Rainfall patterns are highly variable in space and time, and generally rain gauge
networks in river basins and catchments do not accurately measure regional and seasonal
rainfall. Griffith et al. (1978) recognized the transient evolution and extent of cloud-top
temperature as a tool to infer convective activity. Dugdale and Milford (1986) developed
the concept of cold cloud duration (CCD), using the thermal channel of Meteosat, to generate time series of cloud temperatures for tropical altitudes where most rainfall
comes from large convective storms. They suggested that the duration above a threshold
temperature value is representative of the amount of rain that is generated. The success of
the regression between CCD and rainfall varies with the threshold temperature above
which rain occurs (e.g., Stewart et al., 1995). Although there is an essential amount of
empiricism included in this methodology, it helps to interpret rainfall intensities at
unsampled locations between gauges in a network of rain gauges. Successful applications
have been reported in Mexico (Negri et al., 1993) and the Sahel (Rosema, 1990). Petty
(1995) summarized the current status of retrieving rainfall information from satellites.
Simmers (1996) concluded, `the determination of rain rate at the surface from satellite
measurements is still an unresolved problem.' It is expected that the recently launched
Tropical Rainfall Mission satellite (TRMM) dedicated for precipitation mapping will
boost research of this parameter further.
Rainfall patterns are highly variable in space and time, and generally rain gauge
networks in river basins and catchments do not accurately measure regional and seasonal
rainfall. Griffith et al. (1978) recognized the transient evolution and extent of cloud-top
temperature as a tool to infer convective activity. Dugdale and Milford (1986) developed
the concept of cold cloud duration (CCD), using the thermal channel of Meteosat, to generate time series of cloud temperatures for tropical altitudes where most rainfall
comes from large convective storms. They suggested that the duration above a threshold
temperature value is representative of the amount of rain that is generated. The success of
the regression between CCD and rainfall varies with the threshold temperature above
which rain occurs (e.g., Stewart et al., 1995). Although there is an essential amount of
empiricism included in this methodology, it helps to interpret rainfall intensities at
unsampled locations between gauges in a network of rain gauges. Successful applications
have been reported in Mexico (Negri et al., 1993) and the Sahel (Rosema, 1990). Petty
(1995) summarized the current status of retrieving rainfall information from satellites.
Simmers (1996) concluded, `the determination of rain rate at the surface from satellite
measurements is still an unresolved problem.' It is expected that the recently launched
Tropical Rainfall Mission satellite (TRMM) dedicated for precipitation mapping will
boost research of this parameter further.
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