Comparison of the aerosol extinction coefficient retrieved from MAX-DOAS measurements to in-situ measurements P. Zieger 1, K. Clemer 2, S. Yilmaz 3, R. Fierz-Schmidhauser 1, U. Friess 3, H. Irie 4, B. Henzing 5, G. de Leeuw 5,6,7, J. Mikkila 7, T. Wagner 8, U. Baltensperger 1, and E.Weingartner 1 1 Paul Scherrer Institut, 2 Belgium Institute for Space Aeronomy, 3 University of Heidelberg, 4 JAMSTEC, 5 TNO, 6 Finnish Meteorological Institute, 7 University of Helsinki, 8 MPI Mainz CINDI workshop at BIRA, March 2010, Brussels, Belgium

2 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Rel. humidity Global Atmosphere Watch (GAW) guideline for aerosol light scattering measurements: RH < % To keep continuous light scattering measurements comparable.

3 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Humidified nephelometer (WetNeph) Definition: Scattering enhancement factor WetNeph DryNeph Fierz-Schmidhauser et al., 2010 (AMT)  s scattering coefficient;wavelength Set-up in the Cabauw tower

4 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Measurement example (Cabauw) 02 July 0903 July 0904 July 09 Aerosol scattering coefficient

5 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Measurement example (Cabauw) 02 July 0903 July 0904 July 09 Aerosol scattering coefficient

6 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Measurement example (Cabauw) Scattering enhancement factor

7 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data Comparison of ambient in-situ measurements with MAX-DOAS measurements (lowest height level 0-200m) Instruments so far: *retrieval height varied 1.Belgian Institute for Space Aeronomy (BIRA) 2.University of Heidelberg (IUPHD) 3.Japan Agency for Marine-Earth Science and Technology (JAMSTEC) 4.Max Planck Institut (MPI)*

8 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data Ambient aerosol extinction coefficient Absorption coefficientAmbient scattering coefficient  Multi-Angle Absorption Photometer (= 660nm)   =1.05 (Collaud et al., 2010)  No change with hygroscopic growth assumed  DryNeph, WetNeph (=450, 550, 700nm)  RH amb from tower measurements (10-200m)  Interpolation to MAX-DOAS wavelengths (Ångström law)

9 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data Golden day 24 June 2009

10 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data Golden day 24 June 2009

11 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data Golden day 24 June 2009 Ceilometer 24 June 09 (H. Klein Baltink, KNMI)

12 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data BIRA: entire campaign  BIRA with Cimel retrieval (asymmetry factor and single scattering albedo as input parameter)  Clouds don’t really influence comparison AERONET

13 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data All instruments MPI retrieval height varied BIRA retrieval repeated with in-situ measured input parameters

14 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data All instruments – hour of day

15 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data All instruments – AOD from sun photometer

16 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Comparison to MAX-DOAS data All instruments – PBL height PBL height from ceilometer (H. Klein Baltink, KNMI)

17 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Conclusions -MAX-DOAS and in-situ measurements agree better than expected -Agreement better for low AOD and low PBL cases -Retrieval for BIRA improves with ambient in-situ measurements as input -Possible reasons: - Stability of boundary layer, influence of upper layers, influence of homogeneous gradient of aerosol concentration, influence of clouds (unlikely, checked with AERONET data), … - Losses in the inlet system (unlikely), calibration issues (very unlikely), parameterization of f(RH) (small effect), … - Influence of nitrate partitioning ? -> Bas

18 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Outlook -Further analysis, possibly with additional MAX-DOAS instruments (KNMI and IUPB?), MAX-DOAS: unified assumptions, time grid, etc … -Longer time series will bring further insights and might help to prove or disprove our hypotheses (e.g. IUPHD measured until October) -Add Lidar profiles in comparison -Paper on in-situ comparison will be submitted by the end of June 2010 together with the profile paper

19 Paul Zieger, 2nd CINDI workshop, March 2010, Brussels, Belgium Thank you for your attention! … and thank you to all contributors and the CINDI organizers!