Constraining biogenic volatile organic compound emissions at northern high latitude: an integrated satellite, ground/aircraft and model perspective

Abstract:

The Arctic terrestrial ecosystem is undergoing rapid change in recent decades, as a result of vegetation growth and wildfires. However, the biogenic volatile organic compound (BVOC) emission from Arctic and boreal vegetation remains poorly quantified, limiting our capability for understanding biosphere-atmosphere exchange in this region and its feedback on Arctic climate and air quality. Formaldehyde, HCHO, serves as an important indicator for BVOC emissions. Here we use satellite observations of HCHO vertical column densities (VCD) from the TROPOspheric Monitoring Instrument (TROPOMI), ground-based and aircraft measurements, combined with a high-resolution chemical transport model (GEOS-Chem at 0.5°×0.625° resolution), to understand BVOC emissions in Alaska better. We first evaluate the model in comparison to ground-based measurements from Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) and in-situ airborne measurements during ATom aircraft campaign. Then we evaluate model performance in comparison to TROPOMI observations, find that model and TROPOMI HCHO VCDs in Alaska are well correlated spatially and temporally during the summer of 2018 and 2019, despite discrepancies in several regions in Alaska and surrounding ocean. The summertime variability of HCHO VCD in the model is largely driven by isoprene emissions. We further investigate the model-satellite discrepancies with model vegetation type distribution, emission factors, chemical mechanisms in this region.