welkyboy the questions that are coming up talk about the veering/backing as height from surface wind increases.
kghjfg I have bought and read the Pooley's Air Law and Meteorology book. When I ask questions on here it is because the book has conflicted with something else (e.g. PPL Cruiser, or a recent law change) or I'd like to understand in more detail.
Thanks engineno9. This is the link I posted's explanation for a difference at night: "At night, surface friction decreases as surface cooling reduces the eddy motion of the air. Surface winds will back and decrease. During the day, as surface friction intensifies, the surface winds will veer and increase."