University of Bremen IUP/IFE SCIAMACHY WFM-DOAS: Data products
University of Bremen IUP/IFE SCIAMACHY WFM-DOAS: Data products |
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Version 0.4 of the WFM-DOAS product 2003 dataset has now (6. September 2004) been finalized to contain all retrieved data for which calibrated SCIAMACHY Level-1 products have been made available.
We focus on the year 2003, the target year of the EU 5th framework research project EVERGREEN.
We have processed and analysed SCIAMACHY data for 153 days from the time periode January 2003 -October 2003. Single missing days might be processed and added, if required. However the now provided dataset at the current stage is herinafter called the "2003 dataset".
Our WFM-DOAS data products are:
Vertical columns of atmospheric CH4, CO, CO2, O2, and N2O (including CH4, CO2, and N2O to O2 column ratios, denoted XCH4, XCO2, and XN2O, respectively) derived from the SCIAMACHY near-infrared and visible nadir radiance spectra.
If you are interested in these data, e.g., in order to help validating them, please download the data following the instructions given below.
A single WFM-DOAS product file corresponds to one gas (e.g., CH4) and one ENVISAT orbit. Each product file contains the vertical columns (usually in molecules per square centimeter) and their errors (fiterror in percent, 1-sigma). The files are simple ASCII files with a header followed by one line of data per ground pixel (columns, errors, geolocation and time information, cloud mask, etc.).
So far we have focussed on analysing our data for cloud free scenes over land. Over water the scatter of the data is large mainly because of the low ocean albedo.
Whatever you do with the data, please take the errors as given in our data products and the cloud information into account.
The error bars are conservative estimates including "systematic" (still to be investigated) components. Concerning clouds: it is unclear at present how useful the data are for cloud contaminated ground pixels. Please focus on the pixels where the cloud mask indicates a cloud free ground pixel (cloud mask = 0). On the other hand, we are also very interested to know how useful these products are for (partially) cloudy pixels.
For certain reasons, mainly because of calibration issues, it is not planned to process the (entire) SCIAMACHY Validation Data Set by WFM-DOAS, especially not the year 2002 data because of dark signal calibration issues (this would need further investigation).
If you would like to obtain certain SCIAMACHY WFM-DOAS data products not (yet) available via this page, please send an e-mail to Michael.Buchwitz@iup.physik.uni-bremen.de (for 1.1.2003 or later). Please note that our data processing is currently set up to generate all products for a given day. This means for example that we cannot generate products only for a special location (e.g., one FTIR ground station).
After finishing the 2003 dataset processing our focus is now shifted to analysing in order to come up with an improved WFM-DOAS and enhanced product quality in the near future. This has priority over further extensions of the 2003 dataset using WFM-DOAS Version 0.4.
It is planned to add more selected days of processed data in the near future, only if required. As long as our dataset of consolidated SCIAMACHY Level-1b data products will not be further extended for 2003, we would have to use other (incomplete) products as data source, which would be slightly inconsistend with the Version 0.4 processing chain, mainly wrt. dark signal treatment.
We especially encourage all colleagues involved in the validation of (scientific) data products from SCIAMACHY to compare our data products with independent data (e.g., ground based FTIR measurements, measurements from other satellites, global models of chemistry and transport).
The WFM-DOAS data products: Information and download.
If you would like to have a look at sample product files (one product = one orbit) please click on the following links:
CH4 and N2O sample product file
Main references:
Please do not use the products that can be downloaded using the links given below for validation. They are included here mainly for "historical" reasons.
Several days of operational Level 1 data have been processed (27, 28, and 29 January 2003). Very good agreement with independent SSM/I satellite microwave measurements (over ocean) and with analysed meteorological fields provided by ECMWF (over ocean and land) has been found (Noël, S., M. Buchwitz, and J. P. Burrows, First retrieval of global water vapour column amounts from SCIAMACHY measurements, Atmos. Chem. Phys., 4, 111-125, 2004).
According to our current plans, future University of Bremen SCIAMACHY (and GOME) water vapour total column products will be generated by S. Noël using the AMC-DOAS retrieval algorithm. The AMC-DOAS and WFM-DOAS derived water vapour columns are similar in quality. For more information on AMC-DOAS please visit our AMC-DOAS web page.
This data set is discussed in:
Buchwitz, M., and John P. Burrows, Retrieval of CH4, CO, and CO2 total column amounts from SCIAMACHY near-infrared nadir spectra: Retrieval algorithm and first results, Proceedings of SPIE 5235, Remote Sensing of Clouds and the Atmosphere VIII, K. P. Schäfer and A. Comeron and M. R. Carleer and R. H. Picard (Editors), 375-388, 2004. (PDF file)
Product(s): Vertical column and O2 normalized column (XCH4).
Auxillary information: The corresponding CH4 column averaging kernels can be obtained from here.
Available: Preliminary results from two (verification) orbits.
Data access: Verification orbits 4700 and 4701 from 23-January-2003, WFM-DOAS product Version 0.1:
Product(s): Vertical column and O2 normalized column (XCO2).
Auxillary information: The corresponding CO2 column averaging kernels can be obtained from here.
Available: Preliminary results from two (verification) orbits.
Data access: Verification orbits 4700 and 4701 (V3) from 23-January-2003, WFM-DOAS product Version 0.1:
Product(s): Vertical column.
Auxillary information: The corresponding CO column averaging kernels can be obtained from here.
Available: Preliminary results from two (verification) orbits.
Data access: Verification orbits 4700 and 4701 (V3) from 23-January-2003, WFM-DOAS product Version 0.1:
Product(s): Vertical column (used to normalize the columns of CH4 and CO2).
Available: Preliminary results from two (verification) orbits.
Data access: Verification orbits 4700 and 4701 (V3) from 23-January-2003, WFM-DOAS product Version 0.1:
Product(s): Vertical column (and XN2O, i.e., O2 normalized column).
Status: Currently only retrieved as a by-product of CH4 retrieval (see: "CH4 product").
Last modification: 28-June-2006.
Authors: Michael.Buchwitz@iup.physik.uni-bremen.de,
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