The impact of eta model nesting on the weather forecasts. / O impacto do aninhamento no modelo Eta nas previsões de tempo.

AUTOR(ES)

José Roberto Rozante

DATA DE PUBLICAÇÃO

2001

RESUMO

The increase of resolution of a Limited Area Model usually brings forecast improvements, since the phenomena are more detailed. A high resolution regional model nested in a global model of low resolution is computationally cheaper, however this type of nesting may cause inconsistencies in the representation of the physical processes betewen the two models. In order to reduce these inconsistencies, this work purposes a nesting of the Eta model in the lower resolution operational Eta model at CPTEC. Initially, a smaller domain with higher resolution was set up. Experiments were carried out using initial and lateral boundary conditions from NCEP analyses and also using CPTEC global model. The results from the experiments were compared with the operational Eta model forecast. The results obtained from the experiments using NCEP analyses showed that the reduced versions were correctly configured and boundary conditions well treated, these versions showed important improvements. The experiments with the nested versions and with high resolution showed a reasonable increase of performance during the first 24 hours of integration, however, the rest of the integration period indicated a sharp drop. The performance drop of the sea level pressure in the nested models occurred due to the boundary conditions from the operational Eta model. In the case of precipitation, the model nesting contributed to reasonable improvements in the southern portion of the small domain, although the northern portion errors had been intensified after the nesting. An evaluation of the temperature profiles showed that the vertical structure was well represented by the nested models, with errors smaller than those running from the global model forecasts. The evaluated cases used in this study were a cold case on April, 1999 and a warm one (organised convection) in September 2000. The evaluation was done using observational data from synop, metar, radiossonding and NCEP analyses.

ASSUNTO(S)

boundary conditions meteorology melhoria atmospheric models weather forecasting modelos atmosféricos aninhamento alta resolução impacto meteorologia regional model impact. nesting condições de contorno modelo regional improvement higth resolution previsão de tempo

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