GNSS/RO Data Processing for Climate Applications at JPL: Assessing the performance of the next-generation OBS4MIPS atmospheric products retrievals
Presenter:
Mayra Oyola
NASA Jet Propulsion Laboratory
1(1) Jet Propulsion Laboratory, California Institute of Technology |Pasadena, CA, USA; (2) Atmospheric and Environmental Research, Inc., Lexington | MA, USA
Talk
Radio Occultation (RO) techniques have been recognized for their uniqueness to provide reference datasets, triggering a growing interest in using RO for climate modeling inter-comparisons and data assimilation for operational numerical weather prediction (NWP). At the Jet Propulsion Laboratory (JPL), physical parameters such as refractivity and derived atmospheric products (temperature, pressure, moisture) are obtained by applying inversion methodology on the atmospheric delay induced on the occulted signal. Such multi-mission retrieval system has generated nearly two decades of observations, and has allowed the generation of Global Navigation Satellite Systems Radio Occultation (GNSS RO) monthly gridded data for climate model evaluation and other applications (OBS4MIPS).
We present a detailed comparison between the next generation of JPL’s monthly gridded data (Level 3) GNSS RO retrieval products, and two datasets: 1) the newly released ERA-5 climate reanalysis and 2) the Radio Occultation Meteorology Satellite Application Facility (ROM SAF) Climate Data Records. Our comparison focuses on monthly means, seasonal cycles, and interannual variability over a 15-year period (2002–2017). We find that generally, the new retrievals show better global agreement at multiple atmospheric levels than its previous version; however, large bias spreads exist (mostly in higher latitudes), that persist throughout all years. Error quantifications and uncertainty characterization are thus provided within the context of these biases, as well as estimates of the associated retrieval and sampling errors. Despite these biases, this study demonstrates that global observations from GPS/RO provide high quality measurements in the upper troposphere/lower stratosphere, which are necessary for detection of climate signals and improvement of NWP models.
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