Comparison of the aerosol extinction coefficient retrieved from

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, 10 -12 March 2010, Brussels, Belgium

Rel. humidity Global Atmosphere Watch (GAW) guideline for aerosol light scattering measurements: RH < 30 - 40% To keep continuous light scattering measurements comparable. Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 2

Humidified nephelometer (Wet. Neph) Fierz-Schmidhauser et al. , 2010 (AMT) Set-up in the Cabauw tower Definition: Scattering enhancement factor Wet. Neph Dry. Neph ss: scattering coefficient; : wavelength Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 3

Aerosol scattering coefficient Measurement example (Cabauw) 02 July 09 03 July 09 Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 04 July 09 4

Aerosol scattering coefficient Measurement example (Cabauw) 02 July 09 03 July 09 Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 04 July 09 5

Scattering enhancement factor Measurement example (Cabauw) Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 6

Comparison to MAX-DOAS data Comparison of ambient in-situ measurements with MAX-DOAS measurements (lowest height level 0 -200 m) Instruments so far: 1. Belgian Institute for Space Aeronomy (BIRA) 2. University of Heidelberg (IUPHD) 3. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) *retrieval height varied 4. Max Planck Institut (MPI)* Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 7

Comparison to MAX-DOAS data Ambient aerosol extinction coefficient Ambient scattering coefficient ð Dry. Neph, Wet. Neph ( =450, Absorption coefficient ð Photometer ( = 660 nm) 550, 700 nm) ð Multi-Angle Absorption RHamb from tower ð =1. 05 (Collaud et al. , 2010) measurements (10 -200 m) ð No change with hygroscopic growth assumed ð Interpolation to MAX-DOAS wavelengths (Ångström law) Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 8

Comparison to MAX-DOAS data Golden day 24 June 2009 Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 9

Comparison to MAX-DOAS data Golden day 24 June 2009 Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 10

Comparison to MAX-DOAS data Golden day 24 June 2009 Ceilometer 24 June 09 (H. Klein Baltink, KNMI) Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 11

Comparison to MAX-DOAS data BIRA: entire campaign AERONET ð BIRA with Cimel retrieval (asymmetry factor and single scattering albedo as input parameter) ð Clouds don’t really influence comparison Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 12

Comparison to MAX-DOAS data All instruments BIRA retrieval repeated with in-situ measured input parameters MPI retrieval height varied Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 13

Comparison to MAX-DOAS data All instruments – hour of day Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 14

Comparison to MAX-DOAS data All instruments – AOD from sun photometer Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 15

PBL height from ceilometer (H. Klein Baltink, KNMI) Comparison to MAX-DOAS data All instruments – PBL height Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 16

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 Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 17

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 Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 18

Thank you for your attention! … and thank you to all contributors and the CINDI organizers! Paul Zieger, 2 nd CINDI workshop, 10 -11 March 2010, Brussels, Belgium 19