Emerging Spaceborne Doppler Radar for Global In-Cloud Wind Retrieval: Advances and future directions

Accurate observation of global in-cloud wind fields is essential for advancing the understanding of the atmospheric water and energy cycles and for improving the initialization of cloud-resolving numerical weather prediction and general circulation models. In recent years, growing attention from the remote sensing community has driven substantial progress in observational technologies. Among them, spaceborne Doppler microwave radar has emerged as the only viable remote sensing technique capable of penetrating deeply into cloud systems, enabling comprehensive global-scale in-cloud wind measurements. This article presents a comprehensive synthesis of recent developments in spaceborne Doppler radar systems for global in-cloud wind field retrieval. It systematically reviews Doppler velocity estimation techniques, onboard antenna scanning strategies, and wind field retrieval algorithms under the constraints of spaceborne operation. Building upon current technological capabilities and emerging trends, this article highlights several promising research directions, including the implementation of mission-level integrated phased-array multibeam radar simulators to support next-generation global in-cloud wind measurement missions, the execution of airborne prototype system performance evaluation campaigns, the development of high-resolution wind field retrieval algorithms increasingly enhanced by artificial intelligence (AI) techniques, and observing system simulation experiment (OSSE)-based forecast-impact assessment to quantify the potential value of spaceborne in-cloud Doppler wind observations for numerical weather prediction. Together, these directions provide technical guidance for the design of future spaceborne Doppler radar missions.