ENSO impacts on Plains winter seasons in modern and historical periods

The El Niño-Southern Oscillation (ENSO) is known to affect synoptic patterns across the continental United States, particularly by its impact on the upper tropospheric jet stream position, which in turn affects mid-tropospheric ridge and trough locations and thus areas favorable for temperature and precipitation anomalies. These global circulation patterns influence synoptic weather patterns, including those responsible for winter weather systems across the Plains states. Other teleconnection patterns impact winter weather in the Plains, including the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO), but these lack the seasonal predictability of ENSO; thus, they are useful in analysis but less useful in predictive applications.

This study will create a climatology of winter weather seasons based on ENSO phase from the mid-1900s to 2011, including both composites of synoptic fields as well as point-based climatologies for several primary sites in the Plains. Then, those results will be compared to a climatology of winter weather seasons based on ENSO phase from the early 1870s through the mid-1900s, based on historical 20th Century Reanalysis version 2 as well as historical estimates of ENSO phase based Extended Reconstruction Sea Surface Temperature (ERSST.v3b) data. The comparison may allow conclusions to be drawn regarding changes in the nature of synoptic patterns, and associated winter weather conditions, across the Plains from the late 1800s through the present, resulting from climate change and variability across the region. Modulation by AO and NAO events may also be investigated through the period of record. The resulting longer-term climatology can be used to place current and future ENSO episodes in the context of climatology and trends across the Plains region.