Naturespeak 

El Nino is back! But do we really want him?

By Jack Souther,

Whistler Naturalists

Someone has to take responsibility for the wacky weather – Right!

Sun spots and global warming get a fair amount of blame but El Nino, Mary’s little boy, takes most of the flack when things go wrong and most of the credit when they don’t.

Marketing wisdom has it that El Nino brings copious amounts of snow to our corner of ski heaven but I can remember El Nino years when the Sea to Sky corridor had about as much snow as the Ho Chi Minh trail. I’ll deal with the statistics in a later column.

Despite his Spanish name, "little" is one thing that El Nino is not. He and his sister, La Nina, are the principal players in what climatologists refer to as the Southern Oscillation, which is second only to the Earth’s rotation around the sun as the controlling force behind global weather patterns. It all starts in the equatorial Pacific, in a slice of that vast ocean extending 10,000 miles from the coast of South America in the east to the Islands of Micronesia in the west and hemmed in on the north and south by the Coriolis effect. That mysterious force that makes your water spiral out of the bathtub also acts as an invisible barrier on either side of the sunlit girdle of equatorial Pacific water.

In normal years trade winds, blowing across the Andes from east to west, sweep the sun-warmed surface water westward. Cold, nutrient-rich water wells up along the coast of South America and on the opposite side of the Pacific the warm surface water accumulates. Supported by the friction of the trade winds, its surface can be more than a foot higher in the west than in the east.

La Nina is simply an exaggeration of this normal scenario – a time of stronger Trades, more rapid upwelling, and cooler sea temperatures in the eastern Pacific.

But there is nothing at all "normal" about El Nino. At irregular intervals, on average every two to seven years, the pent-up body of warm surface water in the western Pacific slides eastward. A great surge of warm water sloshes against equatorial South America, where it is deflected north and south along the coast of the Americas.

No one is sure what kicks off El Nino. The trade winds slacken, sea temperatures along the Peruvian Coast soar, and in our part of the world sea and air temperatures go up. The distribution of highs and lows, the hills and valleys of the atmosphere that control the jet stream, are disrupted. And those snow-laden storms are diverted to the north or south of our rock-strewn slopes.

Whether you are an Australian farmer burning up in the out back, a Californian flooded out of your home by torrential rains, an Alberta rancher dealing with the worst drought since the ’30s, or a Whistler skier cursing yet another dinged edge, the coming of El Nino is seldom cause for rejoicing.

Upcoming Events.

Monthly bird count, Saturday, Feb. 1 — Meet Michael Thompson at the bottom of Lorimer Road at 8 a.m.

For more information on the Whistler Naturalists, contact Veronica Sommerville at: whistlernaturalists@canada.com

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