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A continuously calibrated infrared (IR) geostationary satellite rainfall estimation technique (CCB4) is introduced, in the context of the Nile River Forecast System, an operational system for hydrological modelling and forecasting. The CCB4 incorporates near‐real‐time rain gauge data to continuously calibrate optimum IR rain/no‐rain thresholds and daily rain rates on a daily time step. The ability of the CCB4 and two comparative techniques to estimate daily rainfall at the regional and pixel scales is assessed, using Meteosat IR imagery and gauge data from six wet season months covering three years. The CCB4 shows improved skill in identifying rain days and estimating daily rain amounts at a range of spatial scales, from regional to pixel scales. At the pixel scale, however, improved root mean square errors remain relatively high, ranging between 66% and 84% of the mean unconditional rain rate. Copyright © 1999 Royal Meteorological Society

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Conventional measurements of rainfall over the ocean are fraught with physical and practical problems and instrument difficulties, leading to spatial and temporal inconsistencies in climate datasets. Estimates of rainfall based on the scattering and emission characteristics of passive microwave radiation, measured by instruments on board orbiting satellites, substantially improve the knowledge of rainfall patterns and processes over open water. A new passive microwave satellite-based Atlas of Rainfall and Wind Speed o6er the Eastern North Atlantic and North Sea has been prepared, including rainfall totals (mm), rates (mm h − 1 ), and percent occurrences (%) for the period 1979 -1996 inclusive. Annual, seasonal and monthly maps have been generated, as well as histogram and time series products.In this paper, the main rainfall patterns over this region are summarised and interpreted in comparison with several other existing datasets. The interpretation of passive microwave-derived wind speed over the eastern North Atlantic and North Sea shall be reported in a future paper. Upon the analysis of above and below normal rainfall periods, significant relationships are revealed with respect to the mean sea level pressure, air and sea surface temperature, and atmospheric precipitable water. It is shown that the location and strength of the belt of prevailing Westerlies, and their interaction with major land masses, dictate the overall rainfall distribution.Results show that rainfall over this area is well-related to various indices of the general circulation. Also, patterns of rainfall over the North Sea are significantly related to the direction and strength of the wind. Finally, it is shown that there is a significant linear relationship between climate station rainfall and the estimate over the nearest open water pixel, although the percent of explained variance seldom exceeds 50%.