Effects of Tianmu-1 Radio Occultation Data Assimilation on the Super Typhoon Gaemi (2024) Predictions

Abstract “Tianmu-1,” the Chinese independently developed commercial radio occultation (RO) remote sensing detection constellation system, boasts all the advantages of RO observation, including full-time, all-weather monitoring, great accuracy and precision, superior vertical resolution, and worldwide coverage. Furthermore, compared to currently mature occultation observing programs, there is a notable increase for “Tianmu-1” in daily data acquisition volume and global navigation satellite system (GNSS) compatibility as a result of large-scale networking. The WRF model and its 3DVAR assimilation system were utilized to assess the impact of with and without the “Tianmu-1” RO profile data in the assimilation on the forecast of Super TY “Gaemi” (2024) from 00 UTC on July 21 st to 00 UTC on July 28 th , 2024. The findings demonstrate that during the pre-simulation phase (the first four days), occultation data assimilation has minimal impact on track prediction. However, at the later stage (5-7 days of the simulation), the path error for the sensitivity test that incorporated Tianmu RO data was reduced by 38%-59% compared to the control test that excluded this data. Although the assimilation of “Tianmu-1” RO data improved the intensity forecasts for “Gaemi,” its overall impact on intensity forecasts was less than that on track forecasts, aligning with previous typhoon assimilation studies used COSMIC RO data.