TROPOMI's CO retrieval code for the Sentinel 5 Precursor mission tested on 10 years of SCIAMACHY's 2.3 μm measurementsTobias Borsdorff, Joost aan de Brugh, Paul Tol, Ilse Aben, Jochen Landgraf

Netherlands Institute for Space Research (SRON)

Spectral mean signal relative to 11 Jan. 2003.

SCIAMACHY’s daily sun measurements

The need for a reflectance retrieval

R=μ

0

π ⋅I Earth

I Sun

S i(t)=α(t)βi(t)S i(t0)+ϵi(t)

The need for a reflectance retrieval

(grey, e.g. gloudemans et al.,2008)

A wider CO retrieval window

Signal to noise of SCIAMACHY spectra

Mean (2003-2012)

Radiometric offset correction

F (x ,a)=F (x)+∑i=0

n=3

a(i ) p i(λ)

Sahara

Australia

Error of clear sky retrievals

Error of cloud contaminated retrievals

CAK[1]

Borsdorff, T., Hasekamp, O. P., Wassmann, A., and Landgraf, J.: Insights into Tikhonov regularization: application to trace gas column retrieval and the efficient calculation of total column averaging kernels, Atmos. Meas. Tech., 7, 523-535, doi:10.5194/amt-7-523-2014, 2014.

Validation: SCIAMACHY vs. NDACC/IRWG

NDACC (pink)SCIAMACHY (black)

47.42N

67.84N

Validation: SCIAMACHY vs. TCCON

TCCON (blue)SCIAMACHY (black)

45.95N

-12.43S

Validation: bias (SCIAMACHY - FTIR)

Data usage: spatial resolution

Mean (2003-2012)

cylindrical equal area projection (nlat=180, nlon=360)

Data usage: temporal resolution

30-day medians

TROPOMI: single overpass over china

CO column [1018 molec cm-2]

Summary and conclusions

● TROPOMI CO retrieval code performs good on real data:

– good agreement with TCCON (0.1 ± 7.5 ppb).

– bias with NDACC/IRWG (-8.9 ± 8.3 ppb)

– good agreement with TM5 over Africa

● Next: TROPOMI cloud retrieval with SCIAMACHY spectra

● Now available: full mission SCIAMACHY CO dataset

(cloud free scenes over land)

Image: ESA

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