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NSFGEO-NERC: Wave-Induced Transport of Chemically Active Species in the Mesosphere and Lower Thermosphere (WAVECHASM)

NSFGEO-NERC：中层和低层热层中化学活性物质的波诱导传输（WAVECHASM）

基本信息

批准号：
NE/T006749/1
负责人：
John Plane
金额：
$ 58.11万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT006749%2F1
关键词：
NSFGEO NERC Wave Induced Transport

项目摘要

Tides, planetary waves and gravity waves play major roles in establishing the thermal structure and general circulation of the mesosphere/lower thermosphere (MLT) region of the atmosphere (70 - 120 km). For example, the summer mesopause region is the coldest place in the atmosphere due to the meridional circulation induced by gravity wave dissipation. Less well known and understood are the equally important roles that waves play in vertical constituent transport, which is a fundamental atmospheric process that has profound effects on the chemistry and composition of the atmosphere below the turbopause at around 105 km.Atmospheric gravity waves are generated by a variety of mechanisms (e.g. orographic forcing, convection, wind shears) in the troposphere and stratosphere. As the waves propagate upwards their amplitudes grow because of the exponentially falling air pressure, causing a fraction of the waves to become superadiabatic and "break". Wave-breaking is the main source of turbulence in the MLT. A final fraction of the wave spectrum can survive and penetrate into the thermosphere.Waves, and the turbulence they generate, contribute to vertical constituent transport by inducing large-scale advection, eddy transport through turbulent mixing, dynamical transport associated with dissipating, non-breaking waves and chemical transport associated with perturbed chemistry. Recently, compelling evidence has emerged that dynamical and chemical transport is significantly underestimated in global chemistry-climate models. The vertical fluxes of Na and Fe atoms, produced from ablating meteors, have recently been measured by the ground-based lidar technique and are 5 to 10 times larger than in a state-of-the-art climate model. The higher fluxes are supported by astronomical models of dust evolution in the solar system. There is also a significant deficit in the modelled concentrations of O atoms and O3 in the MLT. The most likely reason for these apparent model deficiencies is that a fraction of the gravity wave spectrum is not explicitly captured in models because the wavelengths are smaller than the model horizontal grid-scale (typically > 100 km), and these small waves make a major contribution to vertical transport. The computational cost of increasing the horizontal resolution to include small-scale wave transport effects directly in global models - especially incorporating chemistry - is currently prohibitive.The aim of the WAVECHASM project is to produce a parameterization which can be used to calculate all components of vertical transport in a global model. The project will proceed in four stages. First, we will run a global model with the facility to increase the horizontal resolution regionally down to ~ 14 km, in order to demonstrate the importance of short wavelength waves. In the second step we will parameterise a recent mathematical treatment of dynamical and chemical transport, which shows that these transport terms can be computed in a relatively straightforward way from the wave spectrum in each model grid box. For the third stage we will assemble a data-base of measurements of the vertical fluxes of Na, Fe (in some cases) and heat at 6 lidar stations, the Na density at 16 stations, and satellite measurements of Na and other MLT constituents (e.g. O, O3, NOx, CO2). In the final stage, the new global model with wave transport will be run for 20 years (covering the period of these observations), to study the impact of wave transport on the global distribution and seasonal variations of the important, chemically active species. Once the vertical flux of Na atoms can be reconciled with the abundance of Na in the layer around 90 km, we will obtain an accurate estimate of the amount of interplanetary dust entering the atmosphere, and thus constrain astronomical models of dust evolution in the solar system and improve our understanding the impacts of this dust throughout the atmosphere.

潮汐、行星波和重力波在建立大气中层/低热层 (MLT) 区域（70 - 120 公里）的热结构和大气环流方面发挥着重要作用。例如，由于重力波耗散引起的经向环流，夏季中层顶区域是大气中最冷的地方。不太为人所知和理解的是，波在垂直成分输送中发挥着同样重要的作用，垂直成分输送是一种基本的大气过程，对大约 105 公里处涡轮顶以下大气的化学和成分具有深远的影响。大气重力波是由对流层和平流层中的各种机制（例如地形强迫、对流、风切变）产生的。当波向上传播时，由于气压呈指数下降，波幅增大，导致一部分波变得超绝热并“破裂”。破浪是 MLT 湍流的主要来源。波谱的最后一部分可以存活并渗透到热层中。波及其产生的湍流通过引发大规模平流、通过湍流混合的涡流传输、与耗散、非破碎波相关的动力传输以及与扰动化学相关的化学传输，有助于垂直成分传输。最近，令人信服的证据表明，全球化学气候模型中的动力和化学传递被严重低估。最近通过地面激光雷达技术测量了流星消融产生的 Na 和 Fe 原子的垂直通量，该通量比最先进的气候模型大 5 至 10 倍。太阳系尘埃演化的天文模型支持了更高的通量。 MLT 中 O 原子和 O3 的模拟浓度也存在显着不足。这些明显的模型缺陷的最可能原因是模型中没有明确捕获重力波频谱的一部分，因为波长小于模型水平网格尺度（通常> 100 km），并且这些小波对垂直传输做出了重大贡献。目前，提高水平分辨率以将小尺度波浪输运效应直接纳入全球模型（尤其是结合化学）的计算成本令人望而却步。WAVECHASM 项目的目标是产生一种参数化，可用于计算全球模型中垂直输运的所有组成部分。该项目将分四个阶段进行。首先，我们将运行一个全球模型，利用该设施将区域水平分辨率提高至约 14 公里，以证明短波长波的重要性。在第二步中，我们将参数化最近对动力学和化学输运的数学处理，这表明这些输运项可以通过每个模型网格框中的波谱以相对简单的方式计算。在第三阶段，我们将建立一个数据库，其中包含 6 个激光雷达站的 Na、Fe（在某些情况下）和热量的垂直通量测量值、16 个站的 Na 密度以及 Na 和其他 MLT 成分（例如 O、O3、NOx、CO2）的卫星测量值。在最后阶段，新的波浪传输全球模型将运行20年（涵盖这些观测期间），以研究波浪传输对重要化学活性物种的全球分布和季节变化的影响。一旦Na原子的垂直通量与90公里左右层中Na的丰度相一致，我们将获得进入大气层的行星际尘埃数量的准确估计，从而限制太阳系尘埃演化的天文模型，并加深我们对这些尘埃对整个大气层影响的理解。