重力波对中间层和低热层大气环流的影响

Effects of Atmospheric Gravity Waves on the Mesosphere and Lower Thermosphere Circulations

利用β通道准地转近似大气平均运动方程组,采用重力波线性饱和参量化方法,定性地研究大气重力 波对中间层和低热层大气环流的作用.模拟计算得到,大气重力波对平均东西风速可产生100m·s-1／d左右的作 用力和产生120 m2/s的湍流扩散,这些作用平衡了Coriolis扭力,导致大气的平均东西风速大大偏离辐射平衡 风场,中层顶附近的平均东西风速在冬季(夏季)甚至反转为东风(西风).平均东西风速计算结果与冬季和夏季 中频雷达东西风速观测值和大气模式剖面等大致一致.

Atmospheric gravity waves generated in the lower atmosphere, carrying momentum and energies, propagated upward and usually became saturated and breaking in the Mesosphere and Lower Thermosphere (MLT) due to their increasing amplitudes versus increasing height. Linear saturation parameterizations of atmospheric gravity waves were applied with theβ-channel quasi-geostrophic mean flow equations to qualitatively investigate influences of gravity waves on MLT circulations. Three waves with 0m·s-1, 20m·s-1,-20m·s-1 horizontal phase speeds respectively were taken as a parameterization of the discrete spectrum of gravity waves. Simulations show that the accelerations due to waves can be 100m·s-1/d and eddy diffusion coefficients can be 120m2/s in the mesosphere, which balance the Coriolis force due to MLT meridional circulations and induce great departures of the zonal mean zonal winds from the radiation balance zonal winds. The calculations of the zonal mean zonal winds of MLT are qualitatively consistent with the MF radar observations and model profiles both in winter and summer time. Results show gravity waves play significant role in MLT circulations.