 At the Chinese village of Ta-fan-ch’êng close to the watershed irrigation is still required for the fields, and a lively stream coming from the high Bogdo-ula mountains to the north-east serves this purpose.But on the low hills over which Urumchi is approached cultivation depends on rain and snowfall only.This marked change in climatic conditions made its effects strikingly felt when we reached Ta-fan-ch’êng from the south-east ; for there can be no doubt that the violent gales from the north-east for which the plateau is notorious, and one of which obliged us to make a day's halt there under rather trying conditions, are directly due to the ‘ aspiration ’ which draws the cold air of Dzungaria through this great gap of the T’ien-shan down into the deep depression of Turfān, where the atmosphere is warmed, even during the short winter, by far more abundant sunshine.”
Mountain ranges between Dabancheng and Ürümqi create a natural wind tunnel, increasing windspeed in the valley.