R. Hallak

Abstract Hail is considered to be among the most complex extreme weather phenomena of the atmosphere. Every year, notably in the southern Brazilian States, destructive hailstorms result in serious economic losses and cause a great social impact destroying crops, homes, medical facilities and schools. The aim of this study is to document the spatial, annual, and diurnal variation in destructive hailstorm frequency during a 22 year period from 1991 to 2012 in Brazil. The analysis is based on a collection of reports released by the Brazilian National Civil Protection Secretariat – SEDEC. Based on reports of emergency assistance given to the population affected by a disaster, the information discussed in this work is assumed as representative only of destructive hailstorms. The analysis reveals a large spatial variability, with the majority of hailstorm occurrences distributed in the three southernmost Brazilian States. Within those states, the number of hail reports was observed to increase with increasing population density in rural areas. Hailstorms were reported most often in the late afternoon and evening of the winter/spring transition, in agreement with a few other areas in the subtropics with available studies, but different from the majority of studies for temperate zones, which suggest spring/summer as the hail season. Although the results show some discrepancies compared to satellite hail signatures, the findings of this work confirm that southern Brazil is a region prone to the development of strong convective storms, with high annual numbers of destructive hail events.

ABSTRACT Apresenta-se um estudo de caso de vórtice de ar frio associado à presença do padrão nuvem vírgula (invertida no Hemisfério Sul), ocorrido no Paraguai e porções do oeste dos Estados de Paraná, Santa Catarina e Rio Grande do Sul durante 22 de agosto de 1989. São utilizadas as reanálises do modelo de circulação global do ECMWF com resolução horizontal de 1.125ð. As análises diagnósticas são realizadas sobre os campos obtidos em coordenadas isobáricas e em coordenadas isentrópicas, destacando-se as análises com estas últimas, especialmente no que se refere ao conceito de conservação de vorticidade potencial isentrópica e à identificação das esteiras transportadoras fria e quente. Imagens do satélite GOES-7 do período em questão, assim como medidas de precipitação diária acumulada em algumas estações da região em foco e cartas de pressão à superfície, são utilizadas em auxílio à caracterização física do fenômeno. A mesma metodologia de análise diagnóstica é aplicada sobre os campos meteorológicos oriundos de simulações numéricas efetuadas através do modelo de área limitada RAMS. O modelo é rodado a partir de diferentes opções de configuração. O experimento controle foi obtido em apenas uma grade nos níveis horizontais, com espaçamento de 60km entre os pontos de grade sobre o domínio simulado. Do segundo experimento em diante, são utilizadas duas grades, a primeira como no experimento controle e a segunda, aninha. (Continuação) associada ao vórtice de ar frio. Apresenta-se tambem um esboço de modelo conceitual para a formação do sistema estudado, considerando-se os resultados obtidos nas analises isobáricas e isentrópicas, assim como nas simulações numéricas. Dissertação (Mestrado).

This work presents measurements of precipitating systems monitored by the mobile dual polarization Xband Doppler weather radar (MXPOL) of the Laboratory of Hydrometeorology of the University of São Paulo, São Paulo, Brazil. The MXPOL was design to monitor and to nowcast weather systems over the Metropolitan Area of São Paulo (MASP) and the Mar Ridge in Eastern São Paulo State where floods, mood slides, heavy winds, lightning and hail cause significant social and economical impacts (Pereira Filho et al, 2004). Most summer floods are related to local circulation induced by urban heat, topography, land and sea breezes. The main characteristics of the MXPOL are described in Pereira Filho et al. (2007). It is one of the tools of a Hydrometeorological Forecast System (HFS) that is being developed to upgrade an existing forecast system for the MASP. Five measurement campaigns were carried out on Eastern São Paulo State during the testing and training with the MXPOL between February and May...

<p>The Tropical Pacific and Tropical Atlantic Ocean modulate the interannual precipitation over the Amazon region and the decadal and interdecadal variation as well. During El Niño Southern Oscillation (ENSO), below-average rainfall is recorded in the North and Northeast of the Basin, while deficit of precipitation is observed in the West and South. On the other hand, during La Niña years, rainfall is above of normal in the North and Northeast of Amazon Basin. However, there are also drought events, such as in 1964 and 2005, unrelated to the El Niño event, but influenced by warm conditions in the Tropical North Atlantic. In fact, the exceptional drought recorded in 2010 was influenced by a combined effect of the El Niño event during the peak of rainy season, followed by warm conditions in the Tropical North Atlantic during final of rainy season and dry season.</p><p>Therefore, the main aim of this study is exploring the Atlantic Sea Surface Temperature (SST) condition in modulating patterns that influence the development of drought and flood events in the Amazon Basin. First of all, the Atlantic Ocean is divided into Tropical North Atlantic (TNA), Tropical South Atlantic (TSA) and Subtropical South Atlantic (STSA), to analyze the behavior of each region separately. Atlantic Index, in each region, is the first principal component (PC1) time series, which comes from the empirical orthogonal function (EOF) analysis applied to Hadley Center Global Sea Ice and Sea Surface Temperature (HadISST) dataset for the 1870-2107 period. The Tropical North Atlantic, Tropical South Atlantic and Subtropical South Atlantic indices show the main years when drought and flood events reaching the Amazon Basin (droughts in 2005, 2010 and 2015, and floods in 2009 and 2012, mainly), and 5-years moving correlations indicate that these three ocean basin have been coupled and decoupled periodically each other in the last century.</p><p>The equatorial Pacific, North Atlantic and South Atlantic indices were also correlated with rainfall over the Amazon for three databases: the Tropical Rainfall Mission Measurements (TRMM), the Global Precipitation Climatology Centre (GPCC) and the HyBAm Observed Precipitation. All three databases showed the same results. An increase of the SST in Eastern Pacific influences in low precipitation over the central and west of the Amazon Basin during the rainy season (December to February), increase of the SST in Central Pacific influences for droughts over the northeast region and the TSA influences in the central Amazon. Increase of the SST in TNA and STSA influences mainly in the dry season (May to September), intensifying it. TNA is responsible for precipitation below normal over the central and west Amazon Basin, while STSA only influences in the central region of the basin. Finally, analysis of extreme events indicate that droughts and floods in the Amazon are intensified (de-intensified) if we consider warm (cold) phases of the AMO (Atlantic Multidecadal Oscillation) and the PDO (Pacific Decadal Oscillation).</p>

The long-range transport of aerosols is a global issue since it may significantly affect the air quality of regions without
high concentrations of fine particulate matter (PM2.5). Two significant occurrences of long-range transport of aerosols over
the state of Parana in Brazil, which occurred during the periods Aug. 16–18 and Sep. 10–14 of 2016, were studied in order
to characterize the atmospheric synoptic conditions of these events and to estimate their contribution to the air quality
conditions in the northern region of the state. The South American Low Level Jet (SALLJ) was the key meteorological
component used to define the origin of the air mass trajectories over the region. In the first event, the SALLJ lost its
configuration, bringing air masses from the western part of São Paulo (state), while in the second event, the SALLJ formed
over southern Brazil and brought air masses from the northern and central parts of the nation. The significant number of
fires from biomass burning in central Brazil associated with synoptic conditions contributed to the increase in PM2.5
concentrations by approximately 70–87% in the region. The transport of aerosols was a determining factor in PM2.5
exceeding the air quality standard in the region. Therefore, to minimize this problem, it is imperative to control biomass
burning in Brazil.

Hail is considered to be among the most complex extreme weather phenomena of the atmosphere. Every year, notably in the southern Brazilian States, destructive hailstorms result in serious economic losses and cause a great social impact destroying crops, homes, medical facilities and schools. The aim of this study is to document the spatial, annual, and diurnal variation in destructive hailstorm frequency during a 22 year period from1991 to 2012 in Brazil. The analysis is based on a collection of reports released by the Brazilian National Civil Protection Secretariat – SEDEC. Based on reports of emergency assistance given to the population affected by a disaster, the information discussed in this work is assumed as representative only of destructive hailstorms. The analysis reveals a large spatial variability, with the majority of hailstorm occurrences distributed in the three southernmost Brazilian States. Within those states, the number of hail reports was observed to increase with increasing population density in rural areas. Hailstorms were reported most often in the late afternoon and evening of thewinter/spring transition, in agreement with a fewother areas in the subtropics with available studies, but different from the majority of studies for temperate zones, which suggest spring/summer as the hail season. Although the results show some discrepancies compared to satellite hail signatures, the findings of this work confirm that southern Brazil is a region prone to the development of strong convective storms,with high annual numbers of destructive hail events.

ABSTRACT O sistema do tipo nuvem vírgula (invertida no hemisfério sul) ou simplesmente nuvem vírgula é um distúrbio de escala subsinótica que se forma em baixos ou médios níveis dentro da massa de ar frio, na retaguarda de um sistema frontal ou zona baroclínica. Esses sistemas, típicos de inverno, podem provocar chuvas intensas mesmo quando se formam sobre o continente. Carlson (1980) ressalta que o formato de uma vírgula na fase madura não deve ser confundido com outros distúrbios de mesmo padrão, como por exemplo os ciclones extratropicais

ABSTRACT Apresenta-se um estudo de caso de vórtice de ar frio associado à presença do padrão nuvem vírgula (invertida no Hemisfério Sul), ocorrido no Paraguai e porções do oeste dos Estados de Paraná, Santa Catarina e Rio Grande do Sul durante 22 de agosto de 1989. São utilizadas as reanálises do modelo de circulação global do ECMWF com resolução horizontal de 1.125ð. As análises diagnósticas são realizadas sobre os campos obtidos em coordenadas isobáricas e em coordenadas isentrópicas, destacando-se as análises com estas últimas, especialmente no que se refere ao conceito de conservação de vorticidade potencial isentrópica e à identificação das esteiras transportadoras fria e quente. Imagens do satélite GOES-7 do período em questão, assim como medidas de precipitação diária acumulada em algumas estações da região em foco e cartas de pressão à superfície, são utilizadas em auxílio à caracterização física do fenômeno. A mesma metodologia de análise diagnóstica é aplicada sobre os campos meteorológicos oriundos de simulações numéricas efetuadas através do modelo de área limitada RAMS. O modelo é rodado a partir de diferentes opções de configuração. O experimento controle foi obtido em apenas uma grade nos níveis horizontais, com espaçamento de 60km entre os pontos de grade sobre o domínio simulado. Do segundo experimento em diante, são utilizadas duas grades, a primeira como no experimento controle e a segunda, aninha. (Continuação) associada ao vórtice de ar frio. Apresenta-se tambem um esboço de modelo conceitual para a formação do sistema estudado, considerando-se os resultados obtidos nas analises isobáricas e isentrópicas, assim como nas simulações numéricas. Dissertação (Mestrado).

... 1*, Oswaldo Massambani1, Ricardo Hallak1, Cesar AA Beneti2, and Rosangela BB Gin3 1USP, São Paulo; 2SIMEPAR, Paraná; 3UFEI, São Paulo, Brazil ... Tessendorf, SA and SA Rutledge, 2005: Radar observations of a negative cloud-to-ground storm observed during STEPS. ...

Sixth International Conference on Southern Hemisphere Meteorology and Oceanography P2.29. Downscalling of the global climate prediction in SE Brazil using RAMS. Pedro L. Silva Dias, University of São Paulo, São Paulo, Brazil; and R. Hallak. ain range. ...

... Adilson Wagner Gandú 3. Mário Thadeu Leme de Barros 4. Abstract. ... Revista Brasileira de Meteorologia, 6, 513-522. Silva Dias, PL, Etchichury, P., Scolar, J., Pereira Filho, AJ, Satyamurti, P., Silva Dias, MAF, Grammelsbacher, I., Grammelsbacher, E., 1991. ...

... Diogo Arsego1, Otávio Acevedo1, Ronald Souza2, Diogo Custódio1 ... 1. Introdução A região de encontro entre as águas quentes da Corrente do Brasil (CB) e as águas frias da Corrente das Malvinas (CM) no Oceano Atlântico Sudoeste, é considerada uma das regiões mais ...