%0 Thesis
%B Geoscience
%D 1985
%T Tree-ring Response Functions: An Evaluation by Means of Stimulations
%A Cropper, John Philip
%X The problem of determining the response of tree ring width growth to monthly climate is examined in this study. The objective is to document which of the available regression methods are best suited to deciphering the complex link between tree growth variation and climate. Tree-ring response function analysis is used to determine which instrumental climatic variables are best associated with tree-ring width variability. Ideally such a determination would be accomplished, or verified, through detailed physiological monitoring of trees in their natural environment. A statistical approach is required because such biological studies on mature trees are currently too time consuming to perform. The use of lagged climatic data to duplicate a biological, rather than a calendar, year has resulted in an increase in the degree of intercorrelation (multicollinearity) of the independent climate variables. The presence of multicollinearity can greatly affect the sign and magnitude of estimated regression coefficients. Using series of known response, the effectiveness of five different regression methods were objectively assessed in this study. The results from each of the 2000 regressions were compared to the known regression weights and a measure of relative efficiency computed. The results indicate that ridge regression analysis is, on average, four times more efficient (average relative efficiency of 4.57) than unbiased multiple linear regression at producing good coefficient estimates. The results from principal components regression are slight improvements over those from multiple linear regression with an average relative efficiency of 1.45.
%B Geoscience
%I University of Arizona
%V PhD
%G eng
%U http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=753282251&sid=28&Fmt=2&clientId=43922&RQT=309&VName=PQD
%0 Thesis
%B Geoscience
%D 1981
%T Reconstruction of North Pacific Surface Pressure Anomaly Types from Alaskan and Western Candian Tree-ring Data
%A Cropper, John Philip
%X Spatial anomaly patterns of sea level pressure over the North Pacific sector of the Northern Hemisphere are statistically calibrated with principal components of arctic tree growth. Principal component weights of tree growth prior to 1900 are substituted into the calibration equation to construct the occurrence of past pressure anomaly types in the 19th century. The success of the constructions is statistically tested against independently derived reconstructions of the same pressure anomaly types from a grid of 65 tree-ring sites in western North America and against an independently derived temperature reconstruction for Fairbanks, Alaska. Of the 30 initial regression models developed only two passed enough verification tests against independent data to be considered reasonable reconstructions. The two chosen models were both reconstructing the same pressure anomaly type and were averaged to form a final reconstruction. Climatic conditions inferred from the arctic tree data are an anomalous strengthening of the summer North Pacific High, in the period 1920 to 1940, with associated anomalously cold summer temperatures at Fairbanks summer temperatures as occurred in the early 20th century (1920 to 1938). Based upon this work, recommendations are made for future study.
%B Geoscience
%I University of Arizona
%V MS
%G eng