Cloud streets and land–water interactions in the Amazon
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Cloud streets are common feature in the Amazon Basin. They form from the combination of the vertical trade wind stress and moist convection. Here, satellite imagery, data collected during the COBRA-PARÁ (Caxiuanã Observations in the Biosphere, River and Atmosphere of Pará) field campaign, and high resolution modeling are used to understand the streets′ formation and behavior. The observations show that the streets have an aspect ratio of about 3.5 and they reach their maximum activity around 15:00 UTC when the wind shear is weaker, and the convective boundary layer reaches its maximum height. The simulations reveal that the cloud streets onset is caused by the local circulations and convection produced at the interfaces between forest and rivers of the Amazon. The satellite data and modeling show that the large rivers anchor the cloud streets producing a quasi-stationary horizontal pattern. The streets are associated with horizontal roll vortices parallel to the mean flow that organizes the turbulence causing advection of latent heat flux towards the upward branches. The streets have multiple warm plumes that promote a connection between the rolls. These spatial patterns allow fundamental insights on the interpretation of the Amazon exchanges between surface and atmosphere with important consequences for the climate change understanding.
KeywordsCaxiuanã COBRA-PARA Latent flux LES Roll vortices
This research was partially supported by CAPES and PROPESP/UFPA, by the Program-PPG7/FINEP/MCT, process n. 64.99.0425.00, by MCT and CNPq/PADCT, by the Instituto do Milênio, with the Projects n. 62.0056/01-0, and n. 620065/01-0 and by FADESP/SECTAM/PRONEX, contract n. 1082. Leonardo Sá thanks CNPq for the productivity in research grant, process 304981/2007-9, and for Universal Program Support, process n. 481340/2004-1; the authors thank all the participants of the field experiment COBRA-PARA for their dedication, Museu Paraense Emílio Goeldi, UFPA, USP, UFRJ, UFSM, INPA and EMBRAPA that helped for the success of this experiment. Renato Ramos da Silva thanks CNPq for the support. The authors also thank Fundação Djalma Batista for its support.
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