Synoptic conditions during summertime temperature extremes in Alaska

摘要

The atmospheric state and synoptic situation associated with widespread summer June, July, and August temperature extremes in southern Alaska is explored. Using ERA-Interim data and a self-organizing map framework, the evolution of the atmospheric state leading up to days that are defined as experiencing extreme surface temperature are compared with the evolution for non-extreme days. The variables evaluated include circulation at the surface and aloft and surface radiative fluxes. For warm extremes, blocking evident in the 500 hPa flow combined with anomalously large surface downward shortwave radiation allowed surface temperatures to become extreme. For cold extremes, an upper level trough and cold air advection aloft coupled with a more minor role of anomalously negative surface downward shortwave radiation were important. The self-organizing map framework allowed an investigation of these details beyond a composite analysis of all extremes.