Characterizing Anomalous Mid-tropospheric Ridges and Their Trends

We identify large magnitude ridges in the mid-upper level geopotential height field occurring on timescales from one day to seasons. These strong ridges have been conspicuous in the meteorology of extreme weather phenomena. Better characterizing these ridges, their connection to extreme weather events, and their potential link with longer term changes in the general circulation represent important areas of inquiry for meteorology and climate science and may offer new insights for forecasting extreme weather events.

Here we present some initial analyses to contribute to the characterization of these ridges. Using NCEP Reanalysis fields of 500 millibar geopotential height on timescales ranging from daily to seasonal to annual means, we show some of the salient features of the anomalous ridges, including intensity, duration, spatial patterns, and relationships with extreme temperature and precipitation events. We provide an analysis of trends and relative frequencies of occurrence, and compare these to the overall variability of the 500 mb geopotential height field. We also present some suggestions for potential forcing and feedback mechanisms that may help to better understand anomalous ridges.