The blending technique adopted for PR-OBS-4 is based on the "Morphing" concept detailed in Joyce et al. 2004. The method called CMORPH, acronym of the Climate Prediction Center (CPC) morphing, employs the frequent MSG-SEVIRI Infrared (IR) data to derive cloud system advection vectors used to propagate the rain fields estimated by the PR-OBS-1 and PR-OBS-2.
- Coverage: ± 60° latitudes in the H-SAF area
- Cycle: the observing cycle is 3 h
- Resolution: fixed grid (sampling distance) of ~ 8 km intervals, close to the SEVIRI IFOV over Europe
- Accuracy: To be defined
- Timeliness: The PR-OBS04 maps are available at 30 min intervals (sampling time) but we have a timeliness at least of 2 h depending on the availability of the input rain products.
- Dissemination: By dedicated lines to centres connected by GTS - By EUMETCast to most other users, especially scientific
- Formats: The digital data will be coded in GRIB2 while the image-like maps will be available in PNG format
In the PR-OBS-4 algorithm the features of the instantaneous precipitation fields estimated with the Passive MicroWave (PMW) satellite sensors are spatially propagated by using the MSG-SEVIRI IR. The propagation vector matrices are produced by computing spatial lag correlations over successive images of MSG-SEVIRI IR and used to advect the PMW-derived precipitation estimates in time and space when updated PMW data are unavailable at a given location. This process governs the movement of the precipitation features only. At a given location, the shape and intensity of the precipitation features in the intervening half-hour periods between PMW scans are determined by performing a time weighted interpolation between PMW-derived estimates that have been propagated forward in time from the last available PMW observation and those that have been propagated backward in time from the next available PMW scan. This latter step, referred to as "morphing" of the features, produces spatially complete analyses of precipitation every half hour.References
Joyce R.J., J.E. Janowiak, P.A Arkin and P. Xie, 2004: "CMORPH: A method that produces global precipitation estimates from passive microwave and infrared data at high spatial and temporal resolution". J. Hydrometeor., 5, 487-503.