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IGG is pleased to invite you to a scientific seminar to be held in a hybrid format. The main event will take place in the IGIG library (100G). You will be able to connect remotely on the Zoom platform. The presentation entitled "Forward modeling of bending angles with a two-dimensional operator for GNSS airborne radio occultations in atmospheric rivers" will be given by dr Paweł Hordyniec from our institute. The presentation will highlight the results of a research internship carried out within the framework of the NAWA Mieczysław Bekker programme, which Dr Hordyniec completed in Scripps Institution of Oceanography, University of California San Diego.

The seminar will begin at 09:00 AM (CEST) on Thursday 20 April 2023.



Join the Zoom meeting: ZOOM LINK.
Meeting ID: 811 427 0260
Access code: igig


Forward modeling of bending angles with a two-dimensional operator for GNSS airborne radio occultations in atmospheric rivers.
Dr Paweł Hordyniec
Institute of Geodesy and Geoinformatics, UPWr, Wroclaw, Poland,
Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA.


Abstract:.
Atmospheric River Reconnaissance (AR Recon) campaigns collect targeted observations of significant winter weather events contributing to long duration heavy precipitation and flooding on the U.S. West Coast. Observations over the east Pacific Ocean from weather buoys together with dropsonde measurements are supported by atmospheric soundings from GNSS airborne radio occultation (RO) technique serving as key datasets for studying vertical moisture structures in such frontal systems. The airborne radio occultation technique originates from its spaceborne counterpart that has already established value for numerical weather prediction by being routinely assimilated into global models. However, an observation operator needs to be developed to allow assimilation of geophysical variables from airborne occultations in order to improve forecasts of atmospheric rivers. This capability has been achieved by modifying existing state-of-the-art forward operator for spaceborne RO provided in the forward module of ROM SAF Radio Occultation Processing Package (ROPP) thus opening wide range of applications for operational meteorology from airborne platform. Due to significant inhomogeneities associated with atmospheric river events, the operator assumes that the atmosphere has a two-dimensional (2D) structure which is generally a more complex and computationally demanding solution. The developed algorithm allowed to assess measurement uncertainties which is otherwise difficult to achieve since properties of the atmosphere in the RO technique are expressed in terms of bending angle parameter - an unconventional observable for meteorology. The estimation of observation error model is important for the quality control screening in data assimilation systems. The assessment based on meteorological information sourced from ECMWF fields suggests that the agreement in terms of observed minus background statistics for datasets collected during intensive operating periods is on the order of 10 % at the altitude of 4 km and around 4 % at 10 km. Simulations from the 2D operator were compared with outputs from a spherically symmetrical atmosphere (1D) resulting in mismodeling errors on the order of 20 % in the lowermost troposphere further supporting the advantage of more sophisticated approaches for a realistic representation of atmospheric river environments. The developed airborne RO observation operator will be used in data assimilation experiments in the framework of new emerging initiatives such as the Joint Effort for Data assimilation Integration (JEDI) led by the Joint Center for Satellite Data Assimilation (JCSDA) with various observation operators available for the users.

Key words: airborne, forward model, observation operator, bending angle