Abstract
Biogenic isoprene emissions play a very important role in atmospheric chemistry. These emissions are strongly dependent on various environmental conditions, such as temperature, solar radiation, plant water stress, ambient ozone and CO2 concentrations, and soil moisture. Current biogenic emission models (i.e., Model of Emissions of Gases and Aerosols from Nature, MEGAN) can simulate emission responses to some of the major driving variables, such as short-term variations in temperature and solar radiation, but the other factors are either missing or poorly represented. In this paper, we propose a new modelling approach that considers the physiological effects of drought stress on plant photosynthesis and isoprene emissions for use in the MEGAN3 biogenic emission model. We test the MEGAN3 approach by integrating the algorithm into the existing MEGAN2.1 biogenic emission model framework embedded into the global Community Land Model of the Community Earth System Model (CLM4.5/CESM1.2). Single-point simulations are compared against available field measurements at the Missouri Ozarks AmeriFlux (MOFLUX) field site. The modelling results show that the MEGAN3 approach of using of a photosynthesis parameter (Vcmax) and soil wetness factor (βt) to determine the drought activity factor leads to better simulated isoprene emissions in non-drought and drought periods. The global simulation with the MEGAN3 approach predicts a 17% reduction in global annual isoprene emissions, in comparison to the value predicted using the default CLM4.5/MEGAN2.1 without any drought effect. This reduction leads to changes in surface ozone and oxidants in the areas where the reduction of isoprene emissions is observed. Based on the results presented in this study, we conclude that it is important to simulate the drought-induced response of biogenic isoprene emission accurately in the coupled Earth System model.
Original language | English |
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Pages (from-to) | 69-83 |
Number of pages | 15 |
Journal | Atmospheric Environment |
Volume | 183 |
DOIs | |
State | Published - Jun 2018 |
Funding
X. Jiang and A. Guenther were supported by National Science Foundation (NSF) Atmospheric Chemistry program award AGS-1643042 and National Aeronautics and Space Administration (NASA) Atmospheric Composition Campaign Data Analysis and Modeling (ACCDAM) program award NNX15AT62G . Isoprene flux measurements performed by Mark Potosnak during 2011 were supported by the National Science Foundation through a Collaborative Research award entitled Biogenic Volatile Organic Compound Emissions from the Tundra and Arctic Atmospheric Chemistry ( 1025948 ). We would like to acknowledge the use of computational resources ( https://doi.org/10.5065/D6RX99HX ) at the NCAR-Wyoming Supercomputing Center provided by the National Science Foundation and the State of Wyoming, and supported by NCAR's Computational and Information Systems Laboratory . The CESM model is supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy . The views expressed in this article are those of the author(s) and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.
Keywords
- Biogenic isoprene emissions
- Drought
- Modelling