Sung yong and Brandon

From GeoClasses

1 Audio
2 Introduction
3 Explanation
4 Föhn winds in South Korea
5 Föhn winds in America
- 5.1 References

Audio

Introduction

The Chinook in North America and Nop-sae in Korea are a variety of föhn wind patterns (patterns that occur when a deep layer of prevailing wind is forced over a mountain range) that are generally found in the Midwestern portion of North America and East portion of Korea. The winds are named after the Chinook Indians in North America. One popular myth states that the word “Chinook” means “snow eater,” because particularly strong Chinook winds can remove up to a foot of snow in at little as one day. The actual origin of the word, Chinook, is originated from the Latin language, Favonius, which means westerly. This term was used to describe wind that was originated in the Chinook Indian’s territory (which is from across the Rocky Mountains). The Nop-sae is genuine Korean that generally was used to describe “Northeastern winds.” As we learned in class, winds are named based on where they blow from, so this name origin makes sense.

Föhn winds occur as a result of the movement of both high and low pressure systems over the Rocky Mountain range in America and Tae-baek Mountains in South Korea.

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Explanation

Adiabatic Change Graph

In order to understand this process scientifically, adiabatic change should be understood first. Adiabatic exchange is that the air mass expands or compresses without exchanging heat energy with atmosphere. Unlike lapse late, adiabatic change goes little bit differently according to altitude, which decreases 1 degree Celsius per 100m when adiabatic expansion occurs and increases 1 degree Celsius per 100m when adiabatic compression occurs. When high humidity air mass ascends from the ground, it expands because the higher, the less air pressure exists; correspondingly, internal pressure of air mass gets bigger than external pressure on the top of the mountain. As it expands, temperature drops not because it is affected by low temperature in the upper altitude, but simply because the same amount of energy exists in spite of its volume getting bigger. In the same way, as air mass goes down, it compresses and its temperature increases.

As air mass ascends along the eastern slope of the mountain, the air mass saturates and reaches to its dew point because low temperature can hold small amount of humidity as compared to high humidity. While the winds move over and through the mountains, the moisture that is in the air condenses and warms the air by releasing latent heat. Latent heat is described as, “the amount of energy in the form of heat that is required for a material to undergo a change in state”. This causes the weather over the eastern slope to be humid. While the air mass blows down along the eastern slope of the mountain, it warms and dries up rapidly. In the result of this, the weather over the western slope is very dry.

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Föhn winds in South Korea

Föhn winds are called Nop-sae winds in South Korea. This wind is closely related to local people’s living. Nop-sae occurs over the eastern slope during the winter and over the western slope from the late spring to the late summer (May to June).

As the statistics show, area a and b have significant differences when these area are under the effect of Nop-sae winds. Generally, except the period when Nop-sae winds blows, the temperature in a is relatively higher than b due to the effect of warm ocean current, Kuroshio Current. But, the characteristic of the air mass changes into warm and dry while the air mass goes over the Taebaek Mountains, which causes b to have an abnormal weather: warmer than a. The winds ascending along the eastern slope have great quantity of moisture in them, giving birth to high humidity and precipitation over the area a.

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Föhn winds in America

Chinook winds are known to raise Midwestern winter temperatures as much as 60 or 70 degrees Fahrenheit temporarily (for as short a period as a few hours or as long a period as a few days), but after the winds have passed, temperatures always drop back to their original levels. Although 60 or 70 degrees seems like a huge amount, one of the largest occurrences of the Chinook winds occurred in Loma, Montana, on January 15, 1972. On this occasion, the temperature rose 103 degrees Fahrenheit, from -54 Fahrenheit to 49 degrees Fahrenheit.

Chinook Arch in Calgary on november, 19th 2005.

Surreal Place

There are several effects on the people and plants living in the areas affected by the Chinook winds, and most of them seem to be negative. First of all, plants that are dormant are often brought out of their dormancy and even those plants that are able to remain dormant often have their health diminished by persistent Chinook winds. Either way, due to the winds, these plants are made vulnerable to cold waves that may arrive later in the winter. Many plants, including fruit trees and beautiful maple trees, can survive perfectly well in cold areas find it nearly impossible to live in areas affected by the Chinook winds. In the case of humans, Chinook winds also have negative health effects. In the middle of winter, the winds can override the cold air in large cities, causing pollutants to be trapped in the cold air, causing inversion smog. This provides an interesting phenomenon, because at some points the temperature can be cold on the street but much warmed on the tops of buildings. Although there have not been scientific studies done to prove these theories, it is common belief that the winds also cause sleeplessness and irritability. Not only that, but they are also believed to be responsible for a large jump in the number of migraines suffered by locals.

In summary, the Chinook winds are a spectacular natural phenomenon that can have great effects on temperatures. While these winds can seem awe inspiring, they do cause negative effects on the health of both plants and humans.

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