Nathalie Tissot Boiaski

Some mean atmospheric characteristics for snowfall occurrences in southern Brazil

Snowfall is considered a natural disaster in southern Brazil, where a little infrastructure exists up to prevent against the damage it induces, making snowfall forecast a matter of great interest in this region. The present article aims to describe the mean behavior of low, mid, and high atmospheric levels during snowfall occurrences in southern Brazil. Sea-level pressure (SLP), 1000–500 hPa atmospheric thickness, geopotential height at 500 hPa, and wind speed at 200 hPa have been analyzed. One hundred and ninety-six snowfall records from the conventional surface meteorological stations have been selected for the period from 1979 to 2015. The surface synoptic pattern associated with snowfall occurrences has been obtained from ERA-Interim reanalysis data with horizontal spatial resolution of

HYDROCLIMATIC VARIABILITY ON THE RIO NEGRO WATERSHED: A CASE STUDY AT BRAZILIAN AREA

0.75^\circ \times 0.75^\circ

ANÁLISE DE AGRUPAMENTO DA TEMPERATURA DO AR NO SUL DO BRASIL ENTRE 1961-2011

0.75∘×0.75∘ and temporal resolution of 12 h. SLP fields show a high-pressure transient system displacement from the Pacific Ocean to northeastern Argentina. In addition, it is possible to relate snowfall with displacement of a low-pressure system on the coast of southern Brazil. Thickness fields indicate shallow cold air mass intrusions one day before snowfall. Such a cold air continues moving towards low latitudes during consecutive snowfall days and it may be responsible for frost events in climatologically warm regions. Finally, mid and high atmospheric levels show an eastward propagating wave amplified by the Andes.

VARIABILIDADE INTERANUAL DA PRECIPITAÇÃO SIMULADA PELO REGCM4: ANÁLISE DE SENSIBILIDADE À VARIAÇÃO DE ESQUEMAS DE SUPERFÍCIE

Temperature is one of the most important variables used in climate studies. Changes in its time series can cause various social and political impacts, affecting diverse sectors of society, such as agriculture, for example. Southern Brazil is a region that relies heavily on agriculture, contributing to national production. Therefore, it is important to check the air temperature characteristic, i.e., its spatial pattern in this region. For this, daily data of minimum and maximum temperature of the air of the National Institute of Meteorology were used in the period from 1961 to 2011. The statistical technique of cluster analysis was applied to identify the homogeneous regions of temperature and the boxplot for the characterization of each an. In general, the results showed maximum values of temperatures in the west of Rio Grande do Sul. The regions of minimum temperatures presented a more homogenous pattern, with averages around 15 oC. The regions of the maximum temperatures showed average values oscillating between 22 oC and 28 oC.

PADRÃO ESPACIAL DA OSCILAÇÃO ANTÁRTICA NO MODELO HADGEM2-ES

In this article we carried out a hydroclimatological characterization of the upper reaches of the Rio Negro Basin, located in the Brazilian portion. We used rainfall and streamflow data from the Instituto Nacional de Meteorologia (INMET) and the Agencia Nacional de Aguas (ANA) in the 1995-2014 period, collected at different points surrounding the watershed. From the data analysis, we can identify that the average annual precipitation over the basin varies between 1440 and 1480mm. The annual average streamflow was approximately 538,7mm, corresponding to a runoff coefficient of 38%. The accumulated rainfall and streamflow series showed that, as of mid-year 2004, there was a significant reduction of the accumulated streamflow, probably caused by an increase in water demand for agricultural irrigation due to lower volumes of rainfall. Pre-2005 runoff coefficient showed an interannual oscillation between 36% and 42%, after 2005 the runoff coefficient systematically decreased from 45% to 35%. This reduction suggests an increase in the extraction of water for irrigation which consequently favors greater crop evapotranspiration in a period with slightly lower annual precipitation (2005-2014) compared to the previous period (1995-2004).

Space-Time Distribution of Rainfall Anomaly Index (RAI) for the Salgado Basin Spatial Variability of air Temperature in Southern Brazil Between 1961-2011, Ceará State - Brazil

A Peninsula Antartica (PA) e uma das regioes da Terra onde o aquecimento foi mais acelerado nos ultimos 50 anos. Ha indicios de que esta tendencia esteja associada, em parte, ao aumento da atividade intrasazonal (IS) tropical. Utilizando dados de estacoes, este estudo mostrou que a variabilidade da temperatura do ar a superficie (Tsup) sobre a PA apresenta um pico estatisticamente significativo na escala IS (78 dias). A influencia da Oscilacao Madden-Julian (MJO) sobre os eventos IS da Tsup na PA foi quantificada: mais de 60% dos eventos foram associados a MJO, via trem de ondas de Rossby com periodicidade em torno de 30-40 dias. Portanto, outros mecanismos precisam ser investigados para explicar a variabilidade IS da Tsup na PA nao associada a MJO (NMJO). Tanto os eventos NMJO quanto o total de eventos (MJO + NMJO) foram mais frequentes na primavera. Alem disso, nos ultimos 12 anos analisados (1998-2009) houve uma maior frequencia de eventos MJO do que NMJO, principalmente na primavera e no inverno.

Evaluation of Climatology of Air Temperature in Southern Brazil Produced by the Regional Model RegCM4

The economy in the southern Brazil is based on agriculture and livestock sectors which, in turn, depend on the meteorological parameters variability, such as precipitation and temperature. In this study was performed a climatological analysis of the air temperature in the southern Brazil during 1961-2011, using the cluster analysis and thereby providing information about the temperature spatial variability on the region.

Variabilidade intrassazonal extrema da temperatura do ar à superfície na Península Antártica Intraseasonal extreme variability on the air surface temperature in the Antarctic Peninsula

O objetivo desse trabalho foi analisar a variabilidade interanual da precipitacao sobre a AMZ e LPB simulada pelo RegCM4 utilizando duas diferentes parametrizacoes de superficie.