Omega blocking highs can remain in place for several days or even weeks [image credit: UK Met Office]
Another day, another attempt at a climate scare story. That’s a well-identified pattern too. But is this jet-stream pattern really ‘newly’ identified, or was it described by NASA nine years ago? Meteorology uses the term omega block. Which side of the block a region is on determines whether it’s warmer or colder than normal for the duration.
Scientists have identified systematic meanders in the globe-circling northern jet stream that have caused simultaneous crop-damaging heat waves in widely separated breadbasket regions-a previously unquantified threat to global food production that, they say, could worsen with global warming.
The research shows that certain kinds of waves in the atmospheric circulation can become amplified and then lock in place for extended periods, triggering the concurrent heat waves, reports Phys.org.
Affected parts of North America, Europe and Asia together produce a quarter of the world food supply. The study appears this week in the journal Nature Climate Change.
“We found a 20-fold increase in the risk of simultaneous heat waves in major crop-producing regions when these global-scale wind patterns are in place,” said lead author Kai Kornhuber, a postdoctoral researcher at Columbia University’s Earth Institute.
“Until now, this was an underexplored vulnerability in the food system. During these events there actually is a global structure in the otherwise quite chaotic circulation. The bell can ring in multiple regions at once.”
Kornhuber warned that the heat waves will almost certainly become worse in coming decades, as the world continues to warm. The meanders that cause them could also potentially become more pronounced, though this is less certain.
Because food commodities are increasingly traded on a global scale, either effect could lead to food shortages even in regions far from those directly affected by heat waves.
The jet stream is a fast-moving river of air that continuously circles the northern hemisphere from west to east. It generally confines itself to a relatively narrow band, but can meander north or south, due to a feature scientists call Rossby waves.
Among other effects, these atmospheric wobbles may pull frigid air masses from the polar regions, or hot ones from the subtropics, into the populous midlatitudes. The wobbles strongly influence daily weather.
When they become particularly large, they can bring prolonged heat waves, droughts or floods in summer; or in colder seasons, abnormal cold spells.
Full report here.
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Block (meteorology) – Wikipedia
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December 10, 2019 at 04:25AM
Iowa Climate Science Education 