Some Aspects of the Influence of Abnormal Eastern Equatorial Pacific Ocean Surface Temperatures Upon Weather Patterns in the Southwestern United States. Volume II.

摘要

The theories of the late Dr. J. Bjerknes concerning the influence of an abnormally warm equatorial Pacific Ocean upon weather patterns in the southwestern United States are investigated further. Atmospheric circulation and precipitation patterns during the equatorial warm-water seasons of 1957-1958 and 1972-1973 are compared to those of earlier seasons of this type. These examples further confirm Bjerknes' theory that a warm equatorial Pacific Ocean is associated with a strong subtropical jet stream and repeated moderate to heavy storminess over the southwestern United States during winter and spring. In Northern Hemisphere winters of cooler than normal or rapidly cooling equatorial Pacific water, large-amplitude ridges will at times form over the northeastern Pacific, bringing cold storminess and heavy snowfall, or warm and very heavy rainfall, to parts of the southwestern United States. Some historical examples of these types of patterns are discussed. Summer and early fall precipitation over the southwestern United States, especially tropical cyclone rainfall and intense local storms, are also related--indirectly--to warm anomalies in the equatorial Pacific Ocean. Some hydrologic applications of the relationships between precipitation and equatorial ocean temperatures are discussed, and the possibilities of seasonal forecasting are also briefly mentioned.