Abstract
One of the worst haze events to ever hit Peninsular Malaysia occurred in June 2013 due to smoke from Riau, Central Sumatra. While biomass-burning in the region is common, the early occurrence of a haze episode of this magnitude was uncharacteristic of the seasonality of extreme fire events, which usually occur between August and October in the Maritime Continent (MC). This study aims to investigate the phenomenology of the June 2013 haze event and its underlying meteorological forcing agents. The aerosol and meteorological environment during the event is examined using the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire hotspot detections and aerosol optical thickness retrievals, satellite-based precipitation retrievals, and meteorological indices. These datasets are then supported by a WRF-Chem simulation to provide a comprehensive picture of the event’s meteorology and aerosol transport phenomenology. While extreme fire events are more characteristic of El Nino years, the MODIS fire count over the MC in June for the years 2001–2015 was highest in 2013 when neutral El Nino/Southern Oscillation (ENSO) conditions prevailed. Although, the mean daily precipitation for June 2013 was below average for June 2003–2015. An early active tropical cyclone (TC) season occurred in 2013, and results show that the combined induced subsidence and flow enhancement due to TC Bebinca and the dry phases of a strong Madden–Julian Oscillation (MJO) event contributed to the event intensification. Results also show that Bebinca induced a decrease in surface relative humidity of at least 10% over Riau, where fire hotspots were concentrated.
Highlights
Biomass-burning haze (BBH) in Southeast Asia (SEA) is an environmental concern that has attracted much attention during the past decade
While ERA-Interim successfully captures the location of precipitation, it fails to capture the regions of high precipitation over the SCS as compared to Center MORPHing technique product (CMORPH) and WRF-Chem
CMORPH, WRF-Chem, and ERA-Interim all show that while precipitation prevailed over the northern half of the domain, a distinct region of dryness can be observed over Peninsular Malaysia, Sumatra, and Borneo
Summary
Biomass-burning haze (BBH) in Southeast Asia (SEA) is an environmental concern that has attracted much attention during the past decade. Throughout the Maritime Continent (MC), agricultural waste burning, intentional forest fires to convert forests to agricultural land, and related peat burning have been the major causes of extreme haze episodes [1,2,5,6]. Such events are reported to have had alarming detrimental health effects on the populations affected most by the respective episodes [7,8,9,10]. If we understand the meteorological phenomenology that leads to favourable fire weather, we can start to understand and predict burning and its consequences
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