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University of Alberta (2007)

Analysis of non-stationary surface air temperature and a drought index

Shu, Tingting

Titre : Analysis of non-stationary surface air temperature and a drought index

Auteur : Shu, Tingting

Université de soutenance : University of Alberta

Grade : Doctor of Philosophy (2007)

In this thesis, advanced techniques developed in time series analysis and econometrics are used to derive new results on climatic change detection. The empirical mode decomposition (EMD) is used to obtain non-stationary annual cycles (NAC) from daily and monthly surface air temperature data (SAT). The NAC is a better filter for the annual cycle than the thirty-year-mean annual cycle (TAC). The strength of the EMD annual cycles at the ten selected stations in North America increases with the latitude of the station’s location because of the variation in receiving the energy from solar radiation, and is weak for stations near the ocean because of the effect of the heat capacity of the large water body. The local trigonometric function is a compact representation for the NAC from daily SATs. The climate change is found not only in the mean temperature, but also in the amplitude and phase of the NAC. The climatic noises driving the anomaly of NAC are shown to be anti-persistent for time scales of over three months. This result indicates the possible presence of negative feedback from the earth’s climate system. The dynamic factor analysis approach is applied to investigate the source of climate change directly from the observed annual and seasonal SAT data in the contiguous United States over the period 1900-2003. A strong inter-decadal oscillation related to the inter-decadal scale of the North Atlantic oscillation is obtained in the winter and summer seasonal data. A stochastic trend related to anthropogenically-induced change is obtained after the inter-decadal oscillations are removed. The results show that the warming observed during the first part of the twentieth century had different origins in different parts of the US region. The area integrated standardized precipitation index (ASPI) is used to quantify the rainfall deficiency in the Southern Africa region. The temporal and spatial patterns of ASPI and the gridded drought magnitudes show that both short-term and long-term droughts have intensified and rainfall deficits at all time scales have increased considerably after 1980, contributing to the widespread famines in the region. The areas most vulnerable to droughts are identified.


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