Global Temperature Dependency of Biogenic HCHO Columns Observed From Space: Interpretation of TROPOMI Results Using GEOS-Chem Model

Temperature is the principal driver of global atmospheric formaldehyde (HCHO) and its primary oxidation precursor biogenic volatile organic compounds (BVOCs). We revisit such a temperature (T-) dependency globally, leveraging TROPOMI HCHO column data. We find substantial variations in the T-dependency of biogenic HCHO across plant functional types (PFTs), with the highest over Broadleaf Evergreen Tropical Trees (doubling every 6.0 K ± 4.1 K) and lowest over Arctic C3 Grass (doubling every 30.8 K ± 9.6 K). The GEOS-Chem model interprets HCHO columns' T-dependency at the PFT level (r = 0.87), with a 16% discrepancy on average. The discrepancy can be explained by BVOC emissions T-dependency for Broadleaf Evergreen Tropical Trees and Warm C4 Grass and can be attributed to the insensitivity of HCHO columns to BVOC emissions for other PFTs. Our findings underscore a potentially magnified variation of BVOC emissions by GEOS-Chem and MEGAN therein, particularly in regions experiencing greater temperature variations.