MICROCLIMATE

The local climate which distinguishes the physical characteristics of the local region from other regions. The vertical extent of such a climate ends where it can no longer be distinguished from other climates. This is often related to the extent to which the vegetation and so forth affects the air just above it - which is basically the Planetary Boundary Layer (PBL). Trees and plants produce microclimatic variations due to their effect on the air's moisture supply and wind speed. An absence of trees and plants in a city may create a microclimate where it is locally warmer than the surroundings. [See heat island.] Lakes may also vary the microclimate - cooling the surface air in the summertime and warming it in the winter.