Multivariate calibration of a water and energy balance model in the spectral domain

The objective of this paper is to explore the possibility of using multiple variables in the calibration of hydrologic models in the spectral domain. A simple water and energy balance model was used, combined with observations of the energy balance and the soil moisture profile. The correlation functions of the model outputs and the observations for the different variables have been calculated after the removal of the diurnal cycle of the energy balance variables. These were transformed to the frequency domain to obtain spectral density functions, which were combined in the calibration algorithm. It has been found that it is best to use the square root of the spectral densities in the parameter estimation. Under these conditions, spectral calibration performs almost equally as well as time domain calibration using least squares differences between observed and simulated time series. Incorporation of the spectral coefficients of the cross-correlation functions did not improve the results of the calibration. Calibration on the correlation functions in the time domain led to worse model performance. When the meteorological forcing and model calibration data are not overlapping in time, spectral calibration has been shown to lead to an acceptable model performance. Overall, the results in this paper suggest that, in case of data scarcity, multivariate spectral calibration can be an attractive tool to estimate model parameters

Exploring concepts of death and subjective life expectancy: understanding young adults' perceptions of (In)-vulnerability

This study contributes to the understanding of young adults' concepts of death and subjective life expectancy, especially in an era when HIV and AIDS significantly raise morbidity and mortality levels and lower life expectancy. It was meant to inform theory building about subjective life expectancy and its potential impact on individual decision-making. The sample for this specific paper consisted of ten African adolescents aged between fifteen and twenty-two, all of whom living in areas of Cape Town most heavily affected by the AIDS pandemic, as well as by other environmental factors, such as high poverty and crime rates, and high levels of violent deaths especially among young men. Findings show that young people are extremely aware of high death rates in their environments, especially deaths of a premature nature. Causes indicated were HIV and AIDS, but even more prominently crime and violence. Although confronted with the daily reality of death, participants did not consider these high death rates to be part of "a normal life", yet related them often to a general feeling of social and moral chaos in the townships. Different psychosocial mechanisms of dealing with the threat of death showed, with often very high levels of resilience and a focus on the future, but also fear and lack of clarity about that future in general. Subjective life expectancy (SLE) for oneself, however, was generally high and not influenced by the uncontrollable threat of violent deaths; Instead, the motivation behind SLE showed young adults' belief in personal choice and control exercised within their environments characterised by the complex interaction of poverty, crime, HIV and AIDS, peer pressure and modernisation.? HIV and AIDS was mostly taken into account as a factor of influence that one had control over and therefore did not influence SLE. Peers' SLE, however, was rated far lower than their own, taking into account those factors that participants considered controllable

Educational decision-making in an era of AIDS

Includes abstract.Includes bibliographical references (p. 243-267).One of the ways in which AIDS is said to ravage the lives of young people is through its impact on education. Youth and their caregivers might respond to shortened life expectancy by investing less in schooling. No evidence has been presented for this hypothesis, however. Indeed, little is known about educational decision-making outside of a Western, industrialized context. This thesis examines educational decisionmaking in South Africa, and specifically tests the hypotheses that AIDS reduces the perceived value of education. The study combines quantitative and qualitative research, all conducted in the South African city of Cape Town. Whilst it proves difficult to model the effects of HIV/AIDS, the quantitative data from both adolescents (who participated in successive waves of the Cape Area Panel Study) and adults (who participated in the 2005 Cape Area Study) fails to provide support for the hypothesis that AIDS leads to a diminished valuation of the importance of education. Qualitative material was collected through diverse methods, from samples of AIDSaffected and non-affected young adults, and from HIV-positive adult caregivers. The qualitative research shows that young adults make educational decisions as part of a broader process of constructing identities. In a context of ‘fragility’, youth have to decide who they are and want they want to be. They construct positive ‘future selves’ that entail the aspiration for a long and successful life, in the course of which they maintain some control in the face of the chaos, hardship and mortality around them. Investing in education is an important marker of this self-control and positive aspiration, and hence their desired identity. HIV-positive adult caregivers also choose to invest heavily in their children’s education because they want to equip their children with advantages that will endure after their own deaths. HIV/AIDS might induce stress, insecurity and anxiety, but no evidence was found that it leads either caregivers or youth to make negative decisions about education, or to orient their values, attitudes and behaviour towards the short- rather than the long-term

Educational decision-making in an era of AIDS: exploring the narratives of affected young adults in the Cape Flats

This paper analyses how HIV and AIDS affects decisions around education. Data was collected through in-depth interviews with eight young adults, as part of a larger study into educational decision-making among young Black African adults in general. Results indicate that HIV and AIDS heighten psychological problems including stress, insecurity and anxiety, as identified by psychological research. HIV and AIDS add an extra layer to the already existing complexity and fragility of young people's lives and worlds. But no evidence was found that affected young people would more readily make negative decisions about education, or would orient their values, attitudes and behaviour towards the short- rather than the long-term. The AIDS-affected young people in the sample shape their identities by focusing on future success, albeit within a world characterised by fragility, in ways that are similar to non-affected young people. Positive educational decision-making is clearly an integral part of those young people who choose to regard their current situation of deprivation as temporal and to use education as a vehicle towards future success

The stuff that dreams are made of...Narratives on educational decision-making among young adults in Cape Town

This paper examines the narratives of eight young, Black South Africans on their decisions around education. Analysis focuses on these young adults' value of education on the one hand, and the parallels or breaches between that value and education-related choices or actions on the other. It shows that educational decision-making should be regarded as part of a larger process of identity-formation. I argue that the young people in my sample choose different strategies in attempts to create their identity. One such strategy implies a long-term oriented focus on success; choosing in favour of education is an intrinsic part thereof. Another one rests on a more short-term oriented wish for the same type of success, however with little or no concrete plans on how to reach that. The importance of education is not openly rejected by young adults adapting this second strategy, yet it is not a central factor in it either. Strategies such as these are, however, not static, and the distinction between them not as unambiguous as may seem. Shifting factors in a context of 'fragility' may lead young adults to rethink their choices and plans; many move between different strategies, or create 'in-between' versions that leave room for adaptation when necessary