François Hendrick and the NDACC/NORS UVVIS Working Group Demonstration Network Of ground-based Remote Sensing observations in support of the GMES Atmospheric Service Main achievements (11/ /2014) NDACC UV-VIS WG Meeting, Brussels, 9 July

NORS general objective Target NORS data products –Tropospheric and stratospheric O 3 columns and profiles –Tropospheric and stratospheric NO 2 columns and profiles –Tropospheric profiles of HCHO and aerosol extinction –Tropospheric and stratospheric columns of CO –Tropospheric and stratospheric columns of CH 4 4 NDACC techniques + in-situ surface monitoring: –Lidar, MW, FTIR, UV-VIS (MAX-)DOAS + in-situ surface monitoring 4 NDACC pilot stations Perform the required research and developments to optimize the NDACC data products for the purpose of supporting the quality assessments of the future Copernicus Atmosphere Monitoring Service (CAMS) NDACC UV-VIS WG Meeting, Brussels, 9 July

Copernicus NDACC UV-VIS WG Meeting, Brussels, 9 July

NORS general objective Target NORS data products –Tropospheric and stratospheric O 3 columns and profiles –Tropospheric and stratospheric NO 2 columns and profiles –Tropospheric profiles of HCHO and aerosol extinction –Tropospheric and stratospheric columns of CO –Tropospheric and stratospheric columns of CH 4 4 NDACC techniques + in-situ surface monitoring: –Lidar, MW, FTIR, UV-VIS (MAX-)DOAS + in-situ surface monitoring 4 NDACC pilot stations Perform the required research and developments to optimize the NDACC data products for the purpose of supporting the quality assessments of the future Copernicus Atmosphere Monitoring Service (CAMS) NDACC UV-VIS WG Meeting, Brussels, 9 July

NORS pilot stations NDACC UV-VIS WG Meeting, Brussels, 9 July

NORS partners NDACC UV-VIS WG Meeting, Brussels, 9 July

NORS Workpackages NDACC UV-VIS WG Meeting, Brussels, 9 July

WP4: Characterization of NDACC UVVIS data  (MAX-)DOAS data harmonization (DOAS settings, NO 2 and O 3 AMF LUTs, profiling methods,…) NDACC UV-VIS WG Meeting, Brussels, 9 July

NDACC UV-VIS WG Meeting, Brussels, 9 July Harmonisation of spectral inversion: NO 2 RECOMMENDED SETTINGSCOMMENTS Fitting interval nmSettings adequate for simultaneous NO 2 and O 4 retrieval with MAXDOAS instruments. For UV instruments, the alternative nm interval is recommended. Wavelength calibration methodCalibration based on reference solar atlas The Chance and Kurucz (2010) solar atlas is recommended as wavelength registration reference Cross-sections NO 2 Vandaele et al. (1998), 220 K (298K for tropospheric retrievals) This reference is the one included in the HITRAN data base. For stratospheric NO 2 columns, fine adjustment of temperature effects can eventually be performed in a post-processing step using a simple monthly zonal climatology of temperature profiles. For tropospheric NO 2 columns, the temperature dependence of the NO 2 cross sections should be taken into account, at least by selecting cross sections at the appropriate temperature or by adding a second (pseudo) cross sections set. O3O3 Bogumil et al, (2003), 223 KO 3 absorption cross-sections measured with the SCIAMACHY flight-model instrument. H2OH2OHarder and Brault (1997) O4O4 Hermans et al. (2003) Ring effect correction methodChance and Spurr (1997)It is recommended to use of an effective Ring cross-section. A high resolution Ring effect cross-section source (generated after Chance and Spurr, 1997) is provided on the NDACC web site. Note that this approach neglects the impact of the Ring effect on the NO 2 absorption itself (molecular Ring effect). Polynomial termPolynomial of order 3 to 5 maximum Intensity offset correctionSlopeThe intensity offset parameter corrects for spectral stray-light effects and for the wavelength dependence of the probability of Raman scattering (Ring effect). One usually recommends a slope correction (linear). Data filtering for cloudsEnhancement of O 4 and/or H 2 O absorption Clouds have a small effect on stratospheric NO 2. However, it is recommended to remove measurements showing large enhancements of O 4 and/or H 2 O slant columns.

NDACC UV-VIS WG Meeting, Brussels, 9 July Harmonisation of total O 3 and stratospheric NO 2 vertical columns retrieval ParameterValue O 3 profileTOMS TV8: - Latitude: 85°S to 85°N step 10° - Month: 1 (Jan) to 12 (Dec) step 1 - Ozone column: 125 to 575 DU step 50 DU Wavelength440 to 580 nm step 35 nm Surface albedo0 and 1 Station altitude0 and 4 km SZA10, 30, 50, 70, 80, 82.5, 85, 86, 87, 88, 89, 90, 91, and 92° O3O3 ParameterValue NO 2 profile20-60km: HALOE, POAM-III (Lambert et al.’s climatology) -Latitude: 85°S to 85°N step 10° -Month: 1 (Jan) to 12 (Dec) step 1 -Sunrise and sunset 12-20km: SAOZ balloon climatology -Latitude: tropics, mid-, and high- latitudes -Resolved in seasons Wavelength350 to 550 nm step 40 nm Surface albedo0 and 1 Station altitude0 and 4 km SZA10, 30, 50, 70, 80, 82.5, 85, 86, 87, 88, 89, 90, 91, and 92° NO 2 Recommended AMFs for the SCD → VCD conversion:  Look-up tables of O 3 and NO 2 AMFs generated by BIRA and made available with extraction tools at

QA4ECV WP3 Workshop, March 2015, Mainz 11 Harmonisation of total O 3 and stratospheric NO 2 vertical columns retrieval

Performance of profiling methods: Optimal Estimation Method versus parameterization concentration altitude I II III IV 2.0 km (fixed) concentration altitude scale height method A (OEM) method B (parameterization) Two alternative profile parameterizations: Vlemmix et al., AMT, 2015  13 layers (0-4 km)  On-line radiative transfer  Exponentially decreasing a priori profile (SH={0.5,1.0, 1.5 km})  2-4 parameters defining profile shape  Forward simulations: Look-up tables  Least Squares Fit + ensemble approach (50 runs)  No a priori information BIRA-IASB KNMI NDACC UV-VIS WG Meeting, Brussels, 9 July

WP4: Characterization of NDACC UVVIS data  (MAX-)DOAS data harmonization (DOAS settings, NO 2 and O 3 AMF LUTs, profiling methods,…)  (MAX-)DOAS data characterization (spatial representativeness, cloud detection) NDACC UV-VIS WG Meeting, Brussels, 9 July

NDACC UV-VIS WG Meeting, Brussels, 9 July MPIC/Mainz cloud screening method Wagner et al., AMT, see also Gielen et al., AMT, 2015 Cloud classification scheme

MAX-DOAS horizontal representativeness (1) From all scans: d~25-45km From cloud-filtered scans (CF): d~40-65km Gomez et al., AMT, 2014 Modified geometrical approach (INTA): Application to Jungfraujoch (477 nm) 2373 m asl Izana NDACC UV-VIS WG Meeting, Brussels, 9 July

WP4: Characterization of NDACC UVVIS data  (MAX-)DOAS data harmonization (DOAS settings, NO 2 and O 3 AMF LUTs, profiling methods,…)  (MAX-)DOAS data characterization (spatial representativeness, cloud detection)  Development of a GEOMS-compliant template for the creation of HDF files for UVVIS measurements NDACC UV-VIS WG Meeting, Brussels, 9 July

NDACC UV-VIS WG Meeting, Brussels, 9 July UV-vis data format homogeneization From NASA-AMES to GEOMS hdf Clear-sky, thin clouds, thick clouds, broken clouds 4 GEOMS templates (off-axis trace gas + aerosols, zenith, and direct-sun; see AVDC at )AVDC

Pandora vs UV-vis data format UV-vis: 3 templates (off-axis, zenith, and direct-sun) Pandora

WP 3 (RDDS) and WPs 8 and 9 (Validation server) Langerock et al., GMDD, 2014 NDACC UV-VIS WG Meeting, Brussels, 9 July

WP 3: Rapid data delivery system IASB-BIRA rapid data delivery system (UV-VIS data): Absorption spectra at station ftp Absorption spectra on BIRA-IASB server QDOAS analysis DSCDs OEM profiling Vertical profile +information content +error budget Vertical columns +information content +error budget NDACC column retrieval AMF LUTs AVK LUTs HDF files ftp HDF files on NDACC/ NORS data server QA/QC Daily submission (24h delay): JFJ: Stratospheric NO 2 and O 3 VCD Xianghe: tropospheric NO 2, aerosols NDACC UV-VIS WG Meeting, Brussels, 9 July

WPs 8 and 9: NORS validation server Developed by S&T in collaboration with B. Langerock (BIRA) NORS validation server: NDACC/NORS RD database: ftp://ftp.cpc.ncep.noaa.gov/ndacc/RD/ NDACC UV-VIS WG Meeting, Brussels, 9 July

NDACC UV-VIS WG Meeting, Brussels, 9 July MACC validation through the NORS server: Jungfraujoch (46.5°N, 8°E): Stratospheric NO 2

WP 10: Capacity building Export the NORS achievements to new, potential NDACC stations outside Western Europe NDACC UV-VIS WG Meeting, Brussels, 9 July

Conclusions and perspectives Significant progress have been achieved during NORS:  Data harmonization (recommended settings including ancillary data like e.g. cross-sections and AMF)  Data quality assessment (cloud flagging, spatial representativeness)  Data reporting (GEOMS hdf)  Data delivery (daily submission to NORS RD database)  Exportation of the NORS achievements to new stations This significantly improves the usability of UVVIS data for future satellite and model validation efforts (MACC- III, CAMS) NDACC UV-VIS WG Meeting, Brussels, 9 July Should we apply the NORS concepts/data format to NDACC UVVIS ??

NDACC UV-VIS WG Meeting, Brussels, 9 July LATMOS/SAOZ V3 (new AMF climatology) LATMOS/SAOZ V2 Method: SAT extracted within 150km radius and mean value for every day GB: AM VCD photochemically converted to SAT ovp time (considering the effective SZA of the air-masses) and corrected for different NO2 xs T° Compare only common days and then do monthly means of the daily comparisons Mean bias: V2V3 (x10 15 molec/cm 2 ) SH NH Stratospheric NO 2 VCD: SAOZ/GOME-2 comparison ( ) Courtesy G. Pinardi (single AMF based on yearly mean profiles for Tropics, Mid-latitudes or Polar regions )

Xianghe (39.8°N, 117°E): Tropospheric NO 2 MACC validation through the NORS server: NDACC UV-VIS WG Meeting, Brussels, 9 July

Error budget Main error sources have been identified within NORS and some of them have been characterized: Richter, A., and the WP4 teams, NORS D4.3 NDACC UV-VIS WG Meeting, Brussels, 9 July

How to detect clouds from MAX-DOAS observations ? NORS/NDACC/GAW Workshop, 3-5 November 2014, Brussels, BE 28 Clouds are bright => use measured radiance Clouds are white => use colour index (CI=I λ,low /I λ,high ) Clouds change atmospheric radiative transfer => use O 4 absorption and Ring effect Wagner et al., AMT, 2013; see also U. Friess’ talk tomorrow MAX-DOAS trace gas retrievals can be strongly affected by clouds (and aerosols) © T. Vlemmix

Harmonization of DOAS retrievals « Standardisation of retrieval settings and parameters » Ensure the consistency of the DOAS data sets provided to the NORS validation server DOAS method based on two steps: 1.Spectral inversion giving the slant column densities (SCDs) 2.Vertical column and/or profile retrieval from SCDs: Twilight zenith-sky: Total O 3 and stratospheric NO 2 vertical columns MAX-DOAS: Tropospheric profiles (NO 2, HCHO, aerosols) NDACC UV-VIS WG Meeting, Brussels, 9 July