Why do we have weather? Why is it not 25 degrees C and sunny blue skies everywhere? How is this related to BA and my flights?
I'll try to keep things very simple, interesting and fairly short in each of these...hope they are of interest and do not upset too many if I simplify the physics involved!
Effectively it all comes down to temperature.
thermometer by
BA_pics, on Flickr
Yes,
temperature. If we had a 'closed' system (there was no Sunshine heating us unequally from above and the world was flat and heated equally throughout the air with no change or difference in absorption we would indeed have no weather! (don't worry, not going to happen!)
Because we get the Sun heating the atmosphere and the Earth's surface unequally around the world...this causes a difference in temperature both vertically and horizontally...between the air at the surface and the air at the higher levels in our atmosphere...as well as the temperature of the water in the ocean and the soil on land...and in the process of trying to balance out the temperature over both horizontal and vertical distance we get wind.
We would have no wind if the temperature was uniform in our atmosphere. However, luckily for us, there is a strong difference in temperature both in the vertical and horizontal scales...the stronger the difference in temperature, the stronger the wind from the need to try to balance out this difference (A jet stream is nothing more than an extreme difference in temperature between two air masses.)
Jet Stream description on Wikipedia
Once we have some temperature gradient and therefore some wind...we have weather...as once you move a 'cube' of air from one place to another, vertically or horizontally, it changes accordingly to the conditions...it may either contract or expand due to temperature and the fixed amount of moisture in that 'cube' will reflect the change in temperature of that cube, creating clouds, precipitation or dissipating cloud at the other extreme...
The good news is that without these temperature differences we would have a much harder time trying to get from one place to another...as we would have no wind to flow over an airplane wing and no jet streams to help speed us on our way across larger distances making fuel consumption and times much higher (forgetting the fact that life may not exist in a closed system...however, I will simply ignore that fact for this discussion!)
So the next time it is raining or cloudy in the UK or your BA flight is a bit bumpy...remember that this is actually very important and good at the end of the day as otherwise BA would not be flying you to your destination!
On the next episode of weather....
Air Masses...they are massive but there are not masses of them
