The role of SmallSat Radars in the Next Generation Spaceborne Precipitation Observing Systems

The holistic, quantitative understanding of the Earth's water and energy cycle remains one of the grand challenges that the international scientific community needs to address in the next decade. Spaceborne constellations of passive microwave (PMW) radiometers are an essential part of current and future precipitation observing systems, despite their limitations over land and their relatively large footprints. Spaceborne radars such as the NASA's CloudSat Cloud Profiling Radar (CPR) and the joint NASA/JAXA Global Precipitation Measurements (GPM) mission Dual-frequency Precipitation Radar (DPR) provide vertical resolved precipitation measurements with improve sensitivity and resolution and are used as "calibrators" for the PMW-based observing systems.

Today, an opportunity exists for transformational advancements in Earth and space sciences using large constellations of satellites. Technology demonstration missions have made possible time-resolved observations of precipitation structure and storm intensity with a constellation of SmallSats (i.e. The Temporal Experiment for Storms and Tropical Systems; TEMPEST) and radars in a CubeSat (RainCube). These advancements have the potential to alter the way we observe the Earth's water cycle and overcome time-space limitations (i.e. diurnal cycle).

Here, we focus on the role of radars in the next generation spaceborne precipitation observing systems. First, we briefly review the status of the current precipitation observing systems and their shortcomings. Future radar systems that could help to address the shallow oceanic and high latitude precipitation gaps are discussed. Finally, we expand beyond precipitation monitoring and discuss the role of constellations of radars of SmallSats for understanding key processes (i.e. diurnal cycle, dynamics, interaction with the environment).