Articles | Volume 16, issue 22
Atmos. Chem. Phys., 16, 14041–14056, 2016
Atmos. Chem. Phys., 16, 14041–14056, 2016

Research article 15 Nov 2016

Research article | 15 Nov 2016

Aerosol meteorology of the Maritime Continent for the 2012 7SEAS southwest monsoon intensive study – Part 1: regional-scale phenomena

Jeffrey S. Reid1, Peng Xian1, Brent N. Holben2, Edward J. Hyer1, Elizabeth A. Reid1, Santo V. Salinas3, Jianglong Zhang4, James R. Campbell1, Boon Ning Chew5, Robert E. Holz6, Arunas P. Kuciauskas1, Nofel Lagrosas7, Derek J. Posselt8, Charles R. Sampson1, Annette L. Walker1, E. Judd Welton2, and Chidong Zhang9 Jeffrey S. Reid et al.
  • 1Marine Meteorology Division, Naval Research Laboratory, Monterey, CA, USA
  • 2NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 3Centre for Remote Imaging Sensing and Processing, National University of Singapore, Singapore
  • 4Dept. of Atmospheric Science, University of North Dakota, Grand Forks, ND, USA
  • 5Meteorological Service, Singapore
  • 6Space Sciences Engineering Center, University of Wisconsin, Madison, WI, USA
  • 7Manila Observatory, Manila, Philippines
  • 8Jet Propulsion laboratory, Pasadena, CA, USA
  • 9NOAA Pacific Marine Environmental Laboratory Seattle, WA, USA

Abstract. The largest 7 Southeast Asian Studies (7SEAS) operation period within the Maritime Continent (MC) occurred in the August–September 2012 biomass burning season. Included was an enhanced deployment of Aerosol Robotic Network (AERONET) sun photometers, multiple lidars, and field measurements to observe transported smoke and pollution as it left the MC and entered the southwest monsoon trough. Here we describe the nature of the overall 2012 southwest monsoon (SWM) and biomass burning season to give context to the 2012 deployment. The MC in 2012 was in a slightly warm El Niño/Southern Oscillation (ENSO) phase and with spatially typical burning activity. However, overall fire counts for 2012 were 10 % lower than the Reid et al. (2012) baseline, with regions of significant departures from this norm, ranging from southern Sumatra (+30 %) to southern Kalimantan (−42 %). Fire activity and monsoonal flows for the dominant burning regions were modulated by a series of intraseasonal oscillation events (e.g., Madden–Julian Oscillation, or MJO, and boreal summer intraseasonal oscillation, or BSISO). As is typical, fire activity systematically progressed eastward over time, starting with central Sumatran fire activity in June related to a moderately strong MJO event which brought drier air from the Indian Ocean aloft and enhanced monsoonal flow. Further burning in Sumatra and Kalimantan Borneo occurred in a series of significant events from early August to a peak in the first week of October, ending when the monsoon started to migrate back to its wintertime northeastern flow conditions in mid-October. Significant monsoonal enhancements and flow reversals collinear with tropical cyclone (TC) activity and easterly waves were also observed. Islands of the eastern MC, including Sulawesi, Java, and Timor, showed less sensitivity to monsoonal variation, with slowly increasing fire activity that also peaked in early October but lingered into November. Interestingly, even though fire counts were middling, resultant AERONET 500 nm aerosol optical thickness (AOT) from fire activity was high, with maximums of 3.6 and 5.6 in the Sumatra and Kalimantan source regions at the end of the burning season and an average of ∼ 1. AOTs could also be high at receptor sites, with a mean and maximum of 0.57 and 1.24 in Singapore and 0.61 and 0.8 in Kuching Sarawak. Ultimately, outside of the extreme 2015 El Niño event, average AERONET AOT values were higher than any other time since sites were established. Thus, while satellite fire data, models, and AERONET all qualitatively agree on the nature of smoke production and transport, the MC's complex environment resulted in clear differences in quantitative interpretation of these datasets.

Short summary
This paper describes aspects of the 2012 7 Southeast Asian Studies (7SEAS) operations period, the largest within the Maritime Continent. Included were an enhanced deployment of Aerosol Robotic Network (AERONET) sun photometers, multiple lidars, and a Singapore supersite. Simultaneously, a ship was dispatched to the Palawan Archipelago and Sulu Sea of the Philippines for September 2012 to observe transported smoke and pollution as it entered the southwest monsoon trough.
Final-revised paper