Small-scale temperature fluctuations seen by the VeRa Radio Science Experiment on Venus Express
Small-scale temperature fluctuations seen by the VeRa Radio Science Experiment on Venus Express
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DOI：
10.1016/j.icarus.2012.08.023
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发表时间：
2012-11
期刊：
影响因子：
3.2
通讯作者：
S. Tellmann;B. Häusler;D. Hinson;G. Tyler;T. Andert;M. Bird;T. Imamura;M. Pätzold;S. Remus
中科院分区：
文献类型：
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作者：
S. Tellmann;B. Häusler;D. Hinson;G. Tyler;T. Andert;M. Bird;T. Imamura;M. Pätzold;S. Remus
金星快车无线电科学实验VeRa在大约40- 90公里的高度范围内反演金星中间层和对流层的大气廓线。从2006年金星快车进入轨道到2011年7月第11次掩星季节结束，检索了500多个剖面的数据集。大气廓线覆盖了广泛的纬度和当地时间，使我们能够研究垂直小尺度温度扰动对当地时间和纬度的依赖性。为了研究小尺度重力波，从实测的温度剖面中提取了垂直波长为4km或更小的温度起伏。在对流层顶上方约60公里处的稳定大气中发现了显著的波振幅，而在下面邻近的中间云层的近绝热区域中只有浅层温度扰动。重力波活动表现出强烈的纬度依赖性，最小的波振幅位于低纬度范围，波活动随着两个半球纬度的增加而增加;最大的波活动出现在金星最高地形特征伊什塔尔地附近的高北纬范围。我们发现在赤道±30°范围内的低纬范围内的重力波活动的当地时间依赖的证据。重力波振幅在中午开始达到最大值，并持续到下午早些时候，这表明低层大气中的对流是一个可能的波源。测量的垂直波结构与标准线性波理论的比较，使我们能够得到粗略的估计波的固有频率和水平波长，假设所观察到的波结构是纯内部重力波的结果。在65公里高度上，波的水平波长约为300- 450公里，水平相速度约为5- 10米/秒。
The Venus Express Radio Science Experiment VeRa retrieves atmospheric profiles in the mesosphere and troposphere of Venus in the approximate altitude range of 40–90km. A data set of more than 500 profiles was retrieved between the orbit insertion of Venus Express in 2006 and the end of occultation season No. 11 in July 2011. The atmospheric profiles cover a wide range of latitudes and local times, enabling us to study the dependence of vertical small-scale temperature perturbations on local time and latitude. Temperature fluctuations with vertical wavelengths of 4km or less are extracted from the measured temperature profiles in order to study small-scale gravity waves. Significant wave amplitudes are found in the stable atmosphere above the tropopause at roughly 60km as compared with the only shallow temperature perturbations in the nearly adiabatic region of the adjacent middle cloud layer, below. Gravity wave activity shows a strong latitudinal dependence with the smallest wave amplitudes located in the low-latitude range, and an increase of wave activity with increasing latitude in both hemispheres; the greatest wave activity is found in the high-northern latitude range in the vicinity of Ishtar Terra, the highest topographical feature on Venus. We find evidence for a local time dependence of gravity wave activity in the low latitude range within ±30° of the equator. Gravity wave amplitudes are at their maximum beginning at noon and continuing into the early afternoon, indicating that convection in the lower atmosphere is a possible wave source. The comparison of the measured vertical wave structures with standard linear-wave theory allows us to derive rough estimates of the wave intrinsic frequency and horizontal wavelengths, assuming that the observed wave structures are the result of pure internal gravity waves. Horizontal wavelengths of the waves at 65km altitude are on the order of ≈300–450km with horizontal phase speeds of roughly 5–10m/s.