The impact of GPS radio occultation assimilation at the Met Office

Rennie, Michael

doi:10.1002/qj.521

Cited by 111 publications

(97 citation statements)

References 24 publications

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“…The impressive success of the GPS/MET experiment stimulated further development of RO satellites and constellations, including CHAMP and COSMIC experiments. Currently, RO sounding is an important method of monitoring meteorological parameters of the Earth's atmosphere; RO data are assimilated by the world's leading numerical weather prediction centers Yunck et al, 2000;Steiner et al, 2001;Pingel and Rhodin, 2009;Poli et al, 2009;Cucurull, 2010;Poli et al, 2010;Rennie, 2010).…”

Section: Introductionmentioning

confidence: 99%

Fluctuations of radio occultation signals in sounding the Earth's atmosphere

2018

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Abstract. We discuss the relationships that link the observed fluctuation spectra of the amplitude and phase of signals used for the radio occultation sounding of the Earth's atmosphere, with the spectra of atmospheric inhomogeneities. Our analysis employs the approximation of the phase screen and of weak fluctuations. We make our estimates for the following characteristic inhomogeneity types: (1) the isotropic Kolmogorov turbulence and (2) the anisotropic saturated internal gravity waves. We obtain the expressions for the variances of the amplitude and phase fluctuations of radio occultation signals as well as their estimates for the typical parameters of inhomogeneity models. From the GPS/MET observations, we evaluate the spectra of the amplitude and phase fluctuations in the altitude interval from 4 to 25 km in the middle and polar latitudes. As indicated by theoretical and experimental estimates, the main contribution into the radio signal fluctuations comes from the internal gravity waves. The influence of the Kolmogorov turbulence is negligible. We derive simple relationships that link the parameters of internal gravity waves and the statistical characteristics of the radio signal fluctuations. These results may serve as the basis for the global monitoring of the wave activity in the stratosphere and upper troposphere.

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Section: Introductionmentioning

confidence: 99%

Fluctuations of radio occultation signals in sounding the Earth's atmosphere

2018

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“…Com isso, de modo geral mostra-se que ao assimilar dados de refratividade do MetOp-B são impactados também indi-retamente variáveis como UVEL e VVEL dadas as melhorias observadas. Resultado similar a esse foi encontrado em Rennie (2008). Outra variável que reflete essa mesma influência é a VTMP, revelando uma intensificação das melhorias obtidas na TEMP.…”

Section: Resultsunclassified

Impacto da Assimilação de Perfis de Refratividade do Satélite Metop-B nas Previsões de Tempo do CPTEC/INPE Durante os Meses de Janeiro e Agosto de 2014

Banos

Sapucci

Avanço

et al. 2018

Rev. bras. meteorol.

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Recebido em 23 de Março de 2017 -Aceito em 22 de Agosto de 2017 ResumoAtualmente tem crescido o número de satélites de órbita baixa dedicados à rádio ocultação dos sinais do Sistema de Posicionamento Global (GPS). O MetOp-B é um desses novos satélites, mas ainda não foi explorado na assimilação de dados realizada no Brasil. Com o intuito de incluir essa fonte de observação na base de dados utilizada na assimilação do CPTEC/INPE e avaliar o impacto da mesma na melhoria do desempenho do Modelo de Circulação Geral Atmosférica, foi realizado um experimento para os meses de janeiro e agosto de 2014. Os resultados foram comparados com um experimento controle, onde tais dados não foram assimilados. Os resultados mostraram que a inclusão dos perfis de refratividade do MetOp-B impactou beneficamente na assimilação de uma maior quantidade de dados dos demais satélites em operação, COSMIC, TerraSAR-X e MetOp-A. No mês de agosto foram observados resultados mais proeminentes, pois o ganho em valores da raiz do erro quadrático médio foi maior que 40% nas variáveis de estado nas primeiras 24 h de previsão no Hemisfério Sul, variáveis essas diretamente relacionadas com os valores de refratividade. Além disso, os valores do coeficiente de correlação de anomalia sobre a América do Sul indicaram que a inclusão dos dados do MetOp-B impactou de forma indireta as componentes zonal e meridional do vento em 250 hPa, o que evidencia a importância de assimilar tais dados. Palavras-chave: rádio ocultação GPS, assimilação de dados, MetOp-B. Impact of the Assimilation of Metop-B Satellite Refractivity Profiles in the Forecasts of the CPTEC/INPE During the Months of January and August 2014Abstract Currently, there is an increase in the number of low orbit satellites dedicated to radio occultation of GPS signals. The MetOp-B is one of these new satellites, but it has not been explored in the data assimilation performed in Brazil. In order to include this source of observation in the database used in the assimilation of the CPTEC/INPE and evaluate its impact in the performance of the Atmospheric Global Circulation Model used operationally at the center, an experiment with data from January and August 2014 was executed. The results were compared with another experiment without assimilating those data, which showed that the inclusion of the MetOp-B refractivity profiles, has impacted beneficially the assimilation of more data from the other satellites in use, such as COSMIC, TerraSAR-X and MetOp-A. The most prominent results were observed in August, with root mean squared gain values greater than 40% in the state variables for the 24-h forecast over the Southern Hemisphere, variables that are directly related to the refractivity values. Beyond that, the anomaly correlation coefficient values over South America indicated that, adding the MetOp-B data, the zonal and meridional wind components at 250 hPa were indirectly impacted, showing the importance of assimilate such data.

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“…Radio occultation has otherwise provided a very significant amount of atmospheric data worldwide, which has been of particular value over remote areas including oceans and polar regions, e.g. Healy and Thépaut (2006), Cucurull et al (2007), Deblonde (2008), andRennie (2008). These same studies of forecast impact indicate that the low troposphere is the region where direct (refracted-only) radio occultations are less accurate and thus it is here that adding supplemental information would be most helpful.…”

Section: Introductionmentioning

confidence: 95%

Information content in reflected signals during GPS Radio Occultation observations

2018

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Abstract. The possibility of extracting useful information about the state of the lower troposphere from the surface reflections that are often detected during GPS radio occultations (GPSRO) is explored. The clarity of the reflection is quantified, and can be related to properties of the surface and the low troposphere. The reflected signal is often clear enough to show good phase coherence, and can be tracked and processed as an extension of direct non-reflected GPSRO atmospheric profiles. A profile of bending angle vs. impact parameter can be obtained for these reflected signals, characterized by impact parameters that are below the apparent horizon, and that is a continuation at low altitude of the standard non-reflected bending angle profile. If there were no reflection, these would correspond to tangent altitudes below the local surface, and in particular below the local mean sea level. A forward operator is presented, for the evaluation of the bending angle of reflected GPSRO signals, given atmospheric properties as described by a numerical weather prediction system. The operator is an extension, at lower impact parameters, of standard bending angle operators, and reproduces both the direct and reflected sections of the measured profile. It can be applied to the assimilation of the reflected section of the profile as supplementary data to the direct section. Although the principle is also applicable over land, this paper is focused on ocean cases, where the topographic height of the reflecting surface, the sea level, is better known a priori.

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The impact of GPS radio occultation assimilation at the Met Office

Cited by 111 publications

References 24 publications

Fluctuations of radio occultation signals in sounding the Earth's atmosphere

Fluctuations of radio occultation signals in sounding the Earth's atmosphere

Impacto da Assimilação de Perfis de Refratividade do Satélite Metop-B nas Previsões de Tempo do CPTEC/INPE Durante os Meses de Janeiro e Agosto de 2014

Information content in reflected signals during GPS Radio Occultation observations

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