우리나라에 이상 한파를 불러온 제트기류

2012년 12월 5일 어제 저녁 퇴근하다가 고립되어서 죽는줄 알았습니다.

계룡산 터널을 통과해야하는데, 고갯길을 오르던중 차들이 줄지어 서서히 정체하더니, 나중엔 눈속에 고립되고 말았습니다.

어랏, 하필이면 기름도 얼마 안남고, 이러다 기름 떨어지면 여기서 얼어 죽는건 아닌가 하는 걱정이.....

 

이 빌어먹을 12월 초의 폭설과 강추위는 어디서 오는 것인가? 하고 궁금하던 차에 자료좀 찾아봤습니다.

 

관련 포스트

Jet Stream (제트기류)

 

 

 

 

 

지리 수업시간에 종종 등장하는 제트기류 입니다.

 

바람 그자체는 제트기류라고 하지만

5일 간격으로 구불구불 흐르는 용트림하는 것은 'Rossby wave'라고 합니다.

 

저 Rossby wave의 폭이 저위도 지방까지 내려오게 되면, 저위도 지방도 제트기류의 영향을 받을 수 밖에 없습니다.

 

 

 

그럼 이제부터 미국의 사례를 통해 알아보겠습니다.

 

 

 

오늘의 가장 중요한 그림입니다.

 

The Arctic Oscillation이 Positive Phase 일때와 Negative Phase 일때 두가지 상황을 비교해보면 쉽게 이해가 될 겁니다.

 

 

Positive Phase	Negative Phase
극 지방이 매우 춥습니다. 그래서 검은색의 Cold화살표가 래브라도 지역밖에 오지 않습니다. Storm은 영국쪽으로 가면서 강수를 뿌리고 지중해 인근은 맑은 날씨를 유지하고 무역풍은 원래 대로 강력합니다	극 지방이 덜 춥습니다. 그래서 검은색의 Cold 화살표가 미국 중부지역까지 영향을 주고 Storm은 지중해쪽으로 가면서 강수를 뿌리고   지중해 인근은 강수가 많이 집니다. 무역풍은 약화되됩니다.

 

"Foundation fo Physical Geography by James F. Petersen (2011)" - 96page

 

 

 

Negative Phase가 나타나는 이유가 바로 이것이랍니다.

 

관련포스트

북극의 빙하가 가장 많이 줄어들었을때 사진

 

  

 

'북극이 많이 따뜻해 졌다' 이것이 원인이라고 전문가들은 말합니다.

 

seaiceextent.kml<- 여기를 누르세요 (1979년 부터 2012년까지 3월 9월의 북극해의 면적 변화를 Google Earth에서 확인할 수 있습니다)

 

 

이런 현상이 나타나면 미국은 이렇게 됩니다.

 

 

 

 

왼쪽이 Positive 오른쪽이 Negative 때의 모습입니다.

냉기가 미동부 해안가 저위도까지 더 내려오는 것을 관찰할 수 있습니다.

 

 

 

 

 

  

    

 

 

 

 

 

 

이것이 우리나라에는 이렇게 나타난다고 합니다.

 

 

 

 

 

 

 

 

 

The Arctic Oscillation

The Arctic Oscillation refers to opposing atmospheric pressure patterns in northern middle and high latitudes.

The oscillation exhibits a "negative phase" with relatively high pressure over the polar region and low pressure at midlatitudes (about 45 degrees North), and a "positive phase" in which the pattern is reversed. In the positive phase, higher pressure at midlatitudes drives ocean storms farther north, and changes in the circulation pattern bring wetter weather to Alaska, Scotland and Scandinavia, as well as drier conditions to the western United States and the Mediterranean. In the positive phase, frigid winter air does not extend as far into the middle of North America as it would during the negative phase of the oscillation. This keeps much of the United States east of the Rocky Mountains warmer than normal, but leaves Greenland and Newfoundland colder than usual. Weather patterns in the negative phase are in general "opposite" to those of the positive phase, as illustrated below.

Over most of the past century, the Arctic Oscillation alternated between its positive and negative phases. Starting in the 1970s, however, the oscillation has tended to stay in the positive phase, causing lower than normal arctic air pressure and higher than normal temperatures in much of the United States and northern Eurasia.

 

http://nsidc.org/arcticmet/patterns/arctic_oscillation.html

 

 

 

 

 

 

Between late November 2012 and early January 2013, China recorded its lowest temperatures in 28 years. In northeastern China, air temperatures dipped to -15.3°Celsius (4.5°Fahrenheit), according to the state news agency Xinhua. Frigid temperatures and blizzards stranded air and rail passengers, killed roughly 180,000 cattle, and forced authorities to open hundreds of shelters.

 

China’s cold air temperatures were mirrored by low land surface temperatures (LSTs), or how much infrared energy is emitted by the planet’s surface. This map shows LST anomalies—departures from average temperatures—for January 1–8, 2013. The 2013 readings were compared to temperatures for the same dates from 2001 to 2011. The LSTs were compiled from observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.

 

LSTs are sometimes referred to as land “skin” temperatures, and they are a reflection of how hot a surface would feel to the touch. (To learn more about LSTs and air temperatures, read: Where is the Hottest Place on Earth?) In the map, above-normal temperatures appear in shades of red, and below-normal temperatures appear in shades of blue. The darker the color, the greater the anomaly. Gray indicates water or areas with insufficient data (often due to cloud cover).

 

Despite isolated patches of warmer-than-usual temperatures (especially along the borders of India and Nepal), below-average temperatures dominated at the beginning of 2013, including areas of intense cold in western and northeastern China, Mongolia, Russia, and the Korean Peninsula. Frigid conditions froze part of the Yellow River and trapped roughly 1,000 ships in Laizhou Bay, news sources said.

Although cold temperatures were most severe in northern China, many of the emergency shelters were opened in southern China, where residents had fewer resources to heat their homes, USA Today reported. In northeastern China, the increased need to burn fuel likely contributed to China’s severe air pollution in January 2013.

 

 

 

 

 

 

 

 

 

While a high-pressure weather system brought warmer than normal temperatures to Greenland and northern Canada in March 2013, much of North America, Europe, and Asia shivered through weeks of unseasonably cool temperatures. The contrasting temperatures are no coincidence: the same unusual pressure pattern in the upper atmosphere caused both events.

 

Atmospheric pressure patterns are constantly in flux, as air masses of differing temperatures and densities move around the skies. One key measure of pressure that meteorologists track closely is known as the Arctic Oscillation (AO) index, the difference in relative pressure between the Arctic and the mid-latitudes. Changes in the AO have can major impacts on weather patterns around the world.

 

When the AO index is in its “positive” phase, air pressure over the Arctic is low, pressure over the mid-latitudes is high, and prevailing winds confine extremely cold air to the Arctic. But when the AO is in its ”negative“ phase, the pressure gradient weakens. The pressure over the Arctic is not as low and pressure at mid-latitudes is not as high. In this negative phase, the AO enables Arctic air to flow to the south and warm air to move north.

In late March, the AO dropped as low as -5.6. (See this chart published by the Washington Post’s Capital Weather Gang to see how this compares with other periods when AO values reached record-low levels).

 

The temperature anomaly map above, based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, shows how this affected temperatures in the Northern Hemisphere. The map displays land surface temperature anomalies between March 14–20, 2013, compared to the same dates from 2005 to 2012. Areas with above-average temperatures appear in red and orange, and areas with below-average temperatures appear in shades of blue. Much of Europe, Russia, and the eastern United States saw unusually cool temperatures, while Greenland and Nunavut Territory were surprisingly warm for the time of year.

 

Many parts of the Northern Hemisphere saw near record-breaking cool temperatures as the value of the AO fell. The United Kingdom experienced its 4th coldest March since 1962. In late-March, two-thirds of weather stations in the Czech Republic broke records. Germany saw its coldest March since 1883. And Moscow had its coldest March since the 1950s.