RELAÇÃO ENTRE A TURBULÊNCIA DO DOSSEL E DISTRIBUIÇÃO VERTICAL DE GASES REATIVOS NA FLORESTA TROPICAL DA AMAZÔNIA CENTRAL

Ozone plays a crucial role in the chemistry of the tropical atmospheric boundary layer. In the rainforest, ozone sources and sinks are complex due to numerous chemical reactions and surface deposition. Turbulent transport controls the vertical distribution of ozone. A field study in the Amazonia, near Manaus, Brazil during 2014 shows different shapes of ozone profiles as a response to changes in air turbulence during night-to-day and day-to-night transitions. During the night-to-day transition following sunrise ozone levels increase within the canopy due to photochemical production and increased vertical mixing. The vertical transport of ozone to the lower layers of the canopy is enhanced after the thermal inversion in the canopy disappears. At night, the ozone deposition to the ground and the foliage in the lower canopy is strong. After midnight, the lower canopy is devoid of ozone. Relatively high gradients of ozone levels within the forest during the nighttime also result from the decoupling between the in- and above-canopy environment that limits the forest-atmosphere ozone exchange. Processes responsible for the vertical distribution ozone are necessary to estimate the oxidation of the plant-emitted gases whose reaction products are aerosol precursors.O ozônio desempenha um papel fundamental na química da camada-limite atmosférica tropical. Sobre uma floresta tropical, as fontes e sumidouros de ozônio são complexas, devido a numerosas reações químicas e à deposição seca e úmida na superfície. O transporte turbulento controla a distribuição vertical de ozônio. Um estudo de campo na Amazônia, nas proximidades de Manaus, Brasil, durante 2014, revelou diferentes formas para o perfil de ozônio dependendo da turbulência atmosférica durante as transições noite-dia e dia-noite.  Após o nascer do sol, os resultados mostram que durante a transição noite-dia os níveis de ozônio aumentam no dossel devido à produção fotoquímica. O transporte vertical de ozônio para os níveis mais baixos do dossel é intensificado depois que a inversão térmica dentro do dossel desaparece.  Durante a noite, o sumidouro de ozônio no solo é forte, em comparação com a deposição nas folhas. Após a meia-noite, a parte mais baixa do dossel não contém mais ozônio, e como resultado os perfis de ozônio deixam de se modificar durante várias horas.  Gradientes relativamente fortes de ozônio dentro da floresta durante o período noturno também aparecem como resultado do desacoplamento entre o dossel e a atmosfera acima da copa. Isso limita as trocas de ozônio entre a floresta e a atmosfera acima. Dado que o ozônio reage com compostos orgânicos emitidos pela vegetação, e que os produtos dessas reações podem se condensar, o resultado final é a produção de aerossóis: desta forma, a distribuição vertical de ozônio é um indicador importante de quais reações são possíveis, e em particular do potencial de produção de aerossóis

Evaluating Atmospheric Surface Layer Flux Parameterization within the Coastal Regime

Abstract Traditional atmospheric surface layer theory assumes homogeneous surface conditions. Regardless, nearly all surface layer parameterization schemes employed within numerical weather prediction models utilize the same techniques within highly heterogeneous coastal regimes as for homogeneous environments. We compare predicted surface weather and fluxes of momentum, heat, and moisture—focusing mainly on momentum—from regional simulations using the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) atmospheric model to observations collected from offshore buoys, inland flux towers, and radiosonde profiles during the Coastal Land-Air-Sea Interaction (CLASI) project throughout the summer of 2021 around Monterey Bay, California. Results reveal that modeled cross-coastal surface flux gradients are spuriously discontinuous, leading to systematically overestimated fluxes and weak winds inland of the coastline during onshore flow periods. Additionally, contrary to observations, modeled surface exchange coefficients are insensitive to wind direction on both sides of the coast, which degrades predictive skill downstream from the coastline. Over the central bay, prediction degrades when near-surface wind directions deviate from the prevailing flow direction as the parameterized stress–wind relationship fails during these cases. Predictive skill over the bay is therefore linked to variations in wind direction. Offshore of the geographically complex peninsula, systematic biases are less clear; however, bifurcations in drag coefficients based on wind direction were measured here as well. Last, increasing the horizontal grid spacing from 333 m to 3 km does not significantly affect surface layer prediction. This work highlights the need to reevaluate surface layer parameterization methods for modeling within coastal regions. Significance Statement Understanding surface layer weather is critical for many purposes, such as infrastructure design and weather forecasting. Within the context of numerical modeling and weather prediction, skillful forecasts of surface winds and temperature rely on accurate portrayal of the surface layer. By comparing observations collected during the Coastal Land-Air-Sea Interaction field program to numerical model solutions, we show that prediction of the surface layer fluxes of momentum, heat, and moisture break down near the coastline, which leads to biases in the predicted surface layer weather both inland and over the water. As surface layer parameterization methods across nearly all numerical models are rooted in the same practices, our results call into question the use of traditional methods near the coastline

Linking meteorology, turbulence, and air chemistry in the amazon rain forest

A field campaign reveals that the Amazon rain forest produces enough chemical species to undergo oxidation and generate aerosols, which can activate into cloud condensation nuclei and potentially influence cloud formation. © 2016 American Meteorological Society