gnss radio occultation applications for weather forecastinggnss radio occultation applications for...

GNSS Radio Occultation

Applications for Weather Forecasting

Panagiotis Vergados

Jet Propulsion Laboratory, California Institute of Technology

@ 2017 California Institute of Technology. Government sponsorship acknowledged.

GNSS: Global Navigation Satellite Systems

2 AJM/JPL

Outline

November 15, 2017 JPL/Caltech

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)

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What is GNSS Radio Occultation?


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)

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(GNSS)

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GNSS Radio Occultation Timeline


Operational

Experiment on an operational satellite

Operational demonstration

Proof of concept

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CASSIOPE

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Weather Forecasting Benefits – 1


0 2 4 6 8 10 12 14 16 18 20

SYNOP-windAIREP-windDRIBU-windTEMP-windPILOT-windGOES-AMV

MTSAT-AMVMET-AMV

MODIS-AMVSCAT-wind

SYNOP-massAIREP-massDRIBU-massTEMP-mass

HIRSAMSU-A

AIRSIASI

GPS-ROSSMI

AMSR-EMHS

AMSU-BMET 7-RadMET 9-Rad

MTSAT-RadGOES-Rad

FEC %

Relative forecast error reduction per observation system

Percent Reduction in Forecast Error

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.

24-hour forecast

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From S. Healy, ECMWF

Started assimilating COSMIC data in 2006

Temperature error – weather model

Standard deviation

Stratosphere, Summer Hemisphere

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The impact of using RO observations on forecasts of

Hurricane Ernesto’s genesis (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)

Centr

al S

ea L

evel P

ressure

(hP

a)

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Day of August 2006

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Hurricane Intensity Estimation


GNSS RO-based Method of

Estimating Hurricane Intensity

GNSS RO-based Method of

Estimating Hurricane Intensity

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.

First estimates of hurricane intensities

(maximum wind speed) from GPS radio

occultations (GPSRO) and the Wong and

Emanuel [2007] hurricane model.

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

Remote sensing of hurricane intensity could greatly improve

quantity of timely data

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Science Applications


3. Expansion of the tropical belt

01/96

Pre

ssu

re leve

l (h

Pa

)

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

1. Climate monitoring

Tem

pera

ture

(K

)

2. Characterizing the

planetary boundary layer

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4. Electron density irregularities

Wavele

ng

th, km

W

avele

ng

th, km

Altitude, km

Auroral

(64–80o)

Polar

(> 80o)

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COSMIC-2/FORMOSAT-7 Mission


COSMIC-2A launch, 6 satellites: ~March 2018

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COSMIC-2/FORMOSAT-7 Mission


L. Cucurull, NOAA, 2017

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COSMIC-2 observa on density

6

Spa aldistribu onoftheCOSMIC-2AandCOSMIC-2Bobserva onsfor(a)±3hoursassimila on mewindow

Ahigh-inclina onlaunchisnecessarytoobtainglobalanduniformdistribu onofROprofilesandtoimproveweatherforecastskillglobally

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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

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Summary

November 15, 2017 JPL/Caltech PV/JPL

• 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.

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