GNSS Radio Occultation Applications for Weather Forecasting GNSS: Global Navigation Satellite Systems Panagiotis Vergados Jet Propulsion Laboratory, California Institute of Technology @ 2017 California Institute of Technology. Government sponsorship acknowledged. Outline Table of Contents Slide No. ------------------------------------------------------------------------------------------------------- • Introduction to GNSS radio occultation (GNSS RO)................................. (3) • Weather forecasting benefits.....................................................................(5) • Hurricane intensity estimation....................................................................(7) • Other science applications.........................................................................(9) • COSMIC-2/FORMOSAT-7 Mission......................................................... (10) • Summary................................................................................................. (13) November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 2 What is GNSS Radio Occultation? (GNSS) Bending of the GPS signal in the atmosphere provides information on temperature, pressure, and humidity. Unique: very high vertical resolution (~ 100 m), all- weather operation, global coverage, and high accuracy (T: ~0.5 K and q: ~0.1 g/kg). Bending of the GPS signal in the ionosphere provides information on the free electron number density. LEO – Low Earth Orbiter (altitudes 350-1500 km) November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 3 GNSS Radio Occultation Timeline Experiment on an operational satellite Operational Operational demonstration Proof of concept CASSIOPE November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 4 Weather Forecasting Benefits – 1 GOES-Rad MTSAT-Rad Relative forecast error reduction per observation system MET 9-Rad MET 7-Rad AMSU-B MHS AMSR-E SSMI GPS-RO IASI AIRS AMSU-A HIRS TEMP-mass DRIBU-mass AIREP-mass SYNOP-mass SCAT-w ind MODIS-AMV MET-AMV MTSAT-AMV GOES-AMV PILOT-w ind TEMP-w ind DRIBU-w ind AIREP-w ind SYNOP-w ind 0 2 4 6 8 10 12 14 16 18 20 Percent ReductionFE Cin % Forecast Error 24-hour forecast Cardinali, C., and S. Healy (2014), Impact of GPS radio occultation measurements in the ECMWF system using adjoint-based diagnostics, Q.J.R. Meteorol. Soc., 140(684), 2315–2320, doi:10.1002/qj.2300. November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 5 Weather Forecasting Benefits – 2 Stratosphere, Summer Hemisphere Standard deviation Temperature error – weather model Started assimilating COSMIC data in 2006 From S. Healy, ECMWF November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 6 Weather Forecasting Benefits – 3 The impact of using RO observations on forecasts of Hurricane Ernesto’s genesis (2006) Central Sea Level Pressure (hPa) Level Sea Central Day of August 2006 Ensemble mean of 48-h forecasts of Ernesto’s central sea level pressure (hPa) initialized from the analyses at 0000 UTC 25 Aug 2006 (Liu et al., 2012; Monthly Weather Review, doi:10.1175/MWR-D-11-00024.1) November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 7 Hurricane Intensity Estimation Remote sensing of hurricane intensity could greatly improve quantity of timely data GNSS RO-based Method of Estimating Hurricane Intensity First estimates of hurricane intensities (maximum wind speed) from GPS radio occultations (GPSRO) and the Wong and Emanuel [2007] hurricane model. GPSRO-derived hurricane intensities show 0.9 linear correlation with respect to NHC intensities with a small bias. GPSRO shows great potential in augmenting current hurricane datasets, with possible applications to the initial vortex parameterization and intensity forecasting. Vergados P., Z. Luo, K. Emanuel, and A. J. Mannucci (2014), Observation tests of hurricane intensity estimations using GPS radio occultations, J. Geophys. Res. – Atmospheres., 13 p., doi:10.1002/2013JD020934 November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 8 Science Applications 1. Climate monitoring 2. Characterizing the planetary boundary layer Temperature (K) Temperature Pressure level (hPa) level Pressure 01/96 01/97 01/98 01/99 01/00 01/01 01/02 01/03 01/04 01/05 01/06 01/07 01/08 01/09 01/10 Time, months 4. Electron density irregularities 3. Expansion of the tropical belt Auroral (64–80o) Wavelength, km Wavelength, Polar (> 80o) Wavelength, km Wavelength, Altitude, km November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 9 COSMIC-2/FORMOSAT-7 Mission COSMIC-2A launch, 6 satellites: ~March 2018 November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 10 COSMIC-2/FORMOSAT-7 Mission COSMIC-2 observa on density A high-inclina on launch is necessary to obtain global and uniform distribu on of RO profiles and to improve weather forecast skill globally Spa al distribu on of the COSMIC-2A and COSMIC-2B observa ons for (a) ±3 hours assimila on me window 6 L. Cucurull, NOAA, 2017 November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 11 Future Research Satellites: RO+Reflections? Clara Chew, JPL • CHAMP and SAC-C had nadir antennas and observed some reflections from frozen areas • GNOS (RO) has a reflections experiment onboard • CYGNSS (NASA mission) is first GNSS-Reflections constellation November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 12 Summary • RO observations have improved weather forecasting, have demonstrated great potential in extreme weather research, and have provided valuable information in space weather research. • Given the success of previous RO missions, future and follow-on missions will track additional signals of opportunity (beyond the GPS signals). • Synergistic applications between GNSS-RO and GNSS reflections appear to be a viable path forward to begin exploring new science applications. November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 13 jpl.nasa.gov November 15, 2017 JPL/Caltech PV/JPLAJM/JPL 14 .