upwind

Upwind is a directional term used to describe the direction from which the wind is blowing. It denotes the windward side or approach direction relative to wind flow and is opposite to downwind. The reference frame is always the current wind direction, so what counts as upwind can change as the wind shifts.

In sailing and aviation, upwind refers to moving toward the wind. Sailors cannot sail directly into the wind, so they tack or sail at an angle to progress upwind; aircraft also maneuver to gain altitude or position with respect to wind direction.

In architecture, urban planning, and environmental science, the upwind side of a building, street, or area is the side facing into the prevailing wind. This orientation influences ventilation, corrosion risk, moisture, and the transport of airborne pollutants, moisture, and pollen.

In meteorology and air-quality studies, upwind is used to describe the source direction of plumes. Measurements taken upwind of a source aim to characterize background conditions before the plume affects the sampling location.

In wind energy, upwind turbines have rotors located in front of the supporting tower, facing into the wind; downwind designs place rotors behind the tower. Upwind configurations are common in modern large turbines due to control and loading considerations.