Improved Impacts in Observing System Simulation Experiments of Radio Occultation Observations as a Result of Model and Data Assimilation Changes

Abstract

AbstractAs global data assimilation systems continue to evolve, observing system simulation experiments (OSSEs) need to be updated to accurately quantify the impact of proposed observing technologies in weather forecasting. Earlier OSSEs with radio occultation (RO) observations have been updated, and the impact of the originally proposed Constellation Observing System for Meteorology, Ionosphere and Climate-2 (COSMIC-2) mission, with high-inclination and low-inclination components, has been investigated by using the operational data assimilation system at NOAA and a one-dimensional bending-angle RO forward operator. It is found that the impact of the low-inclination component of the originally planned COSMIC-2 mission (now officially named COSMIC-2) has significantly increased as compared with earlier studies, and significant positive impact is now found globally in terms of mass and wind fields. These are encouraging results as COSMIC-2 was successfully launched in June 2019 and data have been recently released to operational weather centers. Earlier findings remain valid indicating that globally distributed RO observations are more important to improve weather prediction globally than a denser sampling of the tropical latitudes. Overall, the benefits reported here from assimilating RO soundings are much more significant than the impacts found in previous OSSEs. This is largely attributed to changes in the data assimilation and forecast system and less to the more advanced one-dimensional forward operator chosen for the assimilation of RO observations.