2013: Year of Big Temperature Anomalies in Alaska

Year of Big Temperature Anomalies in Alaska

So far, this year has been the most anomalous temperature-wise on record for Fairbanks and Anchorage. A near record cold spring was quickly followed by a near record hot summer. Here are some details.

Fairbanks just enjoyed its 36th day of 80°F+ (26.7°C+) temperatures this past Thursday (August 8th) and its 14th day of 85°F (29.4°C+) temperatures on Wednesday August 7th. Both crushed the all-time records for such, the previous records being 30 80°+ days set in 2004, 1923, and 1915 (the last two years having dubious temperature data) and for 85°+ 10 days in 1986 (12 such days were reported in 1918, but again of dubious validity). The summer is on track to be the warmest on record with an average of 66.0°F (18.9°C) as of August 9th (about 5.3°F above normal) The warmest climatological summer (June-August) on record for Fairbanks was that of 2004 with a 64.5° (18.1°C) average. This followed one of the coldest springs (March-May) on record which averaged 23.1°F (about 8.0°F below average). Here are the monthly averages for Fairbanks for the spring and summer period:

FAIRBANKS:



Anchorage has seen a similar trend although not nearly as extreme as Fairbanks being that Anchorage has a marine climate regime rather than the continental type in Fairbanks.

ANCHORAGE



Unlike Fairbanks, the warmest summer on record is unlikely to occur in Anchorage with its 60.0°F average (so far) versus a record value of 60.5° set in 2004. Cooler weather is almost certain for the remainder of August. Anchorage has had 40 days of 70°F+ temperatures already this summer, which may be a record. One stretch of 15 consecutive such days from July 15-31 was a record.

An Analysis by climatologist Brian Brettschneider (of SWCA Environmental Studies, Anchorage, Alaska)

Climatologist and Environmental Scientist Brian Brettshneider (you may remember him from my blog last Wednesday about peak heat weeks in the U.S.—he produced those fantastic maps) has done a very detailed analysis of the temperature anomalies at Anchorage and Fairbanks this year. This is quite technical stuff, so bear with us.

Brian explains the meaning of the three graphics (that he created):

“Here is how to interpret the charts - from bottom to top.

1) The red line shows the annual percentage of days that the temperature was more than three standard deviations either above or below the mean; e.g., +3.2, -3.5, etc. Since it uses percentages, 2013 can be compared to other years on equal footing. Also note that the categories are non-overlapping.

2) The dark blue line shows the percentage of days where the daily temperature anomaly was between 2 and 3 standard deviations either above or below the mean; e.g., +2.1, +2.7, -2.4, etc. The dashed line is the expected value based upon the normal distribution.

3) The solid burgundy line shows the percentage of days where the daily temperature anomaly was between 1 and 2 standard deviations either above or below the mean; e.g., +1.5, +1.2, -1.6, etc. The dashed line is the expected value based upon the normal distribution.

4) The solid green line shows the percentage of days where the daily temperature anomaly was between 0 and 1 standard deviations either above or below the mean; e.g., +0.2, -0.9, -0.7, etc. The dashed line is the expected value based upon the normal distribution.

5) The solid orange line at the top shows the Chi-Squared goodness of fit value. It is a squared, weighted measure of the difference between the actual and expected values and is the gold standard for categorized (grouped) data. A value of zero indicates that the distribution of anomalies exactly fit a normal distribution. Any Chi-Squared value less than 6.0 (with 2 degrees of freedom) indicates that that year's temperatures approximated a normal distribution at he 95th percent significance level. The larger the value, the more anomalous (less normal) the distribution is. It can also be thought of as a measure of distribution extremes. By this metric, Fairbanks in 2013 (through August 7th) has had the most extreme temperatures of any year on record (post-1930) by a large margin. In fact, if the rest of 2013 is exactly normally distributed, it will still be the most extreme year on record. The second most anomalous your on record is 1998. However, 1998 deviated from the normal distribution by having too few extreme days. 83% of days in 1998 were within 1 standard deviation of the mean and the rest were between 1 and 2 standard deviations. It was close to a uniform distribution as opposed to a normal distribution. For Anchorage, 2013 is also in 1st place by a wide margin.”



The important thing to look at here are the huge anomaly margins for both cities in the 3+ sigma range at each end of the temperature spectrum.





All above graphics courtesy of Brian Brettschneider.

What is also interesting to note is that in spite of the amazing temperature anomalies not many daily temperature records have been set (so far) this year at either location: 2 record highs at Anchorage and 0 record lows, 3 record highs at Fairbanks and 5 record lows. The extreme range has been: Anchorage 81° on June 18, -9° on January 27 and 28, Fairbanks: 92° on June 25 and 26, -47° on January 28.

I blogged about the record cold spring in Alaska last May and also about the record Alaska heat in June.

KUDOS: To Brian Brettschneider (of SWCA Environmental Studies, Anchorage, Alaska) and to Rick Thoman of NWS-Fairbanks for Fairbanks temperature data.

Christopher C. Burt
Weather Historian