Midlatitude Geopotential Height Trends across the Continental United States during the Summer Circulation

A positive trend in the midlatitude 500mb geopotential height over the western United States has been observed over the last 70 years during the midsummer months. By utilizing the NCAR Reanalysis 1 data set, these trends are investigated by analyzing decadal changes since 1941 in the 500mb geopotential height over three different regions for the month of July in the western, central, and eastern US. Results indicate a “dipole” trend across the continent (i.e. increasing heights out west, no change in the center, and a decrease in heights out east). Decadal changes and trends are compared and tested for statistical significance. Results have implications for future agriculture across the US in the coming years, as well as potential fire and drought risks in the western US.