Theoretical Studies of the Chemical Composition of the Earth's Atmosphere

该项目涉及使用数值模型来解决对流层和平流层化学中的关键问题。在对流层化学方面，重点是了解控制全球大气甲烷负荷的因素。在过去的250年里，大气中甲烷的浓度有了很大的增加。在过去的二十年里，甲烷的增长速度已经放缓，有人认为大气中的甲烷正在接近稳定状态。利用同化的气象观测数据驱动的三维化学输运模型，研究甲烷及其相关物种一氧化碳和氢的收支情况。化学输运模型将与4箱模型结合使用，以得出更长时间尺度上的甲烷排放历史。就平流层化学而言，本项目的重点是了解水平和垂直混合在确定平流层臭氧分布中的作用。具体来说，测量结果将与具有高垂直分辨率的二维模型的结果进行比较，以检验关于混合和重力波诱导阻力的各种假设的影响。第二个目标是研究从对流层发出的行星波对平流层臭氧分布的影响。这项工作包括使用模式模拟来推断重现观测到的中纬度地区总臭氧和温度变化所需的环流变化幅度。这些结果将与NCAR/NCEP对行星波强迫分析诊断出的变化进行比较。

This project involves the use of numerical models to address key issues in tropospheric and stratospheric chemistry. In terms of tropospheric chemistry, the focus is on understanding the factors controlling the global atmospheric methane burden. During the past 250 years, there has been a major increase in the atmospheric concentration of methane. Over the past two decades, the growth rate has slowed and it has been suggested that methane is approaching steady state in the atmosphere. A three-dimensional chemical transport model driven by assimilated meteorological observations will be used to investigate the budgets of methane and the related species carbon monoxide and hydrogen. The chemical transport model will be used in conjunction with a 4-box model to derive a history of methane emissions over longer time scales. In terms of stratospheric chemistry, the focus of this project is on understanding the role of horizontal and vertical mixing in determining the distribution of stratospheric ozone. Specifically, measurements will be compared with results of a two dimensional model with high vertical resolution to examine the effect of various assumptions about mixing and gravity wave induced drag. A second goal is to study the effect of planetary waves emanating from the troposphere on the distribution of stratospheric ozone. This effort involves the use of model simulations to infer the magnitude of changes in circulation required to reproduce observed change in total ozone and temperature at midlatitudes. These results will be compared with the changes diagnosed from the NCAR/NCEP analysis of planetary wave forcing.