National Overview - February 2015
Alaska Climate Divisions FAQ's

« National Overview - February 2015

Alaska Climate Divisions FAQ's

In March 2015, historical data for thirteen Alaskan climate divisions were added to the nClimDiv database and will be updated each month with the CONUS nClimDiv data. This page provides answers to some questions regarding the new Alaska dataset.

Q. In a nutshell, what is new?

A. Thirteen Alaskan climate divisions and their historical data have been operationally added to the U.S. Climate Division database, which previously only represented the contiguous United States (CONUS). The new Alaska climate division (AKCD) data goes back to 1925.

Q. What are climate divisions and how are they used?

A. Climate divisions are subdivisions of states having roughly consistent climatological behavior within them. Compared to larger regional values, they represent a more local climate signal, but without the "noisiness" or sensitivities of single-station climate records. The 48 CONUS states have 344 climate divisions between them. Rhode Island has only one (statewide) climate division. Some larger CONUS states have 10 climate divisions. Alaska has 13 climate divisions. More information is available at: US climate divisions.

Q. Which NCDC online products include the new Alaskan climate division data?

Q. Where can I access the Alaska climate division data directly?

A. Below are two ways to access the ASCII data:

Q. What basic variables are addressed in the AKCDs?

A. At this time the elements for AK are average temperature, maximum temperature (highs), minimum temperature (lows), and precipitation.

Q. Are there plans for additional products related to the AKCDs?

A. NCDC's climate monitoring suite will incorporate several additional products during spring 2015. These include:

  • maps of Alaska's monthly and seasonal climate outcomes (similar to those for CONUS)
  • dynamic mapping in Climate at a Glance
NOAA's Climate Prediction Center will use the AKCDs to improve and add to their prediction services for Alaska.

Q. Where is technical documentation for the new AKCD data files?

A. Technical information regarding data access, file formats, update schedules, and similar concerns is updated at:

Q. Are there shapefiles for the new Alaskan climate divisions? If so, where may I find them?

A. Yes, the shapefiles for the new AKCDs are available at the following nClimDiv access point:

Q. How were the AKCD boundaries determined?

A. Scientists from the University of Alaska-Fairbanks, National Weather Service - Alaska Region, NCDC Regional Climate Services, Oregon State University, and University of Nebraska-Lincoln used a technique called "cluster analysis" to identify stations with similar climatological behavior. These were combined into rough regional groupings, then further refined, using local expertise, to map more appropriately to Alaskan geophysical features. Members of the American Meteorological Society may read technical details at: (Bienek et al., 2012)

Q. Why does Alaska data begin in 1925, while CONUS climate division data begins in 1895?

A. Alaska's climate observing history, like its broader U.S. territorial and state history, is unique and generally developed much more recently than that of the CONUS. There simply is not adequate station coverage in the early 20th century to construct robust values at a scale as small as climate divisions.

Q. Are there any other differences between the Alaska divisions and those for CONUS?

A. While the basic methodology is the same - monthly values represent calculated station departures gridded and superimposed upon a basic gridded climatological baseline - the baseline is drawn from 1971-2000 averages derived from the PRISM climatological database for Alaska. The baseline gridded climatology for the CONUS draws upon NCDC?s own grids of baseline conditions.

Q. How do I know which climate division my town belongs to?

A. Reference maps of AKCDs with selected towns, cities and historical stations are available here:

Q. Which cities/stations are included in the new AKCD calculations?

A. A monthly inventory file similar to that produced for CONUS is not yet available. It may be available in future releases. However, a list of stations that were used to fill in the historical AKCD data values is available at:

Q. Are degree days included for the AKCDs?

A. Not at this time.

Q. What happened to the old Alaska statewide temperature and precipitation page?

A. That product has been retired. The official NCDC statewide values for Alaska are now computed from the AKCDs, representing a considerable improvement in methodology, and consistent with practice for CONUS states.

Q. Why are there no climate division data for other U.S. locations outside the CONUS?

A. The climate observation histories of Alaska, Hawaii and U.S. Territories, like the broader histories of these places, are unique, and present unique challenges related to longevity of observations and in many cases, unique terrain. NCDC's Monitoring Branch and regional climate services (RCS) program continues to pursue the most appropriate set of indicators for areas outside the CONUS.