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 Chua41School 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
Received: 30 Dec 2016 – Accepted for review: 15 Feb 2017 – Discussion started: 16 Feb 2017
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.
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., doi:10.5194/acp-2016-1179, in review, 2017.