The influence of the Pacific decadal oscillation (PDO) on important hydroclimatic variables during years of neutral ENSO for 84 climate divisions in the western United States is analyzed from 1925 to 1998. When the 34 neutral ENSO years are split by cold (12 yr) and warm (22 yr) PDOs, the resulting winter precipitation patterns are spatially similar to those that occur during years of La Niña-cold PDO and, to a lesser extent, years of El Niño-warm PDO, respectively, although the characteristic ENSO dipole is not evident. The PDO influence is similar when the winter Palmer drought severity index is analyzed, although the core area of influence moves from the Southwest to the northern Rockies. Correlations between Niño-3.4 SSTs and the hydroclimatic variables reverse sign when the neutral ENSO years are split by PDO phase. The greatest difference between correlations occurs in the characteristic dipole between the Pacific Northwest and the desert Southwest. Since seasonal forecast guidance based on ENSO conditions in the tropical Pacific often yields a forecast of "equal chances" during years of neutral ENSO, forecasters may be able to improve their forecasts for the southwestern United States depending on if the PDO is known to be in the cold (drier than normal) or warm (wetter than normal) phase. However, this can be difficult to implement considering the current uncertainty of the phase of the PDO.

Trends in climate variables important to winegrape production in the western United States include fewer frost days, longer growing seasons, and higher spring and growing season temperatures. These trends have been related to a steady increase in wine quality and a decrease in year-to-year variability. While the trends in climate have been linked to increasing sea surface temperatures in the eastern Pacific, it is unknown whether this is caused by climate change or may be part of natural oscillations in the Pacific. In this study, 15 climate variables important to winegrape production were analyzed for 10 wine regions over the western USA. The variables were stratified by phases of the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), both separately and then in combination (modulation effect) to determine if there are any significant differences between teleconnections. 'Wine Spectator' vintage ratings for Cabernet Sauvignon wines from the Napa Valley were also stratified by the same method, and multivariate statistics were used to determine which variables are most important to wine quality. ENSO phase by itself was not found to be important to either climate variability in wine regions in the western USA or wine quality in Napa Valley, but the cold phase of the PDO was found to be associated with increased spring frosts and a shorter growing season that results in lower ratings relative to warm PDO. The combination of neutral ENSO conditions during the cold phase of the PDO was nearly always associated with low quality wine in the Napa Valley, which is a function of cold springs with increased frost risk, cool growing seasons, and ripening period rainfall (cold PDO), and above-average bloom and summer rainfall (neutral ENSO). Although climate trends toward generally warmer growing seasons with less frost risk have occurred, this research highlights the impact of climate variability on wine quality where, should the PDO return to a multi-decadal cold phase, wine growers in the Napa Valley and across the western USA will likely experience greater variability in wine quality.

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Studies of heat-and cold-related mortality in the United States produce widely ranging results due to inconsistent data sources, and this paper describes the methods, assets, and limitations of the most common temperature-related mortality sources.