地表热通量的变化对边界层热力对流卷的影响

以1995年8月14日在Florida观测(SCMS实验期间)的位温、水汽和风速等为初始化的大涡模拟结果,分析研究了边界层对流卷的发展及地表热通量对边界层热力对流卷的影响。分析了热力对流卷的位温、垂直速度及水汽混合比的关系。结果表明在边界层对流卷中,上升气流较暖湿,下沉气流较干冷。还研究了边界层对流卷的演变,结果表明当地表热通量增大时,对流会变得非常活跃,对流层发展的高度也会加深。而当地表热通量增大致超过对流卷维持的临界值时,已经无法观察出对流卷的线性特点。利用地表热通量对对流卷形成和消散的敏感性实验模拟结果,分析得出地表热通量改变时,对流卷的组织性和对流的强度发生的相应变化。减小地表热通量时,对流的强度明显减弱。对流卷的组织性较显著。增加地表热通量时,对流的强度增大,对流会变得很不规则,但当地表热通量太大时,已经看不到有组织的对流卷。研究结果表明对流卷的维持需要一定的地表热通量。

Effects Of Surface Heat Flux On Convection Rolls

Based on August 14,1995 experiment in Florida observation(during SCMS field campaign) which use potential temperature,water vapor ratio and the wind speed as the initial large eddy simulation results,the development of boundary layer convection rolls is analyzed and effected of surface heat flux on convection rolls,analyzed the relations between potential temperature,vertical speed and vapor ratio.The results reveal in the boundary layer convection rolls updrafts are warmer and moister than downdrafts.We also investigate the evolution of the boundary layer convection rolls.The simulated results show when surface buoyancy fluxes increase,the convection will become very active,the development of troposphere height also will deepen.While the surface heat flux increases the critical value more than convection rolls to maintain.Convection rolls’ linear characteristics have been not observed.The experiment about surface heat flux for the sensitivity of the formation and dissipation experimental simulation of convective rolls are also be carried.It indicates when the surface heat flux changes,the organization and strength of convection do the corresponding change.Namely,when the surface heat is reduced flux,the strength of the convection significantly weaken,convection rolls organize more significant.While surface heat flux is increased,convection strength increases,convection will become very irregular.But when the heat flux become larger,organized convective rolls can be not observed.The results of the investigation show that maintaining of convection rolls needs certain surface heat flux.