MSG MPEF Release 2.1 includes changes to RTTOV and OCA and the addition of alternative calibration coefficients to the L1.5 header for Meteosat-9.
Wednesday, 01 April 2015
The upcoming MSG MPEF (Meteorological Product Extraction Facility) Release 2.1, planned to be installed on 22 April at 09:00 UTC, includes changes in four areas.
1. Radiative Transfer Model (RTTOV)
The new MPEF will use version 11.2 of RTTOV, whereas the current MPEF uses RTTOV version 9.3, bringing improvements in the modelled radiances and brightness temperatures.
The new RTTOV version includes the calculation of a so-called 'two path transmission' for the visible channels, which is the transmittance from the top of the atmosphere (TOA) to each standard pressure level and back to the TOA. The only noticeable effect is on the Lifted Index parameter of the Global Instability Index (GII) product, which shows smaller values.
2. Optimal Cloud Analysis (OCA)
The new MPEF will bring two improvements to the OCA product:
- The short-wave channel (0.6, 0.8 and 1.6 micron) atmospheric transmittances were previously obtained from latitude interpolated fixed atmosphere values calculated using LOWTRAN7. The new values are obtained from RTTOV (version 11.2) and are based on forecast atmospheric temperature, water vapour and ozone, i.e. consistent with the long-wave channels.
- Cloud radiative property look-up tables for (liquid) water phase have been extended in effective radius range from 1-23 microns to 1-31 microns.
The main effect comes from the first change, leading to better internal diagnostics (lower values in the cost function) and larger effective radii, especially for water phase.
3. Surface type map
The new MPEF will use an upgraded surface type map, which improves the handling of sun-glint effects in lakes, rivers and coastal regions. This reduces the number of false alarms in the FIR (Active Fire Monitoring) product.
4. GSICS calibration coefficients for Meteosat-9
Alternative calibration coefficients will be added to the L1.5 header for Meteosat-9, based on GSICS inter-calibration.
These alternative calibration coefficients are based on Global Space-based Inter-Calibration System (GSICS) Near-Real-Time Corrections, which are derived from comparisons of collocated observations with Metop/IASI. These have been available for the infrared channels of Meteosat-10 for some time (information here), and are now also generated for Meteosat-9/SEVIRI.
These alternative calibration coefficients are provided in the L1.5 image header in the 'MPEF Cal Feedback' section. Users can optionally apply these instead of the operational calibration coefficients in the 'L1.5 image calibration' section to ensure SEVIRI's calibration is consistent with that of the GSICS reference, and to correct for known radiometric biases in the operational calibration, where these may affect their products. They also provide a backup calibration in case of failure of the on-board system.
For more details, see our inter-calibration page.
For more information, contact our User Service Helpdesk.