Interannual variability of summertime formaldehyde (HCHO) vertical column density and its main drivers in northern high latitudes

Abstract. The northern high latitudes (50–90° N, mostly including boreal forest and tundra ecosystem) has been undergoing rapid climate and ecological changes over recent decades, leading to significant variations in volatile organic compounds (VOCs) emissions from biogenic and biomass burning sources. HCHO, a widely used indicator of VOC emission, exhibits high climate sensitivity. However, the interannual variability of HCHO and its main drivers over the region remain unclear. In this study, we use the GEOS-Chem chemical transport model and satellite retrievals from Ozone Monitoring Instrument (OMI) and Ozone Mapping and Profiler Suite (OMPS) to examine HCHO vertical column density (VCD) interannual variations in summertime of 2005–2019. Our results show that wildfires heavily influence interannual variability of HCHO VCD over Siberia, Alaska, and North Canada, while biogenic emissions and background methane oxidation are the predominant drivers of HCHO interannual variability over East Europe. Solar-induced chlorophyll fluorescence (SIF) from Orbiting Carbon Observatory-2 (OCO-2) provides additional evaluation for HCHO interannual variability from biogenic emission, showing potential of constraining biogenic emission in northern high latitudes.