Next generation of weather radar for the UK C-band national radar network

The UK Met Office has been operating the national radar network for nearly 30 years. It is a relatively dense network of 15 radars generating products from 5km down to 500m resolution every 5 minutes. Over the past 3 decades the UK radar network has been subjected to continuous in-house development to its infrastructure and data processing systems. More recently, the UK Met Office has embarked on its most ambitious engineering project to date. The radar hardware and signal processing systems are being renewed with an in-house design incorporating dual-polarisation capability. The new radars can operate in 2 modes: simultaneous transmit and receive H and V producing ZDR, ρ_HV, and Φ_DP; or transmit H and simultaneous receive H and V to measure LDR. These radars are also capable of performing additional measurements not currently available from commercial offerings (e.g. radar refractivity/humidity measurements, and measurement of emissions to derive attenuation from storms and wet radomes). Dual-polarisation implementation is becoming the standard for National weather radar networks across Europe, aiming to deliver improvements in product scope and quality; improvements that in turn will benefit forecasts particularly of high impact weather events. The quality of the raw dual polarisation parameters is crucial – only high quality raw parameters can be relied on to produce a positive impact on the quality of the radar products to justify this investment. Particular consideration has been placed on the design and testing of the receiver system and the antenna. Receiver tests included monitoring the receiver response to varying temperature levels (between -5°C and +45°C) as well as to varying levels of mechanical stress. The antenna pattern measurements were carried out for each antenna at a test range to optimise the position of the feed-horn and to provide full characterisation of the cross polar isolation, side lobe levels, antenna gain, beam-squint, and beam-width over the 0°, 45°, 90° and 135° cuts. The quality of the overall system is evaluated following each installation through the monitoring of peak ρ_HV and LDR in rain. Results obtained from the first 4 installations repeatedly report high quality system performance with a peak ρ_HV at 0.997 and LDR at -35.5 dB or better.