|dc.description.abstract||This dissertation includes two parts. Part 1 develops a geostatistical method
to calibrate Texas NexRad rainfall estimates using rain gauge measurements. Part 2
explores the asymptotic joint distribution of sample space-time covariance estimators.
The following two paragraphs briefly summarize these two parts, respectively.
Rainfall is one of the most important hydrologic model inputs and is considered
a random process in time and space. Rain gauges generally provide good quality
data; however, they are usually too sparse to capture the spatial variability. Radar
estimates provide a better spatial representation of rainfall patterns, but they are
subject to substantial biases. Our calibration of radar estimates, using gauge data,
takes season, rainfall type and rainfall amount into account, and is accomplished
via a combination of threshold estimation, bias reduction, regression techniques and
geostatistical procedures. We explore a varying-coefficient model to adapt to the
temporal variability of rainfall. The methods are illustrated using Texas rainfall data
in 2003, which includes WAR-88D radar-reflectivity data and the corresponding rain
gauge measurements. Simulation experiments are carried out to evaluate the accuracy of our methodology. The superiority of the proposed method lies in estimating total
rainfall as well as point rainfall amount.
We study the asymptotic joint distribution of sample space-time covariance esti-mators of stationary random fields. We do this without any marginal or joint distri-butional assumptions other than mild moment and mixing conditions. We consider
several situations depending on whether the observations are regularly or irregularly
spaced, and whether one part or the whole domain of interest is fixed or increasing.
A simulation experiment illustrates the asymptotic joint normality and the asymp-
totic covariance matrix of sample space-time covariance estimators as derived. An
extension of this part develops a nonparametric test for full symmetry, separability,
Taylor's hypothesis and isotropy of space-time covariances.||en_US