THE TOMORROW.IO MICROWAVE SOUNDER CONSTELLATION: OBSERVATION IMPACT ASSESSMENTS

R. Honeyager¹, J. J. Guerrette¹, S. J. Munchak¹, E. Nelson¹

¹The Tomorrow Companies, Inc

The Tomorrow.io Microwave Sounder (TMS) is a cross-track radiometer that measures twelve channels in the W, F, and G bands to provide temperature and humidity sounding across a 2200-km swath. The first seven TMS satellites launched August 2024 through April 2025. A further eleven satellites should launch through mid-2027, after which successor instruments should begin launching.

We evaluate real impacts of TMS by running Observing System Experiments (OSEs) through several months of continual numerical weather prediction (NWP) forecast and data assimilation (DA) cycles beginning in January 2025. TMS satellites are deployed using commercial rideshare launches into both sun-synchronous and precessing orbits. These varied orbits fill growing gaps in the global observing system’s microwave backbone; the remaining POES satellites were recently decommissioned, and DMSP and GPM have a proposed end of life within the next year. As TMS satellites continue to launch we are able to demonstrate their ability to fill orbital gaps and also establish the progressive impact of additional microwave observations in NWP systems.

We compare TMS forecast impacts with other instruments already assimilated in the global observing system, such as the Advanced Technology Microwave Sounder (ATMS), and also with recently-launched missions. We are able to demonstrate near-equivalent humidity sounding performance of ATMS and TMS, and this equivalent impact persists across a four-day forecast timeframe. Furthermore, we provide a loose comparison of temperature sounding performance using the 50-70 GHz and 118 GHz oxygen spectral lines. In order to make these comparisons, we have adopted a reference modeled after the NOAA Global Data Assimilation System (GDAS) and the Global Forecast System (GFS) v16. Global forecasts use the C768-L127 (13km) mesh of the Unified Forecast System Finite-Volume Cubed-Sphere (FV3-UFS) atmospheric model, and ensemble members are imported from the Global Ensemble Forecast System (GEFS). Data assimilation is conducted primarily using the Joint Effort for Data Assimilation Integration (JEDI) codes and reflect ongoing migration efforts undertaken by the NOAA Environmental Monitoring Center (EMC) and the Joint Center for Satellite Data Assimilation (JCSDA).