Jets on the Giant Planets

先锋号、旅行者号和伽利略号宇宙飞船的观测以及19世纪开始的地面测量表明，我们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强烈的东西喷射。这些喷流在每个星球上都有不同的形式；木星和土星各有大约20个喷流（10个向东，10个向西），而天王星和海王星各只有大约3个。喷流与温度和云丰度的空间变化有关，这表明整个问题是一个涉及所有动力学变量的耦合问题。是什么原因导致了这些喷流，这是行星大气中最重要的未解决问题之一。亚利桑那大学的Adam Showman将使用一个完全非线性的大气运动数值模型来研究巨行星喷流的动力学和形成过程。将进行两个不同但又相关的数值研究。两者都旨在阐明小尺度对流在抽送射流中的作用。第一个问题是对流的现实参数化，并将主要集中在阐明云水平附近的动力学。第二个问题采用了对流强迫的一个更简单的表示，并研究是否可以从预计会发生湿对流的上层区域驱动极深的射流。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，利用具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，他们将在解决垂直结构的能力上具有开创性，这种垂直结构是由看似合理的射流形成过程产生的。该研究将使用Showman博士在使用方面经验丰富的已建立的数字代码

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.***