Near real-time total ozone, total/tropospheric nitrogen dioxide and total sulfur dioxide



Description: Near real-time Total Column (NTO) products provide information about total and/or tropospheric vertical columns of three trace gases in the atmosphere: O3 (ozone), NO2 (nitrogen dioxide) and SO2 (sulfur dioxide).

Type: Near real-time. The products are available to users in three hours from sensing.

Theoretical basis: NTO products are based on wavelength regions of 325-335 nm for ozone, 425-450 nm for NO2 and 315-326 nm for SO2.

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 4.5 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: Ozone columns are given in Dobson Units (DU), while NO2 columns are given in [molecules/cm2]. GOME-2 has 24 forward-scan pixels with a nominal resolution of 80 km x 40 km, and 8 back-scan pixels with a nominal resolution of 240 km x 40 km. Both forward- and back-scan pixels are processed and written to the products.

Validation: NTO/O3 is validated by Aristotle University of Thessaloniki (AUTH). NTO/NO2 and NTO/NO2Tropo are validated by BIRA-IASB. Validation of NTO/SO2 is shared between these two institutes. The validations are based on detailed comparisons of existing satellite data with ground-based measurements. Visit O3M SAF Total Ozone validation site for further information.

Online quality monitoring: NTO product quality is constantly monitored by KNMI. The online monitoring is based on near real-time validation of total ozone via data assimilation. For further information, visit website: Validation of O3M SAF GOME-2 Total Ozone with data assimilation.

Dissemination: (only operational and pre-operational products)

WMO GTS bulletin identifier:

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File format: NTO products are 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.

NTO documents:

GOME-2 pages at DLR: WDC, ATMOS