Tropospheric Ozone derived from Satellites

A contribution to ACCENT-TROPOSAT-2, Task Group 1

Roeland van Oss

KNMI, Atmospheric Composition Research Division, PO 201, 3730 AE De Bilt, Netherlands
Tel:  +31-(0)30-2206439
 Fax: +31-(0)30-2210407

Ozone profile information can be derived from UV earthshine spectra measured from nadir. Retrieval algorithms have been developed for the similar satellite instruments GOME, SCIAMACHY, OMI and GOME-2. However, the amount of information on the profile in the lower stratosphere and troposphere is very limited and it is very difficult to retrieve the tropospheric column, independently from the stratospheric content, as it is very sensitive to a variety of errors.

Various methods are being developed to infer the tropospheric ozone column using:
column retrievals over clear and (high) cloud-covered scenes in the tropics,
data assimilation of retrieved ozone profiles, and
combination of limb and nadir measurements (for SCIAMACHY).

The first method, the convective-cloud-differential (CCD) method, has been successfully applied using GOME [Valks et al. 2002]. Monthly-mean tropospheric ozone columns for the period July 1998 to June 2003 have been produced and are available from the TEMIS website (www.temis.nl). Next step is to use SCIAMACHY and OMI, which will deliver improved estimates due to the smaller ground pixels.

Data assimilation of retrieved profiles in to a chemical transport model allows the employment of the actual profile information derived from the measurement by using the averaging kernel. The model will provide additional information about ozone concentrations in the lower stratosphere and around the tropopause, for which the nadir UV measurement is less sensitive. The result of the assimilation is an optimal tropospheric ozone column, consistent with the profile measurements and model simulations. This method has been applied to one year of GOME ozone profiles. Extension of this work to other years to SCIAMACHY and to OMI will be conducted.

The SCIAMACHY limb observations can be used to retrieve an accurate estimate of the stratospheric profile. The co-located nadir observation combined with this profile yields an accurate value for the tropospheric column. Limb retrieval is a novel development; the first profiles are currently made available (2004). A nadir-limb combined retrieval algorithm is under development. This algorithm treats the limb and nadir spectra as one measurement vector from which the full ozone profile is derived in a single retrieval.

Time Schedule

 

2004

2005

2006

2007

CCD

 

*

*

*

Profile assimilation

*

*

*

 

Limb-nadir

*

*

*

*

Approximate manpower and cost

 

2004

2005

2006

2007

Personnel / man-years

1

2

2

2

Yearly cost (k)

5

10

10

10

Reported costs are travel expenses only

Likely funding agencies

This work has been funded through the Dutch National User Support Programme (USP) and the ESA DUP project TEMIS. We aim to acquire further support from USP, ESA or EU FP6.

Co-workers

Arjo Segers, Jeroen van Gent and Ronald van der A

 

 

 


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