Temporal and Spatial Variability in ENSO Teleconnections to Daily Weather Donditions in the Pacific Northwest

Abstract:

Classic teleconnection analysis has focused on relationships between modes of variability and seasonal average conditions. Growing needs for seasonally specific planning, as well as an expanding body of research showing instability in teleconnections, suggest that there is a need to evaluate teleconnections over narrower seasonal windows and to investigate variables other than average temperature, snowpack, and total precipitation. Here, ENSO teleconnections to snow-fraction, wet-day frequency and temperature, and air-mass type (using Sheridan’s synoptic classification), as well as to average temperature and precipitation, were evaluated at weather stations across the Pacific Northwest. The analysis was performed separately for early (October/November), middle (December/January) and late (February/March) portions of the cool-season. The stability of these relationships over time was also evaluated. Currently, ENSO has the strongest and most widespread influence on PNW weather late in the cool season, with some effect in the autumn, but little detectable impact in the mid-winter. Earlier in the 20^th century, the autumn peak in ENSO influence was somewhat more pronounced and the spring somewhat less. There were also modest geographic differences in teleconnection patterns, such as a region-wide response in average February-March temperature, but more localized effects on wet-day temperature. Geographic and seasonal distinctions in teleconnections to weather and climate could drive important differences in ecological and hydrological outcomes. This type of daily-level analysis may be useful in meeting the needs of stakeholders interested in using teleconnections for seasonal planning, but who may need more seasonally specific information or non-standard variables. However, this study also demonstrates the need for a thorough understanding of teleconnection spatial patterns, seasonal variability, and temporal flexibility when they are being presented to stakeholders as a decision-making tool.