Fairbanks 2012 Review: A look back

February 6, 2013

The mean temperature for Fairbanks in 2012 was 24.1 degrees Fahrenheit, 3.5 degrees below the long-term average of 27.6 degrees. This makes 2012 the coldest year of the new century and continues the cooling trend observed over the last decade. More information on the recent cooling trend in Alaska can be read in “The First Decade of the New Century: A Cooling Trend for Most of Alaska” that appeared in The Open Atmospheric Science Journal in 2012 and was authored by faculty from the Alaska Climate Research Center. Looking further back in time, 2012 was the second coldest year in the last forty for Fairbanks; only 1999, with a mean of 23.4 degrees Fahrenheit, was colder. The mean temperature for 2012 was more reminiscent of what Fairbanks routinely experienced earlier in the 20th century. Last year was also notably colder than 2011, which had a mean temperature of 28 degrees.

2012 Fairbanks temperature summary, ACRC figure

The highest temperature of 86 degrees Fahrenheit was observed on the 23rd of June, close to the summer equinox with more than 21½ hours of sunlight. June 23rd was also the day with the highest mean daily temperature of 71 degrees. There were only five days with temperatures at or above 80 degrees, less than half the long-term normal of twelve days. The lowest temperature of the year was minus 51 degrees Fahrenheit, occurring January 29th. The 28th of January was the coldest day in terms of the daily mean temperature at minus 46 degrees. There were a total of 26 days with lows at or below minus 40 degrees, more than twice the long-term normal of eleven days. The only temperature record for 2012 was a new daily high set on April 16th, with 61 degrees Fahrenheit, topping the 1993 record of 59 degrees.

Fairbanks 2012 temperature chart, ACRC

 

Looking at the temperature data by month, it is clear that the colder than normal temperatures were not evenly distributed throughout the year. Below average temperatures were more prominent during the winter months, while summer experienced more normal temperatures. January had the greatest deviation of minus 19 degrees Fahrenheit. The actual mean temperature for the month was a frigid minus 26.9 degrees, the coldest January in more than 40 years. Large negative deviations were also observed in December (minus 13.2 degrees), November (minus 11.4 degrees) and March (minus 6.9 degrees), while February was above normal with a positive deviation of 7.2 degrees Fahrenheit. The rest of the year had no other remarkable deviations from the long-term mean.

 

The temperatures of Alaska are strongly affected by the Pacific Decadal Oscillation, which is an index derived from the surface temperature of the waters of the North Pacific Ocean. Warm temperatures in Alaska are related to positive PDO values, while negative values indicate below normal temperatures. Before 1975, this index was predominantly negative and the temperatures up to that time tended to be cool. After 1976, the PDO values switched to predominantly positive and warmer temperatures were observed. With the start of the new century, the PDO values trended to the negative again and a cooling began. With colder surface waters, the semi-permanent Aleutian Low weaken, and less warm air is advected into Alaska. While this is of minor importance in summer as days are long, in winter the solar elevations are low, the days are short and this transport of warmer air from the south greatly influences the Alaska temperatures. For more details of the annual course of temperature for Fairbanks, see the figure below.

 

2012 Fairbanks Mean Daily temperature with respect to normal, ACRC figure

 

For 2012, the precipitation total was 10.62 inches, which was very close to the expected value of 10.81 inches. The highest daily total was 0.82 inches and occurred on August 26th. Five months of the year had precipitation deficits, while six had excesses. February hit its normal value of 0.42 inches. The year followed fairly close to the long-term mean value as can be seen from the third figure. Last year was wetter than 2011, which saw a total of only 9.52 inches. As one might expect from the near normal precipitation, the snowfall of the year was close to normal with a total of 61.7 inches. The year’s snowfall was only 3.3 inches below the normal of 63.6 inches. Interestingly, this is the same snowfall total as 2011.

 

Despite the near normal annual precipitation and snowfall, there were a number of records set in 2012. March 6th saw a snowfall of 2.6 inches, tying the previous record set way back in 1932. The precipitation equivalent was 0.17 inches, and this was a new daily record, breaking the old one of 0.15 inches set in 1967. The storm continued to the next day and 6.9 inches more of snow fell, smashing the 1943 record of 3.5 inches. The precipitation equivalent came to 0.28 inches, a new record that topped the 1985 record of 0.24 inches. On May 25th, a total of 0.52 inches of rain tumbled down, which outdid the 1973 record of 0.50 inches. Two notable precipitation events occurred at the beginning of October. First, 0.21 inches of rain fell on the 6th, tying the 1989 record. This was followed on the 7th with 0.55 inches, eclipsing the 1974 record of 0.28 inches. A final snowstorm in December dropped 9.5 inches of snow on the 12th, which broke the 1972 record of 5.7 inches. On the same day, the precipitation equivalent was 0.72 inches, shattering the 1972 record of 0.17 inches.

 

2012 Fairbanks Cumulative Daily Precipitation, ACRC figure

The last day of seasonal snow cover was April 22nd and the last frost of the winter came on May 14th. Green up occurred on May 10th, which is about normal. Growing degree-days totaled 1,003 and the growing season was 117 days long, which is about average. The first frost hit on September 10th and the snowpack was reestablished on October 15th. As one could expect, heating degree-days were 1,297 above the normal of 13,666. Correspondingly, cooling degree-days totaled just 34. This was 27 less than expected. Mean annual wind speed was 3.3 mph, with lower values in winter when the semi-permanent inversion decouples the surface conditions from the upper circulation.

 

Less than 300,000 acres burned due to forest fires, a relatively low value, as the mean over the last 50 years is about 1 million acres. This is understandable, as there were fewer hot days in 2012. Hotter days cause both a higher number of lightning strikes (starting new fires) and allow existing fires to expand. The most vexing fire for the Fairbanks area was the Dry Creek fire. It started June 23rd about eighteen miles south of North Pole. The fire continued to occasionally send smoke into the unban area until after the middle of September.

 

This information consists of preliminary climatological data compiled by the Alaska Climate Research Center, Geophysical Institute, University of Alaska Fairbanks. For more information on weather and climatology, contact the center at 474-7885 or visit the center web site at http://akclimate.org. Please report any errors to webmaster@akclimate.org.