Let's try and keep things simple.
If air is flowing in a uniform manner over a perfectly flat surface, something is bound eventually to cause a disruption in the status quo. It doesn't matter what, it's just the nature of things.
If a parcel of air is caused to rise, it tends to leave behind it a vacuum, that thing which nature abhors, by all accounts. So, air will try to move from elsewhere in order to fill this space. As the rising air ascends, it will compress the air it passes through, and so the air at altitude will try to relieve the extra pressure by moving to where the pressure is less.
So, probably in a roundabout way, air at altitude changes places with air on the surface, each parcel tending to take with it its original properties, i.e. speed, direction and temperature.
Hope this helps.