“Wind is the movement of air molecules in response to temperature and pressure differences in the atmosphere.” To properly select and site wind instruments the user must first understand the nature of the wind and its component parts that are the objective of the measurement.
The most significant factor in determining wind direction and speed (in combination a vector quantity called wind velocity) at the earth’s surface is the difference in pressure over hundreds of miles between high pressure systems and low pressure systems; we call this synoptic wind as it occurs over a broad area (100’s of miles wide). A secondary factor in the creation of the earth’s surface winds is the local differences in surface temperature or surface features that typically occur within an area of 1-30 miles, we call this local wind.
Point to Ponder: Typically when you see reported wind information the measurement is assumed to be the horizontal component of wind, that wind flowing horizontal to the earth’s surface. Is this the wind that cools or warms a farmers field, or your body , or causes evaporation or is it the combined movement of air molecules in all directions that determines wind chill factors and evaporation factors in our decision making process?