Climate Trends and Variations Bulletin - Autumn 2012
This bulletin summarizes recent climate data and presents it in an historical context. It first examines the national temperature, and then highlights interesting regional temperature information. Precipitation is examined in the same manner.
The national average temperature for the autumn of 2012 was 1.2°C above normal (1961-1990 average), based on preliminary data, which is the 17th warmest observed since nationwide records began in 1948. The record was set in 1998 when the national average temperature was 2.5°C above normal. The autumn of 1986 is the coolest on record (1.8°C below normal). As the temperature departures map below shows, areas of the Northwest Territories, Nunavut, southern British Columbia, northern Quebec and Atlantic Canada had temperatures at least 1°C above normal. Northern Northwest Territories and the northwestern part of Nunavut experiencing temperatures more than 4°C above normal. Southern Yukon, northern B.C., most of Alberta, southern Saskatchewan, and southern Manitoba all experienced cooler than normal temperatures this autumn.
Temperature Departures from Normal - Autumn (Sept, Oct, Nov) 2012
The time series graph below shows that autumn temperatures have remained above normal since 1997. The red dashed linear trend line indicates that autumn temperatures have warmed by 1.5°C over the last 65 years.
Autumn National Temperature Departures and Long-Term Trend, 1948 - 2012
The most pronounced warm anomalies in the autumn of 2012 were observed in the northern parts of the country. Regional temperature anomalies for the autumn of 2012 were amongst the 10 warmest on record for the Arctic Mountains and Fiords (5th warmest, 3.0°C above normal), Arctic Tundra (7th warmest, 2.8°C above normal) and Atlantic Canada (5th warmest, 1.7°C above normal). Three regions had negative departures from normal temperature values this autumn: North British Columbia/Yukon (19th coolest, 0.5°C below normal); Prairies (21st coolest, 0.6°C below normal); and Northwestern Forest (23rd coolest, 0.4°C below normal). The trends, extremes and current year rankings table shows that all eleven climate regions exhibit positive trends in autumn temperatures over the 65 years of record. The strongest increases in autumn temperatures are observed in the Arctic Tundra and the Arctic Mountains and Fiords regions. Linear temperature increases of 2.4oC are observed over the period of record (1948-2012) in both of these regions. The weakest temperature trend is observed in the South B.C. Mountains region (0.4°C over the same period). A table listing the regional and national temperature departures and rankings from 1948 and a table that summarizes regional and national trends and extremes are available on request to CTVB@ec.gc.ca.
As a whole, Canada experienced near normal precipitation in the autumn of 2012. It was the 30th driest autumn in the 65 years of record with national precipitation 2% below the 1961-90 normal. Over the period of record, the wettest autumn was 2005 (13% above normal) and the driest was 1952 (23% below normal). The precipitation percent departure map for autumn 2012 (below) shows drier than normal conditions in central B.C., southern Alberta and Saskatchewan, most of Nunavut and the northern Northwest Territories. Southern B.C., northeastern B.C., northern Alberta, northern Saskatchewan, most of Manitoba, northern Quebec, and part of the Maritimes all experienced wetter than normal conditions this fall.
Precipitation Departures from Normal - Autumn (Sep, Oct, Nov) 2012
It should be noted that "normal" precipitation in northern Canada is generally much less than it is in southern Canada, and hence a percent departure in the north represents much less difference in actual precipitation than the same percentage in the south. The national precipitation rankings are therefore often skewed by the northern departures and do not represent rankings for the volume of water falling on the country.
The national precipitation percent departures graph below shows that the last two autumns have been drier than normal, whereas there has been a tendency for wetter than normal conditions over the last decade.
Autumn National Precipitation Departures with Weighted Running Mean, 1948 - 2012
Three of the eleven regions experienced wetter than normal conditions in the autumn of 2012. Of these three, only the Northwestern Forest experienced one of its ten wettest autumns on record (8th wettest, 18% more precipitation than normal). Far more of the regions (8 of 11) experienced below normal autumn precipitation in 2012. Both the Arctic Mountains and Fiords and Pacific Coast regions ranked amongst the ten driest autumns on record in 2012 (10th driest, 18% below normal). This past autumn’s precipitation rankings for each region, along with the record wettest and driest years, are summarized in the extremes and current year rankings table. A table listing the regional and national precipitation departures and rankings from 1948 and a table that summarizes regional and national extremes are available on request to CTVB@ec.gc.ca.
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