The Role of Inertial Instability and Boundary-Layer Processes in Equatorial Monsoon Regions

热带深处的大部分降雨集中在热带辐合带(ITCZ)。决定赤道附近对流降水分布的动力学，如热带辐合带(ITCZ)的位置，还没有得到很好的了解。全球气候模式(GCM)往往无法捕捉到观测到的分布，并且对模式参数的细节非常敏感。观测证据表明，一个基本的流体动力不稳定性，即惯性不稳定性，对这个问题是重要的。这里将着重讨论边界层内惯性不稳定的作用--地面附近的大气层--以及惯性不稳定与边界层湍流和对流之间的相互作用，从而解决国际热带气旋管制区的位置问题。动力学假设将使用数据驱动的边界层参数化进行检验。关键数据是散射计(QuikSCAT)得出的风速和风应力。从观测研究中推断出的过程将在一组模式实验中得到检验。将执行三项主要任务：1)分析观测数据，以研究惯性不稳定性--特别是零绝对涡度线的位置--与ITCZ位置之间的关系。2)分析边界层内的力平衡，以及从平流到零绝对涡度线上的Ekman(阻力主导)区域的转变。3)分析惯性不稳定的时间尺度和影响ITCZ在不同时间尺度上位置的过程。这项研究的重大影响在于它有可能改进全球模式中热带环流的表示，提高对印度季风和热带气旋成因的理解，并将一些方法应用于涉及次网格尺度过程模拟的相关问题。一名新的研究人员将接受培训，一名本科生将通过与华盛顿大学的合作参与研究。

Much of the rain that falls in the deep tropics is concentrated in the inter-tropical convergence zone (ITCZ). The dynamics that determine the distribution of convective rainfall near the equator, such as the position of the inter-tropical convergence zone (ITCZ), are not well understood. Global climate models (GCMs) often fail to capture the observed distribution, and it is sensitive to details of model parameterizations. Observational evidence suggests that a fundamental fluid dynamical instability, inertial instability, is important for this problem. Here the problem of the position of the ITCZ will be addressed by focusing on the role of inertial instability within the boundary layer - the atmospheric layer near the ground - and interactions between inertial instability and boundary-layer turbulence and convection. Dynamical hypotheses will be tested using boundary-layer parameterizations driven by data. The key data are scatterometer (QuikSCAT) derived winds and wind stresses. Processes inferred from the observational studies will be tested in a set of model experiments.Three major tasks will be carried out:1) Analyses of observational data to investigate the relationship between the inertial instability - specifically the location of the line of zero absolute vorticity - and the location of the ITCZ.2) Analyses of the force balances within the boundary layer, and the transition from advective to Ekman (drag dominated) regimes across the line of zero absolute vorticity. 3) Analyses of the time scales of inertial instability and the processes that contribute to the position of the ITCZ on different timescalesBroader impacts of this research are in its potential to drive improved representations of tropical circulations in global models, improved understanding of the Indian monsoon and of the genesis of tropical cyclones, and in the application of some methods to related problems that involve modeling sub-grid scale processes. A new investigator will be trained and an undergraduate will participate in the research through cooperation with the University of Washington.