中高层大气对低层大气脉冲扰动的响应

从基本的大气运动方程出发,采用二维全隐欧拉格式(FICE)建立极坐标下二维声重波传播的数值模式.对小振幅高斯形态声重波传播过程的模拟结果表明,该数值模式能够再现声重波波包向上的稳定传播过程.应用此数值模式模拟了在没有背景风场和存在背景风场条件下中高层大气对10km高空处近似脉冲点源扰动的响应过程,获得了中高层大气对低层大气脉冲扰动响应的图像.结果表明,电离层高度对重力波扰动的响应不但出现在激发源激发之后,还与激发源具有较大距离,扰动的幅度随高度的增大而增大;有背景风时,顺风情况下重力波波动传播路径较逆风情况下平缓,且传播的水平距离比逆风情况下远,波动的振幅较逆风情况下弱,逆向背景风场能够加速重力波向上传播.同时,模拟还表明脉冲扰动正上方可以激发产生一种以6 min为主要周期,具有声学分支特性的快速波动.本文模拟的扰动结果与2004年12月26日苏门答腊-安达曼地震引起的电离层TEC扰动具有类似的图像. 

Response of Middle and Upper Atmosphere to Pulse Disturbance From Lower Atmosphere

By using a two-dimensional Full Implicit Continuous Eulerian(FICE)scheme and taking the atmospheric basic motion equations as the governing equations,a numerical model for nonlinear propagation of Acoustic Gravity Wave(AGW)disturbance in two-dimensional polar coordinates is solved.Results of numerical simulation show that the AGW packets propagate steadily upward and keep its shape well after several periods.This shows that FICE scheme is reliable for simulating the nonlinear propagation of AGW disturbance in a two-dimensional compressible atmosphere.The re- sponse of middle and upper atmosphere to the pulse disturbance of lower atmosphere in background winds or without background winds is simulated by using this model,and obtain the distribution of a certain physical quantity in time and space from earth's surface to 300 km above.The results reveal that the response of ionosphere occurs at a large horizontal distance from the source and the disturbance becomes greater with increasing of height.The situation when the direction of the background wind is opposite to or the same as the direction of disturbed velocity of gravity-wave is studied.The results show that gravity wave propagating against winds is easier than those propa- gating along winds and the background wind can accelerate gravity wave propagation.Just upon the source,an acoustic wave component with period of 6min can be found.These images of simulation are similar to observations of the Total Electron Content(TEC)disturbances caused by the great Sumatra-Andaman earthquake on December 26 in 2004.