What happens to wind direction and speed during the night closer to the ground in the southern hemisphere?

During the night in the southern hemisphere, closer to the ground, wind direction typically veers and speed decreases. This phenomenon occurs due to several atmospheric processes that impact wind behavior during nighttime.

As the sun sets and temperatures drop, the surface cools, which leads to stable atmospheric conditions. In these stable layers, the friction between the surface and the air slows down the wind speed, causing a decrease in wind velocity. Meanwhile, the shift in wind direction, known as veering, happens as the temperature and pressure gradients change at night. The winds often shift from a diurnal pattern associated with daytime heating and convection to a more subdued pattern.

These changes are essentially a result of the impact of the cooling surface on local atmospheric conditions rather than major weather systems, and this is observed more prominently in stable nocturnal boundary layers.