Quantitative precipitation forecasts (QPFs) were obtained from ensembles of the weather and research forecasting (WRF) model for the Iguaçu river watershed (IRW) in southern Brazil. Thirty-two rainfall events between 2005 and 2010 were simulated with ten configurations of WRF. These rainfall events range from local to synoptic scale convection and caused a significant increase in the level of the Iguaçu river. In the average, the ensembles yielded up to 20% better skill than single WRF forecasts for the events analyzed. WRF ensembles also allow estimating the predictability through the dispersion of the forecasts providing relevant information for decision-making. Phase errors of ensemble forecasts are larger than amplitude errors. More complex microphysics parameterizations yielded better QPFs with smaller phase errors. QPFs were fed to IRW hydrological model with similar phase and amplitude errors. It is suggested that lagged QPFs might reduce phase errors.
Figura 1-1: Gráfico esquemático da qualidade de previsões por conjuntos. Na primeira hipótese, o conjunto possui variabilidade suficiente para reproduzir uma previsão correta. Na segunda hipótese, há uma convergência dos membros do conjunto, porém, indicam uma previsão divergente da observação. Adaptado de Kalnay (2002).
On 23 July 2013, a snowstorm hit southern Brazil causing material damage and two deaths. Radar reflectivity and lightning data revealed a rare thundersnow occurrence. This study revealed that a Rossby wave propagation followed a typical pattern of cold incursions in South America, but some fundamental differences can be pointed out: (1) further northward Rossby wave amplification; (2) strong upward vertical motion within a deep nearly saturated layer and (3) a conditional symmetric instability layer, in response to strong vertical shear, beneath a layer of weak conditional instability, and above a significant near-surface vertical depth where temperatures hover around 0 ∘ C.
ResumoEste trabalho tem por objetivo estudar um evento de tombamento de torre de suporte de Linha de Transmissão de Energia Elétrica (LT) ocorrido no dia 12 de julho de 2016 em Cascavel -PR devido a ocorrência de uma microexplosão. Para o estudo foram utilizados dados de anemômetros sônicos instalados em quatro níveis de altura (10m, 22m, 33m e 44m) da torre de transmissão número 37 da LT Toledo-Cascavel na região oeste do Paraná. Para análise espacial das rajadas e das assinaturas de mesoescala foram utilizados dados de velocidade radial e refletividade do radar meteorológico banda S Doppler de dupla polarização do Simepar instalado em Cascavel. As análises da assinatura de mesoescala principalmente da velocidade radial do radar Doppler indicaram a presença de uma microexplosão a qual gerou rajadas próximas de 45 ms -1 . O registro no anemômetro na torre situada a 300m de distância registrou uma rajada de 32,6 m.s -1 . A microexplosão foi gerada por uma supercélula que se formou no Paraguai e se propagou zonalmente até o oeste do Paraná durante 5 horas com velocidade de propagação de 18,5 ms -1 . Pela análise dos dados de radar no momento do tombamento da torre não foram identificadas assinaturas de tornado. Palavras-chave: rajadas de vento; anemômetros; radar meteorológico; torres de transmissão de energia
AbstractThe objective of this work is to study an event of microburst that blow down a tower of electric transmission line on July 12, 2016 in Cascavel -PR. For the study, data of sonic anemometers installed in four-height levels (10m, 22m, 33m and 44m) of the tower 37 on Toledo-Cascavel line in the western Paraná were used. For the spatial analysis of the microburst and mesoscale signatures it were used radial velocity and reflectivity data of the double-polar Doppler S-band radar of Simepar installed in Cascavel. At the moment of the tower fall, it was found a signature of a microburst in the radial velocity which generated wind gusts approximately to 45 ms -1 . The anemometer, located in a tower 300m away of the blow down tower, recorded a 32.6 ms -1 wind gust. The microburst was generated by a supercell initiated in Paraguay and propagated zonally to the west of Paraná during 5 hours at a propagation velocity of 18.5 ms -1 . It was not found tornado signature in the radar data near the time of tower fall.
Among other applications, radar-rainfall (RR) and QPE (Quantitative Precipitation Estimation) based on radar reflectivity, dual polarization variables, and multi-sensor information, provide important information for land surface hydrology, such as flood forecasting. Therefore, we developed a flood alert system using rainfall-runoff model forced with RR and QPE, and tipping-bucket observations to forecast river water levels (using rating-curves). In this study, we used an hourly dataset from an S-Band dual-polarimetric radar with two tropical R(Z) relations based distrometer data, a polarimetric R(Z,ZDR) algorithm from the literature and a multi-sensor approach using radar, satellite and rain gauge. Two hydrological models were used and calibrated using observed discharge time-series. Although our previous studies indicated accurate RR-based simulations, in some cases floods were not detected when using catchment-lumped rainfall derived from multi-sensor QPE. In this study, we advance further in this subject using improved R(Z,ZDR) relations and QPE for the period of 2016-2017 and flood event-based rainfall-runoff calibration. Thus, we focused on the development (and timing) of floods in the Marrecas River can be complex and strongly related to storms spatiotemporal distribution. To explore this aspect, we also perform a first analysis in using RR in rainfall-runoff model with a nested catchment discretization.
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