Simulations

The circus of atmospheric events we call weather results from the interplay of flow phenomena on all scales, from molecular viscosity to the turbulence of microscale circulations, to the thermally driven mesoscale land and sea breezes and mountain and valley winds, to synoptic scale cyclones and anticyclones, to global scale features of the general circulation. The flow at each scale may be laminar (smooth), turbulent (characterized by rapidly changing eddies and waves of all sizes), or transitional (a blend of laminar and turbulent) properties. The nature of the flow often varies with location, being generally more turbulent close to the earth's surface, for example. The character also varies with scale: thus, sometimes small-scale regions of laminar flow are present within large-scale turbulence patterns; other times, turbulence may be found embedded within laminar flow.

Some forces, particularly Coriolis, are more influential at some scales than at others. At every scale, thermally driven circulations are evident. These include the land and sea breeze, mountain and valley winds, the monsoon, and Hadley cell circulations. Other notable winds are the result of large scale systems interacting with surface topographical features. In this category are lee waves, Chinook and Santa Ana winds, nor'easters, and lake effect snowstorms.

Interactions between atmosphere and oceans affect the atmosphere in a variety of ways. Large scale ocean currents, upwelling circulations, and ENSO are just three examples of interactions that have major impacts on airflow patterns.

The atmosphere demonstrates elements of chaotic behavior which means that future conditions are highly dependent on earlier ones. A related idea is that the smallest atmospheric disturbances may have major influences on much larger systems, a phenomenon known as the butterfly effect. These considerations suggest there may be limits to the atmosphere's long-term predictability.

In this chapter, we will explore only a small sampling of the many atmospheric circulations that exist.

Circulation Simulation10_01 (13728.0K)