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Harmonisation of stratospheric NO 2 /O 3 column data products. F. Hendrick and M. Van Roozendael. Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium. + NDACC UV-VIS Working Group. NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 1. Context. - PowerPoint PPT Presentation
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Harmonisation of stratospheric NO2/O3 column data products
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 1
F. Hendrick and M. Van Roozendael
Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium
+ NDACC UV-VIS Working Group
Context• NDACC UV-vis Working Group meeting at British Antarctic
Survey in November 2007:
« There is a need to harmonize stratospheric O3 and NO2 column retrievals »
• Main reasons:
• Lack of consistency between the stations due to the use of different DOAS settings (e.g., NO2 XS at different temperature) and AMFs
• Satellite groups encountered problems in the validation of their data using the NDACC UV-vis database, e.g. Wetzel et al., ACP, 2007 for the validation of MIPAS NO2
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 2
Harmonisation of O3 column retrieval:
1. DOAS settings
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 3
Parameter Recommendation
Fitting interval 450-550 nm
Wavelength calibration solar atlas
Cross sections
O3 Bogumil et al. (2003), 223°K
NO2 Vandaele et al. (1998), 220°K
H2O Hitran 2004 (Rothman et al., 2005)
O4 Hermans (http://spectrolab.aeronomie.be/o2.htm)
Ring effect NDACC source for Ring effect correction
Molecular and aerosol scattering
Polynomial of order 3, or equivalent non-polynomial high-pass filtering
AMF calculation BIRA-IASB O3 AMF LUTs
Determination of residual amount in reference spectrum
Langley plot (Vaughan et al., 1997)
SZA range for twilight averaging of vertical columns
86-91°SZA
Harmonisation of O3 column retrieval:
2. O3 AMF look-up tables
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 4
• TOMS V8 (TV8) ozone and temperature profile climatology (Bhartia, 2004; McPeters et al., 2007) + total O3 column dependence
Parameter Value
O3 profile 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
Temperature and pressure profiles
TV8
Altitude grid 0 to 120 km step 1 km
Wavelength 440 to 580 nm step 35 nm
Surface albedo 0 and 1
Altitude 0 and 4 km
SZA 30, 50, 70, 80, 82.5, 85, 86, 87, 88, 89, 90, 91, and 92°
• LUTs, AMF extraction routine as well as DOAS settings publicly available at: http://uv-vis.aeronomie.be/groundbased
Validation of new retrieval settings
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 5
V1
V2 Corr temp
Comparison to: Dobson at OHP (44°N, 5.5°E)
Amplitude of Dobson-SAOZ seasonal variation:
V1 6.9% SAOZ Yearly AMF
V2 3.2% SAOZ LUT AMF
Bias / Std Dev after temperature correction:
-1.2% ± 3.7%
Brewer at Sodankyla (67°N, 27°E)
Amplitude of Brewer-SAOZ seasonal variation:
V1 6.5% SAOZ Yearly AMF
V2 2.4% SAOZ LUT AMF
Bias / Std Dev after temperature correction:
1.9% ± 3.2%
Impact on the difference satellites - SAOZ
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 6
Station TOMS GOME SCIA OMI-TOMS OMI-DOAS SCO 8.8/4.8 9.8/9.6 9.0/12.0 3.9/2.4 10.7/12.8 ZHI 8.2/4.9 9.3/6.4 9.6/15.3 6.0/8.4 6.7/11.3 SOD 10.8/6.3 11.0/8.3 2.9/6.0 6.3/4.0 3.5/5.6 OHP 8.0/4.7 4.9/1.2 3.0/2.8 7.7/3.4 4.0/2.0 REU 2.1/1.4 4.4/3.4 2.2/1.8 3.1/2.6 1.9/1.8 BAU 1.8/1.5 3.5/3.0 2.5/3.1 3.6/3.0 2.2/2.8 KER 3.9/2.8 1.9/2.0 1.7/3.1 2.2/1.7 2.2/3.7
•Reduced amplitude of seasonal variation
•Reduced bias
V1 Yearly AMF
V2 LUT AMF
More details on the recommendation and comparison studies in Hendrick et al., ACP, 2011
Harmonisation of NO2 column retrieval:
1. DOAS settings
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 7
Parameter Recommendation
Fitting interval 425-490 nm
Wavelength calibration solar atlas
Cross sections
NO2 Vandaele et al. (1998), 220°K
O3 Bogumil et al. (2003), 223°K
H2O Hitran 2004 (Rothman et al., 2005)
O4 Hermans (http://spectrolab.aeronomie.be/o2.htm)
Ring effect Chance and Spurr (1997)
Molecular and aerosol scattering
Off-set correction
Polynomial of order 3 to 5 maximum, or equivalent non-polynomial high-pass filtering
Slope
AMF calculation BIRA-IASB NO2 AMF LUTs
Determination of residual amount in reference spectrum
Modified Langley plot (Vaughan et al., 1997)
SZA range for twilight averaging of vertical columns
86-91°SZA
Harmonisation of NO2 column retrieval:
2. Stratospheric NO2 AMF LUTs
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 8
• LUTs, AMF extraction routine as well as DOAS settings publicly available at: http://uv-vis.aeronomie.be/groundbased
Parameter Values
Lambert et al.’s NO2 profile
climatology
-Latitude: 85°S to 85°N step 10°-Month: 1 (Jan) to 12 (Dec) step 1-Sunrise and sunset-Altitude range : 20-60 km
SAOZ balloon NO2 profile
climatology
-Latitude: tropics, mid- and high-latitudes-Resolved in seasons (spring, summer, fall, winter)-Altitude range: 12-20 km
Wavelength 350 to 550 nm step 40 nm
Surface albedo 0 and 1
Altitude of the station
0 and 4 km
SZA 10, 30, 50, 70, 80, 82.5, 85, 86, 87, 88, 89, 90, 91, and 92°
Lambert et al.’s climatology consists of a Fourier harmonic decomposition of UARS HALOE v19 and SPOT-4 POAM-III v2 NO2 profile data records.
NO2 questionnaire (1)
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 9
NO2 questionnaire (2)
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 10
Question Recommendation
• Correction for the variation of the stratospheric t° (around 220K) ?
Temperature correction using a simple monthly zonal climatology of temperature profiles. Could be coupled to the AMF climatology.
• Filtering of the data conta-minated by tropospheric NO2
Langley-plot method (data points not lying on 'smooth‘ lines indicate a tropospheric contamination)
• Explicit correction for the impact of the Ring effect on the NO2 SCDs ?
post-processing option, based on simple SZA parameterization
• Should we take into account the NO2 photochemistry and its impact on the AMF ?
Sensitivity tests needed. Explicit correction is rather complex to implement. Could be included in the error budget
• Best estimates of the random and systematic uncertainties ?
Random uncertainty derived from fitting residuals. Systematic uncertainty to be estimated off-line based on sensitivity studies. Should be performed for each station. Note that both errors must be provided separately according to GEOMS.
• AMF correction for the period affected by the Pinatubo aerosols ?
Sensitivity tests needed. Not easy to include in standard recommendations.
Impact of aerosols
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 11
0
-5%
-10%
0
-5%
-10%
Satellites (TEMIS) - SAOZ
NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 12
GOME-2 - SAOZ SCIAMACHY-SAOZ
GOME-SAOZ OMI-SAOZ