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担的因素。 在过去的250年里，大气中甲烷的浓度大幅增加。 在过去的二十年里，增长速度已经放缓，有人认为甲烷在大气中接近稳定状态。 一个由同化气象观测驱动的三维化学输送模式将用于调查甲烷和相关物种一氧化碳和氢的收支。 化学迁移模型将与4箱模型结合使用，以得出较长时间尺度的甲烷排放历史。 在平流层化学方面，该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方面的作用。 具体地说，将测量结果与具有高垂直分辨率的二维模型的结果进行比较，以检查关于混合和重力波诱导阻力的各种假设的效果。 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。 这项工作涉及使用模型模拟来推断重现中纬度地区臭氧总量和温度观测变化所需的环流变化幅度。 这些结果将与NCAR/NCEP分析行星波强迫诊断的变化进行比较。

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.