ABSTRACT Drought is a natural and recurrent phenomenon. It is considered ‘a natural disaster’ whenever it occurs in an intensive manner in highly populated regions, resulting in significant damage (material and human) and loss (socioeconomic). This paper presents the efforts developed to monitor the impact of drought in the semiarid region of Northeast Brazil. In this scope, information from different sources is compiled to support the evaluation and identification of impacted municipalities, with the main objective of supporting emergency actions to mitigate their impact. In the semiarid region of Brazil there are frequent occurrences of dry periods during the rainy season, which, depending on the intensity and duration, can cause significant damage to family-farmed crops, with a farming system characterized by low productivity indices. However, rain-fed agriculture has great economic expression and high social importance due to the region is densely occupied, and contributes to the establishment of communities in the countryside. Specifically, in the present study, the methodology adopted to monitor the impact of agricultural droughts, including an analysis of the hydrological year 2015-2016, is presented, considering different water stress indicators for the identification of the affected municipalities and assessment of the methods and tools developed.

ABSTRACT This study discusses the climatological aspects of the most severe drought ever recorded in the semiarid region Northeast Brazil. Droughts are recurrent in the region and while El Nino has driven some of these events others are more dependent on the tropical North Atlantic sea surface temperature fields. The drought affecting this region during the last 5 years shows an intensity and impact not seen in several decades in the regional economy and society. The analysis of this event using drought indicators as well as meteorological fields shows that since the middle 1990s to 2016, 16 out of 25 years experienced rainfall below normal. This suggests that the recent drought may have in fact started in the middle-late 1990s, with the intense droughts of 1993 and 1998, and then the sequence of dry years (interrupted by relatively wet years in 2007, 2008, 2009 and 2011) after that may have affected the levels of reservoirs in the region, leading to a real water crisis that was magnified by the negative rainfall anomalies since 2010.

The processes of water transfer in the soil-plant-atmosphere system are strongly affected by soil use and management. Differences in the dynamics of soil water transfer between no-tillage (NT) and conventional tillage (CT) practices during a soybean (Glycine max) growing season in southern Brazil were assessed in this study. All the water balance components were analyzed during the soybean growing season (2009/2010). Rainfall, runoff, soil water storage and hydro-physical soil properties were analyzed under two tillage systems. The land-atmosphere water vapor exchanges, obtained from eddy covariance stations, were analyzed with regard to the soybean agroecosystem. Characterizations of soil water storage were also formulated in the 2006/2007 and 2008/2009 soybean growing seasons under the NT system. During the periods without rain, the soil water content under NT was greater than under CT. The soil superficial layer, more porous under NT, contributed to less runoff during rainy events. Moreover, under NT conditions the water supply was always high, between 0.2 - 0.5 m. The total evapotranspiration in the soybean agroecosystem growing season was 410.8 mm.

O aumento das emissões dos gases de efeito estufa (GEE) se configura, atualmente, como um dos principais problemas ambientais, o que pode afetar significativamente as atividades humanas e os ecossistemas terrestres. Um dos principais GEE é o CO2, o qual tem sido emitido indiscriminadamente em função do estilo de vida atual, assim como pela intensificação das atividades agrícolas. Neste contexto, o objetivo da pesquisa foi estudar a relação entre o comportamento espectral da cultura de soja ao longo de seu ciclo de desenvolvimento, utilizando imagens NDVI (Normalized Difference Vegetation Index) e o fluxo de CO2, calculado pelo método de covariância de vórtices (eddy covariance), gerando informações e metodologia para investigar as trocas de carbono em uma área de cultivo de soja no estado do Rio Grande do Sul, durante a safra de 2008/2009. Utilizou-se imagens TM do satélite Landsat 5, dados fenológicos e dados coletados em estação micrometeorológica ao longo do ciclo de desenvolvimento da soja. Os resultados mostraram que o padrão temporal do fluxo de CO2 ao longo do dia é cíclico, sendo que no período diurno apresenta valores negativos (captura) e no período noturno, positivos (liberação). A radiação solar global determina a magnitude do aprisionamento de CO2 pela cultura da soja, mas o fluxo é modulado pelo estádio fenológico da cultura. A atividade fotossintética das plantas de soja é maior durante o estádio vegetativo, quando coincide a maior incidência de radiação solar e o maior aparato fotossintético. O NDVI, obtido de imagens Landsat, é um indicador da evolução da biomassa da soja ao longo do ciclo. Existe correlação entre o NDVI e o fluxo negativo de CO2 (captura), ocorridos no período diurno. Portanto, técnicas de sensoriamento remoto demonstram potencialidade na geração de informações úteis sobre as trocas de CO2 entre a superfície e a atmosfera.

The increasing on the greenhouse gases (GHG) emissions is today one of the main environmental problems, which can significantly affect human activities and land ecosystems. One of the main GHG is CO2, which has been emitted indiscriminately due to the current lifestyle, as well as the intensification of agricultural activities. In this context, the objective of this investigation was to study the relationship between the spectral behavior of soybean during the crop cycle, using NDVI (Normalized Difference Vegetation Index), and the CO2 fluxes, calculated by the eddy covariance method, generating information and methodology to investigate the carbon exchange in a soybean crop area in the State of Rio Grande do Sul, during the 2008/2009 soybean crop. For this, Landsat images 5 (TM), the phenological information and collected data from micrometeorological station throughout the development cycle of soybean were used. The results showed that the temporal pattern of CO2 flux during the day was cyclical, showing negative values (capture) during daytime and positive values (liberation) at night. The global solar radiation determines the magnitude of the trapping of CO2 by soybean, but the flow is modulated by the phenological stage of the crop. The photosynthetic activity of soybean plants is higher during the vegetative stage, coinciding to the higher incidence of solar radiation and the greater photosynthetic apparatus. The NDVI, obtained from Landsat images, is an indicator of the evolution of soybean biomass during the cycle. NDVI and negative CO2 flow (capture) are correlated during the day. Therefore, remote sensing techniques show potentiality in generating of useful information on CO2 exchange between the surface and atmosphere.

Neste artigo apresenta-se o desenvolvimento de uma ferramenta para interpolar os dados meteorológicos oriundos de Modelos Regionais de Previsão de Tempo, ex. BRAMS, permitindo o acoplamento entre estes modelos e os modelos de dispersão atmosférica. Para a avaliação desta ferramenta, os campos de vento da saída do BRAMS são utilizados como dados de entrada no Modelo de Dispersão Atmosférica (Zimora), desenvolvido pelo Laboratório de Micrometeorologia da Universidade Federal de Santa Maria (UFSM).

This paper discusses the development of a data interpolation scheme applicable to the regional numerical weather prediction models (i.e. BRAMS) output, allowing the coupling of these models with atmospheric dispersion models. To evaluate this tool, the BRAMS wind field is used as input to the Atmospheric Dispersion Model (Zimora) developed by the Laboratório de Micrometeorologia of the Universidade Federal de Santa Maria (UFSM).

O objetivo deste trabalho foi testar um método de geração de informações da distribuição espacial e temporal da radiação fotossinteticamente ativa absorvida (RFAa), pela cultura da soja, a partir da quantificação da relação entre o índice de vegetação por diferença normalizada (NDVI) e a fração da radiação fotossinteticamente ativa absorvida (FRFAa) pela cultura. O estudo abrangeu o município de Cruz Alta, um dos grandes produtores de soja do Rio Grande do Sul, durante duas safras: 2008/2009 e 2009/2010. Os dados de radiação fotossinteticamente ativa incidente (RFAi) foram monitorados em área experimental e os dados orbitais, provenientes de duas plataformas: Landsat/TM e Terra/MODIS, ambos com distribuição gratuita, mas com características distintas. Foi estabelecida uma relação linear simples entre o NDVI das imagens MODIS e a FRFAa obtida em dois períodos importantes do ciclo, semeadura e máximo desenvolvimento das plantas. Pelos resultados, observou-se que existe associação entre o NDVI e FRFAa, a qual pode, portanto, ser usada na geração de informações da RFAa pela cultura da soja ao longo do ciclo de desenvolvimento, permitindo, assim, um monitoramento temporal deste elemento.

The objective of this study was to test a methodology of data generation of the spatial and temporal distribution of the absorbed photosynthetically active radiation (RFAa) by the soybean crop based on the quantification of the relation between the normalized difference vegetation index (NDVI) and the fraction of absorbed photosynthetically active radiation (FRFAa) by the crop. The study covered the county of Cruz Alta, one of the largest producers of soybean in Rio Grande do Sul, Brazil, during the period of two harvest seasons: 2008/09 and 2009/10. The data of the incident photosynthetically active radiation (RFAi) were collected on the experimental area and the orbital data came from two platforms: Landsat/TM and Terra/MODIS, both with free distribution, but with distinct characteristics. A simple linear relation was established between the NDVI of the MODIS images and the FRFAa, obtained during two important periods of the cycle: sowing and maximum plant growth. The results showed that there is an association between the NDVI and the FRFAa that can, therefore, be used on the generation of RFAa data by the soybean crop throughout the development cycle, allowing the temporal monitoring of this element.

Neste trabalho analisam-se as características espectrais da turbulência atmosférica na região do Centro de Lançamento de Alcântara (CLA), que sofre a influência de uma falésia e da brisa marítima provinda do oceano, visando obter informações sobre a estrutura turbulenta do local. Determinaram-se os espectros das 3 componentes do vento (u, v e w) na camada limite superficial sobre esse terreno homogêneo, visando aplicações no Projeto e Desenvolvimento dos foguetes de sondagem e do Veículo Lançador de Satélite (VLS) realizado pelo IAE. Os dados foram coletados no mês de agosto do ano de 1999 através de um anemômetro sônico tridimensional. Também se obteve resultados envolvendo as relações σu/u*, σv/u* e σw/u*, todos condizentes com os previstos na literatura.

In this work is analyzed the spectral characteristics of atmospheric turbulence in the Alcântara Launching Center (CLA), which suffers the influence of a cliff and of the sea breeze coming from the ocean. The atmospheric spectra were determined for the 3 wind components (u, v, and w) in the superficial boundary layer, to be used for the Research and Developpment (R&D) of sounding rockets and Satellite Launch Vehicle (VLS) build by IAE. The data were collected during the month of August, 1999 using a 3D sonic anemometer. Results involving the σu/u*, σv/u* and σw/u* relations are obtained, and are all consistent with those reported in literature.

Este artigo apresenta dois estudos de caso com objetivo de investigar a interação do vento local no interior de um vale, com o vento sinótico. A direção e a velocidade do vento local são obtidas de dados de resposta lenta medidos em um trecho leste/oeste do vale do rio da Prata, localizado na região de Nova Roma do Sul, Estado do Rio Grande do Sul. Os dados sinóticos da direção e velocidade dos ventos foram observados às 00, 12 e 18 TMG, em três estações meteorológicas de superfície localizadas na mesorregião do vale estudado. O padrão sinótico é avaliado através de campos meteorológicos construídos com a reanálise do NCEP-NCAR. A análise sinótica e a avaliação empírica do vento local são realizadas com a ajuda de outras variáveis medidas no fundo do vale, tais como radiação solar incidente e temperatura do ar. Os resultados mostram a existência de superposição das forçantes, térmica e canalizada, durante a madrugada e parte da manhã. Porém, quando a temperatura do ar durante a madrugada é baixa, o efeito térmico parece ser mais pronunciado do que o efeito do vento sinótico canalizado. O vento sinótico de norte proporciona um padrão característico do vento local no interior do vale. O escoamento vale abaixo é relativamente mais forte entre a madrugada e a manhã devido à soma dos efeitos, térmico e canalizado. Por outro lado, esses efeitos anulam-se a partir das 12 - 13 h, provocando calmaria no interior do vale.

This paper shows two case studies to investigate the interaction of the local wind within a valley with the synoptic-scale wind. The direction and velocity of the local wind are obtained from slow response data measured within an east/west section of Prata valley in Nova Roma do Sul, Rio Grande do Sul State, Brazil. The synoptic direction and velocity wind were observed at 00, 12 and 18 TMG at three meteorological surface stations, situated in the studied valley. The synoptic pattern is evaluated by the NCEP-NCAR reanalysis of meteorological fields. The synoptic analysis and empirical evaluation of local wind are done with the use of others variables in the bottom of the valley, as incident solar radiation and air temperature. The results showed that there is a superposition of the thermal and the channeled flow forcings within the valley during the first hours and part of the morning. However, when the air temperature during the early morning is low, the thermal effect seems to be more pronounced than the synoptic channeled wind effect. The down-valley wind flow is relatively stronger during the early and the late morning due to the superposition of both thermal and channeled effects. On the other hand, these effects cancel each other from 12-13 hour, causing calm winds within the valley.