Progress on the unification of the SO2 retrieval for GOME-2A/B and OMI

C. Hörmann, S. Beirle, K. Mies and T. Wagner

First German S5P Verification Meeting BremenNovember 28 and 29, 2013

Unification of SO2 DOAS retrieval

- Same DOAS fit properties for all 3 instruments (GOME-2A, GOME-2B, OMI):

- Fit range: 312.1-324 nm

- Used absorption cross sections: SO2 223K (Bogumil et al.) O3 223K (Bogumil et al.)

O3 223K * λ additional O3 cross sections to correct O3 223K ^ 2 for AMF wavelength dependence (Pukite

et al., 2011)

Ring Inverse reference (straylight correction)

- Calibration via single reference spectrum for GOME-2A/B, individual referencespectra for each OMI detector raw

New SO2 DOAS retrieval for OMI

Daily de-striping by subtraction of detector raw dependent offset from Pacific reference sector(red orbit stripes on April 1 due to „OMI Zoom Mode“ individual calibration needed?!?)

Daily data: OMI SO2 VCD (geo.)

lat. dependent offset still visible

eruption of Piton de la Fournaise

Substraction of latitudinal dependent offset (calculated for each grid row, i.e. 0.1°)

offset corrected

Daily data: OMI SO2 VCD (geo.)

Comparison to GOME-2A SO2 VCD (geo.)

Good agreement, only small differences because of different overpass time

GOME-2AOMI

Mean latitudinal SO2 VCD(without latitudinal offset correction)

Latitude [°N]

Mea

n SO

2 VCD

GOME-2AOMI

Mean latitudinal SO2 VCD(latitudinal offset corrected)

Latitude [°N]

Mea

n SO

2 VCD

Monthly mean: OMI SO2 VCD (geo.)

offset corrected

lat. dependent offset again visible

interference with topography and bright surfaces

ice edge

visible

Comparison to GOME-2A SO2 VCD (geo.)

Very good agreement Less interference with topography because of pixel size?

less interference with topography

GOME-2AOMI

Latitude [°N]

Mea

n SO

2 VCD

Mean latitudinal SO2 VCD(without latitudinal offset correction)

GOME-2AOMI

Latitude [°N]

Mea

n SO

2 VCD

Mean latitudinal SO2 VCD(latitudinal offset corrected)

GOME-2A vs. OMI (monthly mean)

Good agreement between GOME-2A and OMI for monthly mean Best correlation for Norilsk region probably because of fairly constant emissions

Popocatépetl/Mexico City Nyiamuragira Norilsk (volcanic/anthropogenic) (volcanic) (anthropogenic)

1:1 slope 1:1 slope 1:1 slope

Comparison of GOME-2A vs. GOME-2B

data format problem (contact R. Lang)

GOME-2A data quality decreased due to degradation (σ2013 ≈ 2 ∙ σ2007) due to narrow swath, global coverage after ≈ 4.5 days

good agreement (almost same overpass time) GOME-2B data blurred compared to GOME-2A (larger pixel size)

GOME-2B SO2 VCD

GOME-2AGOME-2B

Latitude [°N]

Mea

n SO

2 VCD

Mean latitudinal SO2 VCD(without latitudinal offset correction)

strong latitudinal offset (unknown origin)

GOME-2AGOME-2B

Latitude [°N]

Mea

n SO

2 VCD

Mean latitudinal SO2 VCD(latitudinal offset corrected)

Very good agreement after latitudinal offset

correction

GOME-2A vs. GOME-2B (monthly mean)

Good agreement between GOME-2A and GOME-2B for monthly mean Large scatter visible in GOME-2A data

Popocatépetl/Mexico City Nyiamuragira Nevado del Ruiz (volcanic/anthropogenic) (volcanic) (volcanic)

1:1 slope 1:1 slope 1:1 slope

Plans for the near future

1) Further improving SO2 fit ( especially GOME-2A/B)

2) Comparison of timeseries/annual maps (e.g. China, Norilsk…)

3) Evaluation of SCIAMACHY data

4) Implementation of SO2 DOAS fit at larger wavelengths for OMI+ combination approach + intercomparison GOME-2A/B/OMI

5) Analysis and comparison of test data (CAMELOT)