PAZ Neutral Atmosphere Radio Occultation Retrieval Processing
Presenter:
Douglas Hunt
University Corporation for Atmospheric Research (UCAR)
UCAR (first five), Institute of Space Sciences and Institute for Space Studies of Catalonia (last two)
Talk
We present processing strategies and results for radio occultation (RO) retrievals from Spain’s PAZ satellite. PAZ was launched in 2018 and flies a GPS RO payload named “Radio-Occultation and Heavy Precipitation” experiment (ROHP-PAZ). The ROHP-PAZ antenna decomposes the GPS RO signal into horizontally (H) and vertically (V) polarized signals. The receiver then processes the H and V signals in separate hardware and firmware channels by tracking them in combined closed-loop and open-loop modes. The goal of this design is to measure the very small phase shift between H and V signals induced by precipitation.
Standard RO processing can also benefit from the extra information supplied in separate H and V channels. In order to retrieve standard RO products, either H or V can be used or, alternatively, H and V can be combined (H+V) in order to increase the signal to noise ratio (SNR). We have developed new processing algorithms within UCAR’s COSMIC Data Analysis and Archive Center (CDAAC) processing system to produce excess phase for H, V, and H+V. The H+V excess phase is then used to perform neutral atmospheric retrievals to derive vertical profiles of bending angle, refractivity, temperature, and pressure. In this presentation we describe algorithm updates relative to standard RO processing (including a method of combining of H and V), verification of each type of excess phase, and validation of retrieval products via characterization of bending angle profiles and comparisons to global numerical weather prediction (NWP) analyses. We also summarize the architecture and status of CDAAC’s near real-time processing of PAZ data for use in operational NWP.
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