PowerPoint-Pr

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Status paper

• Internal review process until July 15
• Send around to all authors, collect comments by
  August 10
• Submit August 20

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MAX-DOAS profile retrieval (I)

• Optimal Estimation using a priori information
• Online calculation of block-AMFs and describe
  relation between measurements (SCDs of trace gas
  for different elevations) and absorber profile as
  a linear inversion problem
• Solve by Optimal estimation method (therefore
  adding a trace gas a priori profile)
• BIRA, NIWA, WSU, Heidelberg, Leicester/Leeds and
  Bremen

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MAX-DOAS profile retrieval (II)

• Inversion by parametrisation of trace gas
  profiles
• A) mixing layer height MLH (important
  atmospheric parameter)
• B) fraction f of total VCD in boundary layer
  (allows to adjust vertical profile, depending
  e.g. on vertical mixing into free troposphere)
• Lookup tables for AMF, least squares fit
• MPI Mainz, similar approach used by JAMSTEC, KNMI

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Data included three-fold comparison
Simulation(provided by BIRA) Simulation(provided by BIRA) Real Data- focus on Bremen data (fixed aerosol) Real Data- focus on Bremen data (fixed aerosol) Real Data (aerosol retrieval included Real Data (aerosol retrieval included
UV VIS UV VIS UV VIS
BIRA
IUP-B
IUP-H
JAMSTEC
MPI
NIWA
WSU
KNMI
Leeds
To identify each methods possibilities What are
pros and cons?
How consistent are the results in the real
world?
How do they compare to other instruments?
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Simulation study

• IASB-BIRA has provided modeled NO2 slant columns
  for UV and visible, using
• different NO2 scenarios (profiles)
• Two aerosol loadings (AOD 0.14 and 0.54 for 477
  nm)
• Simulations for June 24, 2009 in Cabauw
• 10 Elevation Angles (1,2,4,5,6,8,10,15,30,89)
• SCD error based on real DOAS fit errors plus
  Gaussian noise
• Calculations with RTM LIDORT

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Simulation study
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For all comparisons . ..

• We are focusing on two parameters
• Tropospheric column lt-gt important for satellite
  validation)
• VMR close to the surface lt-gt easy to compare with
  in situ data
• MAX-DOAS as a link between satellite and in
  situ (air pollution) network.

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Conclusions from simulation study

• VC and surface layer values usually captured
  well, difference to true value for most scenarios
  less than 25
• Viewing directions towards sun (RAA lt 20) and
  for high SZA (gt75) for some algorithms difficult
  to retrieve
• LOS lt 3 crucial for proper profile retrieval
• 1.5 lt DoF lt 3
• Results in the visible have less scatter, in
  particular for high aerosol load (not surprising)

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Conclusions from simulation study

• Best settings for OE
• Finer grid gives more details (shallow and very
  shallow layer) and for some algorithms better
  agreement (Bremen, NIWA, WSU) to reference data
• From Bremen experience the retrieval profits from
  using both wavelength regions in parallel