–from "The Chinook Wind," by L. G. Fish

by Irene Ho ’00

It is eight o’clock in the morning and the mist still clings heavily to the spruce and pine trees jutting up like silent sentinels on either side of the road. The mountains have disappeared, their immense bulk hidden by the low clouds. As the bus climbs steadily out of the fog and into the thin morning sun, we catch a glimpse of a grazing elk, then some mountain sheep. "I’m a mountain girl myself. Born and raised here," Meg is saying. "I never tire of seeing the mountains, the glaciers. My kids always say, ‘Mom, they’re just snow and ice. Get over it.’ But I don’t see it that way–they’re just as beautiful every time I look, and I see them at least two or three times a week on this route."

Someone sitting behind me asks how bad the winters get here. "Oh, we get snow as expected, but we also get the Chinook. When that warm wind comes blowing down, the temperature goes up and down, and everybody’s tempers go up and down with it. I know my husband, when the Chinook blows, all I say is ‘Yes dear,’ ‘No dear,’ and ‘Whatever you say dear.’" Everyone laughs.

It was August, and my family and I were on a trip to see the Canadian Rockies. Stopping a few days in Banff, British Columbia, we went on a bus tour led by our driver, Meg. Part of my love for the mountains is a legacy of Meg, who so infectiously communicated her own personal attachment to them. What aroused my curiosity the most that day was her mention of the Chinook, but I will also never forget the mountains: Mt. Rundle, with a profile reminiscent of the symbol for the Prudential. Mt. Snowdome in the Columbia Icefields, one of only two triple-continental divides in the world, the water from its snowcap flowing into three oceans. (The other triple continental divide can be found in Siberia.) The vast blue Athabasca glacier: when we climbed onto it, we were dwarfed on all sides by moraines, our guides informing us that we were standing on one thousand feet of glacial ice.

But long after this trip, I found myself still asking, what exactly was the Chinook?

The chinook wind takes its name from the Chinook Indians who once lived on the Pacific coast, along the Columbia River. The tribe, first described by the Lewis and Clark expedition, made their livelihood mostly from salmon fishing, hunting and trading. They were finally decimated in the early 1800s by infectious diseases against which they had no resistance, passed on from white explorers and traders.

But the Chinook left behind a collection of legends built around the wind that now bears the tribe’s name. The following excerpt (taken from the book The Chinook Indians: Traders of the Lower Columbia River, by Robert H. Ruby and John A. Brown) is one such tale that portrays the wind as a god-like character:

Meteorologically speaking, the chinook, the vengeful youth in the story, is a warm, dry wind that blows down from the Rockies, usually around January. Regions that are affected by this wind see dramatic increases in air temperature. In the resulting warm weather, the accumulated winter snow sometimes can melt and evaporate away in a day. In fact, the word "chinook" itself is translated from the Chinook dialect as "snow-eater." A record air temperature rise occurred on January 22, 1943 in Spearfish, South Dakota, when it shot up 49°F in just two minutes!

The chinook wind is categorized as a katabatic wind, which are any winds that blow downslope of mountains. Specifically, the chinook blows down the eastern slope of the Rocky Mountain chain, affecting a region only a few hundred miles wide, but reaching from northern New Mexico upward into Canada.

How exactly does a wind become a "snow-eater?" Generally speaking, wind on the windward side of any mountain experiences both a drop in temperature and expansion as it rises to overcome the mountainous barrier. The wind then warms and compresses as it descends the other, or leeward, side of the mountain.

Such a leeward wind develops into a snow-eating chinook when the compression is accompanied by the addition of heat on the windward side of the mountain. This latent heat is produced from the changing of phase between gas to liquid in the atmosphere; it accumulates when air currents convect horizontally (referred to as advection) instead of vertically, and prevent the normal cooling of air. Often, cloud formation and precipitation on the windward side of the mountain can also contribute to the development of a chinook because the resultant condensation process makes the wind even warmer and the loss of moisture makes it drier.

The chinook of the Rockies is usually foreshadowed by a characteristic wall of clouds that then remains stationary over the tops of the mountains for as long as the wind blows. It has been documented that many people, apparently including the husband of our Rocky Mountain guide Meg, suffer dramatic mood changes when the chinook blows, but the underlying reason is not yet understood.

The chinook also has an economic impact on the residents of the affected regions. Most people welcome the respite from the cold and snow. However, come spring, the land often has become much drier from the absence of snow, which makes farming and planting of crops more difficult.

The weather paradox that is brought by the chinook is not found only in the Rocky Mountains. A similar and more commonly known katabatic wind is the föhn. Its effects are felt in as varied places as the European Alps, the Asian Caucasus and western regions of the United States. In Argentina, where the Andes Mountains are located, the föhn wind is referred to by the local term, zonda.

In the Alps, aside from drastically warming the air, föhns often cause destructive avalanches. The Santa Ana wind is a warm, dry föhn wind that affects Southern California. It blows in the opposite direction of the chinook, from the east to west down the slopes of the desert plateaus of Nevada. Also unlike the chinook, the Santa Ana wind rarely receives latent heat from precipitation–it is dry enough as it is because of its origins over the desert. The Santa Ana wind’s most damaging effect is its ability to dry out the land, making it especially susceptible to forest and brush fires that occur later in the year.

After another day spent in Banff, we are back on the bus but this time, we are off to Calgary, Alberta. From there, we will fly to Toronto, and then home. As the bus pulls away, Meg glances back and I glance back as well. The Rocky Mountains are there in all their snow-capped, lake-skirted magnificence, harboring mysteries that include prehistoric glaciers, icefields, one triple-continental divide, and a wind called the Chinook.