Testing the Unified System of Equations in Atmospheric Models

在这项资助下进行的研究将开发和测试一套新的全球非流体静力大气模型方程系统。目前的全球大气模式假定空气运动是流体静力的，在模式网格间距为几十到几百公里的情况下，这是一个适当的假设。但是计算能力的提高引起了人们对全球“云分辨”大气模式的兴趣，这种模式的分辨率要高得多，从1公里到10公里，这样就可以分辨出云尺度上发生的非流体静力运动。这种模式被认为是研究各种多尺度大气现象的合适工具，并解决了流体静力学模式中对流参数化所带来的问题。对于整体流体静力模型，有一种标准形式的运动方程，通常称为“原始方程”，但对于非流体静力整体模型，目前还不存在一套标准化的方程。该项目的工作将开发和测试基于统一方程组（UN）的模型。联合国系统适用于全球范围，允许与气象有关的非流体静力运动，同时过滤掉声波，否则会使大气运动的数值模拟复杂化。这项工作的目标是测试联合国系统，并将其与非流体静力全局建模的替代方程集进行比较，包括非弹性系统、伪不可压缩系统和可压缩系统。这项工作将有助于开发用于模拟和预测天气和气候的下一代模型，从而产生更广泛的影响。

Research conducted under this grant will develop and test a new system of equations for global nonhydrostatic atmospheric models. Current global atmospheric models assume that air motions are hydrostatic, which is an appropriate assumption provided that the grid spacing of the model is tens to hundreds of kilometers. But increases in computing power have led to interest in global "cloud resolving" atmospheric models with much higher resolutions, from 1 to 10 kilometers, so that the nonhydrostatic motions occurring on the cloud scale can be resolved. Such models are considered appropriate tools for studying a variety of multiscale atmospheric phenomena, and resolve the problems that arise due to the parameterization of convection in hydrostatic models. For global hydrostatic models there is a standard form of the equations of motion, generally referred to as the "primitive equations", but a standardized set of equations for nonhydrostatic global models does not presently exist. Work in this project will develop and test models based on the Unified System (UN) of equations. The UN system is applicable on a global domain and allows nonhydrostatic motions of meteorological interest while filtering out sound waves, which would otherwise complicate the numerical simulation of atmospheric motions. The goal of the work is to test the UN system and compare it against alternative equations sets for nonhydrostatic global modeling, including the anelastic system, pseudo-incompressible, and the compressible systems.The work will have broader impacts by contributing to the development of next-generation models to be used for the simulation and prediction of weather and climate.