Strange weather for the time of year – A British pre-occupation

Strange weather for the time of year – A British pre-occupation

Posted on 27. Aug, 2010 by in Asia, odd stuff, UK

A stereotypical Brit’s main topic of conversation is the weather. Unlike living closer to the tropics where the weather can often be described as same as yesterday, we seem to be able to have four seasons in one day.

Just as a reasonable summer in the UK was cut short by a cold snap the monsoons let lose their fury in Pakistan. About the same time Russia, India, Japan, Korea and even parts of Pakistan was experiencing record heat waves, forest fires, deaths and vast numbers of people needing hospitalisation from the heat. The world it seems had gone mad, and this year’s headlines rather than hurricanes in the Gulf of Mexico and typhoons in Southern Asia, became the floods in Pakistan.

So what has happened?

Seasoned travellers by aeroplane, know that when you cross the Atlantic, the time for the same journey one way can be vastly different for the same journey in the opposite direction. It all depends on the fast flowing air currents (jet stream) that the plane flies in. Flying with the flow shortens the journey time or against the flow of a jet stream extends it.

Jet streams are caused by the earth’s rotation and atmospheric heating by solar radiation. At the poles the earth and atmosphere hardly rotate at the equator they are obviously moving faster. This differential in the atmosphere speeds from north-pole to the equator and then onto the south-pole, directly and indirectly causes winds. The added point is that different strata in the atmosphere, also moves at different speeds. At the higher levels of the atmosphere there is a tendency for air to “slip” and fall behind the speed of the air below. Also the buildup of pressure behind the “slipped” air causes some streams of air to move faster and play catch up moving in the same direction as the earth’s spin… West to East. These jet streams are also influenced by temperature, moisture etc… So it’s a fairly complex affair.. far more so that this brief out line.

Now to make matters even more complicated imagine this band of jet stream meandering around the northern hemisphere west to east like a cap, it doesn’t move along the same latitude, but undulates… sometimes travelling northward on its eastern journey, sometimes southward, with globally four/six massive dips or troughs and four/six massive crests or peaks around the entire northern hemisphere.

Travelling from the south these meanders bring warmth… travelling from the north these meandering winds bring colder weather. These waves are called Rossby waves, and are all operating at high altitudes.

Summer days

In summer in the UK, the jet stream pick up warm moist air from the tropics and brings it to Britain, giving us those warm summer days with a touch of rain. Since mid July the jet stream has been blocked and diverted away from the UK and colder weather has ensued.

Further west this blocking action of the jet stream has resulted in unusual heat waves in Russia, Japan, Korea, China, etc and even excessive higher than normal temperatures in the Middle east.

In Pakistan

At the same time, as our break in summer, this blocking action movement of the jet stream over Pakistan coincided with the summer monsoons, making them much heavier than usual. The flooding that ensued has resulted in massive loss of life, crops, and has displaced over 2 million people from their homes

Cold snap in the UK. Heat wave of attacks in Parts of Europe and Asia, as well as floods and landslides in Asia in recent weeks are evidence that it is very hard to precisely predict the consequences of weather patterns.

Intergovernmental Panel on Climate Change (IPCC)

Jean-Pascal van Ypersele, vice president of the UN agency that monitors ‘climate change’ on the IPCC, never one to miss an opportunity says that ”weather patterns are consistent with the dramatic climate changes caused by humans. These are events that appear again and even more intensively in the middle of the troubled climate of the greenhouse effect, an extreme event like this is one instance where a dramatic climate change can seem real”.

Although while some meteorologists are certain it has all been caused by human activity, some are unclear on why this specific blocking action has taken place, and some have indicated that low solar activity is probably the cause, rather than man’s efforts.

But whatever causes these changes .. the fact remains that while we can produce computer models to predict the future weather patterns… mother nature always has the last word.

To support the people caught up in the Floods of Pakistan click here.

Photographs and pictures from Wikipedia

Explanation of the world drawings from Wikipedia: Meanders of the northern hemisphere’s jet stream developing (a, b) and finally detaching a “drop” of cold air (c).

Rossby waves in the atmosphere are easy to observe as (usually 4-6) large-scale meanders of the jet stream. When these loops become very pronounced, they detach the masses of cold, or warm, air that become cyclones and anticyclones and are responsible for day-to-day weather patterns at mid- latitudes.

Related articles Climate Change an Observation and Climate Change a Long Rant

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