Comparison of solar absorption FTIR measurements of CO, NH3, CH2O and C2H6 with GEOS-Chem model simulations for the Polarstern cruise ANT XX-3

The atmospheric gases CO, NH3 , CH2O and C2H6 retrieved by solar absorption FTIR spectrometry during the cruise ANT XX-3 of RV Polarstern are compared to GEOS Chem simulations. The cruise was a meridional transect on the Atlantic. It started on the 25th January 2003 in Cape Town (South Africa) and ended on the 16th February in remerhaven (Germany). During this cruise, the ship crossed a biomass burning plume at about 6° N, resulting in a strong increase of CO, NH3 and CH2O concentrations. For carbon monoxide and ammonia model and measurements agree well at all latitudes. The formaldehyde model simulation is significantly lower than the measurements. After caling with the empirically determined factor 3.7, the results of model and measurements agree well. The ethane’s southern hemispheric total columns agree well with the model, while the northern hemispheric values do not agree.