An extreme precipitation categorization scheme, developed to temporally and spatially visualize and track the multi-scale variability of extreme precipitation climatology, is introduced over the continental United States and used as the basis for an observational dataset intercomparison. The categorization scheme groups three-day precipitation totals exceeding 100 mm into five precipitation categories, or "P-Cats". To assess observational uncertainty across a range of precipitation measurement approaches, we compare in situ station data from the Global Historical Climatology Network-Daily (GHCN-D), satellite derived data from the Tropical Rainfall Measuring Mission (TRMM), gridded station data from the Parameter-elevation Regression on Independent Slopes Model (PRISM), global reanalysis from the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA 2), and regional reanalysis from the North American Regional Reanalysis (NARR). While all datasets capture the principal spatial patterns of extreme precipitation climatology, results show considerable variability across the five-platform suite in P-Cat frequency, spatial extent, and magnitude. Higher resolution datasets, PRISM and TRMM, most closely resemble GHCN-D and capture a greater frequency of high-end totals relative to lower resolution products, NARR and MERRA-2. When all datasets are regridded to a common coarser grid, differences persist with datasets originally constructed at a high resolution maintaining the highest frequency and magnitude of P-Cats. Potential future applications of this scheme include tracking change in P-Cats over space and time, climate model evaluation, and assessment of model projected change.

The relationship between the outgoing long-wave radiation (OLR) field over the tropical Pacific and wintertime monthly precipitation for the western U. S. is investigated, using the mid-latitude upper-air circulation as an intermediary. Principal components (PC's) of the 500mb monthly averaged height field over the NE Pacific and western North America are compared with those of the monthly tropical Pacific OLR field. It is found that, of the first 6 PC's of the height field, five are correlated significantly with the first 3 OLR field PC's at lags of between two and six months. Canonical correlations between the two sets of PC's are greatest at a lag of four months and are highly significant. When stratified by different levels of the OLR field PC's, the separations between means of the height field PC's are highly significant as well. Differing distributions of the height field PC ensemble are also found to be associated with different OLR field PC levels. The relationship between the 500mb height field and concurrent western district precipitation is examined. Using a hybrid model including both linear statistical and non-linear physical components it is found that considerably more of the variance in the precipitation can be explained by that of the height field alone than when the precipitation is inferred directly from a linear statistical model. A set of reconstructed height field PC's is predicted from OLR values based on the height field/OLR stratification associations compiled for a period separate from that of the forecast. Applied to the precipitation model, this results in predicted western district precipitation which is better correlated with the observations than is the equivalent precipitation forecast from the linear statistical relationship of precipitation to the Southern Oscillation Index. / Graduation date: 1995

Thesis (M.Sc.)--Memorial University of Newfoundland, 2000. / Bibliography: leaves 160-165.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 97-106).

I assessed the paleoclimatic significance of SD values of pition pine (Pinus edulis and P. monophylla) cellulose nitrate (cn) by developing, testing and applying deterministic and empirical models, in the context of the soil-plant-atmosphere continuum. Stable isotope values of precipitation, soil water, xylem sap, leaf water, atmospheric vapor, annual and sub-annual samples of tree-ring and needle cellulose, and climatic parameters, were measured along a gradient of decreasing summer rain in the southwestern U.S. Stable isotope composition of sap indicated depth of moisture extraction. Over the growing season in New Mexico and Arizona, where monsoon rains are important, trees shifted their water use to shallower depths. In Nevada, where summer rain is scarce, trees shifted to deeper moisture late in the growing season. Evaporation altered δD and δ¹⁸O values of precipitation inputs to soil. Only after heavy monsoons did soil water and sap isotopically resemble recent precipitation. Average precipitation δD values set the baseline for δD(cn). values at each site, but interannual variations in relative humidity and precipitation amount altered wood and leaf δD(cn) values, via leaf water effects. Leaf water (1w) was evaporatively enriched by seasonal moisture stress. δD(1w). and δ¹⁸O(1w) values were strongly correlated with relative humidity on a seasonal basis, but not on a diurnal basis. Measured δ¹⁸O(1w) values fit a steady-state model, with an offset attributable to relative humidity. Measured δD(1w) values were more depleted than predicted by the model, suggesting leaf water - organic matter isotopic exchange. Biochemical fractionation (ε(B)) of hydrogen isotopes between leaf water and cellulose was inversely correlated with relative humidity. Empirical models based on linear regressions demostrated significant correlations between δD(en) values and precipitation seasonality. An El Nirio-Southern Oscillation signal (wood δD(en) values inversely related to winter precipitation amount) was found in New Mexico and Arizona. A summer rain signal (leaf δD(en) values inversely related to summer humidity) was found at all sites. δD(en) values of pirion needles in packrat middens from Sevilleta LTER, New Mexico, suggest that late Pleistocene summers were as wet as today's, and/or that storm tracks could have shifted, bringing in more tropical moisture than currently.

No description available.

No description available.

No description available.

No description available.

No description available.