FORMOSAT-3/COSMIC science mission update

Wu, Bor-Han; Chu, Vicky; Chen, Paul; Ting, T. C. T.

doi:10.1007/s10291-005-0140-z

Cited by 43 publications

(27 citation statements)

References 36 publications

(29 reference statements)

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“…In the future we will operationally include also data from the non-continuous SAC-C and GRACE RO missions, as well as data from the operational MetOp mission and the FORMOSAT-3/COSMIC system (Constellation Observing System for Meteorology, Ionosphere, and Climate), a Taiwan/U.S. RO mission consisting of six receiving satellites, which was successfully launched in April 2006 Wu et al 2005). COSMIC is expected to obtain *2,500 setting and rising occultations per day, providing a very valuable database for RO based climatologies.…”

Section: Ecmwf Analysis Datamentioning

confidence: 99%

Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

et al. 2007

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High quality observations of the atmosphere are particularly required for monitoring global climate change. Radio occultation (RO) data, using Global Navigation Satellite System (GNSS) signals, are well suited for this challenge. The special climate utility of RO data arises from their long-term stability due to their self-calibrated nature. The German research satellite CHAllenging Minisatellite Payload for geoscientific research (CHAMP) continuously records RO profiles since August 2001 providing the first opportunity to create RO based climatologies for a multi-year period of more than 5 years. A period of missing CHAMP data from July 3, 2006 to August 8, 2006 can be bridged with RO data from the GRACE satellite (Gravity Recovery and Climate Experiment). We have built seasonal and zonal mean climatologies of atmospheric (dry) temperature, microwave refractivity, geopotential height and pressure with 10°lat-itudinal resolution. We show representative results with focus on dry temperatures and compare them with analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Although we have available only about 150 CHAMP profiles per day (compared to millions of data entering the ECMWF analyses) the overall agreement between 8 and 30 km altitude is in general very good with systematic differences \0.5 K in most parts of the domain. Pronounced systematic differences (exceeding 2 K) in the tropical tropopause region and above Antarctica in southern winter can almost entirely be attributed to errors in the ECMWF analyses. Errors resulting from uneven sampling in space and time are a potential error source for single-satellite climatologies. The average CHAMP sampling error for seasonal zonal means is \0.2 K, higher values occur in restricted regions and time intervals which can be clearly identified by the sampling error estimation approach we introduced (which is based on ECMWF analysis fields). The total error of this new type of temperature climatologies is estimated to be \0.5 K below 30 km. The recently launched Taiwan/U.S. FORMOSAT-3/COSMIC constellation of 6 RO satellites started to provide thousands of RO profiles per day, but already now the single-satellite CHAMP RO climatologies improve upon modern operational climatologies in the upper troposphere-lower stratosphere and can act as absolute reference climatologies for validation of more bias-sensitive climate datasets and models.

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Section: Ecmwf Analysis Datamentioning

confidence: 99%

Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

et al. 2007

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“…Typically, the observation error standard deviation is estimated to amount to 1 to 4 µrad at this altitude. For more recent RO receivers with nominally higher SNR like the GNSS Receiver for Atmospheric Sounding (GRAS) on MetOp (GRAS-SAG, 1998;Loiselet et al, 2000) or the Integrated GPS Occultation Receivers (IGOR) on the COSMIC constellation (Rocken et al, 2000;Wu et al, 2005), it might be meaningful to raise the lower boundary.…”

Section: The Champclim Retrievalmentioning

confidence: 99%

Retrieval of temperature profiles from CHAMP for climate monitoring: intercomparison with Envisat MIPAS and GOMOS and different atmospheric analyses

et al. 2007

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Abstract. This study describes and evaluates a Global Navigation Satellite System (GNSS) radio occultation (RO) retrieval scheme particularly aimed at delivering bias-free atmospheric parameters for climate monitoring and research. The focus of the retrieval is on the sensible use of a priori information for careful high-altitude initialisation in order to maximise the usable altitude range. The RO retrieval scheme has been meanwhile applied to more than five years of data (September 2001 to present) from the German CHAllenging Minisatellite Payload for geoscientific research (CHAMP) satellite. In this study it was validated against various correlative datasets including the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Global Ozone Monitoring for Occultation of Stars (GO-MOS) sensors on Envisat, five different atmospheric analyses, and the operational CHAMP retrieval product from GeoForschungsZentrum (GFZ) Potsdam. In the global mean within 10 to 30 km altitude we find that the present validation observationally constrains the potential RO temperature bias to be <0.2 K. Latitudinally resolved analyses show biases to be observationally constrained to <0.2-0.5 K up to 35 km in most cases, and up to 30 km in any case, even if severely biased (about 10 K or more) a priori information is used in the high altitude initialisation of the retrieval. No evidence is found for the 10-35 km altitude range of residual RO bias sources other than those potentially propagated downward from initialisation, indicating that the widely quoted RO promise of "unbiasedness and long-term stability due to intrinsic self-calibration" can indeed be realised given care in the data processing to strictly limit structural uncertainty.Correspondence to: A. Gobiet (andreas.gobiet@uni-graz.at)The results thus reinforce that adequate high-altitude initialisation is crucial for accurate stratospheric RO retrievals. The common method of initialising, at some altitude in the upper stratosphere, the hydrostatic integral with an upper boundary temperature or pressure value derived from meteorological analyses is prone to introduce biases from the upper boundary down to below 25 km. Also above 30 to 35 km, GNSS RO delivers a considerable amount of observed information up to around 40 km, which is particularly interesting for numerical weather prediction (NWP) systems, where direct assimilation of non-initialised observed RO bending angles (free of a priori) is thus the method of choice. The results underline the value of RO for climate applications.

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“…In April 2006, FORMOSAT-3/COS MIC (Formosa Satellite Mis sion 3/Con stel la tion Ob serv ing Sys tem for Mete orology, Ion o sphere, and Cli mate, F3C), a Tai wan/US RO mis sion con sist ing of six re ceiv ing sat el lites Wu et al 2005;Schreiner et al 2007) was suc cess fully launched, pro vid ing up to ~2500 RO pro files per day. All six F3C sat el lites were launched from a sin gle launch vehicle into a park ing or bit with ~515 km or bit al ti tude.…”

Section: Introductionmentioning

confidence: 99%

Assessing the Climate Monitoring Utility of Radio Occultation Data: From CHAMP to FORMOSAT-3/COSMIC

Foelsche¹,

Pirscher²,

Borsche³

et al. 2009

Terr. Atmos. Ocean. Sci.

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AB STRACTRa dio Occultation (RO) data, us ing Global Po si tion ing Sys tem (GPS) sig nals, de liver high qual ity ob ser va tions of the at mo sphere, which are well suited for mon i tor ing global cli mate change. The spe cial cli mate util ity of RO data arises from their ac cu racy and long-term sta bil ity due to self-cal i bra tion. Launched in 2000, the Ger man re search sat el lite CHAMP (CHAl leng ing Minisatellite Pay load for geoscientific re search) pro vides the first op por tu nity to cre ate RO based climatologies. Over lap with data from the Tai wan/US FORMOSAT-3/COS MIC (Formosa Sat el lite Mis sion 3/Con stel la tion Ob serv ing Sys tem for Me te o rol ogy, Ion o sphere and Cli mate, F3C) mis sion al lows the test ing for con sis tency of climatologies de rived from dif fer ent sat el lites. We show ini tial re sults for zonal mean climatologies as well as trop i cal tropo pause pa ram e ters based on F3C RO data. Our re sults in di cate ex cel lent agree ment be tween RO climatologies from dif fer ent F3C sat el lites as well as be tween data from dif fer ent RO mis sions. Af ter sub trac tion of the es ti mated re spec tive sam pling er ror, sea sonal tem per a ture climatologies de rived from dif fer ent F3C sat el lites are in agree ment to within < 0.1 K al most ev ery where in the con sid ered do main be tween 8 and 35 km al ti tude. Monthly mean trop i cal tropo pause (lapse rate) tem per a tures and al ti tudes de rived from four dif fer ent RO mis sions show re mark able con sis tency (< 0.2 -0.5 K, < 50 -100 m) and in di cate that data from dif fer ent RO mis sions can in deed be com bined with out need for inter-cal i bra tion. F3C fi nal con stel la tion sam pling er ror es ti ma tion shows a small oscillating local time related error (±0.03 K amplitude) in the extratropics. Sci., 20, 155-170, doi: 10.3319/TAO.2008.01.14.01(F3C) IN TRO DUC TIONAc cu rate, con sis tent long-term data are re quired as ba sis for cli mate stud ies and for at tempts to de tect, un der stand, and at trib ute cli mate vari abil ity and change. Our knowl edge about the tem per a ture evo lu tion in the free at mo sphere is still lim ited, de spite no ta ble en deav ors to build long term upper air tem per a ture re cords. This has been done us ing data from MSU (Mi cro wave Sound ing Unit) as well as AMSU (Ad vanced MSU) in stru ments on board po lar or biting sat el lites (e.g., Christy and Spencer 2005;Mears and Wentz 2005;Vinnikov et al. 2006) as well as us ing data from ra dio sondes (e.g., Sherwood et al. 2005;Thorne et al. 2005). Af ter many years of in tense dis cus sions, tem per a ture trend es ti mates based on these data sets now seem to be con sistent with sur face warm ing es ti mates and re sults from climate mod els but sig nif i cant dis crep an cies still re main (Karl et al. 2006). In de pend ent high-qual ity up per air re cords are there fore de sir able.A prom is ing source for such data sets is the Global Po sition ing Sys tem (GPS) Ra dio Occultation (RO) tech nique, com bin in...

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FORMOSAT-3/COSMIC science mission update

Cited by 43 publications

References 36 publications

Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

Retrieval of temperature profiles from CHAMP for climate monitoring: intercomparison with Envisat MIPAS and GOMOS and different atmospheric analyses

Assessing the Climate Monitoring Utility of Radio Occultation Data: From CHAMP to FORMOSAT-3/COSMIC

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