1. UV-vis data and NORS validation server NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 1 F. Hendrick, B. Langerock, M. Van Roozendael, and M. De Mazière Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium

2. Context NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 2 To develop and implement a web-based application for validation of MACCII products using the NORS data products (NORS WP8) MACC output at 0, 6, 12, 18, 24h UT

3. 1. Temporal interpolation NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 3 For UV-vis data, three different cases need to be considered: Total ozone columns (90° SZA AM and PM) Stratospheric NO 2 columns and profiles (90° SZA AM and PM) + diurnal variation Products from MAX-DOAS observations (every ~30’)

4. Temporal interpolation: total ozone NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 4 Choose a characteristic time-window (e.g., 6h as for FTIR): Time MACC output 6h 90°SZA AM observation 90°SZA PM observation

5. Temporal interpolation: stratospheric NO 2 NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 5 x_MACCII(LT DOAS ) = x_MACCII (LT MACCII ). [ x_model(LT DOAS )/x_model(LT MACCII ) ] with x= NO 2 VCD or [NO 2 ] at altitude z Scaling factor 90°SZA AM 90°SZA PM MACC-II output

6. NORS NO 2 photochemical correction tool NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 6  ‘Off-line’ calculation of look-up tables of NO 2 profile diurnal variation using of the BIRA photochemical box model PSCBOX  Model calculations for the following scenarios: altitude (24 levels), latitude (18 values covering 85°N→85°S by 10° step), longitude set to 0, months 1-12  For each month, use of the SLIMCAT chemical and meteorological fields corresponding to the middle of the month averaged over a period of 10 years (2000-2009)  Look-up tables of NO 2 profile diurnal variation in ASCII  Creation of an interpolation routine in FORTRAN to extract the needed scaling factors

7. Sensitivity tests (1) NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 7 March 15 th chemical field and p, T profiles averaged over 10 years (2000-2009) March 15 th 2000 NO2_model(LT DOAS ) / NO2_model(LT)

8. Sensitivity tests (2) NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 8 March 15 th chemical field and p, T profiles averaged over 10 years (2000-2009) March 15 th 2005 NO2_model(LT DOAS ) / NO2_model(LT)

9. Sensitivity tests (3) NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 9 denoxification

10. NORS NO 2 photochemical correction tool NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 10  ‘Off-line’ calculation of look-up tables of NO 2 profile diurnal variation  Use of the photochemical box model PSCBOX  Model calculations for the following scenarios: altitude (24 levels), latitude (18 values covering 85°N→85°S by 10° step), longitude set to 0, months 1-12  For each month, use of the SLIMCAT chemical and meteorological fields corresponding to the middle of the month averaged over a period of 10 years (2000-2009)  For polar regions in late fall, winter, early spring, additional look-up tables are needed for denoxification conditions; the choice of LUTs (denoxification conditions or not) could be based on the measured NO 2 columns

11. Temporal interpolation: MAX-DOAS products NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 11 Smaller time-window due to the strong short-term variation: Time MACC output 1h MAX-DOAS observations (every ~ 30’) 1h

12. 2. Spatial interpolation NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 12 As for FTIR, calculate the location of the effective airmass of every measurement Interpolate the four surrounding MACC-II model data to this effective airmass location: Is it relevant to proceed like this with UV-vis measurements ? Do we have tools for such calculations ?

13. 3. Smoothing and vertical gridding NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 13 MACC-II profile x MACC must be regridded to the vertical grid of the NORS profile The MACC-II data is smoothed with the averaging kernel of the NORS measurement using: x s,MACC = x a,NORS + A NORS (x MACC – x a,NORS ) IF DOFS < 5, one defines partial column boundaries in between which there is about one DOF. Partial column boundaries should be defined by the PI of the instrument Profile comparisons:

14. MACC-II profile x MACC must be regridded to the vertical grid of the NORS profile The MACC-II data is smoothed with the column averaging kernel of the NORS measurement using: C s,MACC = C a,NORS + (x MACC – x a,NORS ) Suitable for OEM-based retrievals but what we do for total ozone and stratospheric NO 2 column retrievals (no a priori data used) ? 3. Smoothing and vertical gridding NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 14 Column comparisons: