8.2
Astronomical Effects on the Winter Climate of the Midwest
John C. Freeman, Weather Research Center, Houston, TX; and J. F. Hasling
Certain aspects of the orbit of the sun about the center of gravity of the solar system and the orbit of the moon about the earth were found to stratify the years since 1901 into active, moderate and inactive years for notable episodes in the Southern Oscillation (NESO). An active year is one in which the probability of having a NESO is 71%, in a moderate year the probability is 33% and in an inactive year the probability is 13%. A notable episode of the NESO occurs if the Climate Prediction Center has classified a year as being a cold or warm episode. Warm episodes are mostly El Nino’s and cold episodes are mostly La Nina’s.
When the study of the heating degree days (HDD) in the years since 1969 in the vicinity of Chicago was undertaken, active years had fewer HDD than moderate years. Some median values for the area for active and moderate years were: Des Moines 6350 and 6700, Chicago 6300 and 6750, Cleveland 5775 and 6150, Detroit 6225 and 6350, Cincinnati 6300 and 6500, Minneapolis 7950 and 8350, Indianapolis 5275 and 5600, Milwaukee 7050 and 7150, and St. Lewis 4550 and 4700.
The HDD since 1969 were studied because the record was easily available and considered pertinent, but about the time the work was finished Gusienev and Barnett’s work came out and showed that most of the record since 1969 was in what their work called a high North Pacific Oscillation (NPO).
The years 1933 to 1946 were studied also since that was another high NPO period and results similar to the list above were found. When the years 1947 to 1976 were studied it was found that the active years were colder than the moderate years.
Session 8, Advancing Our Understanding of Seasonal to Interannual Climate Variability: Part 1 (Parallel with Joint Session J1)
Wednesday, 12 January 2000, 8:15 AM-1:30 PM
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