The Dynamics of an Upper-Level Trough in the Baroclinic Westerlies: Analysis Based upon Data from a Wind Profiler Network

Bluestein, Howard B.; Speheger, Douglas A.

doi:10.1175/1520-0493(1995)123<2369:tdoaul>2.0.co;2

Cited by 7 publications

(3 citation statements)

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“…A Alta da Bolívia é notada, mas não apresenta um formato simétrico e seu centro não está bem definido. Já o VCAN extratropical ainda estava na sua fase de cavado, com grande amplitude -compondo uma onda curta baroclínica de oeste, típica de sistemas transientes (maiores discussões sobre ondas baroclínicas de oeste em altos níveis são facilmente encontradas na literatura, como por exemplo em Keyser & Shapiro (1986) e Bluestein & Speheger (1995)). Nota-se que o cavado é difluente, o que tende a estar associado à instabilidades em superfície (Bluestein, 1993), e possui inclinação horizontal do seu eixo para oeste, o que concorda com a literatura, como pode ser visto em Satyamurty et al (1998).…”

Section: Análise Sinóticaunclassified

Case Study of Upper Tropospheric Meteorological Systems on South America: Synoptic Analysis

Nunes

2017

Anuário IGEO UFRJ

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ResumoO Vórtice ciclônico de altos níveis (VCAN) sobre o nordeste brasileiro (NeB) e a Alta da Bolívia (AB) são os típicos sistemas de pressão em altos níveis (250 hPa) da América do Sul, especialmente nas estações mais quentes. Somados a eles, também pode-se considerar o VCAN extratropical, de característica transiente e encontrado o ano todo. Neste trabalho, é apresentada uma análise sinótica, baseada na literatura especializada, de um caso observado em 01 de fevereiro de 2005 em que os três sistemas ocorreram simultaneamente. Algumas características encontradas na literatura foram observadas nos sistemas deste caso. O campo de temperatura mais associado ao sistema extratropical foi o de 500 hPa, e não o de 250 hPa. Os movimentos verticais mais relevantes foram encontrados somente no sistema extratropical: intensos movimentos ascendentes à sotavento do eixo do cavado em altos níveis. Não se encontrou um sistema em superfície especificamente associado ao VCAN do NeB, enquanto que se observou a baixa continental (ou Baixa do Chaco) associada à Alta da Bolívia e um intenso ciclone extratropical associado ao VCAN extratropical. Tal ciclone em superfície acarretou em vento sul e consequente resfriamento da camada, o que pôde ser observado pela amplitude do cavado em altos níveis, o que é raro para esta época do ano. Palavras-chave: vórtices ciclônicos de altos níveis; Alta da Bolívia; vento térmico; Palmén; Palmer AbstractThe upper tropospheric cyclonic vortex (VCAN) over northeastern Brazil (NeB) and the Bolivian High (AB) are the South America typical upper level (250 hPa) pressure systems, especially in warmer seasons. Besides these, one can also consider the extratropical VCAN, which has transient feature and is found throughout the year. In this work is presented a synoptic analysis, based on the specialized literature, of a case observed in February 01, 2005, when the three systems occurred simultaneously. Some features found in literature were noted in the systems of this case. The temperature field most associated to the extratropical system was 500 hPa and not 250 hPa. The most significant vertical movements were only found in extratropical system: intense upward movements in the lee of the upper tropospheric trough axis. It has found no system specifically associated to VCAN of NeB, while it was observed the association between the continental low (or Chaco Low) and the Bolivian High and an intense extratropical cyclone associated to extratropical VCAN. Such surface cyclone carries on a southerly and consequent cooling of the layer, what could be observed by the amplitude of the upper tropospheric trough, which is unusual in this season.

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Section: Análise Sinóticaunclassified

Case Study of Upper Tropospheric Meteorological Systems on South America: Synoptic Analysis

Nunes

2017

Anuário IGEO UFRJ

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“…The relative high spatial and temporal resolution of the network over central United States makes it possible to resolve meteorological features, such as sharp baroclinic zones and gravity waves (Bluestein and Speheger 1995;Trexler and Koch 2000). Substantial efforts have also been made to retrieve the mass field from the wind profiler data to further diagnose the structure of these phenomena (e.g., Kuo and Anthes 1985;Gal-Chen 1988;Bussinger et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Assimilation of Wind Profiler Data in the Canadian Meteorological Centre’s Analysis Systems

St‐James¹,

Laroche²

2005

Journal of Atmospheric and Oceanic Technology

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Real-time horizontal wind observations from the National Oceanic and Atmospheric Administration's (NOAA's) Profiler Network (NPN) are assessed in preparation for their assimilation in the Canadian Meteorological Centre (CMC) analysis systems. As a first step, radiosonde winds from 20 stations were compared to the central U.S. profiler stations over the 2001/02 winter season. It was found that profilers are at least as good as conventional radiosonde data. The 2001/02 winter season data were also used to examine the vertical correlation structure of the observation error for profilers. Using a statistical analysis of innovations, the observation error standard deviation of the wind components is estimated as 2.2 m s Ϫ1 and the vertical correlation length is approximately 500 m. These results suggest that the data are vertically correlated because they are available every 250 m. Therefore, a thinning process is proposed in which one out of three data are selected in the vertical for each station.

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“…Six-minute samples and hour-ly consensus averaging of wind profiles constitute a valuable dataset with which to identify and understand phenomena such as gravity waves, convective systems, frontal structure, and jet streak evolution (e.g., Zamora et al 1987;Carlson and Forbes 1989;Bluestein and Speheger 1995;Ralph et al 1995;Trexler and Koch 2000).…”

Section: Introductionmentioning

confidence: 99%

Extraction of Geopotential Height and Temperature Structure from Profiler and Rawinsonde Winds

2001

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Mesoscale height and temperature fields can be extracted from the observed wind field by making use of the full divergence equation. Mass changes associated with irrotational ageostrophic motions are retained for a nearly complete description of the height field. Above the boundary layer, in the absence of friction, the divergence equation includes terms composed of the components of the wind and a Laplacian of the geopotential height field. Once the mass field is determined, the thermal structure is obtained through application of the hypsometric equation.In this paper an error analysis of this divergence method is undertaken to estimate the potential magnitude of errors associated with random errors in the wind data. Previous applications of the divergence method have been refined in the following ways. (i) The domain over which the method is applied is expanded to encompass the entire STORM-FEST domain. (ii) Wind data from 23 profiler and 38 rawinsonde sites are combined in the analysis. (iii) Observed profiler and rawinsonde data are interpolated to grid points through a modified objective analysis, and (iv) the variation in elevation of the profiler sites is taken into account.The results of the application of the divergence method to the combined wind data from profiler and rawinsonde sites show good agreement between the retrieved heights and temperatures and the observed values at rawinsonde sites. Standard deviations of the difference between the retrieved and observed data lie well within the precision of the rawinsonde instruments. The difference field shows features whose magnitude is significantly larger than the errors predicted by the error analysis, and these features are systematic rather than random in nature, suggesting that the retrieved fields are able to resolve mesoscale signatures not fully captured by the rawinsonde data alone.The divergence method is also applied solely to the profiler data to demonstrate the potential of the divergence method to provide mass and thermal fields on a routine basis at synoptic times when operational rawinsonde data are not available. A comparison of the heights derived from the profiler winds with those independently measured by rawinsondes indicates that valuable information on the evolution of atmospheric height and temperature fields can be retrieved between conventional rawinsonde release times through application of the divergence method. The implications of the results for applications of the method in weather analysis and in numerical weather prediction are discussed.

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The Dynamics of an Upper-Level Trough in the Baroclinic Westerlies: Analysis Based upon Data from a Wind Profiler Network

Cited by 7 publications

References 0 publications

Case Study of Upper Tropospheric Meteorological Systems on South America: Synoptic Analysis

Case Study of Upper Tropospheric Meteorological Systems on South America: Synoptic Analysis

Assimilation of Wind Profiler Data in the Canadian Meteorological Centre’s Analysis Systems

Extraction of Geopotential Height and Temperature Structure from Profiler and Rawinsonde Winds

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