Wednesday, December 15, 2010

Canadian Heat Waves Part 4

Top Ten Percent of Hottest Days
29 stations were selected to check for what is happening collectively with TMax. These stations were selected to have a start year before 1920 and have at least 95% of the records within their date range.
These are those stations:
1111CRESTONBritish Columbia19122006270031.1
1340VAVENBYBritish Columbia19132009212032.4
2106LACOMBE CDAAlberta19081993199128.6
2205CALGARY INT'L AAlberta19002009262628.8
2409LAKE LOUISEAlberta19152007223026.
2658BEAVERLODGE CDAAlberta19132007195027.3
3259SCOTT CDASaskatchewan19112009190330.6
3328SASKATOON DIEFENBAKER INT'L ASaskatchewan19002009213631.2
380BELLA COOLABritish Columbia19002002185928.3
3938FORT FRANCESOntario19131995134630.6
3943MINE CENTREOntario19152005156230.5
4333OTTAWA CDAOntario19002010166731.5
588FORT ST JAMESBritish Columbia19002009204427.2
6158FREDERICTON CDANew Brunswick19132000132730.3
6527CHARLOTTETOWN CDAPrince Edward Island19101992181427.2

Each station had their top 10% of high TMax from July, regardless of the year, dropped into a table. Those in turn were baselined for each station from 1961 to 1990, the common range used in the science (for what ever reason they give).

From there the anomalies from those baselines were plotted for the entire dataset.
This is the highest TMax anomaly:

The over all trend is down, fewer hot days across all of Canada. The heat waves peaked in the 1940's, dropping until the 1980s, and flat since. 20 years of no change in heatwaves.

This is the average of the TMax anomaly:

Basically flat over all, with the 1920's to the mid 1940's dominating.

The lowest of the TMax anomalies will be very close to a flat line, no fluctuation because this dataset starts from a minumum value for each location to give the top 10%.

This is the number of days in each year. This had to be more restrictive in the stations, 1920 to 2005 was the cut off range. So no stations with a start year before 1920 and no stations with an end year before 2005. This is only 16 stations that met that criteria. If the entire dataset was used the count would be skewed, the numbers too low, because of missing stations in those outside years.

The trend is also dropping. Fewer days in Canada are above the top 10% temperature now than in the mid 1940's.

No matter how you slice the data, either looking at single stations, or collectively from a range of stations across Canada, the over all trend of TMax is to cooler temps.

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