Lívia Márcia Mosso Dutra

Preliminary Analysis on the Global Features of the NCEP CFSv2 Seasonal Hindcasts

The representation of the CFSv2 ocean-atmosphere ensemble hindcasts is investigated during Dec-Jan-Feb (DJF) and Jun-Jul-Aug (JJA) from 1983 to 2010. The skill anomaly correlations showed that in some continents the forecasts do not have dependency with changes in the initial conditions. Also, in both seasons the model has a higher skill at the 0-month lead time with the largest spatial biases occurring over the North America, South America, and Oceania. Over the continents the largest biases in the nonlinearity of El Nino minus La Nina events are found over the eastern South Africa, part of Oceania, and central-southeastern parts of South America. During DJF the main biases are related to double-ITCZ, strengthening of SPCZ, and deepening of the Aleutian and Icelandic low pressures. The simulation of a warmer SST on the eastern of most austral oceans, the strengthening (weakening) of the Subtropical (Polar) Jet over the Southern Hemisphere, and the weakening of the zonal circulation near the Antarctic continent are also found in both seasons. Over the central-eastern Equatorial Pacific a cooler bias in SST is found during JJA. These biases are interpreted by analyses of the simulated global mean-state and their impact on the main patterns of variability.

PROCESSOS FÍSICOS ASSOCIADOS À GÊNESE DE UM VCAN ENTRE O OCEANO PACÍFICO E A AMÉRICA DO SUL EM ABRIL DE 2013

Esse estudo teve como objetivo avaliar, por meio das equacoes da tendencia da vorticidade e da temperatura, os processos fisicos associados a genese de um vortice ciclonico de altos niveis (VCAN) subtropical proximo a costa oeste da America do Sul (35o-40oS) entre os dias 30 de marco a 1o de abril de 2013. Entre os resultados tem-se que as adveccoes horizontais de vorticidade (300 hPa) e temperatura (500 hPa) sao processos importantes para aprofundar o cavado em 300 hPa levando a genese do VCAN.

Subtropical cyclones over the oceanic basins: a review

Subtropical cyclones are hybrid systems presenting a warm core at low levels, as tropical cyclones, and a cold core at upper levels, as extratropical cyclones. Their genesis can be as proper subtropical system or from the transitions (extratropical to subtropical or tropical to subtropical). Subtropical cyclones occur mostly over the sea and generate intense near surface winds with great impacts on human activities and ecosystems. We present a review of the main features, as obtained from observations and numerical simulations, for subtropical cyclone development over the major oceanic basins.

Severe Weather Events over Southeastern Brazil during the 2016 Dry Season

Southeastern Brazil is the most populated and economically developed region of this country. Its climate consists of two distinct seasons: the dry season, extending from April to September, the precipitation is significantly reduced in comparison to that of the wet season, which extends from October to March. However, during nine days of the 2016 dry season, successive convective systems were associated with atypical precipitation events, tornadoes and at least one microburst over the southern part of this region. These events led to flooding, damages to buildings, shortages of electricity and water in several places, many injuries, and two documented deaths. The present study investigates the synoptic and dynamical features related to these anomalous events. The convective systems were embedded in an unstable environment with intense low-level jet flow and strong wind shear and were supported by a sequence of extratropical cyclones occurring over the Southwest Atlantic Ocean. These features were intensified by the Madden–Julian oscillation (MJO) in its phase 8 and by intense negative values of the Pacific South America (PSA) 2 mode.