CAJ | 학술논문

利用“西北干旱区陆-气相互作用野外观测实验”加密观测期间在敦煌站的观测资料以及大涡模式，模拟了对流边界层的发展，以及示踪物从混合层向残留层传输的时空变化。模拟的对流边界层的结构及演变特征与实测结果基本一致。进一步通过有风切变和无风切变的敏感性数值试验，研究了风切变对垂直速度、位温和示踪物浓度的水平分布以及示踪物传输高度的影响。研究结果表明，在有风切变的试验中（甚至风切变仅存在于近地层中），对流边界层的增长加强，而且示踪物被传输的高度也较高。与浮力驱动的对流边界层相比，由浮力和风切变共同驱动的边界层中上升气流较弱而下沉气流较强，但前者的上升气流与下沉气流的分布在垂直方向上更为倾斜。由于夹卷作用的增强，浮力和风切变共同驱动的对流边界层较浮力驱动的对流边界层暖。在夹卷层，浮力和风切变共同驱动的边界层对流的上升气流和下沉气流都比浮力驱动的边界层对流中的强，而且垂直速度的概率密度函数分布也较对称，其位温和示踪物浓度的概率密度函数分布也比浮力驱动的边界层中的平直。对湍流动能收支的分析也表明风切变对湍流动能有重要影响，尤其对夹卷层中的湍流动能切变产生项影响较大。示踪物浓度的概率密度函数垂直分布显示，浮力驱动的边界层中示踪物浓度随高度变化较小，而浮力和风切变共同驱动的边界层中示踪物浓度随高度递减，但是示踪物传输的高度比较高。
이용“서북간한구륙-기상호작용야외관측실험”가밀관측기간재돈황참적관측자료이급대와모식，모의료대류변계층적발전，이급시종물종혼합층향잔류층전수적시공변화。모의적대류변계층적결구급연변특정여실측결과기본일치。진일보통과유풍절변화무풍절변적민감성수치시험，연구료풍절변대수직속도、위온화시종물농도적수평분포이급시종물전수고도적영향。연구결과표명，재유풍절변적시험중（심지풍절변부존재우근지층중），대류변계층적증장가강，이차시종물피전수적고도야교고。여부력구동적대류변계층상비，유부력화풍절변공동구동적변계층중상승기류교약이하침기류교강，단전자적상승기류여하침기류적분포재수직방향상경위경사。유우협권작용적증강，부력화풍절변공동구동적대류변계층교부력구동적대류변계층난。재협권층，부력화풍절변공동구동적변계층대류적상승기류화하침기류도비부력구동적변계층대류중적강，이차수직속도적개솔밀도함수분포야교대칭，기위온화시종물농도적개솔밀도함수분포야비부력구동적변계층중적평직。대단류동능수지적분석야표명풍절변대단류동능유중요영향，우기대협권층중적단류동능절변산생항영향교대。시종물농도적개솔밀도함수수직분포현시，부력구동적변계층중시종물농도수고도변화교소，이부력화풍절변공동구동적변계층중시종물농도수고도체감，단시시종물전수적고도비교고。
Using the observations measured in the Dunhuang meteorological station during the intensive period of Land-atmos-phere Interaction Field Experiment over the Arid Region of Northwestern China,together with a large eddy model (LEM),the effects of wind shear on the growth of convective boundary layer (CBL)are investigated,and spatial and time variations of the tracer transport from the CBL into the residual layer are analyzed.The simulated convective boundary layer agrees overall with observations.A series of sensitivity experiments with and without wind shear are performed to understand the effect of wind shear on the tracer transport.In wind shear cases (even wind shear exists near the surface layer),the growth of the boundary layer is enhanced and tracer can be transported to a higher level.Compared with buoyancy-driven CBL,weaker updrafts and stronger downdrafts existed in the shear-buoyancy-driven CBL.However,the simulated buoyancy-driven convection exhibits a more skewed distribution of updrafts and downdrafts,with weaker downdrafts than those in the wind shear cases.The shear-buoyancy-driven CBL is warmer than the buoyancy-driven CBL due to enhanced entrainments.In the entrainment layer,the shear-buoyancy-driven convection shows more symmetrical distributions of updrafts and downdrafts with stronger updrafts and downdrafts than those in the simulated buoyancy-driven convection.The distributions of potential temperature and tracer are flatter in wind shear cases than that in cases without wind shear.The analysis of the turbulent kinetic energy (TKE)budget shows that wind shear modifies the vertical profiles of different terms in the TKE budget,especially the shear production term in the entrainment layer.The vertical distribution of probability density functions (PDFs)of tracer concentration shows that tracer concentration keeps constant with the increasing height in buoyancy-driven case,while it declines with tracer being trans-ported to a higher level in wind shear cases.