Interactive biogenic emissions and drought stress effects on atmospheric composition in NASA GISS ModelE
<p>Drought is a hydroclimatic extreme that causes perturbations to the terrestrial biosphere and acts as a stressor on vegetation, affecting emissions patterns. During severe drought, isoprene emissions are reduced. In this paper, we focus on capturing this reduction signal by implementing a n...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/13303/2022/acp-22-13303-2022.pdf |
| Summary: | <p>Drought is a hydroclimatic extreme that causes perturbations to
the terrestrial biosphere and acts as a stressor on vegetation, affecting
emissions patterns. During severe drought, isoprene emissions are reduced.
In this paper, we focus on capturing this reduction signal by implementing a new percentile isoprene drought stress (<span class="inline-formula"><i>y</i><sub>d</sub></span>) algorithm in NASA GISS ModelE based on the MEGAN3 (Model of Emissions of Gases and Aerosols from Nature Version 3) approach as a function of a photosynthetic parameter
(<span class="inline-formula"><i>V</i><sub>c,max</sub></span>) and water stress (<span class="inline-formula"><i>β</i></span>). Four global transient
simulations from 2003–2013 are used to demonstrate the effect without
<span class="inline-formula"><i>y</i><sub>d</sub></span> (Default_ModelE) and with online <span class="inline-formula"><i>y</i><sub>d</sub></span>
(DroughtStress_ModelE). DroughtStress_ModelE is evaluated against the observed isoprene measurements at the Missouri Ozarks AmeriFlux (MOFLUX) site during the 2012 severe drought where improvements in the correlation coefficient indicate it is a suitable drought stress parameterization to capture the reduction signal during severe drought. The application of <span class="inline-formula"><i>y</i><sub>d</sub></span> globally leads to a decadal average reduction of <span class="inline-formula">∼2.7</span> %, which is equivalent to <span class="inline-formula">∼14.6</span> Tg yr<span class="inline-formula"><sup>−1</sup></span> of isoprene. The changes have larger impacts in regions such as the southeastern US. DroughtStress_ModelE is validated using the satellite <span class="inline-formula">Ω</span>HCHO column from the Ozone Monitoring Instrument (OMI) and surface O<span class="inline-formula"><sub>3</sub></span> observations across regions of the US to examine the effect of drought on atmospheric composition. It was found that the inclusion of isoprene drought stress reduced the overestimation of <span class="inline-formula">Ω</span>HCHO in Default_ModelE during the 2007 and 2011 southeastern US droughts and led to improvements in simulated O<span class="inline-formula"><sub>3</sub></span> during drought periods. We conclude that isoprene drought stress should be tuned on a model-by-model basis because the variables used in the parameterization responses are relative to the land surface model hydrology scheme (LSM) and the effects of <span class="inline-formula"><i>y</i><sub>d</sub></span> application could be larger than seen here due to ModelE not having large biases of isoprene during severe drought.</p> |
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| ISSN: | 1680-7316 1680-7324 |