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Title: Aerosols, forest fires and El Niño : air pollution issues in Malaysia
Author: Ashaari, Zulfa Hanan
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2013
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In Malaysia, human activities, particularly biomass burning, have released tiny anthropogenic aerosols into the atmosphere. These tiny particles are intricately linked to the changes in the climate system by altering radiation budget properties, carbon and hydrological cycle. Furthermore, recent studies show that there is urgent need to fill the knowledge gap in understanding the relationship between regional and local controls on aerosols variability, particularly in Malaysia. The understanding of aerosols patterns is essential for predicting future trend and assessing aerosols impact to the regional and global climate evolution. Previous studies show ground based measurements coupled with remote sensing datasets have proved valuable for studying spatial and temporal aerosol distribution. However, such studies have been lacking in Malaysia. Therefore, this study aims to integrate ground-based measurements and satellite observations data to better understand the aerosols patterns in this region. In addition, the spatial-temporal patterns of aerosols load have been investigated in combination with forest fires, ENSO and meteorological analysis in an attempt to understand the aerosol system across Malaysia. This study compares the ground-based measurements data with those of the satellites data to evaluate the reliability of ground-based data. Ground-based data was compared with those of the satellite data of MODIS and OMI covering the years 2005 -2008: and ground-based AERONET data covering the years 2007-2008. Preliminary results of this study show that, in general, monthly mean of MODIS AOD and OMI AI as well as their temporal variation are in good agreement with ground-based data in the south peninsular and western Borneo area, which suggests there might be strong absorbing aerosols occurring in this area. However. MODIS AOD is better in presenting what happens on the ground. The comparison of MODIS and AMI aerosol properties agree well, and indicate the presence of high aerosol loads during ENSO years. The relationship between . AERONET and ground-based data exhibit moderate relationship probably due to the limited data availability. Furthermore. using regression analysis, TOMS Al data was found good to be used as a surrogate data to reconstruct ground data for the period 1980-1992. The relationship between TOMS AI and ground-based data improved when the amount of particulate matter captured by ground instrument is high. Furthermore, this work evaluates spatial, seasonal and inter-annual variability of aerosol load across Malaysia and its relation to forest fires, ENSO events and meteorological factors. for the 1980-2008 periods using rotated principal components analysis. The finding indicates that the variability of ground-based data can be decomposed into three components, each characterising different spatial and temporal variations. The first component characterises the south peninsular subregion with the ground-based data showing strong seasonal cycle with maximum concentrations found during the SW monsoon and minimum concentrations during the NE monsoon. It is found that fires emission from Sumatra contribute largely to aerosol loads during the SW monsoon in this sub-region. In addition, the concentrations in this sub-region are recorded to increase by 20 per cent during ENSO years. The second component characterised the region of the north peninsular; showing bimodality cycle of aerosol variation. This area exhibits two maximum concentrations which occurred during the end of the wet season and during the SW season as well as two minimum which recorded during the inter-monsoon season. It was found that concentrations in this sub-region are not related to Malaysian and Indonesian fires at all. This suggests fires from Indo-China may contribute to this sub-region concentration peaks value. The impact of ENSO events to the concentration in this Sub-region appears clearer between the 1992-2008 period where the concentrations are recorded to increase up to 40 per cent. The third component features the region of western Borneo showing a peak concentration in August-September, which results from the shift of the Inter Tropical Convergence Zone (ITCZ) to the northern-most location. Peaks in August-September are strongly associated to the minimum rainfall amounts. In addition, extreme observations found within this time period are strongly affected by fires emissions from Borneo. It was found that not all ENSO events have significant relationship with aerosol concentration in this sub-region. In general, this study concludes trends in anthropogenic aero sol in Malaysia during 1980-2008 are largely associated with forest tires and ENSO events and are also found to be strongly associated with rainfall cycle and ITCZ fluctuation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available