What is transport wind?
Transport wind is the representative average wind speed and direction through the atmospheric mixed layer, commonly from the surface to the mixing height for fire-weather and smoke-dispersion applications.
Typical units: kt · mph · m/s.
Surface wind is not transport wind
Surface wind describes near-ground conditions. Transport wind represents a deeper atmospheric layer and may differ substantially in speed or direction.
Why transport wind matters
Once smoke rises and becomes mixed through the boundary layer, the wind controlling its movement may differ from the wind measured at the surface. Transport wind therefore links vertical mixing to horizontal smoke movement.
Relationship with mixing height
Transport wind is averaged through the mixed layer. If mixing height changes, the atmospheric layer being averaged can change too.
Relationship with ventilation rate
Ventilation Rate = Mixing Height × Transport Wind
Example: 5,000 ft × 12 kt = 60,000 knot-ft.
Direction matters
A high ventilation rate may improve dilution near a fire while rapidly transporting smoke toward another populated area. Good dispersion is therefore not equivalent to no smoke impact.
Interpretation checklist
- Confirm forecast versus observation.
- Identify the layer over which the wind was averaged.
- Preserve both speed and direction.
- Verify the meteorological “from” direction convention.
- Compare with surface wind but do not substitute one for the other.
- Consider vertical wind shear and local terrain.
Related concepts
Mixing Height · Ventilation Rate · Smoke Dispersion · Atmospheric Stability · Fire Weather
Technical references
National Weather Service — Fire Weather Definitions
National Weather Service — Fire Weather Terms
Tecnobosque Reference Concept · reviewed September 2026. Transport-wind methods and reporting conventions can differ among forecast offices and jurisdictions.