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

The northern high latitude region (mostly including Boreal Forest and Tundra ecosystems) has undergone rapid climate and ecological changes over recent decades. How these changes impact biosphere-atmosphere interactions and air quality in this region remain unclear. Formaldehyde (HCHO) serves as an indicator of biogenic and pyrogenic Non-Methane Volatile Organic Compounds (NMVOCs) emissions, through both primary emission and secondary production from larger VOCs. Here we evaluate the interannual variability of HCHO Vertical Column Density (VCD) in northern high latitudes (50-90°N) over the past 15 years (2005-2019), using a new OMI HCHO retrieval product and the GEOS-Chem chemical transport model. We find that the interannual variability of satellite HCHO VCD largely follows the variations in biomass burning emissions over the Siberian and North American Arctic, suggesting an important role of wildfire in HCHO variability in these regions. In contrast, we find that biogenic emissions dominate the interannual variability of HCHO VCD over Eastern Europe, where the impacts from wildfire appears to be small. We will provide a detailed analysis on the main drivers of summertime HCHO interannual variability in different parts of Pan-Arctic region. Such knowledge may help to better understand future air quality in northern high latitude area under a rapid changing climate.