mountain-valley winds; mountain and valley breeze
A meteorological term referring to local wind systems that blow upslope during the day (valley breeze) and downslope at night (mountain breeze).
Mountain-valley winds are winds that blow from the valley to the mountain during the day and from the mountain to the valley at night.
Compound of 山 (mountain), 谷 (valley), and 風 (wind). The reading やまたにかぜ is a straightforward kun'yomi combination.