Evaluation of Assimilation Effect of Yunhai-2 Occultation Data in Global Numerical Weather Prediction Model

Abstract

Based on the T799L91 global numerical weather forecast model and its four-dimensional variational assimilation system, the assimilation process of Yunhai-2 occultation data was constructed, and a one-month assimilation-forecast experiment for Yunhai-2 occultation data was carried out in July 2019. The evaluation of the assimilation forecast results for East Asia, Northern Hemisphere and Southern Hemisphere shows that: In the global numerical weather forecast model, assimilating Yunhai-2 occultation data can effectively improve the accuracy of the forecast field. With the extension of the forecast time and the increase of the forecast days, the improvement range gradually increases. With the longer time efforts of the 72-hour, 120-hour and 168-hour forecasting, the assimilation effects of Yunhai-2 occultation data and GPS (Global Positioning System) occultation data are similar in the middle and early days, while the assimilation of Yunhai-2 occultation data is gradually better than GPS occultation data in the middle and later days. With the increase of the forecasting days, the advantage of the joint assimilation of Yunhai-2 occultation data with GPS occultation data gradually appears.