Sci­en­tists shrug come rain and shine

Northwest Arkansas Democrat-Gazette - - STYLE - JOANNA KLEIN

Some just call it a sun shower. Oth­ers say that devils are get­ting mar­ried — or the rats, or that the foxes are hav­ing a wed­ding.

In some places, a hyena is giv­ing birth or there’s a hole in the heav­ens.

And al­though un­nerv­ing, some ca­su­ally re­mark that the devil is beat­ing his wife.

These are a few ways peo­ple around the world have de­scribed the phe­nom­e­non of rain fall­ing while the sun is shin­ing.

You won’t find any of those terms in the Amer­i­can Me­te­o­ro­log­i­cal So­ci­ety’s Glos­sary of Me­te­o­rol­ogy, but there’s al­ways a place some­where on this planet where you can stum­ble upon this mag­i­cal weather para­dox. But they don’t make much of an im­pres­sion on me­te­o­rol­o­gists.

“I’m not a fan of the term,” said Gary Lack­mann, an at­mo­spheric sci­en­tist at North Carolina State Univer­sity. He added, “‘Sun show­ers’ are re­ally just rain show­ers that take place with partly cloudy or bro­ken cloud con­di­tions, and they can oc­cur in a few dif­fer­ent ways.”

Of­ten you’ll spot them when the at­mos­phere around you is, in me­te­o­ro­log­i­cal terms, un­sta­ble — which is more likely dur­ing the spring and sum­mer in many parts of the world. In this con­di­tion, tem­per­a­ture vari­a­tions en­cour­age col­umns of air to move ver­ti­cally, ris­ing rapidly in some places and sink­ing in oth­ers. In the ris­ing col­umns, the air cools, con­dens­ing mois­ture within it and al­low­ing clouds and show­ers to de­velop. But the air in the sink­ing col­umns sup­presses clouds, cre­at­ing ar­eas of clear skies be­tween show­ers — and the pos­si­bil­ity of sun show­ers.

But you won’t see them if the sun is straight over­head. Your chances to catch the magic are greater when the sun is low on the hori­zon, like the mid­morn­ing or the midafter­noon, or when a shower moves east. At those mo­ments, the an­gle of the sun al­lows it to shine be­neath the rain clouds. “This is also a good recipe for rain­bows,” Lack­mann said.

And there are less com­mon op­por­tu­ni­ties to see sun show­ers, too. It can take sev­eral min­utes for rain­drops to fall from their cloud homes in the sky to the Earth’s sur­face. And in rare in­stances when a dis­si­pat­ing cloud pro­duces rain, the sun can break through the clouds while the drops are still fall­ing.

“That’s some­thing you see hap­pen in the trop­ics or when the [wind] is blow­ing and push­ing the rain out from un­der the cloud,” Lack­mann said.

In Hawaii, for in­stance, sun show­ers are known lo­cally as pukalani, or pineap­ple juice. Pukalani, also the name of a rainy town, means “hole in the sky.”

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