1. WG Climate, March 6 – 9, 2016 Paris, France
Report of the CGMS International Radio Occultation Working Group – IROWG
Ulrich Foelsche
Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics (IGAM/IP)
Wegener Center for Climate and Global Change
University of Graz, Austria

2. IROWG Rapporteur: Tony Mannucci, JPL, USA
Co-chairs: Sean Healy, ECMWF, UK Ulrich Foelsche, Uni-Graz, Austria
Co-chairs until 2015:
Axel von Engeln, EUMETSAT, Germany
Dave Ector, UCAR/NOAA, USA
SCOPE-CM activity RO-CLIM, Hans Gleisner, DMI, DK Focus: structural uncertainty in Radio Occultation climatologies

3. GNSS Radio Occultation
Radio Signals
  20 cm
Transmitter
GPS GALILEO BeiDou GLONASS
Receiver
MetOp, COSMIC, CHAMP, GRACE, COSMIC-2, FY-3C …

4. Atmospheric Phase Delay
Radio Occultation
Phase Delay
Orbit Information, Ionospheric Correction
Atmospheric Delay
Atmospheric Phase Delay
~ 1 mm Mesopause
~ 20 cm Stratopause
~ 20 m Tropopause
~ 1- 2 km Surface
Orbit Information
Bending Angle
Refractivity
Abel Transform
Temperature
Water Vapor
Density
Clausius-Mossotti Relation
Temperature
Water Vapor
Hydrostatic Integral
Pressure
Ideal Gas Law
(Dry) Temperature
or both
Stratosphere
Upper
Troposphere
Lower/Middle
Troposphere

5. Observing Climate Properties of Radio occultation (RO) measurements:
Long-term stability, because RO data are self-calibrated to a very high degree
High vertical resolution and high accuracy
Global coverage, equal obs. density (and quality) over oceans and continents
All-weather capability, day and night measurements
Modest horizontal resolution is not a disadvantage, since data have to be averaged anyway for climate applications,
RO data are meanwhile a pillar in NWP, and are the only satellite data, which can be assimilated without bias correction.

6. RO Data Quality Bending Angle Statistics between 65 km and 80 km
“Bias” means – difference to MSIS climatology – very similar for all sats
(UCAR data). Annual and semi-annual cycle.
No indications for instrument degradation or instationarities in the RO records
No (clear) signal of the solar cycle for the CHAMP record
Foelsche et al., AMT 2011, Pirscher, PhD Thesis, 2010

7. Refractivity Consistency
Global, monthly refractivity differences relative to the satellite mean
Further reduced when the estimated sampling errors are subtracted

8. Dry Temp. Consistency
Global, monthly dry temperature differences relative to satellite mean
Sampling errors subtracted 15 – 20 km, 25 – 30 km
Increasing CHAMP-Offset – Stat. Optimization, Background Bias

9. Observing System Operational Backbone:
COSMIC/FORMOSAT-3, 6 sat constellation (USA/Taiwan)
sampling the diurnal cycle, launched 2006, near its end
GRAS on MetOPs (EUMETSAT), sun-sync
Future:
EPS-SG (EUMETSAT)
COSMIC-2/FORMOSAT-7 equatorial (NOAA, NSPO)
6 sat, 24° inclination, launch late 2016 (?)
COSMIC-2 polar, 6 sat 72° inclination (???)
Main IROWG recommendation (John, please help!):
Ensure that both, equatorial and polar components of COSMIC-2 are fully funded and launched

10. Next IROWG Workshop
IROWG-5 + OPAC-6 Workshop, Seggau Castle September 8 – 14, 2016 wegcwww.uni-graz.at/opacirowg2016

11. Thank you!
Merci!