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

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.