The Alaska Statewide Temperature Index was designed by Rick Thoman and Brian Brettschneider at UAF to provide an informal but representative estimate of how daily temperatures depart from normal for Alaska as a whole. Because of the vast size and diverse climates of Alaska, a statistical approach was used. A total of 25 Automated Surface Observing System (ASOS) sites maintained by the National Weather Service were selected to provide as geographically representative and consistent a sample as possible. Additionally, each location has 1981-2010 normals published by NOAA’s National Centers for Environmental Information, which includes not only daily average temperatures but also the average standard deviation. The standard deviation is important because otherwise, the typically small temperature variation in coastal areas would be overwhelmed by the often much larger inland range. The average of the standardized departures (departure from average divided by the standard deviation) for the 25 stations are then converted into an unitless index that ranges from +10 to -10, with values near +10 characterizing much above normal temperatures, zero being right at normal and values near -10 representing much below average temperatures. This range can be easily divided into two or three categories that readily characterize the average temperature for Alaska as a whole at the daily basis in near real-time.
The plot is updated once a day.