Altimetry of the Venus cloud tops from the Venus Express observations
Altimetry of the Venus cloud tops from the Venus Express observations
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DOI：
10.1029/2008je003320
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发表时间：
2009-08-13
影响因子：
4.8
通讯作者：
Manoel, N.
中科院分区：
文献类型：
--
作者：
Ignatiev, N. I.;Titov, D. V.;Manoel, N.
金星快车航天器上的可见光和红外热成像光谱仪和金星监测照相机同时观测金星，用于绘制云顶高度图，并将其与紫外线标记联系起来。云顶高度由1.6 μ m处的CO_2吸收带深度反演。在低纬度和中纬度地区，云顶位于74 +/- 1公里处。它向极地下降+/- 50度，在极地地区达到63-69公里。这个低气压与行星漩涡的眼重合。在相同的纬度和时角，云顶可以在几十个小时内经历大约1公里的快速变化，而只有在高纬度地区才观察到几公里的长期变化。紫外线标记与云层高度测量相关，然而，相邻的紫外线暗区和亮区之间的差异不超过几百米。令人惊讶的是，CO2吸收带在暗紫外线特征中往往较弱，这表明这些云可能比邻近的云高几百米或具有更大的尺度高度。紫外线暗旋臂通常出现在-70度左右，对应于较高的高度或云顶高度纬度梯度较强的区域。极地地区的云高度测量揭示了与热发射图相关但在紫外图像中不可见的结构。这意味着UV光学厚极罩在近IR中是透明的。
Simultaneous observations of Venus by Visible and Infrared Thermal Imaging Spectrometer and Venus Monitoring Camera onboard the Venus Express spacecraft are used to map the cloud top altitude and to relate it to the ultraviolet (UV) markings. The cloud top altitude is retrieved from the depth of CO2 absorption band at 1.6 mu m. In low and middle latitudes the cloud top is located at 74 +/- 1 km. It decreases poleward of +/- 50 degrees and reaches 63-69 km in the polar regions. This depression coincides with the eye of the planetary vortex. At the same latitude and hour angle, cloud top can experience fast variations of about 1 km in tens of hours, while larger long-term variations of several kilometers have been observed only at high latitudes. UV markings correlate with the cloud altimetry, however, the difference between adjacent UV dark and bright regions does not exceed several hundred meters. Surprisingly, CO2 absorption bands are often weaker in the dark UV features, indicating that these clouds may be a few hundred meters higher or have a larger scale height than neighboring clouds. Ultraviolet dark spiral arms, which are often seen at about -70 degrees, correspond to higher altitudes or to the regions with strong latitudinal gradient of the cloud top altitude. Cloud altimetry in the polar region reveals the structure that correlates with the thermal emission maps but is invisible in UV images. This implies that the UV optically thick polar hood is transparent in the near IR.