The textbook foehn

In many textbooks and dictionaries, a strong emphasis is laid on the role of latent heat in heating the foehn winds. Yet, it is quite well known to most experts in dynamic meteorology that the warm and dry downslope winds consist at least in many cases of potentially warm air that is brought down from upper layers and that latent heat is not involved. To shed some light on the importance of latent heating for heating the downslope winds, a large collection of cases with southerly winds in Iceland is studied. The data indicates that the warming in N-Iceland is mainly associated with warm air from above reaching the ground, downstream of the mountains. Solar heating of the lee slopes is also of some importance, but there are no indications that release of latent heat is of any importance at all in heating the surface air downstream of the Icelandic mountains. This result should encourage textbook authors and many teachers in meteorology to revise their order of priority when choosing an explanation of the heat of the downslope winds.