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Equatorial jet in the lower to middle cloud layer of Venus revealed by Akatsuki
Nature Geoscience ( IF 18.3 ) Pub Date : 2017-08-28 , DOI: 10.1038/ngeo3016
Takeshi Horinouchi , Shin-ya Murakami , Takehiko Satoh , Javier Peralta , Kazunori Ogohara , Toru Kouyama , Takeshi Imamura , Hiroki Kashimura , Sanjay S. Limaye , Kevin McGouldrick , Masato Nakamura , Takao M. Sato , Ko-ichiro Sugiyama , Masahiro Takagi , Shigeto Watanabe , Manabu Yamada , Atsushi Yamazaki , Eliot F. Young

The Venusian atmosphere is in a state of superrotation where prevailing westward winds move much faster than the planet’s rotation. Venus is covered with thick clouds that extend from about 45 to 70 km altitude, but thermal radiation emitted from the lower atmosphere and the surface on the planet’s nightside escapes to space at narrow spectral windows of the near-infrared. The radiation can be used to estimate winds by tracking the silhouettes of clouds in the lower and middle cloud regions below about 57 km in altitude. Estimates of wind speeds have ranged from 50 to 70 m s−1 at low to mid-latitudes, either nearly constant across latitudes or with winds peaking at mid-latitudes. Here we report the detection of winds at low latitude exceeding 80 m s−1 using IR2 camera images from the Akatsuki orbiter taken during July and August 2016. The angular speed around the planetary rotation axis peaks near the equator, which we suggest is consistent with an equatorial jet, a feature that has not been observed previously in the Venusian atmosphere. The mechanism producing the jet remains unclear. Our observations reveal variability in the zonal flow in the lower and middle cloud region that may provide clues to the dynamics of Venus’s atmospheric superrotation.



中文翻译:

Akatsuki揭示金星的低至中云层的赤道急流

金星的大气层处于超旋转状态,盛行的西风的移动速度比行星的旋转快得多。金星上覆盖着厚约45至70 km的厚云层,但是低层大气和行星夜间表面发出的热辐射逃逸到近红外狭窄光谱窗口的空间。通过跟踪海拔低于57公里的中下部云区域中的云的轮廓,可以将辐射用于估算风。在低纬度至中纬度时,风速的估计范围为50至70 m s -1,在整个纬度处近似恒定,或者在中纬度时风达到峰值。在这里,我们报告了对低纬度风超过80 m s -1的检测使用2016年7月和2016年8月拍摄的来自Akatsuki轨道器的IR2相机图像。围绕行星旋转轴的角速度在赤道附近达到峰值,我们建议这与赤道射流相符,这是以前在金星大气中未曾观察到的特征。产生射流的机理尚不清楚。我们的观察结果揭示了中低层云区域纬向流的变化,这可能为金星大气超旋转的动力学提供线索。

更新日期:2017-09-05
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