Preprints
https://doi.org/10.5194/acp-2021-674
https://doi.org/10.5194/acp-2021-674

  04 Oct 2021

04 Oct 2021

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

Radiative and microphysical responses of clouds to an anomalous increase in fire particles over the Maritime Continent in 2015

Azusa Takeishi and Chien Wang Azusa Takeishi and Chien Wang
  • Laboratoire d’Aérologie, UPS/CNRS, 14 avenue Edouard Belin, 31400 Toulouse, FRANCE

Abstract. The year of 2015 was an extremely dry year for Southeast Asia where the direct impact of strong El Niño was in play. As a result of this dryness and the relative lack of rainfall, an extraordinary amount of aerosol particles from biomass burning remained in the atmosphere over the Maritime Continent during the fire season. This study uses the Weather Research and Forecasting model coupled with Chemistry to understand the impacts of these fire particles on cloud microphysics and radiation during the peak biomass burning season in September. Our simulations, one with fire particles and the other without them, cover the entire Maritime Continent region at a cloud-resolving resolution (4 km) for the entire month of September in 2015. The comparison of the simulations shows a clear sign of precipitation enhancement by fire particles through microphysical effects; smaller cloud droplets remain longer in the atmosphere to later form ice crystals, and/or they are more easily collected by ice-phase hydrometeors, in comparison to droplets under no fire influences. As a result, mass of ice-phase hydrometeors increases in the simulation with fire particles, so does rainfall. On the other hand, we see no clear sign of temperature differences between the two simulations that could stem from the semi-direct effects of aerosols by absorbing the incoming solar radiation. Clouds are more reflective in the simulation with fire particles as ice mass increases. Combined with the direct scattering of sunlight by aerosols, the simulation with fire particles shows higher albedo over the simulation domain on average. The simulated response of clouds to fire particles in our simulations clearly differs from what was presented by two previous studies that modeled aerosol-cloud interaction in years with different phases of El Niño-Southern Oscillation (ENSO), suggesting a further need for an investigation on the possible modulation of fire-aerosol-convection interaction by ENSO.

Azusa Takeishi and Chien Wang

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-674', Anonymous Referee #1, 19 Oct 2021
    • AC1: 'Reply on RC1', Azusa Takeishi, 09 Nov 2021
      • RC3: 'Reply on AC1', Anonymous Referee #1, 16 Nov 2021
  • RC2: 'Comment on acp-2021-674', Anonymous Referee #2, 16 Nov 2021

Azusa Takeishi and Chien Wang

Azusa Takeishi and Chien Wang

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Short summary
Nanometer- to micrometer-sized particles in the atmosphere, namely aerosols, play a crucial role in cloud formation as cloud droplets form on aerosols. This study uses a weather forecasting model to examine the impacts of a large emission of aerosol particles from biomass burning activities over Southeast Asia. We find that additional cloud droplets brought by fire-emitted particles can lead to taller and more reflective convective clouds with increased rainfall.
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