Saturday, December 2, 2023


A couple of days ago, Amanda Young of UAF's Toolik Field Station posted a link to a new tool for visualizing climate data since 1988 at Toolik:

The temperature data is incomplete prior to 1994, and unfortunately precipitation coverage is rather poor until the last few years, but nevertheless the presentation is worthwhile.  It's interesting to note that 2021 was the coldest year since 1999 at Toolik; this is a more significant cold anomaly than I had realized.  Both NOAA/NCEI and ERA5 indicate that 2021's average temperature fell at approximately the 25th percentile compared to the 1991-2020 climate on the north side of the Brooks Range, i.e. not as cold relative to "normal".

The Toolik website also presents hythergraph climate summaries.  This is a visual presentation that I hadn't come across before, although it seems it's been around for more than a century.  I decided to try my hand at the hythergraph, so here's one to illustrate the statewide monthly climate averages, per NOAA/NCEI data:

The chart has several attractive features.  It nicely summarizes the similarity or contrast between different months, with the "vector difference" on the chart showing the difference in this two-dimensional temperature/precipitation phase space.  For example, November is a lot more similar to December than it is to October, on a statewide basis.  The hythergraph also provides a nice synthesis of the combined annual cycles in temperature and precipitation, with the second half of the year being much wetter.

The comparison between the 1951-2010 and 2011-2022 trajectories also provides a useful quick look at how the last 12 years have compared to the earlier climate.  The striking difference has been the increased precipitation in August and September.  It's also notable that winters have been warmer recently.

A possible improvement on the diagram would be to include the typical year-to-year variability in each month, perhaps as a background shading.  This would reveal how significant the recent changes are compared to natural variability.

[Update December 4: Chris Swingley experimented with this idea, see his blog post here:]

Here's one for Fairbanks:

The interesting shape is driven by the heavy concentration of precipitation in the warm season, skewing the top of the diagram to the right.  June through September have been notably wet in the last decade or so, but so have all of the cold season months except (presumably by chance) January.

Finally, Utqiaġvik, where the climate has changed so dramatically in the last 20 years or so.

The differences in September, October, and November are very striking; notice that October and November have become as wet as September and October used to be, respectively.  The much warmer and wetter climate of autumn and early winter is a response to much reduced sea ice, with open water providing not only a warming influence but also a lot of extra moisture.  In fact, every month of the year has been both warmer and wetter in the last 20 years.

I'm sure readers will observe other interesting aspects of this visualization; feel free to leave a comment.


  1. Nice way to note the variability of temperature versus precipitation over a year. Are there statistics associated with this analysis to quantify that variability beyond the visual? There's a centroid associated with each; surely there's a measure of variability around it and trend.

    1. Creating a graph of dispersion over time by month might inform as well.

    2. Hi Gary, yes there are clearly ways to augment the information. I'm pondering the best way to do that.

  2. Not complaining but its been an extremely mild winter so far on the North Slope. It was 18 degrees above zero (snowy too) with and east wind all day here in Kaktovik.
    Reader Mike.

  3. Rick,
    Also a question with this being my first winter living on the north slope. Its been awfully cloudy lately. Reminds me of SE Alaska (I've lived there too). Are cloudy days increasing too? I'd bet they are.

    1. Without looking at any data, I'd say it's extremely likely that cloud cover has increased significantly in recent decades for the North Slope, and especially for this time of year - because of reduced sea ice and more moisture flux from the ocean.

      Of course, the Arctic is extremely cloudy most of the time anyway, except perhaps in late winter and spring.

    2. Here's a good view from above of clouds over Alaska: