Terms of Scale: Synoptic and Mesoscale

As you begin to read about meteorological topics, you will come upon a couple of words that may be unfamiliar to you. (More than a couple, actually. Learning the "language" is an important ingredient to grasping any topic). These words have to do with scale, and they are "synoptic" and "mesoscale". Synoptic and mesoscale might be thought of as describing how closely we are looking at something. There are four basic scales by which we might discuss the weather or climate, and synoptic and mesoscale are the two in the middle. Let's look at all 4:

Global scale
If we were looking at earth from space (seeing the planet as a whole) we would be viewing on a Global Scale. Generally speaking, elements thousands of kilometres and greater in dimension are considered global-scale elements. They include the general circulation features, such as the trade winds, prevailing westerlies, Rossby waves and the jet streams, and regions of the atmosphere such as the tropics, the mid-latitudes, the polar regions and the ozone layer.

Synoptic scale
If we move in a little closer (perhaps using a satellite, or map that is viewing a portion of the planet) such as concentrating on the continental U.S., we are viewing things in synoptic scale. The American Meteorological Society glossary gives two definitions of Synoptic:

Synoptic—

1. 1. In general, pertaining to or affording an overall view.
   In meteorology, this term has become somewhat specialized in referring to the use of meteorological data obtained simultaneously over a wide area for the purpose of presenting a comprehensive and nearly instantaneous picture of the state of the atmosphere. Thus, to a meteorologist, “synoptic” takes on the additional connotation of simultaneity.
2. 2. A specific scale of atmospheric motion with a typical range of many hundreds of kilometers, including such phenomena as cyclones and tropical cyclones.

Synoptic scale covers weather elements such as high and low pressure systems, air masses and frontal boundaries, features commonly found on standard weather maps. The size range of elements found on the synoptic scale are usually from tens to thousands of kilometres in breadth, the area of one continent, and may extend from the surface to the lower stratosphere. It might also be referred to as "continental scale".

Mesoscale
The AMS Glossary defines "mesoscale" as:

Mesoscale—

• Pertaining to atmospheric phenomena having horizontal scales ranging from a few to several hundred kilometers, including thunderstorms, squall lines, fronts, precipitation bands in tropical and extratropical cyclones, and topographically generated weather systems such as mountain waves and sea and land breezes.

Mesoscale weather is what you see on the weather maps and forecasts for a specific area, or a state or province. It may also be referred to as "local scale".

Microscale
Looking even closer, we get to the microscale. The microscale includes all atmospheric processes less than two kilometres in size. This size range can include your backyard or garden, your neighbourhood, or a small lake, hills or wooded area. It can even be seen in differences within your garden or around the outside of your house or school. We don't think too much about the microscale, but it is the one in which we most intimately live and the one we have some ability to modify.

As mentioned, the two you will be seeing most frequently are Synoptic and Mesoscale. When you see "synoptic" (in meteorology) think: a feature that would be discernable on a map of the country. When you see "mesoscale" (in meteorology) think: a feature that would be discernable on a map of a couple of counties (or in the range of one radar unit, perhaps).