• ISSN 2097-1893
    • CN 10-1855/P

    金星大气超级旋转

    Venus’s atmospheric superrotation

    • 摘要: 金星是距离地球最近的行星,自东向西缓慢自转,但其稠密大气整体呈快速的向西运动. 在约65~70 km高度的云顶,纬向风速可达100 m/s,几乎是行星表面运动速度的50~60倍,这一独特而神秘的现象被称为“大气超级旋转”. 自20世纪60年代以来,超级旋转的时空分布特征及其角动量平衡机制一直是行星大气动力学中的核心难题,相关研究持续至今已逾60年. 本文将回顾超级旋转研究的发展历程,并重点介绍近年来的研究进展. 在垂直结构上,超级旋转自行星表面随高度增强,于云顶附近达到最大值,随后逐渐减弱至约110 km的中间层顶,并过渡至昼夜环流主导区域. 在纬向分布上,云顶风速在南北纬50°之间保持近似恒定的极值,向高纬度逐渐减弱. 普遍认为,超级旋转的维持依赖于大气环流与大尺度涡动(如潮汐、行星波等)共同作用下的角动量输运平衡. 近年的观测与模拟结果表明,云顶超级旋转的涡动贡献主要由潮汐驱动,而中低云层(50~60 km)则由行星波主导. 此外,随着长期观测的积累,超级旋转被发现存在多时间尺度的变化,从几天、数百天到可能与太阳活动相关的近12年周期. 最新模拟研究表明,云层中约200天的准周期变化主要由行星波与环流之间角动量输运的动态平衡所调制. 总体而言,超级旋转研究正逐步从“维持机制”向“时空演变机制”拓展,并从大尺度过程延伸至重力波等小尺度过程. 随着数值模式的发展与观测任务的推进,未来有望在气候学框架下更全面地理解金星大气超级旋转的形成与演化.

       

      Abstract: Venus, the planet closest to Earth, has a slowly retrograde rotation in the opposite direction to Earth's, and it has a dense atmosphere that exhibits rapid westward motion. At the cloud top, around 65–70 km in altitude, zonal wind speeds reach up to 100 m/s—about 50–60 times faster than the surface rotation. This striking and enigmatic phenomenon is known as atmospheric superrotation. Since the 1960s, the spatiotemporal characteristics and angular momentum balance mechanisms of superrotation have remained one of the central challenges in planetary atmospheric dynamics, with sustained investigation for over six decades. This review summarizes the historical development of superrotation studies and highlights recent advances. In terms of the vertical structure, superrotation intensifies from the surface upward, peaking near the cloud top, then gradually weakens toward the mesopause at around 110 km, where the circulation is dominated by the diurnal cycle. In the latitudinal distribution, the cloud-top winds maintain nearly constant at its maximum values between 50°N and 50°S before decreasing toward the poles. Superrotation is generally understood to be maintained by angular momentum transport through the combined effects of atmospheric circulation and large-scale eddies (such as tides and planetary waves). Recent observations and modeling results indicate that thermal tides primarily drive eddy contributions at the cloud top. In contrast, those in the middle and lower cloud layers (50–60 km) are mainly controlled by planetary waves. Furthermore, long-term observations have revealed multiple timescales of variability in superrotation, ranging from a few days to several hundred days, and possibly up to ~12 years linked to the solar cycle. State-of-the-art modeling studies suggest that the dynamic balance of angular momentum transport between planetary waves and the general circulation largely regulates the quasi-200-day variability in the cloud region. Overall, research on superrotation has been shifting from a focus on its basic maintenance mechanisms to its spatiotemporal variability, and from large-scale processes to smaller-scale phenomena such as gravity waves. With advances in numerical models and future observational missions, a more comprehensive understanding of the origin and evolution of Venusian atmospheric superrotation within a climatic framework is anticipated.

       

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