In this video, Dr Dave Campbell talks about 4 different time and space scales that are commonly used by meteorologists to describe weather phenomena – global scale, synoptic scale, mesoscale and microscale.
The global scale consists of the largest weather elements and patterns that cover tens of thousands of kilometres and affect large parts of the world. The global scale includes the general circulation features, such as the trade winds and jet streams, and is also used to describe weather patterns in regions of the atmosphere such as the tropics, the mid-latitudes, the polar regions and the ozone layer.
The synoptic scale covers weather elements such as high and low pressure systems, air masses and frontal boundaries, features that can be found on standard weather maps. The synoptic scale ranges from tens to thousands of kilometres in breadth, the area of one continent, and may extend from the surface to the lower stratosphere
The mesoscale describes scales from a few kilometres to tens of kilometres and spans between a few minutes to a day. It includes storms as well as sea-land breezes. Weather maps and forecasts are on the mesoscale.
The microscale includes very small atmospheric processes, usually less than a few kilometres in size – this is the scale in which we live.
DR DAVE CAMPBELL
We often explain the hydrological cycle, or aspects of the hydrological cycle such as the climate system and the weather processes, at a range of space and time scales. The largest space scale of them all relates to the whole planet, and we call that the global scale, and so the global process of water transport, ocean currents are at the global scales, and winds that operate over very long distances and over quite long time scales, so months to years. So those… that is one example of a long time scale that operates over thousands to tens of thousands of kilometres. Then we come down to the spatial scales and time scales that we are more familiar with when we see the weather maps on TV or in the newspaper. Those are what are called the synoptic scale, where we are looking at hundreds to a few thousand kilometres in distance, and we see weather systems change over the time scale of a few days. And then we come down again to perhaps the scale of an individual thunderstorm, which we call the mesoscale or middle scale, and there, weather processes or hydrological processes act over just a few hours or even change quite rapidly over a few minutes. And then we come down to the microscale, and that is very much the scale that we operate in where weather processes are changing second by second – gusts of wind, it’s raining or not raining – over very short periods of time.