SAO OMI formaldehyde, water vapor and glyoxal retrievals

Gonzalo Gonzalez AbadHelen Wang

Christopher MillerKelly Chance

Xiong LiuThomas Kurosu

OMI Science Team Meeting 12th March 2014

Summary• Formaldehyde

– Updates to spectroscopy– Slant column fitting– Air mass factor calculation– Reference Sector Correction– Old vs. new SAO H2CO

• Water vapor– Retrieval set up– Results– Early validation

• Glyoxal– Retrieval set up– Results– OMI vs GOME-2

• New L2 files fields and information

H2CO spectroscopy updates

H2CO cross sections High resolution solar spectrum

H2CO spectroscopy updates:O2-O2 collision complex cross sections

H2CO Slant Column FittingFitting window 327.5 – 356.5 nm

Baseline polynomial 3rd order

Scaling polynomial 3rd order

Instrument slit function Hyper-parameterization of pre-flight measurements, Dirksen et

al., 2006

Wavelength calibration Spectral shift (no squeeze)

Solar Reference Spectrum

Chance and Spurr, 1997

HCHO cross sections Cantrell et al., 1990; 300K

O3 cross sections Macilet et al., 1995; 228K

NO2 cross sections Vandaele et al., 1998 220K

BrO cross sections Wilmouth et al., 1999; 228K

Molecular Ring cross sections

Chance and Spurr, 1997

Sampling correction Computed on-line

Residual common mode spectrum

Computed on-line

Fitting window 328.5 – 356.5 nm

Baseline polynomial 3rd order

Scaling polynomial 3rd order

Instrument slit function Hyper-parameterization of pre-flight measurements, Dirksen et

al., 2006

Wavelength calibration Spectral shift (no squeeze)

Solar Reference Spectrum

Chance and Kurucz, 2010

HCHO cross sections Chance and Orphal, 2011; 300K

O3 cross sections Macilet et al., 1995; 228K & 295K

NO2 cross sections Vandaele et al., 1998 220K

BrO cross sections Wilmouth et al., 1999; 228K

O2-O2 collision complex cross-sections

Thalman and Volkamer, 2013

Molecular Ring cross sections

Chance and Spurr, 1997

Sampling correction Computed on-line

Residual common mode spectrum

Computed on-line

Operational New version

H2CO Slant Column Fitting:Orbit #43214

Shared Air Mass Factor Calculation for H2CO, C2H2O2 and H2O

• New lookup tables for scattering weights and TOA radiances calculated with Vlidort 2.4rt

• 5 years OMLER albedo• OMI L1 surface height information• OMCLDO2 cloud information• Cloudy pixels independent pixel approximation• Monthly GEOS-Chem climatology for 2007• 340 nm for H2CO

• 448 nm for C2H2O2

• 455 nm for H2O

H2CO AMF calculation: Orbit 8537 21st February 2006

H2CO AMF calculation: an example of scattering weights

H2CO reference sector correction

Old vs. new SOA H2CO product: Orbit #43214

H2CO time series and L3 comparison: old vs. new SAO retrievals

H2O retrieval set upFitting window 430 - 480 nm

Baseline polynomial 3rd order

Scaling polynomial 3rd order

Instrument slit function Hyper-parameterization of pre-flight measurements, Dirksen at al., 2006

Wavelength calibration Spectral shift (no squeeze)

Solar Reference Spectrum Chance and Kurucz, 2010

H2O Rothman et al., 2009; 280K

O3 cross sections Brion et al., 1998, 228K

NO2 cross sections Vandaele et al., 1998 220K

Liquid water Pope and Fry, 1997

C2H2O2 Volkamer et al., 2005, 296K

O2-O2 collisional complex BISA, 294K

Molecular Ring cross sections

Chance and Spurr, 1997

Liquid water ring effect Chance and Spurr, 1997

Sampling correction Computed on-line

Residual common mode spectrum

Computed on-line

H2O retrieval results

Exam

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retr

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ult Measured & fitted spectra

Fitting residual

Fitted water vapor + residual

Fitted liquid water + residual

Fitted NO2 + residual

Fitted O3 + residual

Open Ocean Coast

20050714

20070714

20110714

20130714

H2O retrieval results

H2O retrieval validation efforts

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H2O retrieval validation efforts

C2H2O2 retrieval set upFitting window 435 - 461 nm

Baseline polynomial 1st orderScaling polynomial 3rd order

Instrument slit function Hyper-parameterization of pre-flight measurements, Dirksen et al., 2006

Wavelength calibration Spectral shift (no squeeze)Solar Reference Spectrum Chance and Kurucz, 2010

C2H2O2 Volkamer et al., 2005, 296K

O3 cross sections Brion et al., 1998, 228K

NO2 cross sections Vandaele et al., 2003, 220K

Liquid water Pope and Fry, 1997O2-O2 collisional complex Thalman and Volkamer, 2013

Molecular Ring cross sections Chance and Spurr, 1997Sampling correction Computed on-line

Residual common mode spectrum Computed on-lineLiquid water pre-fit 385 – 470 nm (O3,NO2 and O2-O2 collision complex, 1st order

baseline, 5th order scaling)De-stripping Characterization of stripes over the Sahara and applied

elsewhere

C2H2O2 retrieval results

C2H2O2 OMI vs. GOME-2 (Lerot et al.)

New fields in the SAO L2 file

Albedo

GasProfile

ReferenceSectorCorrectedVerticalColumnScatteringWeights XtrackQualityflags

XtrackQualityflagsExpanded

Gonzalez Abad et al., Atmos. Meas. Tech. Discuss., 7, 1-31, 2014Wang at al., Atmos. Meas. Tech. Discuss., 7, 541-567, 2014

Miller at., in preparation

Thanks for your attention

We would like to thank NASA for funding

Water vapor retrieval• Fitting window 430 – 480 nm• H2O, O3, NO2, CHOCHO, O2-O2, Liquid H2O, ring, water

ring, 3rd order polynomials2005-07-14

Typical SCD uncertainty:(1.0-1.7)×1022 molec cm-2

Submitted to AMTD and accepted with corrections, H. Wang et. Al:Water Vapor Retrieval from OMI Visible Spectra

Post-processing reference sector correction

Row anomaly flags

SAO OMI H2O SCD sensitivityto retrieval window

Window Length (nm)

Retrieval Window (nm)

Median SCD

(molecule cm-2)

Median Uncertainty (molecule cm-2)

Median Relative Uncertainty

20 [435, 455] 1.47×1023 2.4×1022 0.19

30 [432, 462] 1.43×1023 2.0×1022 0.17

40 [438, 478] 1.35×1023 1.6×1022 0.15

50 (standard)

[430, 480] 1.32×1023 1.2×1022 0.11

65 [430, 495] 1.23×1023 1.5×1022 0.12

• SCD decreases by ~15% as window length increases from 20 nm to 65 nm.• The smallest uncertainty is achieved by the standard window of [430, 480]nm.

SAO OMI H2O sensitivity tointerfering molecules

Description Median SCD (molecule cm-2)

Median uncertainty (molecule cm-2)

Median RMS

Number of negatives

Standard 1.32×1023 1.2×1022 9.2e-4 1935Without O3 1.19×1023 1.2×1022 9.3e-4 7234Without O2-O2 1.18×1023 1.3×1022 9.9e-4 5076Without NO2 1.05×1023 1.2×1022 9.3e-4 15666Without liquid water 0.90×1023 1.1×1022 9.5e-4 50216Without C2H2O2 1.34×1023 1.2×1022 9.2e-4 1780

• The most important interfering molecules are liquid water, NO2 and O3.

C2H2O2 de-stripping

C2H2O2 de-stripping

H2CO/C2H2O2 ratio