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Forward modeling of bending angles with a two-dimensional operator for GNSS airborne radio occultations in atmospheric rivers
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  • Paweł Hordyniec,
  • Jennifer S Haase,
  • Michael James Murphy,
  • Bing Cao,
  • Anna Maria Wilson,
  • Ivette Hernández Baños
Paweł Hordyniec
Wroclaw University of Environmental and Life Sciences
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Jennifer S Haase
Scripps Institution of Oceanography, University of California San Diego

Corresponding Author:[email protected]

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Michael James Murphy
Goddard Space Flight Center
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Bing Cao
University of California, San Diego
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Anna Maria Wilson
Scripps Institution of Oceanography, UC San Diego
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Ivette Hernández Baños
NSF NCAR Mesoscale and Microscale Meteorology Laboratory
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The Global Navigation Satellite System (GNSS) airborne radio occultation (ARO) technique is used to retrieve profiles of the atmosphere during reconnaissance missions for atmospheric rivers (ARs) on the west coast of the United States. The measurements are a horizontal integral of refractive index over long ray-paths extending between a spaceborne transmitter and a receiver onboard an aircraft. A specialized forward operator is required to allow assimilation of ARO observations into numerical weather prediction models to support forecasting of ARs. A two-dimensional (2D) bending angle operator is proposed to enable capturing key atmospheric features associated with strong ARs. Comparison to a one-dimensional (1D) forward model supports the evidence of large bending angle departures within 3-7 km impact heights for observations collected in a region characterized by the integrated water vapor transport (IVT) magnitude above 500 kg m-1 s-1. The assessment of the 2D forward model for ARO retrievals is based on a sequence of six flights leading up to a significant AR precipitation event in January 2021. Since the observations often sampled regions outside the AR where moisture is low, the significance of horizontal variations is obscured in the average statistics. However, examples from an individual flight preferentially sampling the cross-section of an AR further support the need for the 2D forward model for targeted ARO observations. Additional simulation experiments are performed to quantify forward modeling errors due to tangent point drift and horizontal gradients suggesting contributions on the order of 5 % and 20 %, respectively.
03 Apr 2024Submitted to ESS Open Archive
16 Apr 2024Published in ESS Open Archive