In the current study, we have presented a systematic analysis of the diurnal cycle of rainfall over the Indian region using satellite observations, and evaluated the ability of the Weather Research and Forecasting Model (WRF) to simulate some of the salient features of the observed diurnal characteristics of rainfall. Using high resolution simulations, we also investigate the underlying mechanisms of some of the observed diurnal signatures of rainfall. Using the Tropical Rain-fall Measuring Mission (TRMM) 3-hourly, 0.25 ×0.25 degree 3B42 rainfall product for nine years (1999-2007), we extract the finer spatial structure of the diurnal scale signature of Indian summer monsoon rainfall. Using harmonic analysis, we construct a signal corresponding to diurnal and sub-diurnal variability. Subsequently, the 3-hourly time-period or the octet of rain-fall peak for this filtered signal, referred to as the “peak octet,” is estimated with care taken to eliminate spurious peaks arising out of Gibbs oscillations. Our analysis suggests that over the Bay of Bengal, there are three distinct modes of the peak octet of diurnal rainfall corresponding to 1130, 1430 and 1730 IST, from north central to south Bay. This finding could be seen to be consistent with southward propagation of the diurnal rainfall pattern reported by earlier studies. Over the Arabian sea, there is a spatially coherent pattern in the mode of the peak octet (1430 IST), in a region where it rains for more than 30% of the time. In the equatorial Indian Ocean, while most of the western part shows a late night/early morning peak, the eastern part does not show a spatially coherent pattern in the mode of the peak octet, owing to the occurrence of a dual maxima (early morning and early/late afternoon). The Himalayan foothills were found to have a mode of peak octet corresponding to 0230 IST, whereas over the Burmese mountains and the Western Ghats (west coast of India) the rainfall peaks during late afternoon/early evening (1430-1730 IST). This implies that the phase of the diurnal cycle over inland orography (e.g., Himalayas) is significantly different from coastal orography (e.g., Western Ghats). We also find that over the Gangetic plains, the peak octet is around 1430 IST, a few hours earlier compared to the typical early evening maxima over land. The second part of our study involves evaluating the ability of the Weather Research and Fore-casting Model (WRF) to simulate the observed diurnal rainfall characteristics. It also includes conducting high resolution simulations to explore the underlying physical mechanisms of the observed diurnal signatures of rainfall. The model (at 54km resolution) is integrated for the month of July 2006 since this period was particularly favourable for the study of diurnal cycle. We first evaluate the sensitivity of the model to the prescribed sea surface temperature (SST) by using two different SST datasets, namely Final Analyses (FNL) and Real-time Global (RTG). The overall performance of RTG SST was found to be better than FNL, and hence it was used for further model simulations. Next, we investigated the impact of different parameterisations (convective, microphysical, boundary layer, radiation and land surface) on the simulation of diurnal cycle of rainfall. Following this sensitivity study, we identified the suite of physical parameterisations in the model that “best” reproduces the observed diurnal characteristics of Indian monsoon rainfall. The “best” model configuration was used to conduct two nested simulations with one-way, three-level nesting (54-18-6km) over central India and Bay of Bengal. While the 54km and 18km simulations were conducted for July 2006, the 6km simulation was carried out for the period 18-24 July 2006. This period was chosen for our study since it is composed of an active period (19-21 July 2006), followed by a break period (22-24 July 2006). At 6km grid-spacing the model is able to realistically simulate the active and break phases in rainfall. During the chosen active phase, we find that the observed rainfall over central India tends to reach a maximum in the late night/early morning hours. This is in contrast to the observed climatological diurnal maxima of late evening hours. Interestingly, the 6km simulation for the active phase is able to reproduce this late night/early morning maxima. Upon further analysis, we find that this is because of the strong moisture convergence at the mid-troposphere during 2030-2330 IST, leading to the rainfall peak seen during 2330-0230 IST. Based on our analysis, we conclude that during both active and break phases of summer monsoon, mid-level moisture convergence seems to be one of the primary factors governing the phase of the diurnal cycle of rainfall. Over the Bay of Bengal, the 6km model simulation is in very good agreement with observations, particularly during the active phase. The southward propagation observed during 19-20 July 2006, which was not captured by the coarse resolution simulation (54km), is exceedingly well captured by the 6km simulation. The positive anomalies in specific humidity attain a maxima during 2030-0230 IST in the north and during 0830-1430 IST in the south. This confirms the role of moisture convergence in the southward propagation of rainfall. Equally importantly we find that while low level moisture convergence is dominant in the north Bay, it is the mid-level moisture convergence that is predominant in the south Bay.

The complex and coupled physical processes taking place in the atmosphere, ocean and land surface are described in Global Circulation Models (GCMs). These models have become the main tools to simulate climate variability and project future climate change. GCMs have the potential to give physically reliable estimates of climate change at global, continental or regional scales, but their projections are currently of too course horizontal resolution to capture the smaller scale features of climate and climate change. This situation stems from the fact that GCM simulations, which are effectively three-dimensional simulations of the coupled atmosphere-ocean-land system, are computationally extremely expensive. Therefore, downscaling techniques are utilised to do perform simulations over preselected areas that are of sufficiently detailed to represent the climate features at the meso-scale. Dynamic regional climate models (RCMs), based on the same laws of physics as GCMs but applied at high resolution over areas of interest, have become the main tools to project regional climate change. The research presented here utilises the Conformal-Cubic Atmospheric Model (CCAM), a variable-resolution global atmospheric model that can be applied in stretched-grid mode to function as a regional climate model. As is the case with RCMs, CCAM has the potential to improve climate simulations along rough topography and coastal areas when applied at high spatial resolution, whilst side-stepping the lateral boundary condition problems experienced by typical limited-area RCMs. CCAM has been developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia. The objective in the study is to test capability of a regional climate model, CCAM, to realistically simulate cumulus convection at different spatial scales over regions with steep topography, such as the eastern escarpment of South Africa. Since both GCMs and RCMs are known to have large biases and shortcomings in simulating rainfall over the steep eastern escarpment of southern Africa and in particular Lesotho, the paper “Model simulations of rainfall over southern Africa and its eastern escarpment” (Chapter 3) has a focus on verifying model performance over this region. In the paper the CCAM simulations include six 200 km resolution Atmospheric Model Intercomparison Project (AMIP) simulations that are forced with sea surface temperatures and one 50 km resolution National Centre for Environmental Prediction (NCEP) reanalysis simulation that is forced with sea surface temperatures and synoptic scale atmospheric forcings. These simulations are verified against rain gauge data sets and satellite rainfall estimates. The results reveal that at these resolutions the model is capable of simulating the key synoptic-scale features of southern African rainfall patterns. However, rainfall totals are often drastically overestimated. A key aspect of model performance is the representation of the diurnal cycle in convection. For the case of South Africa, the realistic representation of the complex patterns of rainfall over regions of steep topography is also of particular importance. At a larger spatial scale, the model also needs to be capable of representing the west-east rainfall gradient found over South Africa. The ability of CCAM to simulate the diurnal cycle in rainfall as well as the complex spatial patterns of rainfall over eastern South Africa is analysed in “High Resolution Rainfall Modelling over the Eastern Escarpment of South Africa” (Chapter 4). The simulations described in the paper have been performed at 8km resolutions in the horizontal and span a thirty-year long period. These are the highest resolution climate simulations obtained to date for the southern African region, and were obtained through the downscaling reanalysis data of the European Centre for Medium-range Weather Forecasting (ECMWF). The simulations provide a test of the robustness of the CCAM convective rainfall parameterisations when applied at high spatial resolution, in particular in representing the complex rainfall patterns of the eastern escarpment of South Africa. / M (Geography and Environmental Management), North-West University, Potchefstroom Campus, 2015

The complex and coupled physical processes taking place in the atmosphere, ocean and land surface are described in Global Circulation Models (GCMs). These models have become the main tools to simulate climate variability and project future climate change. GCMs have the potential to give physically reliable estimates of climate change at global, continental or regional scales, but their projections are currently of too course horizontal resolution to capture the smaller scale features of climate and climate change. This situation stems from the fact that GCM simulations, which are effectively three-dimensional simulations of the coupled atmosphere-ocean-land system, are computationally extremely expensive. Therefore, downscaling techniques are utilised to do perform simulations over preselected areas that are of sufficiently detailed to represent the climate features at the meso-scale. Dynamic regional climate models (RCMs), based on the same laws of physics as GCMs but applied at high resolution over areas of interest, have become the main tools to project regional climate change. The research presented here utilises the Conformal-Cubic Atmospheric Model (CCAM), a variable-resolution global atmospheric model that can be applied in stretched-grid mode to function as a regional climate model. As is the case with RCMs, CCAM has the potential to improve climate simulations along rough topography and coastal areas when applied at high spatial resolution, whilst side-stepping the lateral boundary condition problems experienced by typical limited-area RCMs. CCAM has been developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia. The objective in the study is to test capability of a regional climate model, CCAM, to realistically simulate cumulus convection at different spatial scales over regions with steep topography, such as the eastern escarpment of South Africa. Since both GCMs and RCMs are known to have large biases and shortcomings in simulating rainfall over the steep eastern escarpment of southern Africa and in particular Lesotho, the paper “Model simulations of rainfall over southern Africa and its eastern escarpment” (Chapter 3) has a focus on verifying model performance over this region. In the paper the CCAM simulations include six 200 km resolution Atmospheric Model Intercomparison Project (AMIP) simulations that are forced with sea surface temperatures and one 50 km resolution National Centre for Environmental Prediction (NCEP) reanalysis simulation that is forced with sea surface temperatures and synoptic scale atmospheric forcings. These simulations are verified against rain gauge data sets and satellite rainfall estimates. The results reveal that at these resolutions the model is capable of simulating the key synoptic-scale features of southern African rainfall patterns. However, rainfall totals are often drastically overestimated. A key aspect of model performance is the representation of the diurnal cycle in convection. For the case of South Africa, the realistic representation of the complex patterns of rainfall over regions of steep topography is also of particular importance. At a larger spatial scale, the model also needs to be capable of representing the west-east rainfall gradient found over South Africa. The ability of CCAM to simulate the diurnal cycle in rainfall as well as the complex spatial patterns of rainfall over eastern South Africa is analysed in “High Resolution Rainfall Modelling over the Eastern Escarpment of South Africa” (Chapter 4). The simulations described in the paper have been performed at 8km resolutions in the horizontal and span a thirty-year long period. These are the highest resolution climate simulations obtained to date for the southern African region, and were obtained through the downscaling reanalysis data of the European Centre for Medium-range Weather Forecasting (ECMWF). The simulations provide a test of the robustness of the CCAM convective rainfall parameterisations when applied at high spatial resolution, in particular in representing the complex rainfall patterns of the eastern escarpment of South Africa. / M (Geography and Environmental Management), North-West University, Potchefstroom Campus, 2015

Although the effects of both the menstrual and circadian cycles on mood have been well documented, the question of whether the two interact to influence mood has not yet been addressed, despite evidence for such an interaction on other variables. Blood sugar level is a major contributor to the mediation of mood and is easily regulated by dietary intervention; there is also evidence that it is influenced by both the menstrual and circadian cycles. The present research takes a positive psychological approach to managing mood; the aims were to identify where natural variations in mood occur in relation to its underlying physiology, taking an applied approach to suggest ways of effectively managing positive mood and maintaining psychological well-being. A series of studies was carried out to measure fluctuations in mood in relation to biological rhythms, and in response to cognitively demanding situations and simple interventions. Mood was measured throughout the research using the UWIST Mood Adjective Checklist. The most consistent results were in relation to the Energetic Arousal dimension. This was shown to be influenced by both the menstrual cycle and the time of day, as well as an interaction between these two factors, and was consistently related to changes in blood glucose levels. Energetic Arousal also appeared to be more sensitive to the effectsof the suggested interventions. Diurnal changes in mood throughout the course of a normal day were more evident among women in their premenstrual to menstrual phases, and also become more apparent in response to cognitive tasks. Trait Anxiety was a mediating factor in how individuals reacted to such tasks. Mood was closely related to blood glucose levels, and raising blood glucose to a robust but safe level effectivelyenhanced positive mood in cognitively demanding situations. Oral contraceptives generally tended to eliminate menstrual cycle-related effects on mood and responses to intervention. It was concluded that mood states among healthy women are influenced by a complex interplay between biological rhythms, physiological states, individual differences and the context in which these moods take place. Simple interventions that can easily be incorporated into one’s daily routine may be efficacious in maintaining a positive mood state, which has beneficial implications for psychological well-being.

The Hypothalamus-Pituitary-Adrenal axis (HPA-axis) with its end product cortisol mediates the physiological response to stress thereby promoting mobilization of energy. The cortisol levels follow a diurnal rhythm with a distinct awakening response. Regulation of the HPA-axis differs among persons with certain psychiatric disorders when compared with controls. Some reports concern Attention-Deficit/Hyperactivity Disorder (ADHD) but findings are inconclusive. The main aim of the present thesis was to investigate diurnal levels of saliva cortisol in school aged children with ADHD and age matched non-affected comparisons, also taking early adversity, perceived stress and ADHD-medication into consideration. Children with ADHD had lower cortisol levels at awakening, 30 minutes later and before going to bed than comparisons. When the study group was split into three different age groups similar results were found only for children above 10 years of age. Within the ADHD group, subtype of ADHD or co-occurring symptoms did not affect the cortisol levels. Furthermore, children in the ADHD group had to a higher degree been exposed to foetal and childhood psychosocial adversity than comparisons. Since exposure to early adversity has been associated with both ADHD and HPA-axis functioning, such exposures could theoretically explain the low cortisol levels in ADHD via early programming of the HPA-axis. However, no relation was found between exposures to psychosocial adversity and diurnal cortisol levels. Neither did continuous medication with stimulants or atomoxetine explain the low cortisol levels. Possibly, medication may rather increase the levels. Finally, children with ADHD scored higher on perceived stress, measured by the Pressure-Activation-Stress (PAS) scale, than the comparison group. Female sex was also associated with higher stress in both groups, as well as increasing age in the comparison group. As with psychosocial adversity, no association was found between the higher PAS-scores and the lower cortisol levels, indicating the complexity of the stress regulating system. The results indicate a down-regulated or displaced HPA-axis with lower cortisol levels in children with ADHD. Stress related fragility – with more exposure to early stressors, higher perceived stress and lower diurnal cortisol levels – seem to accompany ADHD during childhood.

The zooplankton of Josefův Důl, a large and deep drinking water reservoir recovering from acidification, develop in relation to the improving water chemistry but also predation by salmonid fish re-stocked at the end of the 1990s. Crustacea are represented by small numbers of several species only, and nothing is known about their distribution in the water column. Recently, picocyanobacteria Merismopedia sp. became dominant in the phytoplankton, which hampers substantially the treatability of the raw water. The aim of the thesis is to describe the seasonal dynamics and vertical distribution of Crustacea in the Josefův Důl reservoir, together with parameters of the environment, and to study their possible diurnal vertical migrations in the summer period.

Certain modern radio systems that rely on trans-ionospheric propagation require knowledge of changes in total electron content (TEC). Understanding rapidly changing, small amplitude perturbations in the ionosphere is important in order to quantify the accuracy of those systems. The main aim of this thesis is to collect statistical information on the perturbations and wave structures present in the ionosphere, for use in radio astronomy calibrations and future communication systems planning. To gain this information, TEC calculated from instruments measuring Faraday rotation on signals from geostationary satellites were used. These measurements were collected in Italy over the period of 19751982 and 1989-1991 at one minute intervals. An important class of TEC fluctuations is travelling ionospheric disturbances (TIDs). Here, temporal variations of mid-latitude slant TEC measurements during two solar cycle phases, i.e solar minimum in 1975-1976 and solar maximum in 1989-1990, were studied. Direct inspection of Savitzky-Golay filtered TEC data was used to extract the amplitudes of TIDs. Fourier analysis was used to extract the most dominant periods of the TIDs. Discrete Meyer wavelet together with the ANOVA method to determine TID variation changes in different parts of the day. Another class of TEC fluctuations presented in this thesis is diurnal double maxima (DDM) structures. These structures were observed during mid-day in our TEC measurements between 1975 and 1991. Verification of the DDM observations was sought by using foF2 and hmF2 measurements from an ionosonde in RomeA combination of ionospheric 3-D tomographic imaging and ray propagation theory has been used for the first time to demonstrate a method that can show how the new European radio array LOFAR will be affected by the ionosphere. This was achieved from a case study of a geomagnetic quiet day ionosphere by simulating how ray propagations, at different elevations and frequencies, will behave as they traverse the ionosphere. The important result from this study was that continuous monitoring of the telescope will be important during operation of the array if the errors introduced by the ionosphere are to be accurately corrected for. The study of TEC changes over different short time windows demonstrated that the ionosphere vastly varies over short time scales, thus making the monitory non trivial. Statistical analysis of the TEC changes will also be useful to the new European GPS augmentation system EGNOS as an indicator on whether the ionospheric measurements from the system are realistic.

The human stress response has been shaped by natural selection to manage acute environmental challenges. While short-term activation of this response is imperative for survival, its chronic stimulation can lead to negative health consequences due to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and its end product, the glucocorticoid cortisol. In fact, chronic psychosocial stress has been identified as an important pathway through which lifestyle alterations associated with market integration (MI; the degree of production for and consumption from a market-based economy) impact traditionally-living societies experiencing rapid cultural changes. Few studies, however, have systematically examined the relationships between MI and HPA axis activity. Moreover, limited research has examined how factors associated with MI influence children's perceptions of the shifting cultural milieu. The primary goal of this dissertation was to illuminate the dynamic features of the human stress response among the indigenous Shuar of Amazonian Ecuador with four objectives: 1) To examine HPA axis activity among the Shuar to address fundamental questions about the basic biological mechanisms of the human stress response; 2) To examine individual differences in HPA axis activity as shaped by age, sex, and body mass index (BMI); 3) To evaluate how factors associated with MI influence the HPA axis activity of Shuar children and adolescents; and 4) To utilize a conceptual model (cultural consonance) to better understand how Shuar youth perceive changes in the sociocultural environment. Results suggested that age was positively associated with cortisol levels, while age and sex moderated the relationship between BMI and the decline in cortisol across the day. Factors associated with MI did not directly affect the cortisol patterns of Shuar children and adolescents; however, age, sex, and BMI moderated these relationships. For example, Shuar youth experiencing greater exposure to MI displayed age-related increases in waking cortisol levels. Finally, Shuar children and adolescents with less exposure to MI demonstrated more incongruity with their locally-defined model of lifestyle success due to limited access to items identified as important for “a good life”. These studies illustrate the complexity of the human stress response in the context of culture change. This dissertation includes unpublished, co-authored materials. / 10000-01-01

To understand the function and origins of sleep, sleep needs to be studied across many different species. Although it is well conserved throughout mammals, 95% of papers are restricted to just three species, Homo sapiens, Mus musculus, and Rattus norvegicus. We aimed to characterize sleep and wake in a Murid rodent Acomys cahirinus in greater detail alongside the well-studied laboratory house mouse (Mus musculus) and wild M. musculus using a well validated, non-invasive, piezoelectric system for sleep and activity monitoring. We confirmed A. cahirinus, M. musculus, and wild M. musculus to be primarily nocturnal, but with clearly distinct behavioral patterns. Specifically, the activity of A. cahirinus sharply increases right at dark onset, which is common in nocturnal species, but surprisingly, decreases sharply just one hour later. Using infra-red camera recordings in single and group cage conditions, we found that A. cahirinus is more active early in the night period than late night period in single and group cages, and this decreased activity in the latter half of the night is much greater compared to M. musculus. In order to better understand these differences in activity, we investigated the sleep architecture of A. cahirinus using electroencephalogram (EEG) recordings. Our data show that A. cahirinus have a few key differences in sleep from M. musculus. A. cahirinus have significantly longer daily sleep periods and exhibit a much higher amount of REM sleep. A. cahirinus are awake at dark onset, but sleep more than M. musculus after the middle of the night. Most strikingly, A. cahirinus do not close their eyes virtually at all while sleeping, day or night. In order to test whether the sleep patterns of A. cahirinus are affected by or responsive to different light input, we set up a light flashing experiment during the daytime. While sleep amount did not change significantly during light flashing, A. cahirinus spent significantly less time in REM compared to baseline. In contrast, M. musculus had no difference in REM sleep percentage. Histological studies showed A. cahirinus have thinner retinal layers, but much thicker corneas than M. musculus. Electroretinography (ERG) results, specifically b-wave amplitudes, are significantly different between these two species. While eye closure and sleep have not been systematically studied across mammals, our observation is clearly a rare behavior. This raises further questions about A. cahirinus sleep architecture, the adaptive value of eyes open sleep to A. cahirius and whether they may have limited visual processing even during normal sleep.

Orientador: Orlando Necchi Júnior / Banca: Ricardo Moreira Chaloub / Banca: Gustavo Habermann / Resumo: Respostas de curto período das características fotossintéticas a temperatura e irradiância foram avaliadas na rodófita Batrachospermum delicatulum em condições naturais e em laboratório. A variação diária dos parâmetros fotossintéticos por fluorescência da clorofila foi amostrada em duas épocas (junho, período frio e seco; outubro, quente e chuvoso) em um riacho da região noroeste do Estado de São Paulo (20o43’24-S, 49o18’21-W). Os valores de RQE e RQP (rendimento quântico efetivo e potencial, respectivamente) apresentaram correlação negativa com a irradiância nas duas épocas e valores similares no início e final do dia, indicando respectivamente alta pressão de excitação sobre o fotossistema II (FSII) e boa capacidade de recuperação e ausência de fotodano ao aparato fotossintético. Os valores de NPQ (extinção não-fotoquímica) também apresentaram correlação negativa com irradiância (significativa apenas em junho), o que possivelmente indica baixa capacidade de dissipação da energia absorvida pelos centros de reação. Sob temperatura e irradiância fixas a variação diária para fotossíntese líquida foi caracterizada por dois picos: o primeiro (maior) durante a manhã e o segundo (menor) durante a tarde. Os valores de ETR (taxa de transporte de elétrons) também apresentaram padrão semelhante, o que demonstra a ocorrência de ritmos endógenos que controlam as taxas fotossintéticas. Curvas de fotossíntese-irradiância e de indução escuro/luz foram testadas em laboratório (sob condições de baixa e alta irradiância) e em campo sob luz natural (não-sombreada) e artificialmente sombreada em duas épocas (junho e novembro). O isolado em cultura e as plantas em condições naturais (novembro) tiveram maiores valores de fotossíntese máxima (Fmax), eficiência fotossintética ( ) e rendimento quântico em baixa irradiância... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Short-term responses of photosynthetic characteristics to temperature and irradiance were analyzed in the rhodophyte Batrachospermum delicatulum under natural and laboratory conditions. The diurnal variation of photosynthetic parameters by chlorophyll fluorescence was sampled in two seasons (June, cool and dry season; October, warm and rainy season) in a stream of northwest region of São Paulo state (20o43’24”S, 49o18’21”W). Values of EQY and PQY (effective and potential quantum yield, respectively) were negatively correlated with irradiance in both seasons and had similar values at the beginning and end of the day, indicating, respectively high excitation pressure on photosystem II (PSII) and good recovery capacity and lack of photodamage to the photosynthetic apparatus. Values of NPQ (non-photochemical quenching) were also negatively correlated with irradiance (significantly only in June) possibly indicating low dissipation capacity of absorbed energy by reaction centres. The diurnal variation of net photosynthesis under fixed conditions of temperature and irradiance was characterized by two peaks the first (higher) in the morning and the second (lower) in the afternoon. ETR (electron transport rate) values also presented a similar pattern, suggesting the occurrence of endogenous rhythm that controls photosynthetic rates. Photosynthesis-irradiance and dark/light (induction) curves were tested in laboratory (under low and high irradiance conditions) and in field under natural light (unshaded) and artificially shaded in two seasons (June and November). Specimens from culture isolate and in natural conditions (November) had higher values of maximum photosynthesis (Pmax) photosynthetic efficiency ( ) and EQY at low irradiance, whereas at high irradiance (laboratory and field), values of were significantly higher than at low irradiance. A positive correlation between of ETR with NPQ... (Complete abstract click electronic access below) / Mestre