Factors Associated with Decadal Variability in Great Plains Summertime Surface Temperatures

Decadal variability of summertime Great Plains surface temperature is probed from the perspective of the Great Plains low-level jet (GPLLJ). GPLLJ variability Modes 2 and 5 are shown to be most influential on the evolution and magnitude of Great Plains surface temperature anomalies over the latter half of the twentieth century, including the development of the summertime warming hole, and are further linked to the Pacific Decadal Oscillation (PDO) and Atlantic Multi Decadal Oscillation (AMO), respectively. The influence of remote SST variability on the central U.S. warming hole is broadly consistent with previous modeling studies. However, the pivotal role that GPLLJ variability plays in linking the hemispheric-wide SST variability (through the AMO and PDO) to the regional warming hole is an expanded and clarified perspective.

Notwithstanding the strong influence of natural decadal variability modes, the analysis is further extended to examine the role of external factors (i.e., anthropogenic climate change) in the development of the warming hole and the associated GPLLJ variability through a suite of reforecasts prescribed with the observed CO2 concentrations over the 1982-2012 period using the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS). This dataset contains several thousand realizations for each season under consideration, as opposed to only 31 in nature, and will allow for some insight into the potential trajectory of the warming hole and its implications for decadal climate prediction over the U.S.