Jets on the Giant Planets

来自先驱者号、旅行者号和伽利略号航天器的观测以及从1800年S开始的地面测量表明，太阳系中的四颗巨行星--木星、土星、天王星和海王星--在它们的大气层中有很强的东西向喷流。喷流在每个行星上都有不同的形式；木星和土星各有大约20个喷流(向东10个，向西10个)，而天王星和海王星各自只有大约3个喷流。喷流与温度和云层丰度的空间变化相关联，这表明整个问题是一个涉及所有动力变量的耦合问题。是什么导致了这些喷流的问题是行星大气中最重要的悬而未决的问题之一。亚利桑那大学的Adam Showman将使用大气运动的完全非线性数值模型来研究巨行星喷流的动力学和形成过程。将进行两项截然不同但又相互关联的数字调查。这两项研究的目的都是为了阐明小规模对流在喷流泵送过程中所起的作用。第一个问题使用了一个真实的对流参数，并将主要集中在阐明云层附近的动力学。第二个问题采用了对流强迫的一个更简单的表示，并研究了是否可以从预计发生湿对流的上层地区驱动极深急流。这些研究是第一次对木星云层进行完全非线性的数值模拟，利用一个有许多垂直网格点的模型来解决木星喷流形成的问题。因此，它们将在解决可能的喷流形成过程所产生的垂直结构方面具有开创性的能力。这项研究将使用Showman博士在使用方面经验丰富的既定数字代码。

AST-0206269ShowmanObservations from the Pioneer, Voyager, and Galileo spacecraft as well as ground-basedmeasurements beginning in the 1800's indicate that the four giant planets in our solarsystem, Jupiter, Saturn, Uranus, and Neptune, have strong east-west jets in theiratmospheres. The jets take different forms on each planet; Jupiter and Saturn have abouttwenty jets each (ten eastward and ten westward), whereas Uranus and Neptune have onlyabout three jets each. The jets are correlated with spatial variations in the temperatureand cloud abundance, suggesting that the full problem is a coupled one involving all thedynamical variables. The question of what causes these jets is one of the most importantunsolved problems in planetary atmospheres.Dr. Adam Showman of the University of Arizona will investigate the dynamics and formation processes of the giant-planet jets using a fully nonlinear numerical model of atmospheric motion. Two distinct, yet related, numerical investigations will be conducted. Both are aimed atelucidating the role of small-scale convection in pumping the jets. The first problemuses a realistic parameterization of the convection and will focus predominantly onelucidating the dynamics near the cloud level. The second problem adopts a simplerrepresentation of the convective forcing and investigates whether extremely deep jets canbe driven from the upper regions where the moist convection is expected to occur. Thesestudies are the first fully-nonlinear numerical simulations of Jupiter's cloud layer thataddress the problem of Jovian jet formation using a model with many vertical grid points.As a result, they will be groundbreaking in their ability to address the verticalstructure that results from plausible jet-formation processes. The research will useestablished numerical codes that Dr. Showman is experienced in using.***