Analyses of Energy Field Characteristics and Precipitation in Qilian Mountains

In this paper,using observation data of orographic cloud over the Qilian Mountains,the air current was divided into southwest air current moving pattern,southwest air current obstruction pattern,northwest air current pattern and straight westerly pattern.Wet static total temperature T-σ field and total precipitation field have been calculated with three-dimensional interpolation method.For different macro scale circulation pattern,the relation between precipitation distribution and energy field characteristics in the western Lenglong Range has been analyzed.Contrasting the daily variations of T-σ between the north and south slopes of the range and at the same altitude outside the range,it is found that T-σ inside the range is always higher that outside the range,with a high energy island over the range and energy fronts outside the range.Energy front intensity and T-σ vertical profile are very different for different circulation patterns,corresponding to orographic cloud precipitation very well.The daily mean precipitation has maximum negative correlation with convective instability index(ΔT-σ=surface T-σ subtracts T-σ at 500 hPa).However,it has positive correlation with the T-σ averaged from the surface to 300 hPa.One can see that weak convective instability day with high energy has maximum daily precipitation,whereas strong convective instability day with low energy has less precipitation or not.There is not obvious relationship between energy front intensity and daily precipitation.