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Relation Between Fluctuations in United States Climatic Patterns and 1962-65 Drought
Abstract
Climatic fluctuations are continually taking place over large areas of the world. These fluctuations may last a week, a month, a season, a year, a decade, a century, or upwards to millennia. Meteorologists recognize these fluctuations as integral parts of the total weather picture. This article describes certain features of this climatic fluctuation in terms of rainfall and temperature patterns, relates these features to the prevailing large-scale air currents in the atmosphere well above the earth's surface, and proposes a theory that might explain how these abnormal conditions have been generated and maintained.
Harry Wexler was a close student of developing techniques in the field of long range forecasting, and a contributor to them, realizing that improvement of long range forecasts represents one of the most important goals of meteorology. His scientifically-oriented administrative ability played a large part in enlarging the role of this subject in the United States. Indeed, one of the principal reasons he pioneered in inaugurating the World Weather Watch program was to lay a firmer foundation for long-range forecasting. I was one of many who gained benefit and stimulation from a long friendship with him, and my lecture will recall some of the instances.
First, I want to describe the nature of the long range prediction problem as seen through the eyes of a pragmatist, and to present a balanced picture of what is now possible and what may become possible in the next decade or so. One might hope that this 10-year forecast of “weather predictability” will turn out better than a 10-year forecast of the weather itself!
Next, I will speak on the history of long range forecasting over the past century, as traced through the work of inventors of synoptic, statistical and physical approaches to the problem. In spite of decades of frustration imposed by lack of adequate data, ignorance of large-scale physical processes, and the absence of intensive and large-scale effort, meteorologists working on longe range problems have made encouraging progress.
This article discusses extended and long-range weather forecasting. The article begins by briefly explaining how weather conditions are the result of atmospheric motions of various types and their interactions with one another. These motions are ultimately produced and maintained by the unequal heating of the earth by the sun. The spin of the earth about its axis transforms these motions into curved wind systems. The migrations of these curved wind systems around the earth produce frequent changes in weather. Thus, the earth's spin is responsible for short-period weather changes, whereas the earth's orbital rotation around the sun produces the longer-period changes.
The extensive and persistent warmth of central and eastern North Pacific waters during the last half of 1962 and early 1963 is described and attributed to prevailing abnormal wind and weather systems. Evidence is presented to indicate that the evolution of the large-scale prevailing atmospheric systems was partly determined by the anomalous water temperatures as well as forcing influences due to a seasonal change in the elevation of the sun. The evidence is partly statistic-synoptic and partly physical, involving computations of sensible and turbulent heat exchange as well as radiation balance. Among the more outstanding weather abnormalities treated are the strange behavior of typhoon Freda and the extremely abnormal winter of 1962–1963 over much of the northern hemisphere.