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Title: Nighttime wind and scalar variability within and above an Amazonian canopy
Authors: Oliveira, Pablo E.S.
Acevedo, Otávio C.
Sörgel, Matthias
Tsokankunku, Anywhere
Wolff, Stefan
Araüjo, Alessandro Carioca de
Souza, Rodrigo Augusto Ferreira de
Sá, Marta O.
Manzi, Antônio Ocimar
Andreae, Meinrat O.
Keywords: Atmospheric Chemistry
Boundary Layer
Carbon Dioxide
Forest Canopy
Spectral Analysis
Issue Date: 2018
metadata.dc.publisher.journal: Atmospheric Chemistry and Physics
metadata.dc.relation.ispartof: Volume 18, Número 5, Pags. 3083-3099
Abstract: Nocturnal turbulent kinetic energy (TKE) and fluxes of energy, CO2 and O3 between the Amazon forest and the atmosphere are evaluated for a 20-day campaign at the Amazon Tall Tower Observatory (ATTO) site. The distinction of these quantities between fully turbulent (weakly stable) and intermittent (very stable) nights is discussed. Spectral analysis indicates that low-frequency, nonturbulent fluctuations are responsible for a large portion of the variability observed on intermittent nights. In these conditions, the lowfrequency exchange may dominate over the turbulent transfer. In particular, we show that within the canopy most of the exchange of CO2 and H2O happens on temporal scales longer than 100 s. At 80 m, on the other hand, the turbulent fluxes are almost absent in such very stable conditions, suggesting a boundary layer shallower than 80 m. The relationship between TKE and mean winds shows that the stable boundary layer switches from the very stable to the weakly stable regime during intermittent bursts of turbulence. In general, fluxes estimated with long temporal windows that account for low-frequency effects are more dependent on the stability over a deeper layer above the forest than they are on the stability between the top of the canopy and its interior, suggesting that low-frequency processes are controlled over a deeper layer above the forest. © Author(s) 2018.
metadata.dc.identifier.doi: 10.5194/acp-18-3083-2018
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