| Summary: | Downward longwave radiation (L↓) is a component of net radiation for which it is difficult to precisely measure values. Therefore, different parameterizations have been proposed to estimate it. In this study we evaluated the performance of various parameterizations for estimated L↓ and their interaction with other measured variables as well as the interactions of air temperature and water vapor pressure with L↓ for clear and cloudy sky days in the central region of Amazonia. The datasets used in this study were measured from a micrometeorological tower managed by Large Scale Biosphere Atmosphere experiment in Amazonia (LBA) near the city of Manaus, Amazonas. The results show that precipitation and water vapor pressure exert a large influence on L↓, especially during the wet season. The models for clear-sky conditions proposed, using their original coefficients, a trend that underestimates the measured L↓ flux. The best results for clear-sky estimates were obtained with Idso & Jackson (1969), Brutsaert (1975) and Prata (1996)
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