On the use of nonmethane hydrocarbons for the determination of age spectra in the lower stratosphere
On the use of nonmethane hydrocarbons for the determination of age spectra in the lower stratosphere
复制标题
关于使用非甲烷碳氢化合物测定平流层下部年龄谱
DOI：
--
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
P. Konopka
中科院分区：
文献类型：
--
作者：
D. Ehhalt;F. Rohrer;D. Blake;D. Kinnison;P. Konopka
[1]2001年4月9日，在接近北美大陆西海岸时，美国宇航局TRACE P运动的第20次飞行深入平流层侵入。从那次飞行上的测量，我们得出了以二氯氟甲烷CF2Cl2为高度尺度的平流层下部非甲烷碳氢化合物(NMHC)和其他短期痕量气体的垂直剖面。所有的剖面都呈指数递减，这允许用单一的参数来描述它们的垂直分布，即刻度高度。这些刻度高度以一种独特的方式与各自的寿命相关。在一维扩散模型的近似下，假设涡旋扩散系数K不变，并假设寿命不变，建立了该关系的解析解。通过将这个理论表达式与实验数据进行拟合，我们可以估计K，从而得到Hall和Plumb(1994)给出的近似年龄谱。当我们允许寿命与高度相关，并从一维模型数值计算理论标度高度时，得到了与实验标度高度更好的拟合。优化结果还表明K为常数，但值为0.46m~2/S，大于解析解的拟合值。所获得的年龄谱对于不超过300天的过境时间是有效的。
[1] On 9 April 2001, while approaching the West Coast of the North American continent, flight 20 of the NASA TRACE P campaign penetrated deeply into a stratospheric intrusion. From measurements aboard that flight we derive vertical profiles of nonmethane hydrocarbons (NMHCs) and other short-lived trace gases in the lower stratosphere using Dichlorofluoromethane, CF2Cl2, as the altitude scale. All profiles show an exponential decrease, which permits the description of their vertical distribution by a single parameter, the scale height. These scale heights are shown to be related to the respective lifetimes in a unique fashion. Using the approximation of a 1-D diffusive model with a constant eddy diffusion coefficient, K, and assuming constant lifetimes, we establish an analytical solution for this relation. By fitting this theoretical expression to the experimental data we can estimate K and thus obtain an approximate age spectrum of the form given by Hall and Plumb (1994). A much better fit to the experimental scale heights is obtained, when we allow the lifetimes to be height-dependent and calculate the theoretical scale heights numerically from a 1-D model. An optimization also suggests a constant K, but with a value of 0.46 m2/s, larger than those obtained from the fit of the analytical solution. The obtained age spectra should be valid for transit times not longer than 300 days.