The signature of mid-latitude convection observed by VHF wind-profiling radar

The signature of mid-latitude convection observed by a 46.5 MHz wind-profiling radar at Aberystwyth, UK (52.4°N, 4.0°W), is demonstrated by way of a case study. A key feature of such radars is their ability to measure the vertical air velocity directly, even under conditions of precipitation. Higher frequency radars, which have more typically been used for such studies, measure the net effect of hydrometeor terminal velocities and the air motion under such conditions. The radar is capable of observing both updrafts and downdrafts, with peak updrafts of the order of 10 m s^-1. The signature of convection additionally consists of enhanced values of the radar return spectral width, which cannot be interpreted in terms of turbulence intensity, and reduced reliability of the corresponding radar-derived horizontal wind components. When convection reaches the uppermost troposphere, the radar return signal power can be anomalously large leading to the radar-derived tropopause altitude being overestimated. The presence of convection is confirmed by thermal infrared satellite imagery of high-topped clouds. Use is also made of radiosonde and UHF wind-profiler data.