• Balling, R. C., , and G. B. Goodrich, 2007. Analysis of drought determinant for the Colorado River basin. Climatic Change 82:179194.

  • Brown, D. P., , and A. C. Comrie, 2004. A winter precipitation ‘dipole’ in the western United States associated with multidecadal ENSO variability. Geophys. Res. Lett. 31:L09203. doi:10.1029/2003GL018726.

    • Search Google Scholar
    • Export Citation
  • Burnett, A. W., 1994. Regional-scale troughing over the southwestern United States: Temporal climatology, teleconnections, and climate impact. Phys. Geog. 15:8098.

    • Search Google Scholar
    • Export Citation
  • Gershunov, A., , and T. P. Barnett, 1998. Interdecadal modulation of ENSO teleconnections. Bull. Amer. Meteor. Soc. 79:27152726.

  • Goodrich, G. B., 2004. Influence of the Pacific decadal oscillation on Arizona winter precipitation during years of neutral ENSO. Wea. Forecasting 19:950953.

    • Search Google Scholar
    • Export Citation
  • Gutzler, D. S., , D. M. Kann, , and C. Thornbrugh, 2002. Modulation of ENSO-based long-lead outlooks of southwestern U.S. winter precipitation by the Pacific decadal oscillation. Wea. Forecasting 17:11631172.

    • Search Google Scholar
    • Export Citation
  • Hamlet, A. F., , and D. P. Lettenmaier, 1999. Columbia River streamflow forecasting based on ENSO and PDO climate signals. J. Water Resour. Plann. Manage. 125:333341.

    • Search Google Scholar
    • Export Citation
  • Hanley, D. E., , M. A. Bourassa, , J. J. O’Brien, , S. R. Smith, , and E. R. Spade, 2003. A quantitative evaluation of ENSO indices. J. Climate 16:12491258.

    • Search Google Scholar
    • Export Citation
  • Harshburger, B., , H. Ye, , and J. Dzialoski, 2002. Observational evidence of the influence of Pacific SSTs on winter precipitation and spring stream discharge in Idaho. J. Hydrol. 264:157169.

    • Search Google Scholar
    • Export Citation
  • Heyerdahl, E. K., , P. Morgan, , and J. P. Riser II, 2008. Multi-season climate synchronized historical fires in dry forests (1650-1900), northern Rockies, USA. Ecology 89:705716.

    • Search Google Scholar
    • Export Citation
  • Hurkmans, R., , P. A. Troch, , R. Uijlenhoet, , P. Torfs, , and M. Durcik, 2009. Effects of climate variability on water storage in the Colorado River basin. J. Hydrol. 10:12571270.

    • Search Google Scholar
    • Export Citation
  • Jones, G. V., , and G. B. Goodrich, 2008. Influence of climate variability on wine regions in the western USA and on wine quality in the Napa Valley. Climate Res. 35:241254.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996. The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc. 77:437471.

  • Kalra, A., , and S. Ahmad, 2009. Using oceanic-atmospheric oscillations for long lead time streamflow forecasting. Water Resour. Res. 45:W03413. doi:10.1029/2008WR006855.

    • Search Google Scholar
    • Export Citation
  • Kennedy, A. M., , D. C. Garen, , and R. W. Koch, 2009. The association between climate teleconnection indices and Upper Klamath seasonal streamflow: Trans-Nino index. Hydrol. Processes 23:973984.

    • Search Google Scholar
    • Export Citation
  • Kiladis, G. N., , and H. F. Diaz, 1989. Global climate anomalies associated with extremes in the Southern Oscillation. J. Climate 2:10691090.

    • Search Google Scholar
    • Export Citation
  • Mantua, N. J., , S. R. Hare, , Y. Zhang, , J. M. Wallace, , and R. C. Francis, 1997. A Pacific interdecadal climate oscillation with impacts on salmon production. Bull. Amer. Meteor. Soc. 78:10691079.

    • Search Google Scholar
    • Export Citation
  • McCabe, G. J., , J. L. Betancourt, , and H. G. Hidalgo, 2007. Association of decadal to multidecadal sea-surface temperature variability with upper Colorado River flow. J. Amer. Water Resour. Assoc. 43:183192.

    • Search Google Scholar
    • Export Citation
  • Newman, M., , G. P. Compo, , and M. A. Alexander, 2003. ENSO-forced variability of the Pacific decadal oscillation. J. Climate 16:38533857.

    • Search Google Scholar
    • Export Citation
  • Pagano, T. C., , H. C. Hartmann, , and S. Sorooshian, 2002. Factors affecting seasonal forecast use in Arizona water management: A case study of the 1997-98 El Nino. Climate Res. 21:259269.

    • Search Google Scholar
    • Export Citation
  • Redmond, K. T., , and R. W. Koch, 1991. Surface climate and streamflow variability in the western United States and their relationship to large-scale circulation indices. Water Resour. Res. 27:23812399.

    • Search Google Scholar
    • Export Citation
  • Schoennagel, T., , T. T. Veblen, , W. H. Romme, , J. S. Sibold, , and E. R. Cook, 2005. ENSO and PDO variability affect drought-induced fire occurrence in Rocky Mountain subalpine forests. Ecol. Appl. 15:20002014.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1997. The definition of El Niño. Bull. Amer. Meteor. Soc. 78:27712778.

  • Wang, S-Y., , R. R. Gillies, , J. Jin, , and L. E. Hipps, 2009. Recent rainfall cycle in the Intermountain Region as a quadrature amplitude modulation from the Pacific decadal oscillation. Geophys. Res. Lett. 36:L02705. doi:10.1029/2008GL036329.

    • Search Google Scholar
    • Export Citation
  • Wise, E. K., 2010. Spatiotemporal variability of the precipitation dipole transition zone in the western United States. Geophys. Res. Lett. 37:L07706. doi:10.1029/2009GL042193.

    • Search Google Scholar
    • Export Citation
  • Woodhouse, C. A., 1997. Winter climate and the atmospheric circulation patterns in the Sonoran desert region, USA. Int. J. Climatol. 17:859873.

    • Search Google Scholar
    • Export Citation
  • Woolhiser, D. A., 2008. Combined effects of the Southern Oscillation index and the Pacific decadal oscillation on a stochastic daily precipitation model. J. Climate 21:11391152.

    • Search Google Scholar
    • Export Citation
  • View in gallery

    Circulation data from the reanalysis dataset are available beginning in 1948. This temporal coverage corresponds closely to the most recent cold (1947–76) and warm (1977–98) phases of the PDO, shown as standardized annual index values. This allows for an analysis of winter circulation variability over the western United States during these two discrete climatic periods.

  • View in gallery

    Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) El Niño events during the 1948–76 cold phase of the PDO pattern.

  • View in gallery

    Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) La Niña events during the 1948–76 cold phase of the PDO pattern.

  • View in gallery

    Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) El Niño events during the 1977–98 warm phase of the PDO pattern.

  • View in gallery

    Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) La Niña events during the 1977–98 warm phase of the PDO pattern.

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Winter Circulation Anomalies in the Western United States Associated with Antecedent and Decadal ENSO Variability

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  • 1 NOAA/National Climatic Data Center, Fort Worth, Texas
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Abstract

Previous research has shown that the impacts of ENSO variability on the winter climate of the western United States vary on decadal time scales. In this study, the relationship between fall season ENSO conditions and winter circulation anomalies over the western United States is shown to vary with phasing of the Pacific decadal oscillation (PDO). During the PDO cold phase of 1948–76, the majority of fall season El Niño events did not precede winter troughing anomalies over the southwestern states that are typically associated with above-normal winter precipitation in this region. In contrast, during the PDO warm phase of 1977–98, fall season El Niño conditions did precede southwestern winter troughing anomalies in all but one instance. Fall season La Niña conditions during both the cold and warm phases of the PDO reliably preceded winter season high pressure ridging centered off the Pacific coast. These results highlight uncertainty on decadal time scales surrounding the use of fall ENSO conditions, particularly El Niño events, as a seasonal climate forecast tool.

* Corresponding author address: David P. Brown, NOAA/National Climatic Data Center, 819 Taylor St., Room 10A05C, Fort Worth, TX, 76102. david.p.brown@noaa.gov

Abstract

Previous research has shown that the impacts of ENSO variability on the winter climate of the western United States vary on decadal time scales. In this study, the relationship between fall season ENSO conditions and winter circulation anomalies over the western United States is shown to vary with phasing of the Pacific decadal oscillation (PDO). During the PDO cold phase of 1948–76, the majority of fall season El Niño events did not precede winter troughing anomalies over the southwestern states that are typically associated with above-normal winter precipitation in this region. In contrast, during the PDO warm phase of 1977–98, fall season El Niño conditions did precede southwestern winter troughing anomalies in all but one instance. Fall season La Niña conditions during both the cold and warm phases of the PDO reliably preceded winter season high pressure ridging centered off the Pacific coast. These results highlight uncertainty on decadal time scales surrounding the use of fall ENSO conditions, particularly El Niño events, as a seasonal climate forecast tool.

* Corresponding author address: David P. Brown, NOAA/National Climatic Data Center, 819 Taylor St., Room 10A05C, Fort Worth, TX, 76102. david.p.brown@noaa.gov

1. Introduction

In the western United States, seasonal forecasts of winter precipitation are essential to a wide range of user groups who utilize predictive climate information in their decision-making processes (Pagano et al. 2002). El Niño–Southern Oscillation (ENSO), the leading mode of interannual variability in the tropical Pacific Ocean (Trenberth 1997), comprises the majority of the skill of these seasonal precipitation forecasts. The forecasting of winter precipitation anomalies for the western United States, based largely on ENSO conditions, can be done effectively with a lead time of as many as 6–9 months (Hamlet and Lettenmaier 1999). The strongest lagged relationship between ENSO conditions and western U.S. winter precipitation occurs during the fall season (Harshburger et al. 2002), and this 3-month lead time on which winter precipitation forecasts can be based may be operationally useful to many stakeholders (e.g., McCabe et al. 2007; Jones and Goodrich 2008; Kalra and Ahmad 2009; Hurkmans et al. 2009).

Typically, cold ENSO events (La Niña) during the fall season precede below-average winter precipitation in the southwestern states and above-average precipitation in the Pacific Northwest (Kiladis and Diaz 1989), with ridging anomalies evident in the winter circulation patterns over much of the Pacific coast (Woodhouse 1997). Approximately opposite conditions hold true during warm phases of ENSO, with below-average winter precipitation in the Pacific Northwest and above-average precipitation in the Southwest following a fall season El Niño event and large-scale winter troughing centered over the southwestern states (Burnett 1994). However, these “canonical,” or typical, ENSO teleconnections and impacts may be constrained on interdecadal time scales because of internal ocean–atmosphere dynamics and white noise in the Pacific basin (Newman et al. 2003), dramatically affecting the skill of winter precipitation (e.g., Gutzler et al. 2002), streamflow (e.g., Hamlet and Lettenmaier 1999), and other forecasts across the western United States.

The Pacific decadal oscillation (PDO), a pattern of sea surface temperature (SST) anomalies in the North Pacific with 20–30-yr phasing (Mantua et al. 1997; also see online at http://jisao.washington.edu/pdo), may be a useful diagnostic tool for characterizing decadal-scale ENSO variability, in large part because of its integration of the interannual ENSO signal into the decadal SST pattern of the North Pacific (Newman et al. 2003). Although the PDO is not a mode of climate variability itself, correlations between the PDO and climate variability in the western United States include stakeholder-relevant implications for a range of impacts such as drought (Balling and Goodrich 2007), streamflow (Kennedy et al. 2009), and wildfire (Schoennagel et al. 2005; Heyerdahl et al. 2008). Moreover, the strength of El Niño and La Niña teleconnections to western U.S. winter climate tends to vary with phasing of the PDO pattern (e.g., Woolhiser 2008; Wang et al. 2009), resulting in episodes of “constructive” and “destructive” interference (Gershunov and Barnett 1998).

Although the physical mechanism(s) linking PDO, ENSO, and western U.S. climate variability—such as the PDO’s tendency for multiseason and multiyear persistence (Gershunov and Barnett 1998), its integration of the higher frequency ENSO signal (Newman et al. 2003), and the location and intensity of SST anomalies across the Pacific—remain somewhat unclear, the utility of a PDO index in climate diagnostics applications is increasingly apparent. Recently a spatial anomaly, or “dipole,” has been identified (Brown and Comrie 2004; Wise 2010) whereby fall season El Niño (La Niña) events occurring during cold (warm) phases of the PDO pattern did not have a significant correlation with winter season precipitation anomalies in the Southwest (Pacific Northwest). Other studies have also linked the impacts of neutral ENSO conditions on winter precipitation to PDO phasing (e.g., Goodrich 2004). These findings suggest that the predictable relationship between ENSO and western U.S. climate, specifically the 3-month lagged relationship between fall ENSO conditions and winter precipitation, may not be spatiotemporally consistent but rather may vary in a fashion commensurate with PDO phasing.

2. Objective

The goal of this study is a scientific visualization of winter season atmospheric dynamics across the western United States within the context of both interannual ENSO variability and interdecadal phasing of the PDO pattern. Specifically, analyses of the relationship between fall ENSO conditions and winter circulation anomalies during distinct interdecadal climate regimes are needed to better understand the behavior of the ENSO system on decadal time scales, to identify climatic impacts in the western United States associated with decadal-scale ENSO variability, and to enhance the skill of seasonal climate outlooks for the western United States. To these ends, the following research questions are addressed in this study:

  • How do winter atmospheric circulation anomalies across the western United States associated with antecedent fall season ENSO events differ during warm and cold phases of the PDO pattern?
  • Do winter atmospheric circulation anomalies preceded by fall El Niño and La Niña conditions conform to the expected canonical patterns during both phases of the PDO pattern?

3. Data and methods

To identify winter season [December–February (DJF)] circulation anomalies across the western United States, the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis dataset (Kalnay et al. 1996) was employed. This dataset is a 50+ yr record of global analyses of atmospheric fields designed for climate research and monitoring. A comprehensive data assimilation system is used to ensure data homogeneity by removing false “climate jumps” from the dataset. The reanalysis dataset is ideally suited to a study of circulation variability because of its continuous temporal coverage (1948–present), the availability of a wide range of atmospheric variables at multiple atmospheric levels, and the online data interface and mapping capabilities provided via the National Oceanic and Atmospheric Administration (NOAA)/Climate Diagnostics Center (available online at http://www.cdc.noaa.gov). The reanalysis dataset does have important limitations, especially given that it is model driven more than observation driven over many parts of the globe. This makes its utility and reliability less robust in certain areas, particularly over oceans, and the use of reanalysis data in this study is thus undertaken within the context of these underlying assumptions and limitations. Fortunately, geopotential height fields are among the highest quality elements in the reanalysis dataset (Kalnay et al. 1996), and their widespread use in previous studies lends confidence to their application here.

The time period of the study was chosen as a function of PDO phasing during the twentieth century. Annual values of the PDO index, obtained from the University of Washington’s Joint Institute for the Study of the Atmosphere and Ocean (JISAO; available online at http://www.jisao.washington.edu/data/), are shown in Figure 1. This index of the PDO represents a time series of the first rotated component from an empirical orthogonal function (EOF) analysis of North Pacific sea surface temperatures. Because the reanalysis dataset begins in 1948, circulation anomalies prior to this date could not be analyzed. However, the beginning of the dataset in 1948 closely corresponds to a phase shift in the PDO index that occurred around 1947 (Figure 1), and the temporal coverage of the reanalysis dataset to the present time allowed for circulation variability analysis during two discrete PDO phases: cool (1948–76) and warm (1977–98). Phasing of the PDO since the late 1990s remains unclear and thus was not considered.

The individual winter seasons selected for circulation analysis were chosen based on antecedent fall season [September–October (SON)] ENSO conditions. The Southern Oscillation index (SOI), an atmospherically based measure of tropical Pacific climate conditions that has been used successfully in other western U.S. climate analyses (e.g., Redmond and Koch 1991), was obtained from the NOAA/Climate Prediction Center and used to capture variability in the ENSO system. The SOI has been shown to compare favorably to other ENSO indices as a measure of tropical Pacific variability (Hanley et al. 2003). A 3-month normalized SOI anomaly threshold of ±0.4, utilized in prior analyses (e.g., Brown and Comrie 2004), was used to quantify warm (El Niño) and cold (La Niña) ENSO events for the fall season. These ENSO events were then stratified by PDO phase; 29 fall season ENSO events since 1948 and their delineation by PDO phase determined the 29 corresponding winters used in the circulation analysis (Table 1).

Using the reanalysis dataset, maps of DJF geopotential height anomalies at the 700-mb level were generated for the western United States for winters following SON ENSO events. Circulation patterns at 700 mb are broadly integrative and representative of lower- and midtropospheric conditions, when compared to corresponding height anomalies at 850 and 500 mb (not shown). The maps were grouped by PDO phase and by antecedent SON ENSO conditions, resulting in four sets of maps for each pressure level (i.e., El Niño/PDO cold, La Niña/PDO cold, El Niño/PDO warm, and La Niña/PDO warm).

4. Results

4.1. PDO cold phase (1948–76)

Fall season El Niño conditions, as defined by a 3-month (SON) average SOI threshold of −0.4, occurred 8 times during the PDO cold phase of 1948–76. The winter (DJF) circulation patterns over the western United States following the occurrence of these SON El Niño events exhibited a large degree of heterogeneity. Mean 700-mb DJF geopotential height anomaly maps for three of the eight winters (1952, 1966, and 1973) reveal the presence of lower-than-normal heights over much of the western United States (Figure 2) in a manner consistent with the expectation of a southerly displacement of the midlatitude jet stream associated with El Niño conditions. However, for a majority of the winters (1954, 1958, 1959, 1964, and 1970), this expected El Niño–driven anomaly pattern is either shifted offshore or absent entirely, with higher-than-normal heights (ridging) prevailing instead over much of the west. This suggests that, on average, SON El Niño events that occurred during the 1948–76 cold phase of the PDO were not well correlated with expected DJF troughing patterns, especially over parts of Southern California, Arizona, and New Mexico.

Nine SON La Niña episodes occurred during this same PDO cold phase. In contrast to the winter circulation anomalies associated with fall El Niño events, there is a marked level of consistency in the DJF geopotential height patterns associated with fall La Niña events. At the 700-mb level, seven of the nine winters (1957, 1963, 1965, 1971, 1972, 1974, and 1976) are characterized by the presence of an above-normal height anomaly centered just off the Pacific coast (Figure 3). Moreover, the height patterns during four of the most recent five of these winters show a striking similarity, with a juxtaposition of the offshore ridge and a deep trough located over the central United States. Only the DJF circulation patterns of 1951 and 1956 do not clearly conform to the expected ridge–trough pattern associated with La Niña conditions at any of the three geopotential height levels.

4.2. PDO warm phase (1977–98)

Fall season El Niño conditions prevailed in 10 years during the warm PDO phase of 1977–98, and the circulation anomalies for the majority of the winter seasons that followed reflect the canonical circulation signature typically associated with strong El Niño events. The mean 700-mb DJF geopotential height anomalies for 6 of the 10 winters (1978, 1983, 1992, 1993, 1995, and 1998) exhibit troughing along the Pacific coast and, during the especially strong El Niño events of 1983, 1993, and 1998 (normalized SOI anomaly much greater than ±0.4), across much of the western United States as well (Figure 4). Winters that were preceded by the generally weaker SON El Niño episodes of 1987, 1988, 1991, and 1994 (normalized SOI anomaly close to ±0.4) do not reflect this same height anomaly pattern but instead are biased toward ridging over nearly all of the western United States. Taken together, these circulation anomalies indicate that weak-to-moderate SON El Niño events during the most recent PDO warm phase did not produce the same DJF troughing pattern over the west that the strong SON El Niño events did.

Fall season La Niña conditions occurred only twice during this PDO warm phase, resulting in a very limited sample size from which to make inferences about associated winter circulation variability. Strong ridging is present in the 700-mb DJF geopotential height anomaly maps following both of these SON La Niña events (Figure 5), with a center of ridging located just off the Pacific coast and higher-than-normal heights present over nearly the entire western United States. Despite the small sample size of SON La Niña events during the PDO warm phase of 1977–98, it is worth noting that DJF geopotential height anomalies for both winters in question did conform to the expectation of ridging over much of the West Coast.

5. Conclusions

Seasonal forecasts of winter precipitation in the western United States, based largely on ENSO conditions, benefit a wide range of user groups. Previous studies have shown that the skill of these forecasts and the expected impacts associated with ENSO vary on multidecadal time scales in a manner consistent with phasing of the PDO pattern. The results presented in this paper build on previous analyses (e.g., Brown and Comrie 2004) by highlighting the tendency of fall season (SON) El Niño and La Niña events to correlate with canonical winter (DJF) geopotential height anomaly patterns over the western United States as a function of PDO phase.

During the PDO cold phase of 1948–76, SON El Niño events tended not to precede the expected DJF troughing pattern over the west that would suggest above-normal precipitation in many areas, particularly the southwestern states. However, SON La Niña conditions during this PDO cold phase were well correlated with the occurrence of DJF high pressure ridging centered off the Pacific coast. Thus, during the 1948–76 PDO cold phase, fall season La Niña events were a more reliable predictor of expected ENSO-driven winter circulation patterns over the western United States than were fall season El Niño events.

For the PDO warm phase of 1977–98, the reliability of SON El Niño conditions as a predictor of canonical DJF geopotential height anomalies tended to be tied to the strength of the particular fall season ENSO event. The strongest SON El Niño episodes preceded DJF troughing along the Pacific coast, as would be expected during a strong El Niño regime. Weak-to-moderate SON El Niño events during this PDO warm phase, however, did not produce the same DJF troughing pattern that the strong SON El Niño events did and in fact were more closely associated with DJF ridging over much of the western United States. This suggests that fall season El Niño conditions were generally a reliable predictor of winter circulation anomalies over the western United States during this PDO warm phase only when the SON El Niño event was a moderate-to-strong event. Only two SON La Niña events occurred during this PDO warm phase, but in both cases the DJF geopotential height anomalies did exhibit La Niña–driven ridging along much of the Pacific coast.

Forecast lead times of several months are of particular operational utility in the decision-making processes of many of these stakeholders. The reliability of fall season ENSO events as a predictor of winter precipitation and circulation anomalies in the western United States is especially important because winter climate impacts can affect a range of important physical (e.g., snowpack depth, rain-on-snow flooding) and social (e.g., transportation, energy costs) systems. The results presented here highlight uncertainty at interdecadal time scales surrounding the use of ENSO conditions, particularly El Niño events, as a seasonal climate forecast tool. Further work is necessary to fully understand the physical underpinnings of ENSO teleconnections and impacts on the western United States within the context of interdecadal variability across the Pacific basin, particularly the implication that the regional robustness and predictive value of ENSO-based forecasts may vary substantially on multidecadal time scales.

REFERENCES

  • Balling, R. C., , and G. B. Goodrich, 2007. Analysis of drought determinant for the Colorado River basin. Climatic Change 82:179194.

  • Brown, D. P., , and A. C. Comrie, 2004. A winter precipitation ‘dipole’ in the western United States associated with multidecadal ENSO variability. Geophys. Res. Lett. 31:L09203. doi:10.1029/2003GL018726.

    • Search Google Scholar
    • Export Citation
  • Burnett, A. W., 1994. Regional-scale troughing over the southwestern United States: Temporal climatology, teleconnections, and climate impact. Phys. Geog. 15:8098.

    • Search Google Scholar
    • Export Citation
  • Gershunov, A., , and T. P. Barnett, 1998. Interdecadal modulation of ENSO teleconnections. Bull. Amer. Meteor. Soc. 79:27152726.

  • Goodrich, G. B., 2004. Influence of the Pacific decadal oscillation on Arizona winter precipitation during years of neutral ENSO. Wea. Forecasting 19:950953.

    • Search Google Scholar
    • Export Citation
  • Gutzler, D. S., , D. M. Kann, , and C. Thornbrugh, 2002. Modulation of ENSO-based long-lead outlooks of southwestern U.S. winter precipitation by the Pacific decadal oscillation. Wea. Forecasting 17:11631172.

    • Search Google Scholar
    • Export Citation
  • Hamlet, A. F., , and D. P. Lettenmaier, 1999. Columbia River streamflow forecasting based on ENSO and PDO climate signals. J. Water Resour. Plann. Manage. 125:333341.

    • Search Google Scholar
    • Export Citation
  • Hanley, D. E., , M. A. Bourassa, , J. J. O’Brien, , S. R. Smith, , and E. R. Spade, 2003. A quantitative evaluation of ENSO indices. J. Climate 16:12491258.

    • Search Google Scholar
    • Export Citation
  • Harshburger, B., , H. Ye, , and J. Dzialoski, 2002. Observational evidence of the influence of Pacific SSTs on winter precipitation and spring stream discharge in Idaho. J. Hydrol. 264:157169.

    • Search Google Scholar
    • Export Citation
  • Heyerdahl, E. K., , P. Morgan, , and J. P. Riser II, 2008. Multi-season climate synchronized historical fires in dry forests (1650-1900), northern Rockies, USA. Ecology 89:705716.

    • Search Google Scholar
    • Export Citation
  • Hurkmans, R., , P. A. Troch, , R. Uijlenhoet, , P. Torfs, , and M. Durcik, 2009. Effects of climate variability on water storage in the Colorado River basin. J. Hydrol. 10:12571270.

    • Search Google Scholar
    • Export Citation
  • Jones, G. V., , and G. B. Goodrich, 2008. Influence of climate variability on wine regions in the western USA and on wine quality in the Napa Valley. Climate Res. 35:241254.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996. The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc. 77:437471.

  • Kalra, A., , and S. Ahmad, 2009. Using oceanic-atmospheric oscillations for long lead time streamflow forecasting. Water Resour. Res. 45:W03413. doi:10.1029/2008WR006855.

    • Search Google Scholar
    • Export Citation
  • Kennedy, A. M., , D. C. Garen, , and R. W. Koch, 2009. The association between climate teleconnection indices and Upper Klamath seasonal streamflow: Trans-Nino index. Hydrol. Processes 23:973984.

    • Search Google Scholar
    • Export Citation
  • Kiladis, G. N., , and H. F. Diaz, 1989. Global climate anomalies associated with extremes in the Southern Oscillation. J. Climate 2:10691090.

    • Search Google Scholar
    • Export Citation
  • Mantua, N. J., , S. R. Hare, , Y. Zhang, , J. M. Wallace, , and R. C. Francis, 1997. A Pacific interdecadal climate oscillation with impacts on salmon production. Bull. Amer. Meteor. Soc. 78:10691079.

    • Search Google Scholar
    • Export Citation
  • McCabe, G. J., , J. L. Betancourt, , and H. G. Hidalgo, 2007. Association of decadal to multidecadal sea-surface temperature variability with upper Colorado River flow. J. Amer. Water Resour. Assoc. 43:183192.

    • Search Google Scholar
    • Export Citation
  • Newman, M., , G. P. Compo, , and M. A. Alexander, 2003. ENSO-forced variability of the Pacific decadal oscillation. J. Climate 16:38533857.

    • Search Google Scholar
    • Export Citation
  • Pagano, T. C., , H. C. Hartmann, , and S. Sorooshian, 2002. Factors affecting seasonal forecast use in Arizona water management: A case study of the 1997-98 El Nino. Climate Res. 21:259269.

    • Search Google Scholar
    • Export Citation
  • Redmond, K. T., , and R. W. Koch, 1991. Surface climate and streamflow variability in the western United States and their relationship to large-scale circulation indices. Water Resour. Res. 27:23812399.

    • Search Google Scholar
    • Export Citation
  • Schoennagel, T., , T. T. Veblen, , W. H. Romme, , J. S. Sibold, , and E. R. Cook, 2005. ENSO and PDO variability affect drought-induced fire occurrence in Rocky Mountain subalpine forests. Ecol. Appl. 15:20002014.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1997. The definition of El Niño. Bull. Amer. Meteor. Soc. 78:27712778.

  • Wang, S-Y., , R. R. Gillies, , J. Jin, , and L. E. Hipps, 2009. Recent rainfall cycle in the Intermountain Region as a quadrature amplitude modulation from the Pacific decadal oscillation. Geophys. Res. Lett. 36:L02705. doi:10.1029/2008GL036329.

    • Search Google Scholar
    • Export Citation
  • Wise, E. K., 2010. Spatiotemporal variability of the precipitation dipole transition zone in the western United States. Geophys. Res. Lett. 37:L07706. doi:10.1029/2009GL042193.

    • Search Google Scholar
    • Export Citation
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Figure 1.
Figure 1.

Circulation data from the reanalysis dataset are available beginning in 1948. This temporal coverage corresponds closely to the most recent cold (1947–76) and warm (1977–98) phases of the PDO, shown as standardized annual index values. This allows for an analysis of winter circulation variability over the western United States during these two discrete climatic periods.

Citation: Earth Interactions 15, 3; 10.1175/2010EI334.1

Figure 2.
Figure 2.

Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) El Niño events during the 1948–76 cold phase of the PDO pattern.

Citation: Earth Interactions 15, 3; 10.1175/2010EI334.1

Figure 3.
Figure 3.

Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) La Niña events during the 1948–76 cold phase of the PDO pattern.

Citation: Earth Interactions 15, 3; 10.1175/2010EI334.1

Figure 4.
Figure 4.

Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) El Niño events during the 1977–98 warm phase of the PDO pattern.

Citation: Earth Interactions 15, 3; 10.1175/2010EI334.1

Figure 5.
Figure 5.

Winter (DJF) 700-mb geopotential height anomalies following antecedent fall (SON) La Niña events during the 1977–98 warm phase of the PDO pattern.

Citation: Earth Interactions 15, 3; 10.1175/2010EI334.1

Table 1.

Winter seasons (DJF) selected for circulation analysis, based on the occurrence of antecedent fall season (SON) El Niño or La Niña events (3-month mean SOI anomaly of ±0.4), and stratified by PDO phase.

Table 1.
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