GRAS AHRPT - Metop

The AHRPT Direct Broadcast service provides local user stations with real-time transmission of data, limited to the instantaneous sub-satellite observation. Data received through Direct Readout can be processed further using the local processing software which is available under a licence from the NWP-SAF (AAPP and RTTOVS). The GNSS (Global Navigation Satellite System) Receiver for Atmospheric Sounding (GRAS) probes the vertical profile of the atmosphere by observing GPS (Global Positioning Satellite) in a limb sounding geometry. GRAS observes so-called rising and setting occultations in velocity and anti-velocity direction, providing a minimum of 500 profiles per day with high vertical resolution. The raw data can be processed further to profiles of bending angle over impact parameter at level 1B and to refractivity, temperature, and humidity over altitude at level 2, covering the stratosphere and troposphere. In addition, the ionospheric total electron content can be deduced from the measurement. Metop-A data are available in the Data Centre up to 15/11/2021.