Dehydration of the stratosphere
Dehydration of the stratosphere
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DOI：
10.5194/acp-11-8433-2011
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发表时间：
2011-08
影响因子：
6.3
通讯作者：
M. Schoeberl;A. Dessler
中科院分区：
文献类型：
--
作者：
M. Schoeberl;A. Dessler
抽象的。区域填充，前向轨迹计算被用来检查控制平流层水汽的全球脱水过程。与大多数这种类型的拉格朗日模型一样，水蒸气被瞬间从包裹中去除，以保持相对湿度（RH）相对于冰超过饱和或指定的超饱和值。我们还测试了一个简单的参数化平流层对流增湿通过冰放样和重力波的影响，作为一种机制，可以增加脱水。通过比较MERRA再分析驱动的非绝热和运动学轨迹，我们发现，与Liu等人（2010）的结果不同，运动学计算中由于垂直速度“噪音”而产生的额外传输与观测结果相比，造成平流层过于干燥，水汽磁带记录器信号过于分散。我们还表明，运动学驱动的包裹更有可能遇到最冷的对流层顶温度比非绝热轨迹。非绝热模拟产生的平流层水汽混合比接近奥拉的微波临边探测器所观察到的，并与MERRA热带对流层顶温度偏差是一致的。对流增湿，这将增加平流层HDO，也增加平流层水汽，而参数化重力波的增加则相反。我们发现，虽然热带西太平洋是主要的脱水位置，但热带南美洲也很重要。南极洲也对整个平流层的水蒸气收支作出了很小的贡献，因为冬季涡旋破裂后，南极洲向南半球平流层释放了非常干燥的空气。
Abstract. Domain filling, forward trajectory calculations are used to examine the global dehydration processes that control stratospheric water vapor. As with most Lagrangian models of this type, water vapor is instantaneously removed from the parcel to keep the relative humidity (RH) with respect to ice from exceeding saturation or a specified super-saturation value. We also test a simple parameterization of stratospheric convective moistening through ice lofting and the effect of gravity waves as a mechanism that can augment dehydration. Comparing diabatic and kinematic trajectories driven by the MERRA reanalysis, we find that, unlike the results from Liu et al. (2010), the additional transport due to the vertical velocity "noise" in the kinematic calculation creates too dry a stratosphere and a too diffuse a water-vapor tape recorder signal compared observations. We also show that the kinematically driven parcels are more likely to encounter the coldest tropopause temperatures than the diabatic trajectories. The diabatic simulations produce stratospheric water vapor mixing ratios close to that observed by Aura's Microwave Limb Sounder and are consistent with the MERRA tropical tropopause temperature biases. Convective moistening, which will increase stratospheric HDO, also increases stratospheric water vapor while the addition of parameterized gravity waves does the opposite. We find that while the Tropical West Pacific is the dominant dehydration location, but dehydration over Tropical South America is also important. Antarctica makes a small contribution to the overall stratospheric water vapor budget as well by releasing very dry air into the Southern Hemisphere stratosphere following the break up of the winter vortex.