A comparison study between 1D Abel integral and ray tracing radio occultation observation operators
Radio occultation observations provide a significant positive impact on weather forecast skills. Their use in the data assimilation NWP systems also results in smaller and more accurate bias corrections in infrared and microwave observations. The Radio Occultations are usually available in the form of bending angle or refractivity profiles whereas the most popular observation operator follows the Abel integral formulation. However, the observation operator based on the standard form of the Abel integral is not able to account for waveguides which leads to negative retrieval errors of the refractivity while the waveguide structure cannot be retrieved. One solution is to implement a form of 1D ray equation in a spherically layered medium that uses an invariant resulting in a first-order differential equation that requires the refractivity field instead of its gradient. Relevant numerical experiments comparing the 1D Abel and Ray Tracing operators using Spire Global satellite measurements will be presented. Associated statistics obtained in the presence and absence of waveguide will be also discussed.
Dr. Razvan Stefanescu Spire Global