Previous models of the equilibrium temperature and existence regions of mesospheric aerosols have shown significant radiative heating of the aerosols and, consequently, a substantially reduced existence region. We have developed an iterative model that extends this previous work by incorporating a complete collisional energy transfer algorithm, including the effects of vertical winds and particle fall velocity, that is appropriate for the free molecular flow conditions found in the mesosphere. We have also updated the ice refractive index used in the model and accounted for the dependence of the radiative heating and collisional cooling terms on particle temperature. finally, a radiation model has been used to calculate the solar, terrestrial and atmospheric radiative inputs including the effects of multiple scattering and atmospheric absorption. As with the previous models the particle temperature is calculated under steady-state conditions, assuming the background gas temperature remains constant and the aerosol does not change size, state or altitude. Under these conditions the largest differences from previous models occur as a result of the updated ice index of refraction, particularly in the visible, which produces significantly less aerosol heating. These temperatures are combined with the observed properties of mesospheric aerosols to place limits on the water vapour mixing ratio, vertical-wind speeds, and maximum particle sizes. It is found that H_2O mixing ratios of 10 ppmv and vertical winds of order 0.02 m s~(-1) are consistent with observed particle distributions, and these lead to a radiative limit on the maximum particle radius of 250 nm.
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机译：以前的中层气溶胶平衡温度和存在区域的模型已经显示出气溶胶的显着辐射加热，并因此显着减少了存在区域。我们开发了一个迭代模型，通过合并完整的碰撞能量转移算法（包括垂直风和粒子下落速度的影响）来扩展此先前的工作，该算法适用于在中层层中发现的自由分子流动条件。我们还更新了模型中使用的冰折射率，并说明了辐射加热和碰撞冷却项对颗粒温度的依赖性。最后，使用辐射模型来计算太阳，地面和大气的辐射输入，包括多重散射和大气吸收的影响。与以前的模型一样，假设背景气体温度保持恒定并且气溶胶不改变尺寸，状态或高度，则在稳态条件下计算颗粒温度。在这些条件下，由于更新后的冰折射率（尤其是可见光）的变化，与先前模型的最大差异出现了，这大大减少了气溶胶的加热。这些温度与观测到的中层气溶胶特性相结合，从而限制了水蒸气混合比，垂直风速和最大粒径。发现H_2O的混合比为10 ppmv，垂直风为0.02 m s〜（-1）与观察到的颗粒分布一致，这导致了最大颗粒半径为250 nm的辐射极限。
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