Hydroxyl in the stratosphere and mesosphere – Part 1: Diurnal variability
Hydroxyl in the stratosphere and mesosphere – Part 1: Diurnal variability
复制标题
平流层和中间层中的羟基 - 第 1 部分：昼夜变化
DOI：
--
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
R. Harwood
中科院分区：
文献类型：
--
作者：
K. Minschwaner;G. Manney;S. Wang;R. Harwood
抽象。利用Aura微波临边探测仪（MLS）的测量结果分析了平流层和中间层中羟基（OH）的日变化。OH日变化的主要驱动因素是紫外光化通量，它启动了活性氢物种的光化学产生。该通量的大小主要取决于太阳天顶角（SZA）全天的变化，并且OH日变化很好地近似于SZA割线的指数函数。测量的OH浓度拟合为exp[−βsec（SZA）]形式的函数，其中参数β是高度的函数。我们研究了β的大小，并表明它与臭氧和分子氧的紫外吸收的光学深度有关。SLIMCAT模式模拟的β值与MLS模式模拟的β值显示了相同的垂直结构，模式与测量值之间的平均一致性为6%。MLS的β垂直分布可以用一个简单的解析公式来表示，该公式涉及臭氧和水汽的光解速率。这个公式是用来推断的高度依赖性的主要生产机制OH：激发态原子氧与水蒸气的反应与水蒸气的直接光解。
Abstract. Diurnal variations in hydroxyl (OH) in the stratosphere and mesosphere are analyzed using measurements from the Aura Microwave Limb Sounder (MLS). The primary driver for OH diurnal variations is the ultraviolet actinic flux that initiates the photochemical production of reactive hydrogen species. The magnitude of this flux is governed largely by changes in solar zenith angle (SZA) throughout the day, and OH diurnal variations are well approximated by an exponential function of the secant of SZA. Measured OH concentrations are fit to a function of the form exp[−βsec(SZA)], where the parameter β is a function of altitude. We examine the magnitude of β and show that it is related to the optical depths of ultraviolet absorption by ozone and molecular oxygen. Values of β from SLIMCAT model simulations show the same vertical structure as those from MLS and the average level of agreement between model and measurements is 6%. The vertical profile of β from MLS can be represented by a simple analytic formulation involving the ozone and water vapor photodissociation rates. This formulation is used to infer the altitude dependence of the primary production mechanisms for OH: the reaction of excited-state atomic oxygen with water vapor versus the direct photodissociation of water vapor.