Effects of temperature and soil water parameterization improvements in MEGAN-CLM Isoprene emissions: a model-observations assessment.

Isoprene accounts for half of the global BVOC emissions from terrestrial ecosystems. Consequently, refining its representation in numerical models is essential for accurately assessing its effects on Ozone and Secondary Organic Aerosols and, more generally, on the role of vegetation in modulating atmospheric physico-chemical processes. Here, we present an analysis and preliminary results of an improved parameterization of Isoprene emissions factor sensitivity to water availability and surface air temperature within the MEGAN model coupled with the Community Land Model (CLM-4.5). Overall, by comparing our results with three (quasi-)observational datasets, the new parameterization yielded more accurate estimates of global annual Isoprene emissions, despite still exhibiting less pronounced seasonal variability. Notably, more realistic values are obtained in the Arctic during boreal summer, as well as stronger emission reductions occur during periods of droughts in the tropics and in subtropical latitudes. Although uncertainties still persist in specific geographic regions, we investigate the specific model and environmental factors contributing to these discrepancies.