2006
DOI: 10.1256/qj.04.182
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Assimilation experiments with CHAMP GPS radio occultation measurements

Abstract: SUMMARYA one-dimensional bending-angle observation operator for assimilating GPS radio occultation (RO) measurements has been integrated into the ECMWF four-dimensional variational assimilation (4D-Var) system. We have performed forecast impact experiments with 60 days of CHAMP RO measurements, in addition to the latest set of conventional and satellite data that are assimilated operationally, including radiances from the Atmospheric Infrared Sounder. It is demonstrated that the CHAMP measurements provide extr… Show more

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Cited by 264 publications
(215 citation statements)
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“…Although the primary focus of this work is the forecast impact of COSMIC measurements, we have also assimilated CHAMP and GRACE-A measurements 112 S. B. Healy (Wickert et al, 2001;Beyerle et al, 2005;Wickert et al, 2005) when they are available. The GPSRO bending angle profiles, α, are assimilated using a onedimensional operator (Healy and Thépaut, 2006).…”
Section: Description Of Assimilation System and Observationsmentioning
confidence: 99%
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“…Although the primary focus of this work is the forecast impact of COSMIC measurements, we have also assimilated CHAMP and GRACE-A measurements 112 S. B. Healy (Wickert et al, 2001;Beyerle et al, 2005;Wickert et al, 2005) when they are available. The GPSRO bending angle profiles, α, are assimilated using a onedimensional operator (Healy and Thépaut, 2006).…”
Section: Description Of Assimilation System and Observationsmentioning
confidence: 99%
“…Above 10 km, the standard deviation of the error is assumed to be 1% of the observed value, until this reaches a lower absolute limit of 6 × 10 −6 radians (6 µrad). Note that the assumed errors in the Troposphere used here are larger than those used in previous work (Healy and Thépaut, 2006). Given the order of magnitude increase in the number of GPSRO observations, it was decided initially to adopt a conservative approach and reduce the weight given to an individual profile.…”
Section: Description Of Assimilation System and Observationsmentioning
confidence: 99%
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“…A atmosfera afeta as transmissões dos sinais durante essa ocultação fazendo com que as ondas viagem relativamente mais lentas do que no vácuo e em uma trajetória curva, ao invés de em linha reta (Bevis et al, 1992). Desde o ponto de vista da RO, na literatura a atmosfera é dividida em duas camadas de referência: a ionosfera, que corresponde à camada superior da atmosfera da Terra ionizada pela radiação solar, estendendo-se desde aproximadamente os 60 km até acima dos 1000 km, e a atmosfera neutra, onde os componentes são eletricamente neutros e que se estende desde a superfície até próximo aos 60 km de altura (Jin et al, 2014). Os sinais são afetados pelos gradientes da densidade de elétrons na ionosfera e pela densidade e gradientes de vapor d'água na atmosfera neutra.…”
Section: Técnica De Rádio Ocultação Por Gps (Ro-gps)unclassified
“…Assim, a eficácia dos modelos de previsão é cada vez mais dependente de todo o conjunto dos sistemas de observações da atmosfera terrestre (Ucar, 2015). Atualmente com a melhoria dos instrumentos de medição, o desenvolvimento de novas metodologias, em especial as baseadas em satélites, e densificação das redes terrestres de observações, bem como das técnicas de processamento de dados, tem-se alcançado uma melhoria nas previsões de tempo e clima (Jin et al, 2014).…”
Section: Introductionunclassified