Abstract Cyanobacterial blooms are a potential threat to human communities and ecosystems. Since the late 1980s, researchers have reported harmful cyanobacterial colonies in Patos Lagoon (PL), the largest coastal lagoon in South America. Most studies concerning harmful blooms in PL have focused on its biology and on its southernmost estuarine region, with little information about its displacement inside the lagoon and the influence of physical forces on its dynamics. This study uses satellite-derived information (normalized difference chlorophyll-a index – NDCI), river discharge data, and meteorological data (wind speed and direction, rainfall, and air temperature) to analyze two bloom episodes in PL, during the austral summer of 2019/2020, specifically in its larger, limnic portion. A 30-year meteorological time series was used to contrast the same summer period. Two remote sensing images from Sentinel-2 were taken of PL margins, near their central portion. The summer of 2019/2020 was drier when compared with the historical data, characterizing low river discharge. This environmental condition was coupled with high temperature, which implies thermal stratification in summer even at 2-m depth sites, which might have promoted cyanobacterial growth and accumulation inside PL. Moreover, weak winds (<<6 m s−1) seemed to accumulate cyanobacterial patches on the water surface, including after vertical mixing caused by strong winds (>6 m s−1). The NDCI values represented the two days of blooms, with higher values occurring under higher water temperatures and low wind speeds. ecosystems 1980s s , (PL) America region dynamics satellitederived satellite derived normalized chlorophylla chlorophyll NDCI, NDCI) direction rainfall temperature 20192020 2019 2020 larger portion 30year year 30 period Sentinel2 Sentinel 2 Sentinel- margins 2019/202 2m sites Moreover <<6 6 (<< s−1 s1 1 surface >6 (> s−1. . speeds (PL 2019202 201 202 3 2019/20 << (< s− > ( 201920 20 2019/2 < 20192 2019/

Resumo O aumento na frequência de eventos extremos associados às alterações climáticas podem modificar as curvas IDFs existentes. A metodologia para definição de curvas IDF considerando cenários futuros consistiu em calibrar o modelo estocástico para gerar séries sintéticas diárias de precipitação com base em dados observados do município de Porto Alegre e gerar séries sintéticas perturbadas a partir de seis MCGs, três cenários A1B, A2 e B1 para os períodos de 2046 a 2065 e 2080 a 2099. Na elaboração das IDFs foram desagregados os dados sintéticos diários, tanto para a linha de base (1974 a 2014), quanto para os cenários projetados, utilizando as relações de desagregação da IDF atual de Porto Alegre. Os resultados obtidos após a calibração indicaram ser o modelo estocástico utilizado eficiente na representação dos dados local. Os resultados encontrados para as projeções no primeiro período indicam que as simulações dos modelos são razoavelmente aplicáveis, sugerindo a utilização da curva IDF atual com uma majoração de 10 a 20% no dimensionamento de obras hidráulicas. Já para o segundo período de projeção em função da grande variabilidade nos resultados encontrados para os diferentes modelos não há confiança na aplicabilidade destas projeções.

Abstract The increase in the frequency of extreme events associated with climate change can modify the existing IDF curves. The methodology for defining IDF curves considering future scenarios was to calibrate the stochastic model to generate daily synthetic precipitation series based on observed data from the city of Porto Alegre and to generate perturbed synthetic series from six MCGs, three scenarios A1B, A2 and B1 for the periods 2046 to 2065 and 2080 to 2099. In the elaboration of the IDFs, the daily synthetic data were disaggregated, both for the baseline (1974 to 2014) and for the projected scenarios, using the disaggregation relationships of the current IDF of Porto Alegre. The results obtained after the calibration indicated that the stochastic model used was efficient in the local data representation. The results for the projections in the first period indicate that the simulations of the models are reasonably applicable, suggesting the use of the current IDF curve with a 10 to 20% increase in the design of hydraulic works. Already in the second projection period due to the great variability in the results found for the different models, there is no confidence in the applicability of these projections

RESUMO O objetivo deste trabalho foi elaborar e testar um modelo agrometeorológico-espectral para a estimativa da produtividade de grãos de arroz irrigado para o Estado do Rio Grande do Sul. Para as seis regiões orizícolas do Estado, foram utilizados dados de área cultivada e rendimento de grãos de arroz irrigado, dados meteorológicos e imagens do Índice de Vegetação por Diferença Normalizada (NDVI) do sensor Moderate Resolution Imaging Spectroradiometer (MODIS), de agosto a abril, para as safras de 2000/2001 até 2009/2010. A temperatura mínima do ar e o NDVI estão associados ao rendimento de grãos de arroz irrigado em diversos períodos do desenvolvimento da cultura. O modelo agrometeorológico-espectral para estimativa de produtividade de grãos, ajustado através da abordagem orientada pelas relações clima-planta, é adequado às estimativas em nível regional, podendo fornecer estas com cerca de um mês de antecedência ao final da colheita.

ABSTRACT The objective of this study was to estimate the irrigated rice grain yield through the adjustment of the agrometeorological-spectral model in the State of Rio Grande do Sul, Brazil. For the six rice-growing regions of the State, the data on irrigated rice grain yield and crop area, meteorological data and the Normalized Difference of Vegetation Index (NDVI) images of moderate resolution imaging spectroradiometer (MODIS) sensor were used from August to April, for the 2000/2001 to 2009/2010 crop seasons. The minimum air temperature and NDVI are associated to the irrigated rice grain yield in several crop development periods. The agrometeorological-spectral model to estimate irrigated rice grain yield, adjusted through the oriented approach by the climate-plant relationship, is adequate for the estimates at regional levels. This could predict the estimates one month before the end of the harvest.

O objetivo deste trabalho foi elaborar e testar modelos para a estimativa de rendimento de arroz irrigado, no Estado do Rio Grande do Sul. O estudo foi realizado com dados meteorológicos de temperatura mínima do ar, radiação solar global e dados de estatísticas agrícolas de rendimento de arroz irrigado, das seis regiões orizícolas do Rio Grande do Sul, referentes às safras 1982/1983 até 2005/2006. Foram feitas análises de tendência tecnológica dos rendimentos, e foram estabelecidos os indicadores agrometeorológicos para o ajuste de modelos de estimativa de rendimento de arroz irrigado, para o Rio Grande do Sul. Existe tendência tecnológica de aumento nos rendimentos de arroz irrigado no Estado. As variáveis meteorológicas avaliadas - dias com temperatura mínima do ar inferior a 15°C e radiação solar global - podem ser usadas como indicadores do rendimento de arroz irrigado. Os modelos agrometeorológicos elaborados para as seis regiões orizícolas e para o Estado do Rio Grande do Sul apresentam características de precisão, fácil implementação e baixo custo e podem, portanto, ser introduzidos ao programa nacional de previsão de safras.

The objective of this work was to elaborate and test models to estimate the irrigated rice yield, in Rio Grande do Sul State, Brazil. The study was carried out using meteorological data of minimum air temperature, global solar radiation and data of agricultural statistics about the irrigated rice yield, involving six rice production regions of Rio Grande do Sul, relative to crop years from 1982/1983 to 2005/2006. Analyses of yield technological tendencies were performed, and agrometeorological indicators for model adjustments of irrigated rice yields were established. There is a technological tendency of increasing the irrigated rice yield in the State. The analyzed meteorological variables - global solar radiation and days with minimum air temperature below or equal to 15°C - can be used as indicators of the irrigated rice yield. The adjusted agrometeorological models, elaborated for the six rice production regions and for the Rio Grande do Sul State, show characteristics of accuracy, easy implementation and low cost, which make them able to be introduced in the national program of crop forecast.