Economical and Effective Upgrades to an Airborne Cloud Radar With a Dual Pulsing Scheme

The High-Performance Instrumented Airborne Platform For Environmental Research (HIAPER) Cloud Radar (HCR) is an airborne 94.4-GHz W-band Doppler radar, which is deployed in field campaigns in an underwing pod on the National Science Foundation (NSF) National Center for Atmospheric Research (NCAR) HIAPER aircraft. Upgrades to the radar hardware and software allowed for the implementation of a new pulsing scheme, which alternates blocks of short pulses with a length of 256 ns and a pulse repetition time (PRT) of 0.1 ms, with long pulses with a length of 512 ns and a PRT of 0.15 ms. The short pulses preserve the high range resolution of previous operations, while the newly added long pulses increase sensitivity and the maximum range. Combining the different pulses increases the unambiguous velocity to 15.6 ms⁻¹. The new pulsing scheme was tested on the ground in the summer of 2024 in CO, USA, during the Make Everything Operate Well (MEOW) test project. The observations collected during MEOW confirmed the ~6-dB increase in sensitivity predicted by theory, which led to a 17% increase in cloud observations. A method was developed which merges the short- and long-pulse radar moments into one set of observations, preserving the advantages of both pulse lengths. In regions with strong echoes, the short-pulse observations with their high range resolution are used, while in regions of weak echoes, the radar moments are filled in with long-pulse observations, utilizing their high sensitivity.