Landry B, Allen M, Yung Y L
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91125, USA.
Icarus. 1991;89:377-83. doi: 10.1016/0019-1035(91)90184-u.
A simple one-dimensional model of the Jovian atmosphere including the coupling between a rapidly mixed troposphere and a stagnant stratosphere is presented. We treat analytically the case of a chemically unreactive species flowing downward through the stratosphere and troposphere with a constant flux. The calculated concentration profile has a maximum value approximately one atmospheric scale height above the tropopause. The corresponding mixing ratio rapidly decreases in the lower stratosphere. The contrast between the peak stratosphere and tropopause concentrations reflects the variation between the lower stratosphere and upper troposphere eddy diffusion coefficients. Numerical simulations of unreactive CO and C2H6, considering high-altitude photochemical sources (yielding downward fluxes to the troposphere) and deep troposphere thermochemical sources, demonstrate that upper troposphere abundances may have a large photochemical contribution. Recent observations of CO near 5 bar can be reproduced by a model using any one of three different tropospheric eddy diffusion profiles: a constant value of approximately 10(8) cm2 sec-1, a constant value of < or approximately 10(4) cm2 sec-1, or a two-layer model with a rapidly mixed (10(8) cm2 sec-1) layer below 20 bar and a slower mixing layer (10(4) cm2 sec-1) between 100 mbar and 20 bar. In the latter two scenarios, the photochemical source is an important and/or dominant source of upper tropospheric CO. However, the upper tropospheric C2H6 abundances are distinctly different among the three cases. These calculations suggest objectives for higher spectral resolution observations, critical vertical scales for planning experiments on future missions to Jupiter, and predictions that can be tested with the Galileo probe mass spectrometer.
本文提出了一个简单的一维木星大气模型，该模型考虑了快速混合的对流层与静止平流层之间的耦合。我们对一种化学惰性物质以恒定通量向下流经平流层和对流层的情况进行了分析处理。计算得出的浓度剖面在对流层顶上方约一个大气标高处有一个最大值。相应的混合比在平流层下部迅速下降。平流层峰值浓度与对流层顶浓度之间的差异反映了平流层下部与对流层上部涡动扩散系数的变化。对化学惰性的一氧化碳和乙烷进行的数值模拟，考虑了高空光化学源（产生向下流入对流层的通量）和对流层深部热化学源，结果表明对流层上部的丰度可能有很大的光化学贡献。利用三种不同的对流层涡动扩散剖面中的任何一种，一个模型都能再现最近在5巴附近对一氧化碳的观测结果：约10⁸平方厘米每秒的恒定值、小于或约为10⁴平方厘米每秒的恒定值，或一个两层模型，在低于20巴处有一个快速混合（10⁸平方厘米每秒）层，在100毫巴至20巴之间有一个较慢的混合层（10⁴平方厘米每秒）。在后两种情况下，光化学源是对流层上部一氧化碳的一个重要和/或主要来源。然而，三种情况下对流层上部乙烷的丰度明显不同。这些计算为更高光谱分辨率的观测提出了目标，为规划未来木星任务的实验确定了关键垂直尺度，并做出了可用伽利略探测器质谱仪进行检验的预测。
