The beneficial impact of radio occultation observations on Australian region forecasts

The radio occultation (RO) technique, employing the GPS constellation of satellites and radio receivers in low earth orbit, can provide valuable atmospheric profile information (Ware et al. 1996; Kursinski et al. 1996; Rocken et al. 1997; Wickert et al. 2001). The radio occultation technique has been long used in the study of planetary atmospheres (e.g. Fjeldbo et al. 1971) where it has provided much valuable information. The radio occultation technique is based on measuring the bending of radio waves by refractive index gradients in the atmosphere. By observing this bending, a vertical profile of bending angle or refractive index can be derived and subsequently a profile of temperature/moisture. In the datasparse southern hemisphere, observations of this type are vital for analysis, forecasting and climate monitoring. These data have recently been employed in some analysis centres around the globe where they have been shown to improve operational global numerical weather prediction (e.g. Cucurull and Derber 2008; Cucurull et al. 2007, 2008). Here we describe the use of COSMIC/FORMOSAT-3 Mission (Anthes et al. 2008), MetOp and GRACE radio occultation data in the ACCESS-G forecast system at the Bureau of Meteorology. The beneficial impact of radio occultation observations on Australian region forecasts