Interannual temperature variability and cyclone frequency over eastern Canada and the New England States : a case study: winter seasons 1931-32 to 1984-85

Interannual variability of temperature and cyclone frequencies for Eastern Canada and the New England States have been investigated for the winter seasons 1931-32 to 1984-85. Seasonal analyses have revealed that cyclone frequency has decreased by 21% over the research area; the highest losses occurring over the Maritimes and the New England States (30%) and in the southern Quebec-southwestern Ontario region (31%). The seasonal average temperature has remained fairly stable during the research period. However, the Temperature Variability Index (TVI) suggests that the interannual variability of temperature has been through some changes since 1931-32. The latest shift indicates that, since the early seventies, the temperature variability appears to be increasing during the winter season. Half-month periods were analyzed which revealed some features of the climatic variability during the winter season since 1931-32. Average temperature for the first 15 days of January recorded a significant decrease over the last 54 years. On the other hand, the last half of February presented a general increase in temperature. Parallel to that, the last half of January and the first 15 days of February have recorded substantial decreases in cyclone frequency. Thus, these half-month periods reveal trends which indicate that the overall winter season of the mid-seventies--early eighties differs from the prevailing winter climatic conditions of the thirties and forties