Structure and Maintenance of Potential Vorticity in the Midlatitude Atmosphere

9627040中村 该项目涉及对地球中纬度大气位涡（PV）平均结构的数值和理论研究。 特别感兴趣的是（1）如何非保守过程（摩擦，辐射，潜热等）。与平流过程相互作用以维持高度不均匀的PV结构，例如在对流层顶和平流层极涡边缘处发现的PV结构和（2）对流层PV的值和梯度如何维持。 将采用一种新的诊断技术来确定平均PV分布，该技术基于拉格朗日质量坐标，最近由主要研究者开发。 在一个从传统的纬向和时间平均方法的根本出发，该方法的特点等熵运输PV轮廓之间的质量重新分配，非保守过程，如扩散是必不可少的。 混沌平流被视为PV轮廓的拉伸，影响微尺度扩散的可用界面。 这种拉格朗日诊断似乎比传统方法更好地识别强PV梯度。 在这个框架内，将根据对流层的质量收支，考虑平流层-对流层的质量交换和地面的质量汇/源（热通量），以及调节这些过程的斜压涡旋引起的搅动，对斜压调整和对流层顶高度进行研究。 使用二维模式，PI将首先模拟斜压大气的统计稳定状态，并检查对流层顶形成和维持的机制。 基于GFDL的SKYHI全球环流模式的高分辨率模拟，分析将扩展到三维。 同样的方法将被用来研究平流层极涡边缘的维持，只是打破Rossby波将取代斜压波作为搅拌剂。 这些研究的目的是寻找中纬度大气环流各方面的统一理论。 ***

9627040 Nakamura This project involves numerical and theoretical investigations of the mean structure of the potential vorticity (PV) in the earth's midlatitude atmosphere. Of particular interest are (1) how the nonconservative processes (friction, radiation, latent heating, etc.) interact with advective processes to maintain the highly inhomogeneous PV structures such as those found at the tropopause and at the edge of the stratospheric polar vortex and (2) how the values and gradients of the tropospheric PV are maintained. A new diagnostic technique to define the mean PV profile, based on the Lagrangian mass coordinate and recently developed by the principal investigator, will be employed. In a radical departure from the conventional zonal- and time-mean approaches, the method characterizes the isentropic transport as redistribution of mass between PV contours for which nonconservative processes such as diffusion are essential. Chaotic advection is viewed as the stretching of the PV contours, affecting the available interface for microscale diffusion. This Lagrangian diagnostic appears to identify strong PV gradients much better than conventional methods. Within this framework the baroclinic adjustment and the height of the tropopause will be investigated in terms of the mass budget of the troposphere, considering both the stratosphere-troposphere mass exchange and the mass sink/sources (heat fluxes) at the ground, with stirring due to baroclinic eddies regulating these processes. Using a two-dimensional model, the PI will first simulate a statistical steady state of the baroclinic atmosphere and examine the mechanism of tropopause formation and maintenance. The analysis will be extended to three dimensions, based on the high resolution simulations with the GFDL's SKYHI global circulation model. The same approach will be used to investigate the maintenance of the stratospheric polar vortex edge except that breaking Rossby waves will replace baroclinic waves as the stirr ing agent. These studies are directed at finding unifying theories of various aspects of the midlatitude general circulation. ***