Transport processes and ozone budgets in the upper troposphere- a synthesis of EOS MLS measurements and chemistry transport model studies

大气最底层10-15公里（对流层）的臭氧是第三大温室气体；自前工业时代以来，臭氧的增加被认为是同期二氧化碳温室气体变暖的四分之一。在对流层的上部，臭氧作为温室气体是最有效的。为了能够预测这种温室气体的浓度在未来将如何变化，以及对未来气候的影响，我们了解控制该地区当前臭氧的过程是很重要的。对流层上层臭氧的“收支”是由化学过程和输送过程控制的。在热带地区，由闪电放电产生的氮氧化物对对流层上层臭氧的形成尤为重要。其他的排放源起源于地球表面。这些排放物，或由这些排放物“就地”形成的臭氧，通过对流上升气流或由盛行的天气系统输送到对流层上层。对流层上层臭氧的另一个来源来自平流层的输入，平流层是对流层上方的大气层。我们将应用复杂的计算机模型来模拟地球大气中的物理和化学过程，以了解臭氧是如何在对流层中形成和运输的。这些模型依靠观察来判断它们模拟所有这些相关过程的能力。然而，在对流层上层，特别是在亚热带和热带地区，观测很少。卫星测量可以帮助解决这个问题，但是大多数仪器（称为最低点观测仪器）只能测量对流层中更大的一部分，而不仅仅是对流层的上部区域。2004年7月，携带地球观测系统（EOS）微波边缘测深仪（MLS）的Aura卫星发射升空。MLS是能够以相对较高的垂直分辨率（几公里）对对流层上层臭氧进行精确测量的首批卫星仪器之一。本建议的目的是结合使用MLS测量和模式模拟，研究不同排放源和不同传输过程在确定对流层上层臭氧的季节和区域变化方面的相对重要性。然后，我们将研究随着气候变暖，由于对流和降雨的区域变化，闪电和运输在未来可能如何变化，以及对热带对流层上层臭氧的影响。

Ozone in the lowest 10-15km of the atmosphere (the troposphere) is the third most important greenhouse gas; increases in ozone since the pre-industrial era are thought to have contributed the equivalent of about one quarter of the CO2 greenhouse gas warming over the same period. It is in the upper part of the troposphere that ozone is most effective as a greenhouse gas. It is important that we understand the processes that control present-day ozone in this region in order to be able to make predictions of how the concentrations of this greenhouse gas will change in the future, and the consequences for future climate. The 'budget' of ozone in the upper troposphere is controlled by both chemical and transport processes. In the tropics, nitrogen oxides generated by lightning discharges are particularly important for ozone formation in the upper troposphere. Other emission sources have their origin at the Earth's surface. These emissions, or ozone formed 'in-situ' from these emissions, are transported in convective updraughts, or by prevailing weather systems, to the upper troposphere. Another source of ozone in the upper troposphere comes from import from the stratosphere, which is the atmospheric layer above the troposphere. We will apply complex computer models that simulate physical and chemical processes in the Earth's atmosphere to understand how ozone is formed and transported in the troposphere. These models rely on observations to judge their ability to simulate all these relevant processes. However, in the upper troposphere, especially in the sub-tropics and tropics, observations are scarce. Satellite measurements can help to solve this problem, but most instruments (called nadir-viewing instruments) can only make measurements that represent a much larger portion of the troposphere than just its upper region. In July 2004, the Aura satellite was launched with the Earth Observing System (EOS) Microwave Limb Sounder (MLS) on board. MLS is one of the first satellite instruments able to make accurate measurements of ozone in the upper troposphere with relatively high vertical resolution (a few km). The aim of this proposal is the combined use of MLS measurements and model simulations, to investigate the relative importance of both different sources of emissions, as well as different transport processes, in determining the seasonal and regional variation of ozone in the upper troposphere. We will then investigate how lightning and transport may change in the future, due to regional shifts in convection and rainfall as the climate warms, and the implications for ozone in the tropical upper troposphere.