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Volume 18, issue 9
Atmos. Chem. Phys., 18, 6461-6482, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5)...

Special issue: The ACRIDICON-CHUVA campaign to study deep convective clouds...

Atmos. Chem. Phys., 18, 6461-6482, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 07 May 2018

Research article | 07 May 2018

Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

Luiz A. T. Machado1, Alan J. P. Calheiros1, Thiago Biscaro1, Scott Giangrande2, Maria A. F. Silva Dias3, Micael A. Cecchini3, Rachel Albrecht3, Meinrat O. Andreae4,14, Wagner F. Araujo1, Paulo Artaxo5, Stephan Borrmann4, Ramon Braga1, Casey Burleyson6, Cristiano W. Eichholz1, Jiwen Fan6, Zhe Feng6, Gilberto F. Fisch8, Michael P. Jensen2, Scot T. Martin7, Ulrich Pöschl4, Christopher Pöhlker4, Mira L. Pöhlker4, Jean-François Ribaud1, Daniel Rosenfeld9, Jaci M. B. Saraiva10, Courtney Schumacher11, Ryan Thalman12, David Walter4, and Manfred Wendisch13 Luiz A. T. Machado et al.
  • 1National Institute for Space Research (INPE), Sao José dos Campos, Brazil
  • 2Brookhaven National Laboratory, Upton, New York, USA
  • 3Institute of Astronomy, Geophysics, and Atmospheric Sciences, University of São Paulo, São Paulo, Brazil
  • 4Max Planck Institute for Chemistry, Mainz, Germany
  • 5Institute of Physics, University of São Paulo, São Paulo, Brazil
  • 6Pacific Northwest National Laboratory, Richland, WA, USA
  • 7Harvard University, Cambridge, Massachusetts, USA
  • 8Department of Aerospace Science and Technology, São José dos Campos, Brazil
  • 9Hebrew University of Jerusalem, Jerusalem, Israel
  • 10Amazon Protection System (SIPAM), Manaus, Brazil
  • 11Texas A & M University, College Station, Texas, USA
  • 12Snow College, Richfield, UT, USA
  • 13Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany
  • 14Scripps Institution of Oceanography, University of California, San Diego, CA 92037, USA

Abstract. This study provides an overview of precipitation processes and their sensitivities to environmental conditions in the Central Amazon Basin near Manaus during the GoAmazon2014/5 and ACRIDICON-CHUVA experiments. This study takes advantage of the numerous measurement platforms and instrument systems operating during both campaigns to sample cloud structure and environmental conditions during 2014 and 2015; the rainfall variability among seasons, aerosol loading, land surface type, and topography has been carefully characterized using these data. Differences between the wet and dry seasons were examined from a variety of perspectives. The rainfall rates distribution, total amount of rainfall, and raindrop size distribution (the mass-weighted mean diameter) were quantified over both seasons. The dry season generally exhibited higher rainfall rates than the wet season and included more intense rainfall periods. However, the cumulative rainfall during the wet season was 4 times greater than that during the total dry season rainfall, as shown in the total rainfall accumulation data. The typical size and life cycle of Amazon cloud clusters (observed by satellite) and rain cells (observed by radar) were examined, as were differences in these systems between the seasons. Moreover, monthly mean thermodynamic and dynamic variables were analysed using radiosondes to elucidate the differences in rainfall characteristics during the wet and dry seasons. The sensitivity of rainfall to atmospheric aerosol loading was discussed with regard to mass-weighted mean diameter and rain rate. This topic was evaluated only during the wet season due to the insignificant statistics of rainfall events for different aerosol loading ranges and the low frequency of precipitation events during the dry season. The impacts of aerosols on cloud droplet diameter varied based on droplet size. For the wet season, we observed no dependence between land surface type and rain rate. However, during the dry season, urban areas exhibited the largest rainfall rate tail distribution, and deforested regions exhibited the lowest mean rainfall rate. Airplane measurements were taken to characterize and contrast cloud microphysical properties and processes over forested and deforested regions. Vertical motion was not correlated with cloud droplet sizes, but cloud droplet concentration correlated linearly with vertical motion. Clouds over forested areas contained larger droplets than clouds over pastures at all altitudes. Finally, the connections between topography and rain rate were evaluated, with higher rainfall rates identified at higher elevations during the dry season.

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Short summary
This overview discuss the main precipitation processes and their sensitivities to environmental conditions in the Central Amazon Basin. It presents a review of the knowledge acquired about cloud processes and rainfall formation in Amazonas. In addition, this study provides a characterization of the seasonal variation and rainfall sensitivities to topography, surface cover, and aerosol concentration. Airplane measurements were evaluated to characterize and contrast cloud microphysical properties.
This overview discuss the main precipitation processes and their sensitivities to environmental...