CINDI – Profiling by Tim Hay

Read DSCD or SCD file Write SZAs, SAzs, elevations, & viewing Azs to geometry file for RT Read prescribed profiles and settings: T, P, density profile Aerosol profile, SSA, asymmetry parameter, etc. Trace gas profiles & cross-sections Wavelengths, surface albedo, etc. Inversion routineForward model: NIMO spherical MC RT model Read geometry file, apriori profile & retrieval layers from inversion routine For each viewing elevation and direction use adjoint RT method to simultaneously simulate radiances for all solar geometries Calculate box-AMFs and DSCDs using radiances and photon path information Calculate weighting functions in terms of partial VCD perturbations of retrieval layers Read modelled DSCDs & weighting functions for whole day from NIMO The trace gas retrieval algorithm Select subset of DSCDs, modelled DSCDs and WFs for current time interval Do linear optimal estimation calculation Day finished? NoYes Save profiles file & finish

NO2 profiles from NIWA instrument – 18 th 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

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

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

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

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

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!