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The present study aimed to characterize the dynamics of NDVI and meteorological conditions, relating both to the annual dynamics of biomass accumulation in natural pastures of the Pampa biome as a way of subsidizing growth modeling. Forage accumulation rate data from a long-term experiment, NDVI data from the MODIS images, and meteorological data measured at the surface were used. We verify that the agrometeorological element associated to the accumulation of forage in the natural grasslands is different according to the season, which is typical of the subtropical climate. Winter is the critical season for livestock production due to the lower forage accumulation rate and lower IRRIGATION AND AGROMETEOROLOGY Article NDVI and meteorological data as indicators of the Pampa biome natural grasslands growth Denise Cybis Fontana1*, Amanda Heemann Junges2, Carolina Bremm2, Laura Pigatto Schaparini1, Vagner Paz Mengue3, Ana Paula Luz Wagner4, Paulo Carvalho1 1.Universidade Federal do Rio Grande do Sul Faculdade de Agronomia Porto Alegre (RS), Brazil. 2.Fundação Estadual de Pesquisa Agropecuária Porto Alegre (RS), Brazil. 3.Universidade Federal do Rio Grande do Sul Centro Estadual de Pesquisas em Sensoriamento Remoto e Meteorologia Porto Alegre (RS), Brazil. 4.University of Florida Institute of Food and Agricultural Sciences Agricultural and Biological Engineering Department Gainesville (FL), United States. *Corresponding author: [email protected] Received: Jul. 5, 2017 – Accepted: Oct. 24, 2017 values of NDVI, conditioned by the decrease of solar radiation and air temperature. In the summer, the limiting factor to forage accumulation is the hydric condition. It was also verified that the variability in the growth of grasslands can be associated with the ENSO phenomenon, being the El Niño favorable and the La Niña unfavorable, especially in the spring-summer period. Considering the verified associations, spectral indices combined with agrometeorological elements are recommended to the adjustment of models of forage accumulation in the Pampa biome natural grasslands.