BVOC emission simulation for the Vienna region during an extreme heat event.

Biogenic volatile organic compounds (BVOC) are emitted by trees. In the presence of NOx they can help to produce tropospheric ozone. During heat waves this can cause a critical additional stress for human wellbeing, especially in areas exhibiting high NOx concentrations. Heat wave intensity and frequency is expected to increase.

To estimate the potential threat, we simulate BVOC emissions over the Vienna region during an extreme heat wave using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) (Guenther et al. 2012) in its latest version 3.  We adapted the model to directly ingest the files used and produced by the land surface model SURFEX8.1 (Surface Externalisée, in French) (Boone et al. 2017) and its preprocessors. In this poster we present our methodology and first results showing the spatial distribution and time series of selected BVOCs.

The chosen heat wave covers 5 days during August 2015, with an average daily 2 m air temperature of 36.3 °C, and represents a significant event with a 15 year return period (of the period 1988-2017).

The LAI and soil parameters field capacity and wilting point are taken from the physiographic fields derived from ECOCLIMAP,  soil moisture and temperature from the prognostic SURFEX output fields calculated for urban and non-urban areas, the 2m air temperature from the diagnostic output fields of SURFEX.

The meteorological forcing is used to create daily meteorology parameters and together with LAI maps run the canopy meteorology module. Further we use the soil emission activity module to calculate a soil temperature and soil moisture dependent isoprene soil emission activity factor. Using these datasets the emission activity factors are calculated. Finally, the emission activity factors are converted from 20 to 201 species and lumped according to the RACM2 mechanism. 

First results, show the strong dependence of isoprene emissions on incoming photosynthetically active radiation and LAI. In the course of the
heat wave isoprene emissions decline, which correlates with the decline in soil water availability and consqequent decreased stomatal opening. 

 

Boone, A., Samuelsson, P., Gollvik, S., Napoly, A., Jarlan, L., Brun, E., & Decharme, B. (2017). The interactions between soil–biosphere–atmosphere land surface model with a multi-energy balance (ISBA-MEB) option in SURFEXv8 – Part 1: Model description. Geoscientific Model Development, 10(2), 843–872.

Guenther, A. B., Jiang, X., Heald, C. L., Sakulyanontvittaya, T., Duhl, T., Emmons, L. K., & Wang, X. (2012). The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): an extended and updated framework for modeling biogenic emissions. Geoscientific Model Development, 5(6), 1471–1492.