Radar products for hydrological applications in the UK

Abstract

High-resolution precipitation estimates from weather radar and radar-based precipitation forecasts are key inputs to hydrological applications and, in particular, to flood forecasting models. This paper examines the processes applied to the radar-measured reflectivity data from the UK weather radar network in order to derive products useful for hydrological applications. This starts with the quality control of the reflectivity scan data then looks at processes to convert the measured reflectivity into estimates of precipitation rate close to the ground. The approaches applied operationally at the UK Meteorological Office are compared with other operational approaches. In order to use radar data for hydrological applications, it is important to understand the likely error characteristics of the precipitation estimates. Two different approaches to representing this uncertainty are outlined. The first considers a quality index, formed by combining a number of different components, representing different sources of error, multiplicatively. The second approach considers the generation of ensemble precipitation estimates which represent the likely spread of errors. The use of the precipitation estimates in generating short-period probabilistic precipitation forecasts is discussed. The methodology adopted in the short-term ensemble prediction system is outlined. Characteristics of these radar products are illustrated with a precipitation event.

A radar‐based rainfall climatology of Great Britain and Ireland

“…The results of this study are consistent with prior com parisons between the UK radar-derived precipitation composite and gauge measurements (Biggs and Atkinson, 2011;Harrison et al, 2012;Parkes et al, 2013). However, most prior comparisons considered high-impact precipitation events, whereas this study considers all times with or without precipitation.…”

“…However, use of a microphysical species-based Z-R relationship may only reduce the error in the precipitation rate retrieval by 10% (Koistinen et al, 2004). The retrieved precipitation rate is then corrected for orographic enhancement (Georgiou et al, 2011) and adjusted to match local gauge observations on a radar-by-radar basis (Kitchen et al, 1994;Lewis and Harrison, 2007;Harrison et al, 2012). These single-radar rain-rate retrievals are then composited to a uniform grid, weighting by both distance to the radar and pixel quality (Harrison et al, 2009;.…”

The DYMECS Project: A Statistical Approach for the Evaluation of Convective Storms in High-Resolution NWP Models

“…We tracked storms in the Met Office rainfall radar data, which provide radar-derived surface-rainfall rates at 1-km resolution every 5 min (Harrison et al 2012). Using a rain-rate threshold of 4 mm h -1 to isolate convective storms, storm features with an area of at least 4 km 2 were given a unique identifier and tracked throughout their life cycle, so that life-cycle statistics could be derived for model evaluation.…”

Fuzzy logic filtering of radar reflectivity to remove non-meteorological echoes using dual polarization radar moments

“…Rainfall intensities for all scans can be calculated, in a first instance, through use of the Marshall-Palmer relation, taking the standard coefficients as used in the UK operational radar network (Harrison et al, 2012):…”