I nstitute for G eophysics, A strophysics, and M eteorology / U niversity of G raz A tmospheric R emote S ensing and Cli mate Sys tem Research Group ARSCliSys — on the art of understanding the climate system Climate Change Monitoring by Climate Change Monitoring by Radio Occultation: Radio Occultation: From Simulation Studies via CHAMP to From Simulation Studies via CHAMP to COSMIC and ACE+ Constellations COSMIC and ACE+ Constellations Gottfried Kirchengast ARSCliSys Research Group, IGAM, University of Graz, Austria ( www.uni-graz.at/igam-arsclisys ) Invited Talk; COSMIC RO Science Workshop/Session “Climate+Meteorology“; August 23, 2002; UCAR, Boulder, CO, U.S.A.
ARSCliSys Research Group Atmospheric Remote Sensing and Climate System — ARSCliSys — on the art of understanding the climate system (founded 1996, status August 2002) RO RO to... Thanks to... RO Thanks Gottfried n o t i a t l u c c O Sabine Christoph o Kirchengast d i a RO R - O R Tschürtz Bichler Ulrich Andrea Foelsche Steiner Members (at IGAM) Johannes Head Marc Fritzer Schwärz 2 Senior Scientists RO 2 Post-Doc Scientists 5 Ph.D. Students 1 M.Sc. Student 1 Admin. Assistant RO Colleagues Colleagues at IGAM Worldwide RO RO Christian Andreas Retscher Gobiet Christoph Armin Josef Rehrl Löscher Ramsauer
Climate Change Monitoring by Radio Occultation Climate Change Monitoring by Radio Occultation Outline Outline • Radio Occultation (RO) – Climate Change Monitoring Promise - on the principle of spaceborne occultation measurements - RO methods (GNSS-LEO, LEO-LEO) and close friends - relevance for climate monitoring and research • Simulation Studies – Climate Monitoring Simulation 2001-2025 - a climate GNSS RO observing system simulation experiment - results of performance analysis (JJA 1997 “testbed” analysis) - perspectives for the full experiment (time period 2001-2025) • CHAMP, COSMIC, ACE+,… – Current & Future RO Research - RO-related research aims at IGAM/Univ. of Graz - on current research (START- and ENVI-ATCHANGE, ESA-R&D) - on initialized future research (ECCMAR/CHAMPCLIM, ACE+) • Concluding Remarks
Climate Change Monitoring by Radio Occultation Climate Change Monitoring by Radio Occultation RO – – Climate Change Monitoring Promise Climate Change Monitoring Promise RO • Radio Occultation (RO) – Climate Change Monitoring Promise - on the principle of spaceborne occultation measurements - RO methods (GNSS-LEO, LEO-LEO) and close friends - relevance for climate monitoring and research • Simulation Studies – Climate Monitoring Simulation 2001-2025 - a climate GNSS RO observing system simulation experiment - results of performance analysis (JJA 1997 “testbed” analysis) - perspectives for the full experiment (time period 2001-2025) • CHAMP, COSMIC, ACE+,… – Current & Future RO Research - RO-related research aims at IGAM/Univ. of Graz - on current research (START- and ENVI-ATCHANGE, ESA-R&D) - on initialized future research (ECCMAR/CHAMPCLIM, ACE+) • Concluding Remarks
− Climate Change Monitoring Promise RO − Climate Change Monitoring Promise RO principle of spaceborne principle of spaceborne occultation measurements occultation measurements Occultation Methods Signal • exploit extinction and/or refraction of Source EM Signals electromagnetic signals along limb paths Signal • providing measurements of transmission Source and/or Doppler shift profiles LEO Sensor • leading via absorption or column density, bending angle, and (complex) refractivity Signal Source • to key climate parameters such as temperature, humidity, ozone, and geopotential height. [basic figures from D. Feng, Univ. of Arizona, priv. communications, 2001 (modified)] Inversion of Occultation Data • is a virtually well-posed and close LEO to linear problem solved by Transmitted • direct inversion/retrieval or Signals Received Signals • data assimilation.
− Climate Change Monitoring Promise RO − Climate Change Monitoring Promise RO GNSS- GNSS -LEO radio occultation LEO radio occultation GNSS-LEO Radio Occultation GNSS • exploits (mainly) refraction of L1 and L2 Signals L-band signals along limb paths • providing self-calibrated GNSS measurements of Doppler shift LEO • leading via atmospheric bending angle and refractivity profiles GNSS • to key atmosphere and climate [basic figure from D. Feng, Univ. of Arizona, priv. communications, 2001 (modified)] parameters such as temperature, humidity, and geopotential height. Inversion of GNSS Occultation Data • is a virtually well-posed and close to linear problem solved by • direct inversion/retrieval or • data assimilation.
− Climate Change Monitoring Promise RO − Climate Change Monitoring Promise RO LEO- LEO -LEO radio occultation LEO radio occultation LEO-LEO Radio Occultation LEO • exploits absorption & refraction of X/K Band Signals (9.8, 17.2, 22.6 GHz) X/K-band signals along limb paths • providing self-calibrated measure- ments of attenuation and Doppler LEO • leading via absorption, bending angle, and (complex) refractivity Atmosphere • to key atmosphere and climate parameters such as temperature T , [basic figures from D. Feng, Univ. of Arizona, priv. communications, 2001 (modified)] humidity q , and geopotential height. Inversion of LEO-LEO Occultation Data LEO Tx • similar to GNSS-LEO but providing T LEO Rx and q independently; also solved by Transmitted • direct inversion/retrieval or Signals Received Signals • data assimilation.
− Climate Change Monitoring Promise RO − Climate Change Monitoring Promise RO close friends of radio occultation close friends of radio occultation Close friends of GNSS- and LEO-LEO occultation are Stellar and Solar/Lunar Occultation GNSS-LEO occultation exploits refraction of radio signals along limb paths Stellar and Solar/Lunar occultation exploit extinction of optical signals along limb paths I ( z i ) I 0 I ( z i ) (Source: Dornier Satellite Systems, Friedrichshafen, Germany, 1998) Tr ( z i ) = Transmission I 0 (Source: C. Zehner, ESA/ESRIN, Frascati, Italy, 2001; adapted) Intensity Intensity � � Wavelength Wavelength Wavelength 80 km I 0 50 km I ( z i ) z 20 km I ( z i ) LEO-LEO occultation exploits extinction & refraction of MW signals along limb paths • Each of these complementary methods exploits the unique properties of the occultation principle. LEO Tx LEO Rx • Each of them addresses a different height range/ Transmitted Received Signal different parameters with optimal sensitivity. Signal (Source: D. Feng et al., Inst. of Physics/Univ. of Arizona, U.S.A., 2001; adapted)
− Climate Change Monitoring Promise RO − Climate Change Monitoring Promise RO relevance for climate monitoring and research relevance for climate monitoring and research ...from the 9 “high priority areas for action” noted in the recent IPCC 2001 report (Summary for Policymakers, IPCC Working Group I, page 17): “- sustain and expand the observational foundation for climate studies by providing accurate, long-term, consistent data including implementation of a strategy for integrated global observations.” Such accurate, long-term, consistent data on the thermal ( T ), moisture ( q ), and geopotential height ( Z ) structure of the troposphere and stratosphere can be furnished by a constellation of 4 – 24 micro-satellites carrying • GNSS- and LEO-LEO radio occultation sensors (CHAMP, GRACE, COSMIC/BJ-GPS, METOP/GRAS, ACE+/AGRAS&CALLS,...) These occultation sensors deliver an unique combination of • global coverage (equal observation density above oceans as above land) • all-weather capability (virtual insensitivity to clouds and aerosols; wavelengths > 1 cm) • high accuracy and vertical resolution (e.g., T < 1 K, q < 5% at ~1 km resolution) • long-term stability due to intrinsic self-calibration (drifts < 0.1 K, < 2%r.h. / decade)
Climate Change Monitoring by Radio Occultation Climate Change Monitoring by Radio Occultation Climate Monitoring Simulation Study Climate Monitoring Simulation Study • Radio Occultation (RO) – Climate Change Monitoring Promise - on the principle of spaceborne occultation measurements - RO methods (GNSS-LEO, LEO-LEO) and close friends - relevance for climate monitoring and research • Simulation Studies – Climate Monitoring Simulation 2001-2025 - a climate GNSS RO observing system simulation experiment - results of performance analysis (JJA 1997 “testbed” analysis) - perspectives for the full experiment (time period 2001-2025) • CHAMP, COSMIC, ACE+,… – Current & Future RO Research - RO-related research aims at IGAM/Univ. of Graz - on current research (START- and ENVI-ATCHANGE, ESA-R&D) - on initialized future research (ECCMAR/CHAMPCLIM, ACE+) • Concluding Remarks
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