Use of radar data for characterizing extreme precipitation at fine scales and short durations

Abstract

Extreme precipitation is one of the most devastating forms of atmospheric phenomenon, causing severe damage worldwide, and is likely to intensify in strength and occurrence in a warming climate. This contribution gives an overview of the potential and challenges associated with using weather radar data to investigate extreme precipitation. We illustrate this by presenting radar data sets for Germany, the U.S. and the UK that resolve small-scale heavy rainfall events of just a few km2 with return periods of 5 years or more. Current challenges such as relatively short radar records and radar-based QPE uncertainty are discussed. An example from a precipitation climatology derived from the German weather radar network with spatial resolution of 1 km reveals the necessity of radars for observing short-term (1–6 h) extreme precipitation. Only 17.3% of hourly heavy precipitation events that occurred in Germany from 2001 to 2018 were captured by the rain gauge station network, while 81.8% of daily events were observed. This is underlined by a similar study using data from the UK radar network for 2014. Only 36.6% (52%) of heavy hourly (daily) rain events detected by the radar network were also captured by precipitation gauging stations. Implications for the monitoring of hydrologic extremes are demonstrated over the U.S. with a continental-scale radar-based reanalysis. Hydrologic extremes are documented over ∼1000 times more locations than stream gauges, including in the majority of ungauged basins. This underlines the importance of high-resolution weather radar observations for resolving small-scale rainfall events, and the necessity of radar-based climatological data sets for understanding the small-scale and high-temporal resolution characteristics of extreme precipitation.

Towards advancing scientific knowledge of climate change impacts on short-duration rainfall extremes

“…Similarly, improvements in the representation of urban landscapes would improve related atmospheric feedbacks, such as rainfall intensification from urban heat island effects [113], and CPMs could be really useful for examining the effects of planned urban/peri-urban expansion on micro-climates, guiding local adaptation measures, such as the implementation of city-wide green infrastructure. Alongside this, we suggest that comparison of CPM versus gauge observations will be useful in understanding network density effects, which have also been observed from radar versus gauge comparisons [24,151], and may severely affect our estimates of regional return levels, crucially needed for design decisions.…”

“…The Global Sub-Daily Rainfall (GSDR) dataset [20] comprises observations from more than 25 000 gauges, quality-controlled using open-source Python codes [21]. This quality-controlled data has been used to develop UK-wide gridded 1 km resolution hourly precipitation products [22], blended gauge-radar-satellite datasets [23] and to examine the ability of hourly gauge data to capture hourly rainfall extremes [24]. The GSDR has also been used, together with reanalyses and remotely sensed products, to produce global 0.1° daily and 3-hourly precipitation probability distribution climatologies for 1979–2018 [25].…”

Stewardship Maturity Assessment Tools for Modernization of Climate Data Management

“…The data set was developed within the research project RADKLIM (Winterrath et al, 2017) and has now transferred to an operational data product. The driver is the assumption that the majority of heavy precipitation events were missed by gauges, now confirmed by Lengfeld et al, (2020). This data set starts in 2001 and is extended by the observations of the previous year on an annual basis.…”

A historical flash flood chronology for Britain

“…Some storms are missed entirely by ground based raingauges and there are thus many events with severe flooding where there are no rainfall records. An analysis of data from Germany and the United Kingdom suggests that the sparse gauge network is only able to capture around 20% of intense short‐duration (hourly) rainfall events seen in the radar record (Lengfeld et al, 2020). Blended, gridded datasets such as the UKGrsHP high‐resolution radar‐gauge‐satellite product (1 km, 1 h resolution: Yu, Li, Lewis, Blenkinsop, & Fowler, 2020), with complete spatial coverage, have the potential to provide improved information on the frequency of short‐duration intense storms that trigger surface water flash flooding, but since the radar and satellite records are short, only start in the early 2000s.…”