Comparison of Concurrent Radar and Aircraft Measurements in Florida Thunderstorm Cirrus Anvils

Concurrent measurements of anvil cirrus clouds are obtained using the highly instrumented North Dakota Citation Research Aircraft and the Cloud and Precipitation Radar with Discrete Hydrometeor Detection (CPR-HD), a C-band, high-resolution radar on the Atlantic coast of Florida. The CPR-HD alternatively transmits two waveforms, a lower-resolution (narrowband) beam and a high-resolution (wideband) beam with along-beam range resolutions of 34 and 0.5 m, respectively. A specialized operating strategy allows the range windows of the CPR HD to lock onto the Citation Research Aircraft using downlinked position information and track the aircraft in real time for the duration of the flight, providing nearly concurrent in situ and remote observations in space and time. Radar reflectivity factor with uncertainty is calculated using a combined particle size spectrum obtained from in situ cloud probes. Comparing the derived reflectivity factor to the observed wideband reflectivity factor for the 1 August 2015 flight shows that 84% of the 1-s-averaged data agree within their respective uncertainties across the sampled range from −15 to 20 dBZ. Uncertainties within the analyzed cases are ±2.6 dBZ on average for derived reflectivity factor and ±3.0 dBZ for the wideband reflectivity factor. A derived relationship between CPR-HD reflectivity factor and particle mass allows vertical profiles of water content in cirrus anvil clouds to be determined from CPR-HD observations with a known uncertainty.