So now its the new year and resolutions have already fallen by the wayside it seems like a good time to look back at what has happened over the last year.
It began with the coldest winter (Dec-Feb) here in the UK since 1978-79, while there were record high temperatures in Russia as Moscow sweltered in 38.2C heat, the warmest for 91 years, causing drought and the warmest summer on record. The year ended with floods in Queensland, Australia that are currently submerging much of the city of Brisbane.
NOAA’s map of significant events for last year (click image for large view)
Wind is all around us but what is it and what actually causes it? Here we examine one of the simplest aspects of weather and some of the terminology that surrounds it.
Wind simply is the movement of air. And the air moves because of differences in temperature and pressure around the globe.
This difference in temperature and pressure is because at the equator (the hottest area on earth) the hot air rises before cooling and sinking as it moves towards the poles. This leads to the basic concept of atmospheric circulation… the three-cell model (see right).
As the air cools it shrinks and as it heats it expands. This is the basis of air pressure, with high pressure essentially pushing down harder on the Earth’s surface because there is more air present it is just more dense.