EarthCARE Observations of Vertical Motion and Cloud Microphysical Structure in Tropical Cyclones

Abstract. The Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) satellite mission provides the first spaceborne Doppler radar measurements, enabling new insights into the vertical structure of clouds and precipitation. In this study, we construct a dataset of EarthCARE overpasses of tropical cyclones (TCs) by collocating satellite observations with the International Best Track Archive for Climate Stewardship (IBTrACS). Based on 14 months of observations, we examine the radial structure of radar reflectivity, Doppler velocity, retrieved air motion, and cloud particle types. The results show a transition from convective-like structures in the eyewall to stratiform-like characteristics in the rainband region. The eyewall exhibits stronger updrafts, enhanced reflectivity, and broader Doppler velocity distributions. In contrast, the rainband region shows that weaker vertical motions and Doppler signals are more strongly influenced by hydrometeor fall speeds. We further evaluate TC simulations using the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) with two different cloud microphysical configurations of hydrometeor fall speeds. Both experiments reproduce the overall TC structure but exhibit more confined distributions of radar reflectivity, Doppler velocity, and air velocity compared to the observations. Differences between the two simulations highlight the sensitivity of vertical structure to hydrometeor fall speeds. These results indicate that EarthCARE Doppler observations provide valuable constraints on the coupling between dynamics and cloud microphysics in TCs.