Abstract The areal reduction factor (ARF) is a concept widely used in many hydrological applications. In this paper, assuming a “storm-centered” approach, new empirical laws for ARF estimation have been derived for the Calabria region (southern Italy), which are distinguished according to rainfall generation mechanisms typical of the Mediterranean area. Specifically, using data from the regional rain gauge network for the period 2002-2015, extreme events were separated into Convective Cells and Frontal Systems through a heuristic criterion to identify type-dependent ARFs. Significant differences were observed: more intense convective precipitation events evidenced a more pronounced decrease in empirical ARFs than storms related to frontal systems, with reductions up to approximately 50% for the median values at about 2000 km2. Results were also compared to some of the most widely used “fixed-area” laws for ARF evaluation; overall, these lead to larger values compared to storm-centered ARFs derived for the investigated region. The proposed storm-centered methodology can find important applications in providing reference limits of ARF values to be properly used in the engineering design of hydraulic and hydrological infrastructures, and appears particularly suited for effective and reliable flood defense in early warning systems.

中文翻译：

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固定面积与以风暴为中心的面积减少因子：地中海案例研究

摘要 面积折减系数（ARF）是一个广泛用于许多水文应用的概念。在本文中，假设采用“以风暴为中心”的方法，已经为卡拉布里亚地区（意大利南部）推导出了新的 ARF 估计经验法则，这些法则根据地中海地区典型的降雨生成机制进行了区分。具体而言，使用 2002-2015 年期间区域雨量计网络的数据，通过启发式标准将极端事件分为对流单元和锋面系统，以识别类型相关的 ARF。观察到显着差异：更强烈的对流降水事件证明经验 ARF 的减少比与锋面系统相关的风暴更显着，在约 2000 平方公里的中值减少高达约 50%。结果还与一些最广泛使用的 ARF 评估“固定区域”法则进行了比较；总体而言，与为调查区域得出的以风暴为中心的 ARF 相比，这些导致更大的值。提出的以风暴为中心的方法可以在提供 ARF 值的参考限值方面找到重要的应用，以便在水利和水文基础设施的工程设计中正确使用，并且似乎特别适合早期预警系统中有效和可靠的洪水防御。