Evaluation of areal versus point rainfall with sparse data

Abstract

A theoretical methodology is proposed to establish a relationship between the rainfall at a fixed point and the associated mean rainfall over a geographically fixed area. The distribution relation for mean rainfall over a specific area was derived using an exponential distribution function for hourly point rainfall. Values of the areal correction factor were estimated at equal levels of exceedance probability for point and areal mean rainfalls. Contrary to previous indications for a moving point, it was found that the areal correction factor for a fixed point and fixed area was not always equal to or less than unity. Furthermore, the areal correction factor was found to vary with the return period.

Impacts of Climate Change on Rainfall Extremes and Urban Drainage Systems

“…When areal and point rainfall statistics are studied, systematic differences exist, which for a given region depend on the rainfall intensity or return period, the aggregation level, the area and the distance between the point rainfall location and the centre of the area considered (Willems & Berlamont, 2002a). The ratio between the mean rainfall over an area and the point rainfall intensity is called the Areal Reduction Factor (ARF) (Nguyen et al 1981). Vaes et al (2005) considered two types of areal reduction factors, namely those based on individual historical events and those based on rainfall intensities for specific return periods.…”

“…More details on the derivation of ARFs and upscaling of point rainfall can be found in NSSP (1961), NERC (1975, Rodriquez-Iturbe and Mejia (1974), Sivapalan and Blöschl (1998), Nguyen et al (1981), WMO (2009c) and other references. Literature on the inverse problem of assessing point precipitation (extremes) based on rainfall intensities defined at large spatial scales can be found in for example Booij (2002).…”

An Area‐Based Approach for Estimating Extreme Precipitation Probability

“…Misrepresenting the spatial and temporal variability of precipitation causes runoff model error (Fontaine ; Ruelland et al ). For the purpose of flood response, storm water management, and infrastructure design, point‐based estimation of IDF needs to be scaled to areal estimates to provide more accurate rainfall‐runoff model inputs (Nguyen, Rousselle, and Mcpherson ).…”