Wind- und Temperaturverhältnisse an ungestörten Schönwettertagen im Dischmatal bei Davos

Wind and temperature conditions in the Dischmatal near Davos (Switzerland) during undisturbed clear days

Birmensdorf

1964

S. 389-441

19 Abb., 5 Tab., 20 Lit. Ang.

Bandaufführung

1265

157501

Temperature and wind conditions have been studied in the Dischmatal, near Davos, a high mountain valley oriented in a SE-NW direction. For this purpose a detailed investigation along a cross section was made for days typically influenced by radiation (good, clear weather) during the snow-free season. Five weater stations were istalled: on in the valley bottom, one half way up on each slope an one on both ridges. The daily course of wind speed, wind direction and temerature is discussed in detail because the radiation conditions differ notably between stations. The following features are important: typical fluctuations of temperature, in the valley bottom; the initiation of up an down valley winds; heat loss on the shady slope compensated by adiabatic sinking of air masses; strong warming on the ridges caused by subsidence processes in the free atmosphere during autumn. The daily course by subsidence processes in the free atmosphere by means of observations near the ground, is subdivided into seven phases (see fig. 13): a) Midnight until sunrise on the east facing slope: down-valley winds on the valley bottom, down-slope winds above the upper limit of the temerature inversion. b) Sunrise on the east slope: No change on the valley bottom and on the west slope; soon after sunrise on the east slope, up,slope winds begin starting from above. c) The entire valley in sunlight: Winds turn up-valley on the bottom and up-winds begin also on the west slope. d) Decreasing radiation on the east slope: On the east slope winds turn parallel to the valley, first on the upper, then progressivley on the lower parts of the slope. e) Sunset on the east slope and onthe bottom: In the lower air layers wind circulate across the valley from the shady to the sunny slope. f) Before sunset on the west slope: The cross circulation now includes about half the slopes; on the bottom winds turn down-valley. g) After sunset until midnight: On both slopes down-winds begin, the cycle is then repeated from a).