Análise e modelagem dos Distúrbios Ondulatórios de Leste que atuam na costa leste do Nordeste do Brasil

AUTOR(ES)

Roger Rodrigues Torres

DATA DE PUBLICAÇÃO

2008

RESUMO

- This study analyzed the Easterly Waves Disturbances (EWDs) that reached the Eastern Coast of Northeast Brazil (NEB) during the period of April through July of 2005 and 2006. As rainfall in this region has not been forecasted properly from the numerical models, it was carried out 40 experiments with Eta model, using different horizontal resolutions (10 and 40 km) and convective parameterization schemes (Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) schemes). The performances of these experiments were evaluated on 15 May 2005 and 20 June 2006. Using the NCEP analysis data in 700 hPa 26 EWDs were identified on the latitude of 5◦S. The disturbances showed period of 5 days, phase speed of 10 ms-1 and wavelength of about 4000 km. Analyzing 700 hPa wind fields, both experiments with horizontal resolution of 40 km and 10 km, represented well a trough propagating westward, from about 20◦W until NEB, with predictability of 5 days. Evaluating the model sensitivity to different convective parameterization, all the experiments were very similar and they underestimated the total precipitation in most of domain. Objective evaluation of precipitation forecasts showed higher scores at weaker thresholds, indicating that the model forecasted well rain areas. Neither convective scheme was better than the other in all the analyzed parameters. The Equitable Threat Score, Bias score and Probability of Detection showed that the Eta model forecasts had higher precipitation predictability with KF scheme, mainly for KF10. On the other hand, RMS index indicated that simulations using BMJ scheme showed smaller errors. These results suggest that is necessary to expand this analyze for a wide number of cases and a detailed study of cumulus parameterization should be taken improving rainfall forecast in NEB, mainly on the Eastern Coast.

ASSUNTO(S)

para modelo eta eta model betts-miller-janjic and kain-fritsch betts-miller-janjic e kain-fritsch easterly waves disturbances northeast brazil distúrbios ondulatórios de leste nordeste do brasil etrização de cúmulus cúmulus parameterization

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