Formaldehyde and nitrogen dioxide over the remote western Pacific Ocean: SCIAMACHY and GOME-2 validation using ship-based MAX-DOAS observations 1Institute of Environmental Physics (IUP), University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
27 Nov 2012
2Institute of Environmental Physics (IUP), University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany
Received: 04 Jun 2012 – Published in Atmos. Chem. Phys. Discuss.: 28 Jun 2012 Abstract. In October 2009, shipborne Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)
measurements were performed during the TransBrom campaign over the western Pacific Ocean
(≈ 40° N to 20° S). Vertical tropospheric trace gas columns
and profiles of nitrogen dioxide (NO2) and formaldehyde (HCHO) as well as
stratospheric NO2 columns were retrieved in order to validate corresponding measurements
from the GOME-2 and SCIAMACHY satellite instruments and to estimate tropospheric background
concentrations of these trace gases.
Revised: 18 Oct 2012 – Accepted: 05 Nov 2012 – Published: 27 Nov 2012
All instruments reproduced the same characteristic, latitude-dependent shape of stratospheric
NO2. SCIAMACHY and GOME-2 data differ by about 1% from each other while yielding lower
vertical columns than MAX-DOAS morning values as a consequence of measurement time and
stratospheric NO2 diurnal cycle. Due to this diurnal cycle, an increase of
8.7 ± 0.5 × 1013 molec cm−2 h−1 of stratospheric NO2 was estimated from
MAX-DOAS data at low latitudes during the day.
Tropospheric NO2 was above the detection limit only in regions of higher anthropogenic
impact (ship traffic, transport of pollution from land). A background column of
1.3 × 1014 molec cm−2 (or roughly 50 ppt boundary layer concentration) can be estimated as upper
limit for the remote ocean, which is in agreement with GOME-2 monthly mean values. In the marine
boundary layer close to the islands of Hokkaido and Honshu, up to 0.8 ppbv were retrieved
close to the surface.
Background HCHO concentrations over the remote ocean exhibit a diurnal cycle with maximum
values (depending strongly on weather conditions) of 4 × 1015 molec cm−2
for the vertical column at noontime. Corresponding peak concentrations of up to 1.1 ppbv
were retrieved in elevated altitudes (≈ 400 m) around noon while maximum concentrations in the
evening are close to the ground. An agreement between MAX-DOAS and GOME-2 data was found for
typical vertical columns of 3 × 1015 molec cm−2 over the remote ocean at the
time of overpass.
Citation: Peters, E., Wittrock, F., Großmann, K., Frieß, U., Richter, A., and Burrows, J. P.: Formaldehyde and nitrogen dioxide over the remote western Pacific Ocean: SCIAMACHY and GOME-2 validation using ship-based MAX-DOAS observations, Atmos. Chem. Phys., 12, 11179-11197, doi:10.5194/acp-12-11179-2012, 2012.