Impact of TROPICS Radiances on Tropical Cyclone Prediction in an OSSE.

As part of the NASA Earth Venture-Instrument program, the Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission, to be launched in January 2022, will deliver unprecedented rapid-update microwave measurements over the tropics that can be used to observe the evolution of the precipitation and thermodynamic structure of tropical cyclones (TCs) at meso- and synoptic scales. TROPICS consists of six CubeSats, each hosting a passive microwave radiometer that provides radiance observations sensitive to atmospheric temperature, water vapor, precipitation, and precipitation-sized ice particles. In this study, the impact of TROPICS all-sky radiances on TC analyses and forecasts is explored through a regional mesoscale observing system simulation experiment (OSSE). The results indicate that the TROPICS all-sky radiances can have positive impacts on TC track and intensity forecasts, particularly when some hydrometeor state variables and other state variables of the data assimilation system that are relevant to cloudy radiance assimilation are updated. The largest impact on the model analyses is seen in the humidity fields, regardless of whether or not there are radiances assimilated from other satellites. TROPICS radiances demonstrate large impact on TC analyses and forecasts when other satellite radiances are absent. The assimilation of the all-sky TROPICS radiances without default radiances leads to a consistent improvement in the low- and midtropospheric temperature and wind forecasts throughout the 5-day forecasts, but only up to 36-h lead time in the humidity forecasts at all pressure levels. This study illustrates the potential benefits of TROPICS data assimilation for TC forecasts and provides a potentially streamlined pathway for transitioning TROPICS data from research to operations postlaunch. Significance Statement: As the Global Observing System evolves, smaller satellites such as CubeSats are emerging as inexpensive alternatives for providing important observations of Earth as compared to traditional satellites. TROPICS, to be launched in January 2022, is one of the NASA CubeSats missions that will deliver unprecedented rapid-update microwave measurements over the tropics. This study examines the impacts of simulated radiances from the TROPICS constellation of satellites for tropical cyclone analyses and forecasts in a regional mesoscale model and demonstrates the potential benefits of TROPICS data assimilation on TC forecasts. The infrastructure to incorporate the new TROPICS datasets into the operational model that was developed for this study will facilitate a transition from research to operations once the TROPICS data becomes available after the mission launch. [ABSTRACT FROM AUTHOR]