TY - THES T1 - Analysis and reconstruction of the relationship between a circulation anomaly feature and tree rings: Linear and nonlinear approaches Y1 - 2000 A1 - Ni, Fenbiao KW - Statistics AB - Tree rings can be reliable recorders of past weather and climate variations. Tree rings from mountain regions can be linked to upper air atmospheric sounding observations and large-scale atmospheric circulation patterns. A “synoptic dendroclimatology” approach is used to define the relationship between tree rings and a specific upper air anomaly feature that affects climate in the western US. I have also reconstructed this anomaly feature using both regression and fuzzy logic approaches. Correlation analysis between 500 mb geopotential heights and tree rings at a site near Eagle, Colorado reveals an important anomaly centered over the western US. This center can be viewed as a circulation anomaly center index (CACI) that can quantitatively represent the relationship between atmospheric circulation and tree growth variations. To reconstruct this index from tree rings, I used both a multiple linear regression (MLR) and a fuzzy-rule-based (FRB) model. The fuzzy-rule-based model provides a simple structural approach to capture nonlinear relationships between tree rings and circulation. The reconstructing capability of both models is validated directly from an independent data set. Results show that the fuzzy-rule-based model performs better in terms of calibration and verification statistics than the multiple linear regression model. The reconstructed anomaly index can provide a long-term temporal context for evaluation of circulation variability and how it is linked to both climate and tree rings. PB - University of Arizona VL - PhD UR - http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=731915311&sid=23&Fmt=2&clientId=43922&RQT=309&VName=PQD ER - TY - THES T1 - Climate variability in the southwestern United States as reconstructed from tree-ring chronologies Y1 - 1996 A1 - Woodhouse, Connie Ann KW - Paleoecology AB - The primary goal of this research is to gain a better understanding of the spatial and temporal relationships between atmospheric circulation features and winter climate variability in the southwestern United States, and to investigate the variations in these relationships over the past three centuries. A set of six circulation indices is compiled that describes circulation features important to winter climate variability in this region. This set includes pre-existing indices such as the SOI and a modified PNA index, as well as regionally-tailored indices. A network of 88 tree-ring chronologies is then used to reconstruct the indices and the regional winter climate variables: numbers of rainy days (a variable not previously reconstructed with tree rings) and mean maximum temperature. Analyses suggest that three types of circulation features have influenced winter climate in the Southwest over the past three centuries. Although ENSO-related circulation patterns have been an important factor, especially in the 20th century, circulation patterns featuring a southwestern low appear to be as important if not more important to climate in some time periods. Results suggest that low frequency variations in atmospheric circulation patterns have occurred over the past three centuries and have had spatially and temporally varying impacts on winter climate in the Southwest. PB - University of Arizona VL - PhD UR - http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=739718221&sid=24&Fmt=2&clientId=43922&RQT=309&VName=PQD ER - TY - THES T1 - Synoptic Dendroclimatology in the Upper Marmada River Basin: An Exploratory Study in Central Asia T2 - Geoscience Y1 - 1996 A1 - Wood, Michelle Lee AB - Dendrochronological analysis of teak (Tectona grandis) collected from stumps in the Malpathar National Reserved Forest of the upper Narmada River Basin in central India has the potential to provide continuous and long-term information about changes in both the local climate of the Malpather National Reserved Forest site and the Indian monsoon circulation… JF - Geoscience PB - University of Arizona VL - MS ER - TY - THES T1 - Hydroclimatology of flow events in the Gila River Basin, Central and Southern Arizona T2 - Geosciences Y1 - 1985 A1 - Hirschboeck, K. KW - floods KW - Hydrology KW - mixed populations AB -

Traditional flood-frequency techniques are based on the assumption that the observed flood record represents a sample that has been drawn from a single climatically homogeneous population of floods. A hydroclimatic approach was used to evaluate this assumption by identifying the circulation patterns and atmospheric flood-generating mechanisms which control the temporal and spatial variability of flooding. Mean monthly discharges and instantaneous peak flows of the partial duration series were analyzed for thirty gaging stations in the climatically sensitive, semiarid, Gila River basin for the period 1950 to 1980. Correlation fields and composite maps were constructed to define the relationship between 700 mb height circulation anomalies and mean monthly streamflow. Individual flood events were linked to climate by analyzing daily synoptic weather maps and classifying each flood event into one of eight hydroclimatic categories on the basis of the atmospheric mechanisms which generated each flow. The analysis demonstrated that floods and anomalously high streamflow in the Gila River basin originate from a variety of atmospheric processes which vary spatially, seasonally, and from year-to-year. The mechanisms most important for generating floods included winter fronts, cutoff lows, tropical storms, snowmelt, and widespread and localized summer monsoon-related circulation patterns. When flood discharges were grouped into hydroclimatically homogeneous categories, histogram plots of their frequency distributions exhibited means and variances that differed from those of the overall frequency distribution of the entire flood series. The means of the discharges generated by frontal precipitation and tropical storms tended to plot above the mean of the overall series, while the means of floods generated by snowmelt tended to plot below the overall mean. Flood estimates computed from a series containing mixed distributions were not the same as flood estimates computed from climatically homogeneous subsets of the same series. These results have implications for traditional flood-frequency analysis and other stochastic methods of analyzing hydrologic time series. The hydroclimatically-defined subgroups in the flood series of the Gila River basin indicate that nonhomogeneity and nonstationarity can be imparted to a hydrologic time series by differing atmospheric mechanisms alone.

JF - Geosciences PB - University of Arizona VL - PhD UR - http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=753278081&sid=23&Fmt=2&clientId=43922&RQT=309&VName=PQD ER - TY - THES T1 - The Response of Flooding in the Upper Mississippi Valley to Twentieth Century Climatic Fluctuations 1925-1969 T2 - Geography Y1 - 1975 A1 - Hirschboeck, K. JF - Geography PB - University of Wisconsin VL - MS ER -