Annual (perihelion-aphelion) cycles in the photochemical behavior of the global Mars atmosphere
Annual (perihelion-aphelion) cycles in the photochemical behavior of the global Mars atmosphere
复制标题
全球火星大气光化学行为的年度（近日点-远日点）循环
DOI：
--
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
H. Nair
中科院分区：
文献类型：
--
作者：
R. Clancy;H. Nair
火星大气的地面温度和水蒸气分布表明，由于椭圆形火星轨道的影响，整个低至中纬度大气的水蒸气饱和高度或湿层顶每年都有很大的变化[Clancy等人，1996年]。我们研究这样一个每年的变化在湿层顶高度（从30公里）上的火星大气的光化学的影响。Nair等人[1994]的一维扩散传输光化学模型是以日平均模式运行的，用于计算低至中纬度火星光化学的年度行为。该模型采用了一个指定的水蒸气剖面的年度变化，根据微波观测火星水蒸气和温度剖面与季节（太阳经度，LS）。由于其长的光化学寿命，火星CO和O2预计和发现是在显着的不平衡与每年变化的水蒸气（因此HOx）密度，并提出几乎恒定的丰度代表的年平均水蒸气剖面。相比之下，火星O3的光化学寿命为几个小时，并表现出非常大的年度变化，以响应每年的变化在湿层顶高度。在20 - 40公里高度的全球范围内，O3的丰度预计从火星远日点附近的> 109 cm − 3（北方春/夏，Ls = 71 °）到火星近日点附近的108 cm − 3（南方春/夏，Ls = 251 °）不等。这些模型臭氧变化是在不同的火星5号（1974年[Krasnopolsky和Parshev，1979年]）和火卫一（1989年[布拉蒙和Chassefiere，1993年]）在35 - 50公里高度低纬度臭氧密度测量的背景下讨论的，以及哈勃空间望远镜在1995年火星远日点期间对增强的低纬度臭氧的观测[Clancy等人，本问题]。
Ground-based temperature and water vapor profiling of the atmosphere of Mars point to large annual variations in the water vapor saturation altitude, or hygropause, of the entire low-to middle-latitude atmosphere, as forced by the elliptical Mars orbit [Clancy et al., 1996]. We examine the effects of such an annual variation in the hygropause altitude (from 30 km) on the photochemistry of the Mars atmosphere. The one-dimensional, diffusive transport photochemical model of Nair et al. [1994] is run in a diurnally averaged mode for time-dependent calculations of the annual behavior of Mars photochemistry at low to middle latitudes. The model incorporates a specified annual variation of the water vapor profile, based on the microwave observations of Mars water vapor and temperature profiles versus season (solar longitude, Ls). Due to their long photochemical lifetimes, Mars CO and O2 are expected and found to be in significant non-equilibrium with the annually varying water vapor (and hence HOx) densities, and to present nearly constant abundances representative of the annual average water vapor profile. In contrast, Mars O3 has a photochemical lifetime of hours, and exhibits very large annual variations in response to the annual variation in the hygropause altitude. The global-scale abundance of O3 at altitudes of 20–40 km is predicted to vary from >109 cm−3 around Mars aphelion (northern spring/summer, Ls = 71°) to ∼108 cm−3 around Mars perihelion (southern spring/summer, Ls = 251°). These model ozone variations are discussed in the context of the disparate Mars 5 (1974 [Krasnopolsky and Parshev, 1979]) and Phobos (1989 [Blamont and Chassefiere, 1993]) measurements of low-latitude ozone densities at 35–50 km altitude, as well as Hubble space telescope observations of enhanced low-latitude ozone during the 1995 aphelion of Mars [Clancy et al., this issue].