Diurnal and Secular Variability of the Venus Mesosphere

金星中间层是低层大气纬向旋转和热层昼夜亚声速环流之间的动力过渡区。它也是一个关键的光化学活性区域，其中SOx， COx和HOx催化循环控制其下边界大量硫酸盐云层的形成，维持co2大气对光解离解的稳定性，并限制大气水的长期逸出。金星中间层上下的大气环流和化学的极端差异导致其环流和成分的日变化和年际变化非常大，这使我们对这一显著动态状态的理解变得混乱。空间科学研究所的r·托德·克兰西博士将领导一个数据分析和观测研究项目，以调查金星中层大气的可变热量和成分状态。12CO、13CO和HDO的毫米谱线可以在70-110 km高度内获得温度、CO和水蒸气密度的独特垂直剖面。将对现有的未分析的12CO、13CO和HDO毫米和亚毫米光谱进行100多次单独测量，以确定1990-1999年期间CO和温度的日变化和年际变化。对这些观测资料的粗略分析表明，全球中间层温度在80-95公里高度处有突然的短期变化，在95-100公里高度处有日侧中间层顶，以及中间层水汽丰度的强烈日变化。这些是对金星中层大气日变化和长期变化的独特发现，需要对全部数据集进行全面分析，以量化和公布结果。此外，将在2000-2003年期间进行新的毫米和亚毫米测量，以扩大C0/温度/水回收的时间和垂直覆盖范围，并确定中层SO、so2、H2SO4和O2的丰度。分析的一个主要目标是尽可能用最广泛的垂直、参数（温度和成分）和时间描述来确定金星中间层的日变化和年际大变化。这些观测的1990-2003年期间将放在之前的毫米（1982-1990年），先锋金星轨道器（1978-1985年）和伽利略（1991年）飞掠观测的背景下，以最大限度地提高这些现有中间层测量的科学回报，并支持未来对金星大气层的航天器探索。特别是对金星中间层的研究，与最近才定义的控制脆弱的地球平流层的化学和动力学过程有着强烈的相似之处

AST 0098614ClancyThe Venus mesosphere is a dynamical transition region between the zonal rotation of the massive lower atmosphere and the subsonic day-to- night circulation of the thermosphere. It is also a region of key photochemical activity, in which SOx, COx, and HOx catalytic cycles control formation of the massive sulfate cloud layer at its lower boundary, maintain stability of the C02 atmosphere to photolytic dissociation, and limit long-term escape of atmospheric water. The extreme differences in atmospheric circulation and chemistry above and below the Venus mesosphere lead to very large diurnal and interannual variations in its circulation and composition, which have confounded our understanding of this remarkably dynamic regime. Dr. R. Todd Clancy, of the Space Science Institute, will lead a data analysis and observing research program to investigate the variable thermal and compositional state of the Venus middle atmosphere. Millimeter spectral lines of 12CO, 13CO, and HDO enable unique vertical profile retrievals for temperature, and CO and water vapor densities at 70-110 km altitudes within the mesosphere. Over 100 separate measurements of existing, unanalyzed 12CO, 13CO, and HDO millimeter and sub-millimeter spectra will be modeled to determine the diurnal and interannual variabilities of CO and temperatures over the 1990-1999 period. Cursory analysis of these observations indicates abrupt, short-term variations in global mesospheric temperatures at 80-95 km altitudes, a dayside mesopause at 95-100 km altitudes, and strong diurnal variation in mesospheric water vapor abundances. These are unique discoveries of diurnal and secular variabilities in the Venus middle atmosphere that require comprehensive analyses of the full data set to quantify and publish results. In addition, new millimeter and sub-millimeter measurements will be taken over the 2000-2003 period to extend the temporal and vertical coverages of the C0/temperature/water retrievals, and to determine mesospheric abundances for SO, S02, H2SO4, and O2. A primary objective of the analysis is to define the diurnal and large interannual variations of the Venus mesosphere with the broadest vertical, parameter {temperature and composition) , and temporal description possible. The 1990-2003 period of these observations will be placed in the context of prior millimeter (1982-1990), Pioneer Venus orbiter (1978-1985) , and Galileo (1991) flyby observations to maximize the scientific return of these existing mesospheric measurements, and to support future spacecraft exploration of the Venus atmosphere. Study of the Venus mesosphere, in particular, draws strong parallels from the chemical and dynamical processes only recently defined to control the fragile terrestrial stratosphere.***