Structure and meteorology of the middle atmosphere of Venus: Infrared remote sensing from the Pioneer Orbiter
Structure and meteorology of the middle atmosphere of Venus: Infrared remote sensing from the Pioneer Orbiter
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金星中层大气的结构和气象学：先锋轨道飞行器的红外遥感
DOI：
10.1029/ja085ia13p07963
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发表时间：
1980
影响因子：
--
通讯作者：
J. Gille
中科院分区：
文献类型：
--
作者：
F. Taylor;R. Beer;M. Chahine;D. Diner;L. Elson;R. Haskins;D. Mccleese;J. Martonchik;P. E. Reichley;S. P. Bradley;J. Delderfield;J. Schofield;C. B. Farmer;L. Froidevaux;J. Leung;M. Coffey;J. Gille
利用从地面气象卫星上研制的红外遥感仪器，从先锋金星轨道器上对金星中层大气（60至140公里）的结构和可变性进行了研究。观测到的波长的选择，使垂直温度廓线，云不透明度廓线，和远红外不透明度由于水蒸气从数据中推断。测得的温度场被用来模拟该区域的动态，热通量和太阳通量被用来计算行星辐射收支。在给定高度上的温度日变化的结果表明，在约95公里的高度上，温度日变化的振幅相当小，在该高度以上，昼夜对比度随高度迅速增加。在赤道，平流层（65 - 95 km）温度对太阳经度的依赖性主要由振幅约为10 K的波数2太阳潮决定。包括行波在内的瞬态特征也存在于广泛的尺度上。赤道到极地的梯度比预期的要大，平流层在极地的温度通常比赤道高15到20 K。中间层（95 ~ 140公里）的夜面温度一般都很低，除了在反日点附近有一个局部最高值，在120公里以上的地方，局部热力学平衡的破坏是很明显的。诊断环流模式中测得的温度场强迫的风表明，“4天”纬向风随云上高度迅速减小，到80或90公里时变得很小。高度平均纬向分量在大约相同的高度反转，在100 km以上产生高达100 m s−1的极赤道风。关于云形态最重要的发现是一个戏剧性的“偶极子”结构，由两个跨越极点的云中的空地组成，每2.7天围绕它旋转一次。这些空地被认为是极地涡旋中心大气下沉的证据。其他地方缺乏下降运动的相应证据，这表明一个单一的大环流圈可能充满了北方半球云顶附近的水平。一个新月形的“领”区，由异常和变化的温度和云结构组成，在70°N左右围绕着极点，大约在平均云顶高度以上15公里;它有一个太阳固定的组成部分，有时包含螺旋条纹。这一特征和双涡眼是由于不明来源的行星尺度波而导致的与平均环流的大而持久的偏差。目前还没有解释在赤道和极纬地区波数2结构占主导地位，而中纬度地区则由波数1特征（极环）主导。北方半球被一层薄薄的、无处不在的薄雾覆盖，包括极地特征。大气的远红外不透明度在下午比任何其他当地时间都要大，并且在高纬度地区也趋于增加;最可能的原因是少量但可变的水蒸气。散射太阳光强度的角度依赖性符合由1微米水滴组成的云模型。在金星北方半球积分时，观测到的总反射太阳能和发射热通量的角分布和行星分布与辐射平衡一致，在初步计算的精度范围内。
The structure and variability of the middle atmosphere of Venus (60 to 140 km) were studied from the Pioneer Venus orbiter by using an infrared remote sensing instrument developed from those on terrestrial weather satellites. The wavelengths observed were selected to allow the vertical temperature profile, the albedo, the cloud opacity profile, and the far infrared opacity due to water vapor to be inferred from the data. The measured temperature field has been used to model the dynamics of the region, and the thermal and solar fluxes have been used to compute the planetary radiation budget. The results for the diurnal variation of temperature at a given height show fairly small amplitudes up to an altitude of about 95 km, above which the day to night contrast increases rapidly with height. At the equator the dependence of temperature in the stratosphere (65 to 95 km) on solar longitude is dominated by a wave number 2 solar tide with an amplitude of about 10 K. Transient features including traveling waves are also present on a wide range of scales. The equator to pole gradients are larger than expected, and the stratosphere is typically 15 to 20 K warmer at the pole than at the equator. Nightside temperatures in the mesosphere (95 to 140 km) are generally low except for a local maximum near the antisolar point, and breakdown of local thermodynamic equilibrium is evident above about 120 km. The winds forced by the measured temperature field in a diagnostic circulation model show the ‘4-day’ zonal wind decreasing rapidly with height above the clouds and becoming very small by 80 or 90 km. altitude. The mean meridional component reverses at about the same altitude and pole-to-equator winds as high as 100 m s−1 are produced above 100 km. The most significant discovery concerning the cloud morphology is a dramatic ‘dipole’ structure, consisting of two clearings in the cloud at locations straddling the pole and rotating around it every 2.7 days. The clearings are thought to be evidence for subsidence of the atmosphere at the center of a polar vortex. The absence of corresponding evidence for descending motions elsewhere suggests that a single large circulation cell may fill the northern hemisphere at levels near the cloud tops. A crescent-shaped ‘collar’ region, consisting of anomalous and variable temperature and cloud structure, surrounds the pole at about 70°N and rises perhaps 15 km above the mean cloud top elevation; it has a solar-fixed component and sometimes contains spiral streaks. This feature, and the double vortex eye, are large, persistent deviations from the mean circulation due to planetary-scale waves of unknown origin. No explanation is offered at present for the dominance of wave number 2 structures at equatorial and polar latitudes, while the mid-latitudes are dominated by a wave number 1 feature (the polar collar). A thin, ubiquitous haze is found covering the northern hemisphere, including the polar features. The far-infrared opacity of the atmosphere is greater in the afternoon than at any other local time and also tends to increase at high latitudes; the most likely cause is a small but variable amount of water vapor. The angular dependence of the intensity of scattered sunlight fits a cloud model consisting of 1-µm droplets. The observed angular and planetographic distribution of total reflected solar energy and emitted thermal flux, when integrated over the northern hemisphere of Venus, are consistent with radiative balance to within the accuracy of a preliminary calculation.