When does winter informally begin in Fairbanks, or Anchorage, or Juneau? Is it the same date
for all cities or are there difference? I have always argued that the seasons, especially
here in Alaska, do not neatly correspond to strict climatological or astronomical definitions.
In addition, the seasons are not all the same length. Winter certainly lasts longer in Barrow
than in Anchorage.
After thinking about the idea of seasonal definitions for a while (see First Snow Date, and First Sub Freezing High Temperature) I have finally come up with a first draft of seasonal definitions for Alaska. Coincidentally, Rick gave this some thought last January and came up with some suggested criteria. One of his ideas was to use a running mean of temperatures as a threshold value to transition from one season to the next.
Since every location, from Barrow, to Adak, to Ketchikan, receives freezing temperatures and snow, it is only natural to use those criteria to define the winter season. But what about summer? For this first iteration, only temperatures are used. The beginning of winter is arbitrarily defined as the first day that a 5-day average of the daily temperature is under 30°F. The last day of winter is the last day that a 5-day average of the daily temperature is under 30°F. The beginning of summer is arbitrarily defined as the first day that a 5-day average of the daily temperature is over 55°F. The last day of summer is the last day that a 5-day average of the daily temperature is over 55°F. Spring is defined as the time period between Winter and Summer and Fall is defined as the period between Summer and Winter.
There were 142 stations used in the analysis. Each of them contained (relatively) complete records between 1980 and 2012. Of that 32-year period, at least 15 were necessary for inclusion in the analysis. For some North Slope stations, there were years when so Summer occurred by these definitions.
I promise, this is the last one of these for a while!
Click HERE to see the complete list of dates for all 142 stations
A list of the individual files:
After thinking about the idea of seasonal definitions for a while (see First Snow Date, and First Sub Freezing High Temperature) I have finally come up with a first draft of seasonal definitions for Alaska. Coincidentally, Rick gave this some thought last January and came up with some suggested criteria. One of his ideas was to use a running mean of temperatures as a threshold value to transition from one season to the next.
Since every location, from Barrow, to Adak, to Ketchikan, receives freezing temperatures and snow, it is only natural to use those criteria to define the winter season. But what about summer? For this first iteration, only temperatures are used. The beginning of winter is arbitrarily defined as the first day that a 5-day average of the daily temperature is under 30°F. The last day of winter is the last day that a 5-day average of the daily temperature is under 30°F. The beginning of summer is arbitrarily defined as the first day that a 5-day average of the daily temperature is over 55°F. The last day of summer is the last day that a 5-day average of the daily temperature is over 55°F. Spring is defined as the time period between Winter and Summer and Fall is defined as the period between Summer and Winter.
There were 142 stations used in the analysis. Each of them contained (relatively) complete records between 1980 and 2012. Of that 32-year period, at least 15 were necessary for inclusion in the analysis. For some North Slope stations, there were years when so Summer occurred by these definitions.
I promise, this is the last one of these for a while!
Click on Image to See Animation of Seasons (~3.1Mb)
A list of the individual files:
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