20 Apr 2021

20 Apr 2021

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

How weather events modify aerosol particle size distributions in the Amazon boundary layer

Luiz Augusto Toledo Machado1,2, Marco A. Franco2, Leslie A. Kremper1, Florian Ditas1,a, Meinrat O. Andreae1,3,4, Paulo Artaxo2, Micael A. Cecchini2, Bruna A. Holanda1, Mira L. Pöhlker1, Ivan Saraiva5, Stefan Wolff1, Ulrich Pöschl1, and Christopher Pöhlker1 Luiz Augusto Toledo Machado et al.
  • 1Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
  • 2Instituto de Física, Universidade de São Paulo, São Paulo, Brazil
  • 3Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA
  • 4Department of Geology and Geophysics, King Saud University, Riyadh, Saudi Arabia
  • 5Sistema de Proteção da Amazônia, Manaus, Brazil
  • anow at: Hessian Agency for Nature Conservation, Environment and Geology, 65203 Wiesbaden, Germany

Abstract. This study evaluates the effect of weather events on the aerosol particle size distribution (PSD) at the Amazon Tall Tower Observatory (ATTO). This research combines in-situ measurements of PSD and remote sensing data of lightning density, brightness temperature, cloud top height, cloud liquid water, and rain rate and vertical velocity. Measurements were obtained by a scanning mobility particle sizers (SMPS), the new generation of GOES satellites (GOES-16), the SIPAM S-band radar, and the LAP 3000 radar wind profiler recently installed at the ATTO-Campina site. The combined data allow exploring changes in PSD due to different meteorological processes. The average diurnal cycle shows a higher abundance of ultrafine particles (NUFP) in the early morning, which is coupled with lower concentrations in Aitken (NAIT) and accumulation (NACC) mode particles. From the early morning to the middle of the afternoon, an inverse behavior is observed, where NUFP decreases and NAIT and NACC increase, reflecting a typical particle growth process. Composite figures show an increase of NUFP before, during, and after lightning was detected by the satellite above ATTO. These findings strongly indicate a close relationship between vertical transport and deep convective clouds. Lightning density is connected with a large increase in NUFP, beginning approximately 100 minutes before the maximum lightning density and reaching peak values around 200 minutes later. In addition, the removal of NACC by convective transport was found. Both the increase in NUFP and the decrease in NACC appear in parallel with the increasing intensity of lightning activity. The NUFP increases exponentially with the thunderstorm intensity. In contrast, NAIT and NACC show a different behavior, decreasing from approximately 100 minutes before the maximum lightning activity and reaching a minimum at the time of maximum lightning activity. The effect of cloud top height, cloud liquid water, and rain rate shows the same behavior, but with different patterns among seasons. The convective processes do not occur continually but are modulated by gravity waves in the range of 1 to 5 hours, creating a complex mechanism of interaction with a succession of updrafts and downdrafts, clouds and clear sky situations.

The radar wind profiler measured the vertical distribution of the vertical velocity. These profiles show that downdrafts are mainly located below 10 km, while aircraft observations during the ACRIDICON-CHUVA campaign had shown maximum concentrations of ultrafine particles mainly above 10 km. Our study opens new scientific questions to be evaluated in order to understand the intricate physical and chemical mechanisms involved in the production of new particles in Amazonia.

Luiz Augusto Toledo Machado et al.

Status: open (until 15 Jun 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Luiz Augusto Toledo Machado et al.

Luiz Augusto Toledo Machado et al.


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Short summary
Several studies evaluate aerosol-cloud interactions but, there were only a few attempts to describe how clouds modify the aerosol properties. This study evaluates the effect of weather events on the PSD at the ATTO, combining remote sensing and in-situ data. The ultrafine, Aitken, and accumulation particles modes have different behaviors for the diurnal cycle as well as for rainfall events. This study opens new scientific questions that need to be pursued in detail in new field campaigns