If Alaskans feel wetter than usual, it's not just in their heads, and it's not just the recent fall rain.
As temperatures in Alaska continue to creep upward over the years -- faster in the north, in this era of human-caused global warming -- data show a trend of statewide precipitation increasing, too.
National Weather Service climate researcher Brian Brettschneider is back for another installment of Ask a Climatologist. As he told Alaska Public Media's Casey Grove, that increased statewide precipitation is despite places like Anchorage and -- if you can believe it -- Southeast Alaska being slightly drier than normal this summer.
This interview has been lightly edited for length and clarity.
Brian Brettschneider: Well, once again, it was a pretty wet summer statewide. A majority of the state, about three-quarters of the state, finished wetter than normal for the summer months. And that's continuing a trend that's been going on for quite a long time. Now, in fact, 11 of the last 12 summers have been wetter than normal, and only 2019 was drier. But there really has been a shift in the last decade, little bit longer, toward wetter over the course of the year, not just the summer, but certainly the summers have been noticeably wetter than they were in prior decades.
Casey Grove: And, I mean, you're a climatologist, are you ready to say that that's the new normal, that we're just going to see more precipitation in Alaska in the summer?
BB: Well, you know, there is a long-term trend, so over many decades, of increasing precipitation. It can be tempting to say, "Hey, this is a new normal based on just the last couple of years," but we really want to see a longer period before we say there really has been a regime shift. Because we've been kind of tricked before, when something happens for a couple of years in a row, and we think that's the new situation, and then it flips back. So it's hard to say where that's going to go.
But if you look at, say, the last 12 months of precipitation, a 12-month running average for several years in a row, we're kind of running at a value that would would have been a record in any other year. And we've been stuck there for a couple of years now at a record value, essentially. So it's very unusual, not ready to call it the new normal yet, though.
CG: Gotcha. Now, you mentioned different parts of the state, things were different. Juneau was actually a little bit drier than average, but there are parts of the state that saw a lot of precipitation this summer. Tell me about that.
BB: I mean, if you draw a line, say, from Anchorage to Fairbanks, most places south and east that line were at or slightly drier than normal. But pretty much every place north and west of that line — so Bethel, McGrath, Bettles, Nome, Kotzebue — most every location was between wetter to much wetter than normal, and in some cases by large amounts.
Now, of course, we're in the fall now, but we're seeing a lot of rivers that have flooded, and a large contribution of that is the rainfall that fell over many weeks during the summer. So even modest amounts of rain now falling on a basin that already has a lot of water in it keeps that flooding going.
CG: So, you know, sometimes we have these conversations, (and) people's perceptions of the weather come up versus what the actual data says. And I think we had talked about people complaining, here in Anchorage, thinking that it was a rainier than usual summer. And the data didn't really bear that out. Then you did an analysis of the weekends and whether or not it was rainier on the weekends. And remind me, what did you find last year and then what happened this year?
BB: Well, it was two summers in a row, there was approximately the same amount of rain in Anchorage, but one summer, everyone was constantly complaining about how wet it was, and the next they weren't. And I theorized that the summer that everyone was complaining about how rainy it was, that rain fell mostly on the weekends, or predominantly on the weekends, whereas last year, not so much.
And I finally did crunch some numbers this year, now that we're through the end of the summer for here in Anchorage. And if you say, "Well, how often was it raining?" Not how many days, but if, during the day, when people are out doing stuff, so, say, from 8 a.m. to 8 p.m. on just the weekends. And we actually had the fewest number of rainy hours, rainy weekend hours, of any summer in at least 25 years, where we have good hourly data, and by a large margin, actually. So even though in Anchorage, the highest temperature the entire summer was 72 — so certainly not a summer filled with really warm days — there was very little rainfall when people were out and about. So my interpretation, what I've been hearing from people was, "Yeah, it was a pretty good summer," even though, again, by temperature standards, it was pretty underwhelming.
