Daytime along-valley winds in the Himalayas as simulated by the Weather Research and Forecasting (WRF) model

Abstract. Local along-valley winds in four major valleys on the southern slope of Nepal Himalayas are studied by means high-resolution meteorological modelling. The Weather Research and Forecasting model is run with a 1 km horizontal grid spacing covering 4 d period December 2014. Model evaluation against observations from three automatic weather stations Khumbu Valley (one valleys) shows good agreement between modelled observed daily cycle near-surface wind speed direction. Well-defined daytime up-valley found all during this period. night-time weak magnitude flow mostly Differences their parts. As under similar large-scale forcing, differences assumed to be due valley topographies. Parts steep floor inclination (2–5∘) associated weaker shallower compared parts that have nearly flat floors (<1∘). In valleys, ridge heights also increase along valley, meaning does not necessarily lead reduction volume atmosphere. This way, dominant driving mechanism winds, within could shift effect buoyant forcing inclination. Two high barrier entrances plain. Winds at these two open entrances. Strong shallow resembling down-slope leeward followed deeper entrance, 20 towards barrier. Although was long-term climatology, impact different flows thermally driven considered. topic addressed future performing longer simulation.