Diurnal Winds in the Himalayan Kali Gandaki Valley. Part II: Modeling

Abstract

Abstract The Penn State–NCAR mesoscale model MM5 is used to simulate and better understand the wind observations in the Kali Gandaki Valley reported in the first part of this paper. The Kali Gandaki River originates in Nepal near Tibet, flows southward through the Mustang Basin, crosses the Himalayas in a gorge, and descends to the lowlands of Nepal. Extremely strong diurnal upvalley flow in the gorge and the basin alternates with rather weak drainage flow in the night. As proposed in Part I, the Mustang Basin and the Tibetan Plateau can be considered as an elevated heat source driving the upvalley flow during the day. However, the extreme strength of the diurnal upvalley winds and the order-of-magnitude asymmetry between day and night cannot be explained with a simple plateau circulation theory. The model is successful in simulating almost all aspects of the observations. The simulations strongly suggest that the observed acceleration of the upvalley winds near the entrance to the Mustang Basin is linked...