The Mainz Profile Algorithm (MAPA)
Abstract. The Mainz profile algorithm (MAPA) derives vertical profiles of
aerosol extinction and trace gas concentrations from MAX-DOAS measurements of
slant column densities under multiple elevation angles. This paper presents
(a) a detailed description of the MAPA (v0.98), (b) results for the CINDI-2
campaign, and (c) sensitivity studies on the impact of a priori assumptions
such as flag thresholds. Like previous profile retrieval schemes developed at MPIC, MAPA is based on a
profile parameterization combining box profiles, which also might be lifted,
and exponential profiles. But in contrast to previous inversion schemes based
on least-square fits, MAPA follows a Monte Carlo approach for deriving those
profile parameters yielding best match to the MAX-DOAS observations. This is
much faster and directly provides physically meaningful distributions of
profile parameters. In addition, MAPA includes an elaborated flagging scheme
for the identification of questionable or dubious results. The AODs derived with MAPA for the CINDI-2 campaign show good agreement with
AERONET if a scaling factor of 0.8 is applied for O4 , and the
respective NO2 and HCHO surface mixing ratios match those derived
from coincident long-path DOAS measurements. MAPA results are robust with
respect to modifications of the a priori MAPA settings within plausible
limits.