Source and variability of formaldehyde (HCHO) at northern high latitudes: an integrated satellite, aircraft, and model study

Here we use satellite observations of formaldehyde (HCHO) vertical column densities (VCD) from the TROPOspheric Monitoring Instrument (TROPOMI), aircraft measurements, combined with a nested regional chemical transport model (GEOS-Chem at 0.5 x 0.625 degrees resolution), to better understand the variability and sources of summertime HCHO in Alaska. We first evaluate GEOS -Chem with in-situ airborne measurements during the Atmospheric Tomography Mission 1 (ATom-1) aircraft campaign.

We show reasonable agreement between observed and modeled HCHO, isoprene, monoterpenes and the sum of methyl vinyl ketone and methacrolein (MVK+MACR) in the continental boundary layer. In particular, HCHO profiles show spatial homogeneity in Alaska, suggesting a minor contribution of biogenic emissions to HCHO VCD. We further examine the TROPOMI HCHO product in Alaska in summer, reprocessed by GEOS-Chem model output for a priori profiles and shape factors.