First results of the aerosol profiling group IUP Heidelberg BIRA-IASB MPIC Mainz IUP Bremen JAMSTEC WSU KNMI NIWA Univ. Leicester PSI TNO RIVM KNMI

The participants: MAX-DOAS  JAMSTEC → aerosol extinction profiles → VIS → 1km grid; parameterized  IUP HDB → aerosol extinction profiles → VIS → 200m grid  BIRA → aerosol extinction profiles → UV and VIS → 200m grid  MPI → aerosol extinction profiles → UV → AOD + surface ext. + layer height + f=0.9  IUP Bremen → AOD → VIS → ?; parameterized

 CIMEL sunphotometer (TNO) → AOD at different wavelengths & ssalb, phase-function  Nephelometer (PSI,TNO) → surface extinction & ssalb, phase-function  Ramen LIDAR (RIVM) → aerosol extinction profiles  Ceilometer (KNMI) → boundary layer height  Backscatter lidar (RIVM) → boundary layer height The participants:  …

Results; BIRA

AOD time series

AOD MAXDOAS vs. CIMEL

Measured O 4 DSCD are reduced by ~20% for BIRA, MPI, IUP HDB Not for JAMSTEC and IUP Bremen

With correctionWithout correction AOD MAXDOAS vs. CIMEL

Correcting the O 4 DSCD

Case: 30° elevation, pointing north, clear-sky, AOD<0.15 Correcting the O 4 DSCD Based on the Beijing dataset → Measured and simulated O 4 DSCD should be equal But sim. O 4 DSCDs = meas. O 4 DSCDs * 0.8  0.1

12 Measured DS SCD O4 is within 2% of the simulated using Hermans et al. cross section at room T (477 nm). Direct sun results VIS; Elena Spinei

Correcting the O 4 DSCD ? Are we really sure that the simulations are correct. That the differences are not caused by errors in other forward model parameters Aerosol optical properties, … Error in measured O 4 DSCD Error in the spectra Error in DOAS fit ? O 4 cross-section No Yes or ? ?

Influence of ssalb and g

BIRA VIS Heidelberg VIS JAMSTEC VIS Contour plots

BIRA UV MPI UV Contour plots

BIRA VIS Heidelberg VIS JAMSTEC VIS Contour plots; identical scales

BIRA UV MPI UV But; better results for f=1.1 Uplifted aerosol layer Contour plots; identical scales

BIRA VIS Heidelberg VIS JAMSTEC VIS Contour plots

BIRA UVMPI UV Contour plots

BIRA VIS Heidelberg VIS JAMSTEC VIS Contour plots; identical scales

BIRA UV MPI UV Contour plots; identical scales

Aerosol inter-comparisons: plans for the future Retrieving synthetic profiles:  BIRA will provide O 4 DSCDs and relative intensities at 4 wavelengths for 4 aerosol cases: low AOD and high AOD; surface layer and up-lifted layer  Try to retrieve the profiles using your best settings; the settings agreed on for the real data. MAXDOAS → Focus on both AOD and profiles

+ Sensitivity tests concerning ssalb, phase function,… Aerosol inter-comparisons: plans for the future Real data  On your own data set  On the Heidelberg dataset (data until October the 5th)  Retrievals using your own best settings  Retrievals using settings as similar as possible  Apriori extinction: exponential profile, SH=1km, AOD=0.1;  Height grid for the simulations: 200m grid to 4km.  Covariance matrix: 100% of apriori; 100m or 500m (HDB suggestion).  Atmosphere (P,T): USstandard  O3+NO2: USstandard  Lambertian surface albedo: 5%  Aerosol: optical properties are based on mean Nephelometer: g=0.65 and single scattering albedo = 0.95;  wavelengths: 360, 477, 577, 630nm if possible

MAXDOAS vs other instruments  Insitu data, nephelometer (Paul Zieger)  Aerosol extinction from Raman LIDAR (Arnoud Apituley) Paper on MAXDOAS intercomparison and the Nephelometer paper by June-July → deadline for data submission: end March Aerosol inter-comparisons: plans for the future

Summary The agreement between the different aerosol retrievals has already improved compared to the previous workshop Questions What’s up with the O 4 DSCD? What can we actually achieve? (what is our sensitivity, how sensitive are we towards forward model parameters and towards a-priori information, can we obtain “substitute aerosol profiles” for clouds,…) Conclusion for now We are making progress But we still have a lot of work to do; a lot of questions to answer