Spatial Patterns and Scales

Abstract

Processes in the atmospheric boundary layer occur at varying scales in both time and space. This chapter introduces the fundamental concepts of scale and explains in detail the two broad areas within boundary layer meteorology where this becomes important, “scale-invariance” and “scale-dependency”. “Scale-invariance” involves coming up with ways to describe common features of different boundary layers, using simple relationships, or scaling factors, otherwise known as similarity theory. This will allow us to understand and define useful relationships that work at every scale. For example, to define a common vertical wind profile in the boundary layer as a function of scales of turbulence shear strength, surface roughness, and stability. Or to define the universal nature, or power-law scaling exponent, of energy transfer from large to small eddies. “Scale-dependency” is used when discussing how characteristic spatial scales or boundaries of features of the surface below and the atmosphere above the ABL modify profiles and structures of temperature, humidity, winds, and clouds in the boundary layer. Understanding which spatial scales matter and how, and how to incorporate those into numerical models of the boundary layer, is a core goal for this area.