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Near real-time total HCHO column

Composite images of the latest overpasses

NOTE: Metop-B+C image is for demonstrational purposes only, such multi-satellite product is not processed or disseminated.

Metop-B

Metop-C

Metop-B+C

Image gallery

Description

Near real-time total HCHO column product provides information about vertical column densities of formaldehyde in the atmosphere.

Type

Near real-time. Based on product requirements, the product files must be available to users in three hours from sensing.

Theoretical basis

The retrieval of the product is based on GOME-2 (ir)radiance measurements in the wavelength region of 328.5-346 nm.

Processing

DLR generates vertical column products with Universal Processor for UV/VIS Atmospheric Spectrometers (UPAS), inside which the GOME Data Processor (GDP) operational algorithm is the baseline algorithm for the trace gas column retrievals from GOME-2.

The latest GDP 4.8/4.9 uses an optimised DOAS (Differential Optical Absorption Spectroscopy) algorithm to determine the trace gas slant column. The DOAS slant column fitting is followed by Air Mass Factor (AMF) conversions to generate vertical columns.

Units and spatial resolution

HCHO columns are given as densitites (molecules/cm2).

GOME-2/Metop-A has 24 forward-scan pixels with a nominal resolution of 40 km × 40 km, and 8 back-scan pixels with a nominal resolution of 120 km × 40 km.

GOME-2/Metop-B and GOME-2/Metop-C have 24 forward-scan pixels with a nominal resolution of 80 km × 40 km, and 8 back-scan pixels with a nominal resolution of 240 km × 40 km.

Both forward- and back-scan pixels are processed and written to the products.

Validation

This product is validated by Belgian Institute for Space Aeronomy (BIRA-IASB). The validation is based on an end-to-end approach, that has been developed to evaluate independently all critical components of the level-1-to-2 retrieval chain, using correlative observations performed by ground-based and satellite instruments. Visit BIRA HCHO validation page for further information.

Online quality monitoring

The product quality is constantly monitored by BIRA-IASB. The online monitoring is based on TBD. Visit BIRA quality assessment page for further information.

Dissemination

See NRT access information.

File format

This product is available in two formats: HDF5 and BUFR (only BUFR via GTS). Each file contains one PDU (Product Dissemination Unit), equal to three minutes of satellite data.

Algorithm version information

Time period GOME-2 / Metop-A GOME-2 / Metop-B GOME-2 / Metop-C
04.01.2007 – 15.07.2013 GDP 4.6 N.A. N.A.
15.07.2013 - 27.10.2016 GDP 4.7 GDP 4.7 N.A.
27.10.2016 - 01.05.2020 GDP 4.8 GDP 4.8 N.A.
01.05.2020 onwards GDP 4.8 GDP 4.8 GDP 4.9

Important algorithm changes in GDP 4.8

  • Improved retrieval algorithms and quality flags
    • HCHO: improved algorithm (two-step DOAS approach), provision of Averaging Kernels
    • Cloud algorithm improvements (OCRA & ROCINN)

Documents

GOME-2 pages at DLR: WDC,ATMOS