Our Common Atmosphere: TIME AND SPACE

The study of the weather is divided into different areas of emphasis depending on the time and space scales of interest. At one end of the spectrum is climatology – the statistics of past weather with the time scale of history. Climatology tells us things like the daily records, the average conditions over a year, and when it is safe for farmers to plant to avoid frost. At the other end of the spectrum is the current weather – what is happening right now – is it raining, is there lightning or blowing snow? The timescale within this spectrum ranges from hours to days, and meteorology (the study of now weather) separates into micro-, meso-, synoptic and global scales.

Microscale meteorology is the study of phenomena of about 1 km in size and less like individual thunderstorms and flows around obstacles like a house or a small hill. It is also the scale of weather in support of agriculture.

 Mesoscale meteorology is the study of phenomena with horizontal scales ranging from about 1 to 350 km with a vertical scale that starts at the surface and includes the troposphere and the lower section of the stratosphere. Events on this scale can last from less than one day to weeks. Typical events in this scale are squall lines, fronts, precipitation bands in hurricanes and cyclones and waves generated by mountains, and sea and land breezes.

Synoptic scale meteorology is all the rest up to about continental in scope. It includes things like the jet stream and frontal zones. The minimum spacing for these phenomena is about 350 km which is the distance between major upper air observing systems from which instrumented balloons are flown every 12 hours.

 The largest scale is global – which is the study of weather patterns related to the transport of heat from the tropics to the poles. On this scale, very large oscillations are studied – ones that bring the seasons, as well as events like El Ni?o. The global scale moves meteorology into climatology. And climate change is the study of how these global oscillations cause both climate and weather disturbances in the synoptic and mesoscale.