Development of EarthCARE - GPM coincidence dataset with combination of spaceborne cloud and precipitation radars

The Global Precipitation Measurement (GPM) Dual-Frequency Precipitation Radar (DPR) (Ku- and Ka-band) provides vertically resolved information on rain and ice water under moderate to heavy precipitation conditions across the tropics and mid-latitudes (Hou et al. 2014, Skofronick-Jackson et al. 2017). Owing to the unique asynchronous orbit of the GPM Core Observatory with the DPR and the GPM Microwave Imager (GMI), its orbital ground tracks intersect with those of many other sun-synchronous satellites. The CloudSat - GPM coincidence dataset (CSATGPM; Turk et al. 2021), focusing on intersections with the W-band cloud radar onboard CloudSat, which excels at observing clouds and light precipitation, offers "pseudo three-frequency" radar profiles of near-coincident observations. In addition, simultaneous observations by CloudSat and the Tropical Rainfall Measuring Mission (TRMM; Kummerow et al. 1998) satellite, the predecessor of GPM, are also available (CSATTRMM; Turk et al. 2021), which includes a larger number of cases compared to CSATGPM, as it covers the period before CloudSat transitioned to day-time only operation in 2011. These datasets have been utilized for many scientific purposes, such as studies of cold-season precipitation, ice microphysics, and light rainfall.

The Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) satellite (Illingworth et al., 2015; Wehr et al., 2023), launched in May 2024, is equipped with four sensors employing different observation methods: radar, lidar, imager, and radiometer. In particular, the Cloud-Profiling Radar (CPR), developed by the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT), is the first spaceborne W-band radar with Doppler capability. It continues the cloud and precipitation observations performed by the CloudSat while introducing the novel measurements of vertical cloud motion from space. Building on the CSATGPM dataset, we are constructing a coincident observation dataset for the EarthCARE era.

From August to December 2024, the two satellites recorded several hundred coincident observation events per month, with approximately one-third of these events detecting precipitation on both satellites. An examination of the vertical profiles of radar reflectivity revealed that while the DPR detected large raindrops and snow particles in advanced stages of growth, the CPR captured detailed features within clouds at higher altitudes. In stratiform precipitation cases, Doppler velocity observations from the CPR showed slower downward motion at altitudes above the bright band detected by the DPR, and faster downward motion at lower altitudes. Furthermore, in addition to using DFR from three-frequency observations during the CloudSat era to classify solid precipitation particles, the incorporation of Doppler velocity as a new constraint suggests the potential for more advanced microphysical analysis of ice particles.

The combination of active observations from the W-band radar and 13-channel (10–183 GHz) GMI is also useful for algorithm development and evaluation, sensitivity studies of snow and light rain, cloud process studies, and radiative transfer simulations. In this presentation, we will also introduce preliminary results from coincident observations of the EarthCARE/CPR and the GMI radiometer.