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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2016-1179
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
16 Feb 2017
Review status
A revision of this discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Vertical distribution of aerosols over the Maritime Continent during El Nino
Jason Blake Cohen1, Daniel Hui Loong Ng2, Alan Wei Lun Lim3, and Xin Rong Chua4 1School of Atmospheric Sciences, Sun Yat-Sen University, Guangzhou, China
2Tropical Marine Science Institute, National University of Singapore, Singapore
3The Chinese University of Hong Kong, Hong Kong, China
4Princeton University, Princeton, NJ, USA
Abstract. The vertical distribution of aerosols over Southeast Asia, a critical factor of aerosol lifetime, and impact on radiative forcing and precipitation, is examined for the 2006 post El-Nino fire burning season. Additionally, through analysis of measurements and modeling, we have reconfirmed the hypothesis that fire radiative power is underestimated. Our results are significantly different from what others are using. The horizontally constrained Maritime Continent’s fire plume median height, using the maximum variance of satellite observed Aerosol Optical Depth as the spatial and temporal constraint, is found to be 2.17 ± 1.53 km during the 2006 El Nino season. This is 0.96 km higher than random sampling and all other past studies, with 62 % of particles in the free troposphere. The impact is that the aerosol lifetime will be significantly longer, and that the aerosols will disperse in a direction different from if they were in the boundary layer. Application of a simple plume rise model using measurements of fire properties underestimates the median plume height by 0.34 km and more in the bottom-half of the plume. The center of the plume can be reproduced when fire radiative power is increased by 20 % (range from 0 % to 100 %). However, to reduce the biases found, improvements are required in terms of measurements of fire properties when cloud covered, representation of small scale convection, and inclusion of aerosol direct and semi-direct effects. The results provide the unique aerosol signature of fire under El-Nino conditions.

Citation: Cohen, J. B., Ng, D. H. L., Lim, A. W. L., and Chua, X. R.: Vertical distribution of aerosols over the Maritime Continent during El Nino, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2016-1179, in review, 2017.
Jason Blake Cohen et al.
Jason Blake Cohen et al.
Jason Blake Cohen et al.

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Short summary
Measured aerosol heights over the Maritime Continent are higher than previously thought, with 62 % of aerosols above the boundary layer. These aerosols should hence have a larger impact on the climate. The use of a plume rise model cannot match the measurements, unless the measured fire energy is increased by 20 %–100 %. Furthermore, the model is too spread, indicating the importance of including convection and aerosol/radiation interactions. Significant model improvements will be required.
Measured aerosol heights over the Maritime Continent are higher than previously thought, with...
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