Blenkinsop Stephen, Lewis Elizabeth, Chan Steven C, Fowler Hayley J
Water Resource Systems Research Laboratory, School of Civil Engineering and Geosciences Newcastle University Newcastle upon Tyne UK.
Water Resource Systems Research Laboratory, School of Civil Engineering and Geosciences Newcastle University Newcastle upon Tyne UK; Hadley Centre Met Office Exeter UK.
Int J Climatol. 2017 Feb;37(2):722-740. doi: 10.1002/joc.4735. Epub 2016 Apr 24.
Sub-daily rainfall extremes may be associated with flash flooding, particularly in urban areas but, compared with extremes on daily timescales, have been relatively little studied in many regions. This paper describes a new, hourly rainfall dataset for the UK based on ∼1600 rain gauges from three different data sources. This includes tipping bucket rain gauge data from the UK Environment Agency (EA), which has been collected for operational purposes, principally flood forecasting. Significant problems in the use of such data for the analysis of extreme events include the recording of accumulated totals, high frequency bucket tips, rain gauge recording errors and the non-operation of gauges. Given the prospect of an intensification of short-duration rainfall in a warming climate, the identification of such errors is essential if sub-daily datasets are to be used to better understand extreme events. We therefore first describe a series of procedures developed to quality control this new dataset. We then analyse ∼380 gauges with near-complete hourly records for 1992-2011 and map the seasonal climatology of intense rainfall based on UK hourly extremes using annual maxima, n-largest events and fixed threshold approaches. We find that the highest frequencies and intensities of hourly extreme rainfall occur during summer when the usual orographically defined pattern of extreme rainfall is replaced by a weaker, north-south pattern. A strong diurnal cycle in hourly extremes, peaking in late afternoon to early evening, is also identified in summer and, for some areas, in spring. This likely reflects the different mechanisms that generate sub-daily rainfall, with convection dominating during summer. The resulting quality-controlled hourly rainfall dataset will provide considerable value in several contexts, including the development of standard, globally applicable quality-control procedures for sub-daily data, the validation of the new generation of very high-resolution climate models and improved understanding of the drivers of extreme rainfall.
次日极端降雨可能与山洪暴发有关，尤其是在城市地区。但是，与日尺度的极端降雨相比，许多地区对次日极端降雨的研究相对较少。本文介绍了一个新的英国每小时降雨数据集，该数据集基于来自三个不同数据源的约1600个雨量计。这包括英国环境署（EA）的翻斗式雨量计数据，这些数据是为业务目的收集的，主要用于洪水预报。在使用此类数据分析极端事件时存在重大问题，包括累计总量的记录、高频的雨量桶翻动、雨量计记录误差以及雨量计的非运行状态。鉴于在气候变暖的情况下短历时降雨加剧的前景，如果要使用次日数据集来更好地理解极端事件，识别此类误差至关重要。因此，我们首先描述了为该新数据集进行质量控制而开发的一系列程序。然后，我们分析了1992 - 2011年有近乎完整每小时记录的约380个雨量计，并使用年最大值、n个最大事件和固定阈值方法，根据英国每小时极端降雨绘制强降雨的季节气候图。我们发现，每小时极端降雨的最高频率和强度出现在夏季，此时通常由地形定义的极端降雨模式被较弱的南北模式所取代。在夏季以及某些地区的春季，还发现每小时极端降雨存在强烈的日循环，在傍晚至深夜达到峰值。这可能反映了产生次日降雨的不同机制，夏季以对流为主。由此产生的经过质量控制的每小时降雨数据集将在多个方面提供重要价值，包括为次日数据开发标准的、全球适用的质量控制程序、验证新一代超高分辨率气候模型以及更好地理解极端降雨的驱动因素。
