Level 2A

 GRM-01 N  GRM-40 N  GRM-09/47 N

GRM-01/40: NRT Refractivity Profile

_Values Remarks
Units Refractivity units (N) _
Domain 0-50 km Surface to
~1 hPa
Range0-450 N-units_
Requirement on
target accuracy
0-5 km: 0.6%-2%
5-30 km: 0.6%
30-50 km: 0.03 N-units
Requirement on
vertical resolution
150-250 m_
GRM-01 status OperationalMetop-A
GRM-40 status OperationalMetop-B
Current product version (GRM-01): 1.4
Previous product versions: 1.0 (demo), 1.1 (demo), 1.2 (pre-op), 1.3
Current product version (GRM-40): 1.4
Previous product versions: 1.0 (demo), 1.1 (demo)

Product description

The NRT refractivity product contains a profile of neutral refractivity as a function of height (geometric and geopotential) above the EGM-96 geoid. GRM-01 contains refractivity from the GRAS instrument onboard Metop-A, GRM-40 from Metop-B.

Algorithm description

Each product profile is the result of one radio occultation. Signals from the occulting GPS satellite are measured by the GRAS receiver onboard the EPS/Metop satellite, downlinked, and processed by the ROM SAF into refractivity. More details can be found in the Algorithm Theoretical Baseline Document, on the Radio Occultation Theory page, and in the Validation Report for GRM-01 and GRM-40.

Data characteristics

GRAS measures about 700 GPS occultations per day. The product is output in both NetCDF and BUFR format, and disseminated via GTS/RMDCN (BUFR) and EUMETCast (NetCDF and BUFR). NetCDF files are also stored in the ROM SAF Product Archive.

Product validation and monitoring

Accuracy of the current version of the product is described in the Validation Reports. Daily monitoring of the processing and dissemination can be seen on the Monitoring Page.

Product documentation

All ROM SAF NRT and Offline products are described in the Product User Manual.
To retrieve this product please go to the Product Archive.

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