Cold, hot or dry: Persistent weather extremes associated with decreased storm activity

winter
Credit: Larisa Koshkina/public domain

A decrease in storm activity over large parts of the US, Europe, Russia, and China is found to influence weather extremes—cold ones in winter, hot or dry ones in summer. This is now shown in a study by scientists from the Potsdam Institute for Climate Impact Research. The observed changes in storm activity are likely related to changes in other atmospheric dynamics like the jet stream—strong westerly winds circling the Northern hemisphere high up in the sky.

"Less or less severe storms in the mid-latitudes, this at first sight seems to be good news - but unfortunately it isn't," says lead-author Jascha Lehmann. "These storms have a moderating effect on land temperatures as they bring maritime air from the oceans to the continents and a lack of them can thus favor extreme temperatures."

In the Northern Hemisphere mid-latitudes, much of the day-to-day weather variability is determined by the storm track regions located over the Atlantic and Pacific oceans. Here, weather systems, including storms, are generated and travel eastwards to the continents. In winter, storms bring air from the relatively warm oceans to the continents and thus have a warming effect. In summer, the effect reverses with winds bringing relatively cool and moist air from the sea. The authors show that a lack of such weather systems can thus favor more persistent heat and drought events in summer, and cold spells in winter.

"This summer a severe drought in China's northern bread basket region Liaoning threatened crop yields, while California has been experiencing a prolonged drought for no less than three consecutive years," says Lehmann. Comprehensive analysis of satellite weather data shows that these are indeed regions where significant reductions in storm activity are detected during the rainy season. In summer, storm activity calmed down over as much as 80 percent of the land area in the mid-latitudes. In winter the changes are more patchy, yet pronounced reductions are found over eastern US and large parts of Europe and Asia. This includes regions like New York and Chicago which suffered from record-breaking cold temperatures in recent winters.

These detected changes in mid-latitude storm tracks are likely linked to changes in the jet stream and planetary waves in the atmosphere. Such dynamical changes favor certain types of weather situations in some regions and others elsewhere. "Regional changes are mostly due to natural variability but on top of that we see this pronounced overall weakening in summer storm activity," says co-author Dim Coumou, "This is also something projected by climate models under future emission scenarios. However, the data so far is not sufficient to say whether the storm activity changes are caused by climate change - this has to be investigated further."

Although average summer decreases, the most intense winter storms are projected to increase in frequency under continued global warming. This could have severe implications for heavy rainfall events. Also, the most intense hurricanes and typhoons in the tropics are likely to increase under future warming because they're driven by rising ocean surface temperatures. In the Northern mid-latitudes, the main driver is the temperature difference between the warm equator and the cold Arctic; a difference that is shrinking because man-made warming is over-proportionate in the Arctic.

"Altogether our study highlights how sensitive regional weather conditions are to any changes in large-scale atmosphere dynamics," says Coumou. "This can have serious impacts for people on the ground."


Explore further

Summer storm weakening leads to more persistent heat extremes

More information: Lehmann, J., Coumou, D. (2015): The influence of mid-latitude storm tracks on hot, cold, dry and wet extremes. Scientific Reports. DOI: 10.1038/srep17491
Journal information: Scientific Reports

Citation: Cold, hot or dry: Persistent weather extremes associated with decreased storm activity (2015, December 11) retrieved 18 September 2019 from https://phys.org/news/2015-12-cold-hot-persistent-weather-extremes.html
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Dec 11, 2015
The article is written to create alarm. The evidence is that some things change other things. We don't know the magnitude of either, the damage caused by one or the other. We don't know if the net effect is positive or negative or irrelevant. Yet the article is written with a tone that suggests alarm is warranted. We have had more storms and less storms, extreme highs and extreme lows without "climate change" so it is not clear what difference any of this makes.

Another highly confusing aspect is the idea that jet streams are modified or other patterns are modified. Okay, those things also change for what appear to be random reasons. Are they really related and what is the consequence or what relationships have you identified that are statistically significant and what do those depend on in terms of starting conditions?

It seems to me this article like many is searching desperately for something that would be useful but it has none.

Dec 11, 2015
You got to admire the AGW Cult. If you run out of blatant lies, then try comedy.

Dec 11, 2015
Another highly confusing aspect is the idea that jet streams are modified or other patterns are modified. Okay, those things also change for what appear to be random reasons.
@john
if they were changed by "what appear to be random reasons" then it would not (& could not) have been predicted by Francis et al... that simple fact destroys your whole post

also note, the prediction and reasons were validated, and were also spot on...

to tell you the same thing i told dog:
just because you choose to ignore the evidence doesn't mean it will go away or that it isn't real

Dec 11, 2015
A decrease in storm activity over large parts of the US, Europe, Russia, and China

Hmm....but according to AGW Cult dogma...er..excuse me.. "science", Globull warming was responsible for an INCREASE in storm activity. But then, reality put a dent in that, so they came up with an INCREASE in the STRENGTH of storms. Then again, reality did not cooperate, so now Globull warming is responsible for all the terrible snow.

Dec 12, 2015
Too many storms; global warming, too few storms; global warming, strong storms; global warming, weak storms; global warming.... it's the snake oil theory of science. It's like they think we can't remember the stuff they said before.

Dec 12, 2015
A decrease in storm activity over large parts of the US, Europe, Russia, and China

What you deniers fail to realize is that the US, Europe, Russia, and China is not the globe.

Dec 12, 2015
Hey, sugar daddy, someone's written a great app for refuting the chicken littles! It's almost as cool as your naked links. http://www.thegua...eractive

That's our arguments all right. Kind of scary that a program could do that. AI must be much further along than we knew. I thought I was reading your enlightening posts for a moment.

Dec 12, 2015
No, that random selection of quotes demonstrates far more logic and intelligence than your or your masturbation partner have ever managed.

And there's Stumpy. Humpin' away to keep the pimps happy. Argue wid dem chickens, boy! Bring daddy home the bacon. Keep 'em interested!

Dec 13, 2015


Brevity is the soul of wit. I got nuthin'

Dec 14, 2015
Less or less severe storms in the mid-latitudes, this at first sight seems to be good news - but unfortunately it isn't

So it is true. To the AGW Cult, every cloud has a dark lining.

Dec 14, 2015
The article is written to create alarm.

So were the schematics for your smoke detector, am I to assume you have no belief in fire either?

Dec 14, 2015
am I to assume

Ha...ha... you sure know how to make an ass out of u.
You should try to think pass the anal in analogy, before posting.

Dec 14, 2015
make... ass... think... in analogy

You're an idiot, asses only think in metaphor.

Yeah, I can cherry pick and misquote too.

Dec 14, 2015
There you go failing again. Asses i.e. you, don't even think, but as you have confirmed, you sure do, stupidly, assume.

Dec 14, 2015
Wow, they almost made it to the end without mentioning climate change. Astounding. More astounding however is how everything is now correlated to climate change. Severe weather, mild weather, more storms, fewer storms, more ice, less ice, more vegetation, less vegetation, more rain, less rain... basically if we have the capacity to measure a change (defined as a variation from averages of our amazingly limited observations) then something is wrong. I wonder if alarmists realize their panic will be never-ending?

Dug
Dec 15, 2015
I believe it was 2005 that climate change alarmist were saying that we would have larger and more frequent storms. Do we just forget the climate models that failed that test?

Dec 16, 2015
And there's Stumpy. Humpin' away to keep the pimps happy. Argue wid dem chickens, boy! Bring daddy home the bacon. Keep 'em interested!
@whopper
before you continue this particular line of attack, perhaps you should contact me at sciforums and discuss what i am really up to?

i've already mentioned it here on PO about 30 times
so it makes me wonder why you would continue to attack while not comprehending what it is that is really going on

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