4.4 --- Standard response of the model --- p.54 / Chapter 4.5 --- Limitation of the model --- p.57 / Chapter 5 --- Behavior of the ENSO model --- p.59 / Chapter 5.1 --- Introduction --- p.59 / Chapter 5.2 --- Numerical results of the model --- p.60 / Chapter 5.3 --- Effects of the parameters --- p.62 / Chapter 5.3.1 --- Introduction --- p.62 / Chapter 5.3.2 --- Coupling constant parameters --- p.62 / Chapter 5.3.3 --- Rayleigh friction --- p.66 / Chapter 5.3.4 --- The oceanic Kelvin wave speed --- p.69 / Chapter 5.3.5 --- The ocean basin length --- p.69 / Chapter 5.3.6 --- Reflections at the western boundary --- p.74 / Chapter 5.4 --- Modification of the model background state --- p.76 / Chapter 5.4.1 --- Introduction --- p.76 / Chapter 5.4.2 --- The results of the modified model --- p.77 / Chapter 5.4.3 --- Sensitivity of the western boundary of the modified model --- p.81 / Chapter 5.4.4 --- Parameters sensitivities of the modified model --- p.83 / Chapter 5.5 --- Conclusion and discussion --- p.87 / Appendix A --- p.91 / Appendix B --- p.112 / Bibliography --- p.120

This study examines the inter-annual variability of the thermal regime of two lakes, Quesnel Lake a very long residence-time lake and Kamloops Lake a short residence-time river-dominated lake. The changes are compared to local climate conditions as well as inter-annual variability associated with the El Nino Southern Oscillation (ENSO). Observations include that higher air temperatures in El Nino years are associated with higher surface water temperature, as well as earlier onset and longer duration of summer stratification. Observed lake heat content calculated from temperature profiles balanced well with the sum of heat fluxes calculated from meteorological data. Results indicate differences in the importance of heat flux components to the heat budgets of these lakes especially the river throughflow in Kamloops Lake. Since climate projections indicate more warming for this region the different potential impacts to the thermal regime of these lakes should be considered in environmental and resource management decisions.

The condition at settlement of the western rock lobster pueruli presumably reflects both their energetic condition in reaching the near shore and subsequent recruitment into adult populations. In recruiting to the near shore the pueruli swim across the continental shelf where oceanographic conditions are complex and likely influence the success of recruitment. The results from the biochemical studies are interpreted in light of the oceanography off the coast of Western Australia. I investigated the nutritional condition of larval phyllosomata, post-larval puerulus and first instar post-pueruli juveniles of the spiny lobster, Panulirus cygnus, to determine energy use during the non-feeding transitional puerulus stage. Biochemical analyses of lipid, fatty acid (FA) and protein revealed that lipid, in particular phospholipids, is primarily used for energy during the nonfeeding puerulus stage. Monounsaturated FA showed the greatest decline with development, whereas the polyunsaturated FA showed a high degree of sparing, suggesting these FA are not used as a substrate for energy production. The knowledge gained on the biochemistry of energy use in P. cygnus was then used to investigate the spatial and temporal variability in the nutritional condition, in particular lipid condition, of puerulus collected at three near shore locations (Alkimos, Jurien Bay and Dongara) along the Western Australia coast, and one offshore location (Houtman Abrolhos Islands). The one offshore location was chosen as I hypothesised that arriving pueruli are likely to be in a better state of nutrition than those arriving at more coastal locations where the potential journey from offshore larval feeding grounds to the near shore is considerably greater. This element of my research showed lipid levels to be inversely related, generally, to shelf width but were variable, suggesting pueruli may travel complex trajectories to reach nearshore settlement. The lipid and FA composition of pueruli was also consistent with spatial and seasonal variation in Leeuwin Current and coastal productivity regimes.

Ocean tides worldwide have exhibited secular changes in the past century, simultaneous with a global secular rise in mean sea level (MSL). The combination of these two factors contributes to higher water levels, and may increase threats to coastal regions and populations over the next century. Equally as important as these long-term changes are the short-term fluctuations in sea levels and tidal properties. These fluctuations may interact to yield locally extreme water level events, especially when combined with storm surge. This study, presented in three parts, examines the relationships between tidal anomalies and MSL anomalies on yearly and monthly timescales, with a goal of diagnosing dynamical factors that may influence the long-term evolution of tides in the Pacific Ocean. Correlations between yearly averaged properties are denoted tidal anomaly trends (TATs), and will be used to explore interannual behavior. Correlations of monthly averaged properties are denoted seasonal tidal anomaly trends (STATs), and are used to examine seasonal behavior. Four tidal constituents are analyzed: the two largest semidiurnal (twice daily) constituents, M2 and S2, and the two largest diurnal (once daily) constituents, K1 and O1. Part I surveys TATs and STATs at 153 Pacific Ocean tide gauges, and discusses regional patterns within the entire Pacific Ocean. TATs with statistically significant relations between MSL and amplitudes (A-TATs) are seen at 89% of all gauges; 92 gauges for M2, 66 for S2, 82 for K1, and 59 for O1. TATs with statistically significant relations between tidal phase (the relative timing of high water of the tide) and MSL (P-TATs) are observed at 55 gauges for M2, 47 for S2, 42 for K1, and 61 for O1. Significant seasonal variations (STATs) are observed at about a third of all gauges, with the largest concentration in Southeast Asia. The effect of combined A-TATs was also considered. At selected stations, observed tidal sensitivity with MSL was extrapolated forward in time to the predicted sea level in 2100. Results suggest that stations with large positive combined A-TATs produce total water levels that are greater than those predicted by an increase in MSL alone, increasing the chances of high-water events. Conversely, negative correlation between sea level and tidal properties may mitigate somewhat against sea level rise; changes in total water levels in 2100 at stations with a negative combined A-TAT are less than that predicted by MSL rise alone. Climate change scenarios that take into account greater increases in MSL due to increased Antarctic ice melt show larger changes in total water levels over the same time period. Part II examines the mechanisms behind the yearly (TAT) variability in the Western Tropical Pacific Ocean. Significant amplitude TATs are found at more than half of 26 gauges for each of the two strongest tidal constituents, K1 (diurnal) and M2 (semidiurnal). For the lesser constituents analyzed (O1 and S2), significant trends are observed at ten gauges. Frictional mechanisms related to the El Nino Southern Oscillation (ENSO) are found to be important in influencing tides in the Western Pacific, as well as resonant triad interactions, a nonlinear coupling that exchanges energy between the M2, K1, and O1 tides. Both of these factors contribute to the observed tidal variability in the Solomon Sea region. Part III analyzes the seasonal behavior of tides (STATs) at twenty tide gauges in the Southeast Asian waters, which exhibit variation by 10-30% of mean tidal amplitudes. A barotropic ocean tide model that considers the seasonal effects of MSL, stratification, and geostrophic and Ekman velocity is used to explain the observed seasonal variability in tides due to variations in monsoon-influenced climate forcing, with successful results at about half of all gauges. The observed changes in tides are best explained by the influence of non-tidal velocities (geostrophic and Ekman), though the effect of changing stratification is also an important secondary causative mechanism. From the results of these surveys and investigations, it is concluded that short-term fluctuations in MSL and tidal properties at multiple time scales may be as important in determining the state of future water levels as the long-term trends. Global explanations for the observed tidal behavior have not been found in this study; however, significant regional explanations are found at the yearly time scale in the Solomon Sea, and at the seasonal time scale in Southeast Asia. It is likely that tidal sensitivity to annual and seasonal variations in MSL at other locations also are driven by locally specific processes, rather than factors with basin-wide coherence.