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CINDI – Profiling by Tim Hay

CINDI – Profiling by Tim Hay. The trace gas retrieval algorithm. Inversion routine. Forward model: NIMO spherical MC RT model. Read DSCD or SCD file. Read prescribed profiles and settings: T, P, density profile Aerosol profile, SSA, asymmetry parameter, etc.

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CINDI – Profiling by Tim Hay

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  1. CINDI – Profiling by Tim Hay

  2. The trace gas retrieval algorithm Inversion routine Forward model: NIMO spherical MC RT model Read DSCD or SCD file • Read prescribed profiles and settings: • T, P, density profile • Aerosol profile, SSA, asymmetry parameter, etc. • Trace gas profiles & cross-sections • Wavelengths, surface albedo, etc. Write SZAs, SAzs, elevations, & viewing Azs to geometry file for RT Read modelled DSCDs & weighting functions for whole day from NIMO Read geometry file, apriori profile & retrieval layers from inversion routine Select subset of DSCDs, modelled DSCDs and WFs for current time interval For each viewing elevation and direction use adjoint RT method to simultaneously simulate radiances for all solar geometries Do linear optimal estimation calculation Calculate box-AMFs and DSCDs using radiances and photon path information No Yes Day finished? Calculate weighting functions in terms of partial VCD perturbations of retrieval layers Save profiles file & finish

  3. NO2 profiles from NIWA instrument – 18th June 2009 • Common retrieval settings: • 200m grid – 0 to 4km • apriori linear 0.3 ppb to 0.01 ppb • Sa 80% of apriori • Correlation length 100m • Retrieval interval = 30 min • Elevations: 1, 2, 4, 8, 15, 30, 90 • Aerosol profiles: • VIS1 for NIWA instrument • VIS1 and UV1 for Bremen instruments. Surface NO2 retrieved from NIWA and Bremen instruments • “Best” retrieval settings: • 50m grid – 0 to 4km • apriori same as for common • Sa 100% of profile up to 0.5km • Minimum Sa 70% of profile peak • Sa 70% of profile from 0.5 – 4km • Correlation length 25m

  4. Retrieval using prescribed VIS1 aerosol extinction profile Retrieval using prescribed VIS2 aerosol extinction profile Note the effect of the higher aerosol extinction (VIS2): Higher retrieved surface NO2

  5. NO2 profiles from NIWA instrument – 23rd June 2009 Surface NO2 retrieved from NIWA and Bremen instruments

  6. NO2 profiles from NIWA instrument – 24th June 2009 Surface NO2 retrieved from NIWA and Bremen instruments

  7. NO2 profiles from NIWA instrument –25th June 2009 Surface NO2 retrieved from NIWA and Bremen instruments

  8. Note that all the surface NO2 comparisons are my retrievals. So when I show the Bremen instrument surface NO2 it is my retrieval of their measurements. My "best" retrieval settings result in higher surface NO2 because they try to put more of the NO2 in the lowest 500m (my assumed boundary layer height) than the common settings (the common settings are the ones everyone has to use as well as their own best settings). Note that the provided aerosol profile VIS2 has much higher extinction than VIS1, so the retrieval needs to increase the NO2 concentration in order to simulate the measurements. i.e. more aerosols means MAXDOAS is less sensitive. • Another point to note. My interpretation (if the Empa insitu instrument is accurate) is that the days when the retrieved surface NO2 values are closer to Empa might be where the prescribed aerosol profile matches closer to reality. For instance, on the first golden day (18th June) the Empa values are much lower than the retrieved values. Perhaps this was a cleaner day for aerosols, i.e. the aerosol extinction was less than the values given in the VIS1 profile. • I have been updating my profile retrievals on cindi-share and I am close to submitting the complete set. However, its probably too late for Folkard to include them in his talk unless he is very efficient!

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