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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 08 May 2019

Research article | 08 May 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Planetary boundary layer evolution over the Amazon rain forest in episodes of deep moist convection at ATTO

Maurício I. Oliveira1,a, Otávio C. Acevedo1, Matthias Sörgel2, Ernani L. Nascimento1, Antonio O. Manzi3, Pablo E. S. Oliveira1, Daiane V. Brondani1, Anywhere Tsokankunku2, and Meinrat O. Andreae2,4 Maurício I. Oliveira et al.
  • 1Universidade Federal Santa Maria, Departamento de Física, Santa Maria, RS, Brazil
  • 2Max Planck Institute for Chemistry, P.O. Box 3060, 55020, Mainz, Germany
  • 3Instituto Nacional de Pesquisas da Amazônia (INPA), Clima e Ambiente (CLIAMB), Av. André Araújo 2936, Manaus-AM,CEP 69083-000, Brazil
  • 4Scripps Institution of Oceanography, University of California San Diego, La Jolla, USA
  • afor Analysis and Prediction of Storms, and School of Meteorology, University of Oklahoma, Norman, Oklahoma, USA

Abstract. In this study, high-frequency, multi-level measurements performed from late October to mid-November of 2015 at a 80-m tall tower of the Amazon Tall Tower Observatory (ATTO) project in central Amazonas State, Brazil, were used to diagnose the evolution of thermodynamic and kinematic variables as well as scalar fluxes during the passage of outflows generated by deep moist convection (DMC). Outflow associated with DMC activity over or near the tall tower was identified through the analysis of storm echoes in base reflectivity data from S-band weather radar at Manaus, combined with the detection of gust fronts and cold pools utilizing tower data. Four outflow events were selected, three of which took place during the early evening transition or nighttime hours and one during the early afternoon. Results show that the magnitude of the drop in virtual potential temperature and changes in wind velocity during outflow passages vary according to the type, organization, and life cycle of the convective storm. Overall, the nocturnal events highlighted the passage of well-defined gust fronts with moderate decrease in virtual potential temperature and increase in wind speed. The early afternoon event lacked a sharp gust front and only a gradual drop in virtual potential temperature was observed, probably because of weak or undeveloped outflow. Sensible heat flux (H) experienced an increase at the time of gust front arrival, which was possibly due to sinking of colder air. This was followed by a prolonged period of negative H, associated with enhanced nocturnal negative H in the storms' wake. In turn, increased latent heat flux (LE) was observed following the gust front, owing to drier air coming from the outflow; however, malfunctioning of the moisture sensors during rain precluded a better assessment of this variable. Substantial enhancements of Turbulent Kinetic Energy (TKE) were observed during and after gust front passage, with values comparable to those measured in grass fire experiments, evidencing the highly turbulent character of convective outflows. The early afternoon event displayed slight decreases in the aforementioned quantities in the passage of the outflow. Finally, a conceptual model of the time evolution of H in nocturnal convective outflows observed at the tower site is presented.

Maurício I. Oliveira et al.
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Maurício I. Oliveira et al.
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Short summary
In this study, data collected during 4 deep convection events at the 80-m tower from the Amazon Tall-Tower Observatory are analyzed. It provides a unique view on how such events affect the local boundary layer and how it recovers after their passage. Quantities analyzed include mean wind speed, virtual potential temperature, turbulent kinetic energy, sensible and latent heat fluxes. A conceptual model for boundary layer structure along the passage of deep convection events is proposed.
In this study, data collected during 4 deep convection events at the 80-m tower from the Amazon...