Preprints
https://doi.org/10.5194/acp-2020-1098
https://doi.org/10.5194/acp-2020-1098

  22 Oct 2020

22 Oct 2020

Review status: this preprint is currently under review for the journal ACP.

What Drives Daily Precipitation Over Central Amazon? Differences Observed Between Wet and Dry Seasons

Thiago S. Biscaro1, Luiz A. T. Machado1,3, Scott E. Giangrande2, and Michael P. Jensen2 Thiago S. Biscaro et al.
  • 1National Institute for Space Research, Cachoeira Paulista, São Paulo, 12630000, Brazil
  • 2Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA
  • 3Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany

Abstract. This study suggests a new approach on how diurnal precipitation is modulated by the nighttime events developed over Central Amazon using data from the Observations and Modelling of the Green Ocean Amazon (GoAmazon 2014/5) field campaign in the Central Amazon as well as radar and satellite data. Local observations of cloud occurrences, soil temperature, surface fluxes, and planetary boundary layer characteristics are coupled with satellite data to identify physical mechanisms that control the diurnal rainfall in Amazonas during the wet and dry season. This is accomplished by evaluating the atmospheric properties during the nocturnal periods from the days prior to rainfall and non-raining events. Comparisons between non-rainy and rainy transitions are presented for the wet (January to April) and dry (June to September) seasons. The results suggest that wet season diurnal precipitation is modulated mainly by night-time cloud coverage and local effects such as turbulence, while dry season rain events are mainly controlled by large-meso scale circulation.

Thiago S. Biscaro et al.

 
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Status: final response (author comments only)
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Thiago S. Biscaro et al.

Thiago S. Biscaro et al.

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Short summary
This study suggests that there are two distinct modes driving diurnal precipitating convective clouds over central Amazon. During the wet season, local factors such as turbulence and nighttime cloud coverage are the main controls of daily precipitation, while dry season daily precipitation is modulated primarily by the mesoscale convective pattern. The results imply that models and parameterizations must consider different formulations based on the seasonal cycle to correctly resolve convection.
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