Development of a Synoptic Climatology for the Northeast Gulf of Alaska

Abstract

The subjective, sea level pressure-based, synoptic climatologies of Sorkina and Putnins have been specialized for the coastal region of southern Alaska. The results of the subjective typing were compared to the automated correlation technique for surface chart typing proposed by Lund. The subjective and automated approaches point to four persistent patterns: the Aleutian low, the low over the southern Gulf of Alaska, high pressure centered over the eastern Gulf of Alaska, and high pressure centered over the western Gulf of Alaska. Beyond these four patterns, migratory low-pressure centers were divided into various groups. Matching individual synoptic charts to the map patterns, or sequencing, was done both subjectively and objectively by correlation with the National Meteorological Center grid point analyses. For the period 1968?77 75% of the twice daily sea level pressure charts could be sequenced objectively by matching one of the subjective subtypes with a correlation >0.7. Correlation-based techniques for determining types, as in the Lund approach, and as a basis for sequencing are not sensitive to high-wavenumber features in the fields or features near the edge of the region when compared to subjective techniques.