Gravity Wave Sources and Parameterization

重力波源和参数化

• 批准号: 0632378
• 负责人: M Joan Alexander
• 金额: $ 43.41万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0632378&HistoricalAwards=false
• 关键词: Gravity; Wave; Sources; Parameterization

This three-year project will improve the parameterization of subgrid-scale gravity wave effects in global models. Gravity wave forcing of the global-scale mean flow is used to correct common deficiencies in modeled stratospheric circulations: (1) A cold-pole problem in the winter stratosphere that has links to errors in temperature-sensitive ozone chemistry in chemistry-climate models and links to errors in planetary wave propagation and reflection, (2) A delayed onset of easterly winds in the springtime that also affects the propagation of planetary waves and the occurrence of stratospheric warmings in the early spring season, and (3) the lack of a quasibiennial oscillation in the tropical lower stratosphere that also affects planetary wave propagation, stratospheric ozone, and propagation of equatorial waves. In addition to the mean-flow forcing effects of gravity waves on the global scale, other effects are emerging as important that are not yet parameterized in global models. In cirrus clouds, for instance, wave vertical motions control crystal sizes, number densities, precipitation rates, and cloud lifetimes, which in turn can have global-scale radiative and ozone chemistry effects. In the troposphere, upward-propagating gravity waves generated by mature convective storms may reflect from higher altitudes back towards the boundary layer and influence further convective initiation there.There are two essential components to gravity wave forcing parameterizations: (1) the specification of the wave source, and (2) the estimation of the wave dissipation as a function of height. There are several methods for parameterization of the wave dissipation with height in use in global models currently, but no clear way to distinguish between them. The approach in this project focuses on the wave sources, and on constraining those rigorously with observations. This will not only make the parameterizations more realistic, but it may also eventually distinguish between the different dissipation methods. Mountain wave sources have been specifically parameterized in global forecasting and climate models for two decades. Because mountain waves are stationary, their dissipation can only drag the mean flow toward zero wind speed. Mountain wave sources are also limited geographically. Waves from other sources are nonstationary so their dissipation can cause either deceleration or acceleration of the mean flow. The focus in this project is on wave generation by convection. Convection is known to generate waves with a broad range of nonstationary phase speeds and is likely the dominant gravity wave forcing mechanism throughout the tropics and in summer midlatitudes. The intellectual merit of the work crosses traditional boundaries in the atmospheric sciences, using tools of cloud-modeling and precipitation radar observations to understand the origin and nature of small-scale waves generated by convection. Through parallel linear model studies and comparison to existing parameterization methods there will be increased understanding of the essential physics of gravity wave generation. Finally, through collaboration with global modeling groups, parameterization improvements to the subgrid-scale gravity wave forcing and feedbacks in global models will be evaluated. The broader impacts of this work will be advances in understanding of gravity wave generation and gravity wave effects across altitude regions ranging from the top of the boundary layer into the upper atmosphere. In addition to the main goal of improving parameterizations of gravity wave mean-flow forcing in global models, results will also be valuable in cirrus cloud studies, and in studies of convection initiation in the troposphere. The project involves training of graduate student and postdoctoral researchers. Initially, the project will be conducted solely by female researchers, a rare occurrence because females are still under-represented in the atmospheric sciences. The project also begins partnerships with two global climate modeling groups, one in the US and and the other in Europe. While subgrid-scale gravity wave effects are not the primary obstacle to improving global weather forecasting and climate models today, many global modeling groups recognize the importance of raising their model upper boundaries to mesospheric altitudes, and this intensifies the need for improved parameterizations of gravity wave effects.

这个为期三年的项目将改善全球模型中亚网格级重力波效应的参数化。重力波强迫强迫全球尺度的平均流量用于纠正模型平流层循环中的常见缺陷：（1）冬季平流层中的一个冷极问题与化学气候模型中温度敏感的臭氧化学的误差有关，并与行星传播和反射的错误相关，（2）延迟的延伸时间（2）延迟的序列，（2）行星波和平流层变暖在早春季的发生，（3）在热带下部平流层中缺乏准周年振荡，这也影响了行星波传播，平流层臭氧和赤道波的传播。 除了重力波对全球尺度的平均河流强迫效应外，其他效果还出现同样重要，在全球模型中尚未参数化。例如，在卷云中，波垂直运动控制晶体尺寸，数量密度，降水速率和云寿命，进而可以具有全球尺度的辐射和臭氧化学效应。 在对流层中，由成熟的对流风暴产生的向上传播的重力波可能反映了较高的高度向边界层朝向边界层，并影响那里进一步的对流启动。有两个基本组成部分，用于重力波强迫参数化参数化：（1）波源的规范，以及（2）（2）（2）波浪耗散的估计量表范围为高度。 当前在全局模型中使用高度，有几种方法可以将波耗散参数化，但没有明确的方法来区分它们。 该项目中的方法集中在波源上，并通过观察来严格限制这些方法。 这不仅会使参数化更现实，而且最终也可能区分不同的耗散方法。 二十年来，在全球预测和气候模型中已在全球预测和气候模型中进行了特异性参数。 由于山波是静止的，因此它们的耗散只能将平均流动拖到零风速。山波来源在地理上也受到限制。来自其他来源的波是非组织的，因此它们的耗散会导致平均流量的减速或加速。 该项目的重点是通过对流产生波浪。 已知对流会产生具有广泛的非组织相速度的波，并且很可能是整个热带地区和夏季中纬度的主要重力波强迫机理。作品的智力优点跨越了大气科学中的传统边界，使用云模块和降水雷达观测的工具，了解对流产生的小规模波的起源和性质。通过平行线性模型研究和与现有参数化方法的比较，对重力波产生基本物理的理解将增加。最后，通过与全球建模组的合作，将评估对全球模型中亚网格级重力波强迫和反馈的参数化改进。这项工作的更广泛的影响将是了解从边界层顶部到上层大气的高度区域的重力波产生和重力波效应的进步。除了改善全球模型中重力波均值强迫参数化参数化的主要目标外，结果在卷云研究以及对流层中对流启动的研究中也将是有价值的。该项目涉及培训研究生和博士后研究人员。最初，该项目将仅由女性研究人员进行，这是罕见的情况，因为女性在大气科学中的代表性仍然不足。该项目还与两个全球气候建模群体建立了伙伴关系，一个在美国，另一个在欧洲。尽管亚网格尺度的重力波效应并不是当今改善全球天气预测和气候模型的主要障碍，但许多全球建模组都认识到提高其模型上限对中层高度的重要性，这加剧了重力波浪效应参数的需求。