Periodic Interannual Variations of Midwestern United States Temperatures in December.
Three strong periodicities are observed in the time series of December temperature at St. Cloud, Minnesota (1893-1980). These three frequencies (.3868 cycles/year, .2263 cycles/year, and .1132 cycles/year) are shown to have a time and space 'sensitivity.' December is a sensitive time becau...
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| Format: | Text |
| Language: | English |
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1982
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| Online Access: | http://www.dtic.mil/docs/citations/ADA119025 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA119025 |
| Summary: | Three strong periodicities are observed in the time series of December temperature at St. Cloud, Minnesota (1893-1980). These three frequencies (.3868 cycles/year, .2263 cycles/year, and .1132 cycles/year) are shown to have a time and space 'sensitivity.' December is a sensitive time because synoptic flow patterns are transitional from a fall regime (i.e. a Gulf of Alaska low) to a winter regime (i.e. an Aleutian low). The north-central United States is a sensitive area because mean air mass confluence zones (i.e. stronger temperature gradients) lie in and near this region in December. A periodic shifting of the pressure pattern (forcing) should result in similar periodic changes in the temperature pattern (response) in sensitive locations near strong mean temperature gradients. This hypothesis is tested using temperature data across the United States and Canada. Because temperature patterns are related to synoptic pressure patterns, pressure data (1899-1978) are examined for analogous frequencies. The results indicate that the region of northwest Canada may force a response in temperature data 2600 km to the southeast. |
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