夏季金塔绿洲效应的理想数值试验研究

Idealized Numerical Tests of Oasis Effect in Jinta Oasis in Summer

利用复杂地形下高分辨率边界层数值模式BLASIUS,基于"绿洲系统非均匀下垫面能量水分交换和边界层过程观测与理论研究"实验期间的观测资料,通过一系列的理想数值试验,探讨了沙漠与绿洲间地表温差、浮力频率以及背景风速对绿洲效应的影响。结果表明:绿洲与沙漠间地表温差的增大对金塔绿洲上空"冷岛效应"和"湿岛效应"的增强作用主要表现在500 m高度以下,使得"冷岛"的宽度增加,"湿岛"的高度降低,且对"湿岛效应"的影响较"冷岛效应"滞后约1 h;增大浮力频率,绿洲上空的上升气流增多,1.5 km高度以上沙漠与绿洲过渡带的垂直速度增大;增大背景风速,绿洲与沙漠间的垂直环流的对称性减弱,环流中心的高度降低、强度减弱。

Based on the observation data during the period of the experiment with ‘theoretical study and observations of water and energy exchange and planetary boundary layer on inhomogeneous underlying surface in oasis system’, the influences of surface temperature difference between desert and oasis, buoyancy frequency(Brunt-V?is?l? frequency) and background wind velocity on oasis effect were discussed by a series of idealized numerical tests of BLASIUS(boundary layer above stationary, inhomogeneous uneven surface) model with high resolution and complex terrain. The results show that the cold island effect and humid island effect enhanced with the increase of surface temperature difference between oasis and desert, and the enhancing action mainly occurred below 500 m over the ground. The horizontal range of ‘cold island’ over oasis enlarged and the vertical height of ‘humid island’ decreased with increase of surface temperature difference. The influence on ‘humid island effect’ was about an hour later than that on ‘cold island effect’. The updraft airflow over the oasis increased and the vertical velocity increased over the transition area above 1.5 km height with increase of buoyancy frequency. The symmetry of vertical circulation between oasis and desert decreased with increase of initial background wind speed, and the height of circulation center decreased and the strength weakened.