Understanding and Quantifying Biogenic Emissions from Tropical Terrestrial Ecosystems Using Satellite Observations

预测未来气候的最大不确定性之一包括对流层臭氧对气候变化的反应。对流层臭氧是一种温室气体，在氮氧化物存在的情况下，一氧化碳和天然和人造碳氢化合物通过光化学氧化产生。它也是一种空气污染物，浓度升高会导致呼吸系统疾病和作物减产。我们对对流层臭氧的理解的一个主要弱点是，目前对自然和人造气体的排放估计存在很大的不确定性，这些气体随后会影响臭氧。地面观测的结果只代表较短的距离，很难与全球对流层联系起来。卫星对微量气体的观测提供了地球大气的全球覆盖，这是研究对流层臭氧及其前体排放的关键。在这里，我们建议利用卫星观测来改进热带生态系统碳氢化合物的排放估计。热带生态系统的排放量占全球植被排放量的75%以上，因此了解和量化尤为重要。作为这个项目的结果，我们将对对流层臭氧有更好的了解，这将有助于解决空气质量问题，并可能将其在未来气候中的作用降至最低。热带生态系统排放大量的各种活性碳氢化合物，有助于推动对流层中的氧化剂化学。这些通量的大小和时空变异性，以及它们如何对天气和气候(例如地表温度)的变化作出反应，目前还不是很清楚。目前的理解包括来自实验室和地面测量的有限数据集的经验关系，这些数据描述了植被排放如何对天气和气候变化做出反应。热带生态系统在许多空间和时间尺度上是异质的，这使得地面测量很难与更大的区域相关。卫星对示踪气体的新观测代表了更大的空间尺度，更适合于了解热带生态系统。它们有可能给气候研究带来革命性的变化，但它们的解释并不直接，因为它们往往代表与感兴趣的量(例如，该气体的浓度)有关的复杂的导出量(例如，对特定气体吸收或发射辐射的电磁光谱的测量)。这些卫星数据在不同热带生态系统和不同季节的时空变异性可以用天气和气候的变化来解释。我们将利用这些数据开发一个更准确的热带生态系统排放模型，描述不同大陆不同季节的大规模植被对天气和气候的反应。将排放模型应用到更大的大气计算机模型中，其中包括空气中的化学反应，这对于评估这些更准确的热带排放估计对对流层氧化化学的重要性是必要的。这最终将导致对气候的更准确的模拟。热带生态系统是我们目前对地球气候演变的理解中的一个重要弱点。我提出的研究将为我们提供一个更全面的地球观点，对我们理解气候具有深远的影响。

One of the largest uncertainties in predicting future climate includes the response from O3 in the troposphere to climate change. Tropospheric O3 is a greenhouse gas that is produced by the photochemical oxidation of CO and natural and man-made hydrocarbons in the presence of nitrogen oxides. It is also an air pollutant that at elevated concentrations causes respiratory illnesses and reduced crop yields. One of the main weaknesses in our understanding of tropospheric O3 is the large uncertainty associated with current emission estimates of natural and man-made gases that subsequently affect O3. Findings from surface observations, representative of only short distances, are difficult to relate to the global troposphere. Satellite observations of trace gases, which provide global coverage of Earth's atmosphere, are key to studying tropospheric O3 and its precursor emissions. Here, we propose to use satellite observations to improve emission estimates of hydrocarbons from tropical ecosystems. Emissions from tropical ecosystems represent more than 75% of global emissions from vegetation and are therefore particularly important to understand and quantify. As a result of this project we will have a better understanding of tropospheric O3 that will help tackle air quality problems and perhaps minimize its role in future climate. Tropical ecosystems emit large quantities of a wide range of reactive hydrocarbons that help to drive oxidant chemistry in the troposphere. The magnitude and spatial and temporal variability of these fluxes, and how they respond to changes in weather and climate (e.g., surface temperature), is not well understood. Current understanding includes empirical relationships, derived from a limited dataset of laboratory and ground-based measurements, which describe how emissions from vegetation respond to changes in weather and climate. Tropical ecosystems are heterogeneous over many spatial and temporal scales, making ground-based measurements difficult to relate to larger regions. New satellite observations of trace gases that are representative of much larger spatial scales are better suited to understanding tropical ecosystems. They have the potential to revolutionize the study of climate, but they are not straightforward to interpret because they often represent complicated derived quantities (e.g., measurements of the electromagnetic spectrum where a particular gas absorbs or emits radiation) that are related to the quantities of interest (e.g., concentration of that gas). The spatial and temporal variability of these satellite data over different tropical ecosystems and during different seasons can be explained by changes in weather and climate. We will use these data to develop a more accurate emission model of tropical ecosystems that describes how large-scale vegetation on different continents during different seasons responds to weather and climate. Implementing the emission model into a larger computer model of the atmosphere, which includes chemical reactions in the air, is necessary to assess the importance of these more accurate tropical emission estimates on oxidant chemistry in the troposphere. This will ultimately lead to a more accurate simulation of climate. Tropical ecosystems represent an important weakness in our current understanding of the evolution of Earth's climate. My proposed research will provide us with a more integrated view of Earth with far-reaching implications for our understanding of climate.