The Middle Atmosphere In the Absence of Dynamical Heat Fluxes
The Middle Atmosphere In the Absence of Dynamical Heat Fluxes
复制标题
没有动态热通量的中间大气
DOI：
10.1002/qj.49711347610
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发表时间：
2007
影响因子：
8.9
通讯作者：
K. Shine
中科院分区：
文献类型：
--
作者：
K. Shine
一种新的辐射传输方案是为平流层和中间层的三维动力学模型而开发的，用于考虑在没有动态热通量的情况下中层大气的假设状态。该领域的大多数先前工作都考虑了使用固定太阳强迫的辐射平衡温度。该平衡状态与使用太阳强迫季节性周期计算的状态不同。特别是，发现冬季极地更温暖，并且极夜边缘的纬度温度梯度更小。这种差异是由两个过程造成的。首先，夏至时极夜边缘的纬度地区只在很短的时间内处于黑暗中。其次，随着温度降低，辐射时间尺度大大延长，因此在太阳重新出现之前无法达到平衡。
最近的臭氧气候学用于在模型上施加现实的臭氧年度循环。研究发现，与以前的仅辐射计算相比，平流层下部的模拟与观测结果的一致性要好得多。在大多数情况下，由于使用了新的臭氧气候学，模拟效果更好。研究还表明，为了很好地模拟夏至时的极地平流层顶，真实的臭氧分布是必要的。
南半球平流层低层极地地区的观测和计算温度年循环的比较表明，该地区受到强烈的辐射控制。这与北半球同一地区隐含的强烈动力控制形成鲜明对比。
A new radiative transfer scheme, developed for use in a three-dimensional dynamical model of the stratosphere and mesosphere, is used to consider the hypothetical state of the middle atmosphere in the absence of dynamical heat fluxes. Most previous work in this area has considered radiative equilibrium temperatures using a fixed solar forcing. This equilibrium state is shown to be different from a state calculated using a seasonal cycle of solar forcing; in particular, the winter pole is found to be warmer and the latitudinal temperature gradient across the edge of the polar night is found to be smaller. This difference is due to two processes. Firstly, latitudes just polewards of the edge of the polar night at solstice are in darkness for only a short period. Secondly, radiative time scales lengthen greatly as temperatures decrease, so that equilibrium cannot be reached before the sun reappears.
Recent ozone climatologies are used to impose a realistic annual cycle of ozone on the model. It is found that the simulation of the lower stratosphere is in considerably better agreement with observations than previous radiation-only calculations. the better simulation is shown to be, in most cases, due to the use of the new ozone climatology. It is also shown that a realistic ozone distribution is necessary for a good simulation of the polar stratopause at the summer solstice.
A comparison of the observed and calculated annual cycle of temperature in the polar regions of the southern hemisphere lower stratosphere indicates that this region is under strong radiative control. This contrasts with an implied strong dynamical control for the same region in the northern hemisphere.