| dc.description.abstract | This study investigates the impact of global navigation satellite system (GNSS) radio occultation (RO) data assimilation (DA) on the cyclogenesis of ten tropical cyclones in the northwestern Pacific region from 2020 to 2022. Employing a hybrid 3DEnVar in the WRFDA system, four DA experiments are conducted: assimilating conventional data only (GTS), further incorporating only with GNSS RO data (EPH) or with radiance data (RAD), and assimilating all the above observations (ALL). Statistical analyses reveal significant improvements on time and location predictions of tropical cyclogenesis, particularly when both GNSS RO and radiance data are assimilated. ALL demonstrates superior predictive capabilities in capturing tropical cyclogenesis, with an averaged spatial error reduction. However, EPH outperforms others in simulating vortex formation within a 24-h prediction error range, highlighting the positive impact of GNSS RO data on improving cyclogenesis forecasting.
The verification over a larger region shows that incorporating RO and radiance data significantly improves synoptic environment modeling and particularly cyclogenesis forecasts. The global ERA5 reanalysis confirms that the experiments using satellite data (EPH, RAD, and ALL) outperform the conventional data experiment (GTS), especially in reducing mean errors and root mean square errors for water vapor mixing ratio and temperature. EPH excels above 850 hPa for water vapor mixing ratio, but ALL provides the best results from 550 hPa and higher. For temperature, RAD shows the most significant improvements above 500 hPa. Case studies on two specific typhoons, Chanthu (2021) and Hagupit (2020), further underscore the efficacy of GNSS RO and radiance DA in improvement of moisture and temperature predictions, crucial for cyclogenesis forecasts. Besides, assimilating GNSS RO data leads to an increase in the lower-mid-tropospheric moisture, organized convection, strong vertical motions at the grid scale, and the development of midlevel vorticity, and all these conditions are favorable for tropical cyclogenesis. Through the analysis of potential vorticity tendency budget, the significance of diabatic heating in influencing the development and maintenance of vortices is highlighted with latent heat release identified as a crucial factor. | en_US |