Impact of Airborne Radio Occultation Observations on Atmospheric River Precipitation Forecasts on the US West Coast
Presenter:
Jennifer S. Haase
Scripps Institution of Oceanography, University of California San Diego
(2) University of California, Davis; (3) Center for Western Weather and Water Extremes, University of California, San Diego
Talk
Because of its high vertical resolution and global sampling, spaceborne GNSS radio occultation has had a large impact on operational numerical weather prediction. Implementation of this technology on aircraft greatly increases the density of this type of observations for use in field campaigns and provides the capability to target observations in sensitive regions where the forecast can potentially be improved. Airborne radio occultation (ARO) measures signal propagation delay from rising and setting GNSS satellites below the local horizon that sample the atmosphere in the region up to 600 km to the sides of the aircraft. The derived profiles are thus complementary to dropsondes released directly below the aircraft. We have flown a simplified version of the GNSS Instrument System for Multistatic and Occultation Sensing (GISMOS) in field campaigns targeting atmospheric rivers, where both ensemble and adjoint methods were used to determine sensitive areas for potential rapid uncertainty/error growth. The lightweight ROC2 receiver is a prototype for future deployment on stratospheric balloons. We show how ARO measurements from ROC2 augment the impact of dropsonde data assimilation using a high-resolution Weather Research and Forecasting (WRF) simulation of a heavy precipitation event. We also show how using true GNSS (GPS plus Galileo) expands that area still further, and increases confidence in observation errors assigned to the data type in data assimilation.
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