Blended SEVIRI Convection area / LEO MW Convective Precipitation

Instantaneous precipitation maps generated by IR images from operational geostationary satellites “calibrated” by precipitation measurements from MW images in sun-synchronous orbits, processed soon after each acquisition of a new image from GEO (“Rapid Update”). The calibrating lookup tables are updated after each new pass of a MW-equipped satellite.

• Coverage: The rectangular area of the Meteosat field of view that includes the H-SAF area limited to 60° N [i.e. 25-60°N lat instead of 25-75°N lat, 25°W-45°E long] - degradation expected at very high latitudes
• Cycle: 15 min - Every new SEVIRI image (at 15 min intervals)
• Resolution: Resolution changing cross Europe: 8 km in average, Sampling: 5 km in average, Sampling dependent of SEVIRI IFOV
• Accuracy: 25% (optimal) - 90% (threashold) [> 10 mm/h], 50% (optimal) - 120% (threashold) [1-10 mm/h], 90% (optimal) - 240% (threashold) [< 1 mm/h]
• Timeliness: Within 15 min from the end of (real time) acquisition
• Dissemination: By dedicated FTP Server for the H-SAF users - By EUMETCast to most other users, especially scientific
• Formats: Values in grid points of the Meteosat projection (GRIB-2)

The blending technique adopted for P-IN-SEVIRI-CO is called “Rapid Update (RU)”; see, for instance, Turk et al. 2000[1]. Key to the RU blended satellite technique is a real time, underlying collection of time and space-intersecting pixels from operational geostationary IR imagers and LEO MW sensors. Rain intensity maps derived from MW measurements are used to create global, geo-located rain rate (RR) and TBB (equivalent blackbody temperature) relationships that are renewed as soon as new co-located data are available from both geostationary and MW instruments. The association of MW retrieved rain rate and the SEVIRI TBB is performed only within the part of clouds that NEFODINA individuate in the growing, mature and dissipating convective cell. In the software package these relationships are called histograms. To the end of geo-locating histogram relationships, the globe (or the study area) is subdivided in equally spaced lat-lon boxes (2.5°×2.5°). As new input datasets (MW and IR) are available in the processing chain, the MW-derived rain rate pixels are paired with their time and space-coincident geostationary 10.8-μm IR TBB data, using a 15-minute maximum allowed time offset between the pixel observation times.

[1] Turk J.F., G. Rohaly, J. Hawkins, E.A. Smith, F.S. Marzano, A. Mugnai and V. Levizzani, 2000: “Analysis and assimilation of rainfall from blended SSMI, TRMM and geostationary satellite data”. Proc. 10th AMS Conf. Sat. Meteor. and Ocean., 9, 66-69.