A growth factor is the ratio of the T-year extreme value to an index extremevalue such as the mean of annual maxima. Whereas a record length of ten or moreyears may suffice to estimate the index variable, it is generally necessary toblend data from several sites if estimates of exceptional extreme values are tobe obtained. Methods of rainfall growth estimation are reviewed, includingtraditional methods which extend frequency curves to long return period by adistributional assumption, and methods which study spatial dependence in extremerainfalls. It is desirable that estimates at neighbouring sites, and acrossdifferent durations and return periods, are internally consistent. The reviewconcludes that rather special techniques may be required if this goal ofestimation extreme rainfall depth consistently is to be met. The motivation ofthe Focused Rainfall Growth Extension (FORGEX) method is presented.
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机译：增长因子是 T 年的极值与指数极值（例如，年度最大值的平均值）之比。尽管记录长度为十年或十年以上就足以估计指数变量，但是，如果要获得异常极值的估计值，通常有必要将来自多个站点的数据进行混合。回顾了降雨增长估算的方法，包括通过分配假设将频率曲线扩展到较长返回期的传统方法，以及研究极端降雨中空间依赖性的方法。期望相邻站点的估计以及不同持续时间和返回周期在内部是一致的。审查结论认为，如果要始终如一地达到估算极端降雨深度的目标，则可能需要使用相当特殊的技术。提出了聚焦降雨增长扩展（FORGEX）方法的动机。
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