Diurnal variation of surface wind
The diurnal variation of wind is a regular, time-of-day dependent fluctuation of surface wind speed. Most pronounced on clear summer days with high pressure.
Source: WMO Guide; DWD Klima-Atlas; AMS Glossary of Meteorology.
Typical diurnal pattern — summer high pressure (undisturbed radiation day)
A common diurnal variation of the surface wind in summerly high pressure conditions (undisturbed radiation day) is low speeds at night and in the morning, rising over the day weakening again towards the evening:
| Time | Surface wind |
|---|---|
| Night | Weak to calm — surface inversion decouples surface from upper wind |
| Morning | Still weak, starting to rise after sunrise |
| Midday/afternoon | Maximum — sun warms ground, vertical mixing brings upper wind down |
| Evening | Weakens again — inversion re-forms |
Physical explanation
Night
- Ground cools by IR radiation.
- Surface inversion: cool stable layer near surface, decoupled from free atmosphere.
- Surface wind strongly damped — calm possible.
Day
- Sun warms ground → thermal convection → vertical mixing.
- Faster wind from the free atmosphere is brought down → surface wind rises.
- Maximum late morning to afternoon.
Evening
- Solar input drops → ground cools quickly.
- Inversion re-forms → surface wind decreases.
Practical use for VFR pilots
- Plan take-off early in the morning (before midday wind peak) on short runways or near crosswind limits.
- Landing in the evening is often more comfortable (less crosswind).
- Thermal activity correlates with the wind peak — gliding optimum in the afternoon.
Modifying factors
- Clouds: dampen the diurnal cycle (less heating).
- Wind fronts: override the diurnal cycle.
- Coastal areas: thermal land/sea breeze superimposes on the general diurnal pattern.
Klima-Atlas Deutschland*; AMS Glossary of Meteorology Diurnal Wind Variation.*