GOME-2 surface LER & DLER database

The GOME-2 surface LER database contains the Lambertian-equivalent reflectivity (LER) of the Earth's surface at 27 one-nm wide wavelength bins between 328 and 772 nm. The LER albedo values were derived from GOME-2 data using the Doubling-Adding KNMI (DAK) polarised radiative transfer code. The model consists of an atmosphere for which Rayleigh scattering and ozone absorption are taken into account, and which is bounded below by a Lambertian surface. The surface LER is available for each month of the year and for the following wavelengths: 328, 335, 340, 354, 367, 380, 388, 416, 425, 440, 463, 494, 510, 526, 546, 555, 564, 585, 610, 640, 670, 685, 697, 712, 747, 758, and 772 nm. Next to this, we also provide a GOME-2 surface LER database which is based on PMD band measurements.

Since version 3.0 the GOME-2 surface LER database additionally contains the so-called directionally dependent Lambertian-equivalent reflectivity (DLER) of the surface. In the GOME-2 surface DLER product, the viewing-angle dependence of the reflectivity of the surface, due to the BRDF of the surface, is taken into account, which improves the product considerably, especially for the longer wavelengths.


Some examples of the database:

Examples of the GOME-2 surface LER: dependence on the month of the year (left) and dependence on the wavelength (right).

Archive:

The following databases based on GOME-2A + GOME-2B + GOME-2C observations are available:

GOME-2_MetOp-ABC_MSC_025x025_surface_LER_v4.1.nc   (2.3 GB)

GOME-2_MetOp-ABC_PMD_025x025_surface_LER_v4.1.nc   (1.6 GB)

Previous versions of the databases can be downloaded here.

Most users will only be interested in the GOME-2 surface LER database that was based on Main Science Channel (MSC) observations. The wavelength bands (listed above) are more or less monochromatic (one nm wide) and suitable as input for the retrieval of most atmospheric species. The intrinsic resolution of the MSC-LER database is 1°×1°, but increased to 0.25°×0.25° near coastlines and certain snow covered mountain ranges. The spatial resolution of the database grid therefore is 0.25°×0.25°.

Next to the normal MSC-LER database, there also exists a GOME-2 surface LER database based on the PMD bands. This PMD-LER database is mostly relevant to users that use GOME-2 PMD band measurements for their retrievals. Note that some discrepancies between the radiometric calibration of the main science channels and the PMD bands have been reported in the past (PDF). The intrinsic resolution of the PMD-LER database is 0.5°×0.5°, but increased to 0.25°×0.25° near coastlines and over the Sahara desert. The spatial resolution of the database grid therefore is 0.25°×0.25°.

The format and the contents of the files are explained here. The current version of the database is 4.1.


Developments / Improvements:

In version 2.0 the concept of dynamical gridding was introduced, resulting in an increased spatial resolution near coastlines and for other specific regions. In version 2.3 new wavelength bands at 328, 585, 685, 697, and 712 nm were added. The new wavelength bands at 685, 697, and 712 nm, together with the already existing wavelength band at 670 nm, are meant to support the retrieval of cloud and/or aerosol information from the oxygen B-band. To achieve an optimal retrieval of the surface LER for the wavelength bands at 697 and 712 nm we included water vapour absorption in the radiative transfer calculations. Since version 2.5 a bilinear interpolation scheme smoothens the low-resolution regions to the high-resolution database grid which makes it easier for users to handle the data. Also, the error calculation has been improved and now the product contains systematic and statistical uncertainty estimates. In version 3.0 the DLER was introduced. Since version 3.1 the file format used is NetCDF-4. In version 4.0 an additional wavelength band at 747 nm was introduced.


Origin / Creator:

The GOME-2 surface LER databases are provided by KNMI in the framework of the EUMETSAT Satellite Application Facility on Atmospheric Composition Monitoring (AC SAF).






 
Data use / License / Citation:

The GOME-2 surface LER databases are free to use for commercial and non-commercial purposes. If you use any of the databases for a publication (research or otherwise), or for any other purpose, please refer to the following publications:

L.G. Tilstra, O.N.E. Tuinder, P. Wang, and P. Stammes, Surface reflectivity climatologies from UV to NIR determined from Earth observations by GOME-2 and SCIAMACHY, J. Geophys. Res. Atmos. 122, 4084-4111, doi:10.1002/2016JD025940, 2017. (PDF)

L.G. Tilstra, O.N.E. Tuinder, P. Wang, and P. Stammes, Directionally dependent Lambertian-equivalent reflectivity (DLER) of the Earth's surface measured by the GOME-2 satellite instruments, Atmos. Meas. Tech. 14, 4219-4238, doi:10.5194/amt-14-4219-2021, 2021. (PDF)

We suggest that you include the following acknowledgement: "We acknowledge the free use of the GOME-2 surface LER database provided through the AC SAF of EUMETSAT. The GOME-2 surface LER database was created by the Royal Netherlands Meteorological Institute (KNMI)."


Documentation:

• Algorithm Theoretical Basis Document (v4.3)

• Product User Manual (v4.2)

• Validation Report (v2024a)

• L.G. Tilstra, O.N.E. Tuinder, P. Wang, and P. Stammes, Directionally dependent Lambertian-equivalent reflectivity (DLER) of the Earth's surface measured by the GOME-2 satellite instruments, Atmos. Meas. Tech. 14, 4219-4238, doi:10.5194/amt-14-4219-2021, 2021. (PDF)

• L.G. Tilstra, O.N.E. Tuinder, P. Wang, and P. Stammes, Surface reflectivity climatologies from UV to NIR determined from Earth observations by GOME-2 and SCIAMACHY, J. Geophys. Res. Atmos. 122, 4084-4111, doi:10.1002/2016JD025940, 2017. (PDF)

• L.G. Tilstra, O.N.E. Tuinder, P. Wang, and P. Stammes, Surface albedo databases determined from PMD measurements performed by the GOME-2 instrument, Proceedings of the 2017 EUMETSAT Meteorological Satellite Conference, 2017. (PDF)

• Presentation: Introduction of the GOME-2 and SCIAMACHY surface LER databases (PDF)

• Presentation: Improvements and developments for the GOME-2 and SCIAMACHY surface LER databases (PDF)

• Presentation: Directional surface albedo from GOME-2 and TROPOMI (PDF)

• Report KNMI-RP-2011-01: Intercomparison of the GOME-2 spectral channels and PMD bands (PDF)