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Title:	Tropospheric and daily maximum ground level ozone variability in the West Coast of Peninsular Malaysia
Authors:	Fatimah Pk Ahamad (P63141)
Supervisor:	Mohd Talib Latif, Prof. Dr.
Keywords:	Troposphere Atmospheric ozone Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	1-Aug-2016
Description:	High tropospheric ozone (O3) concentrations are a major concern due to its potential risk to human health, increased mortality rate as well as reduction of crop yields. This study attempts to determine the variability of tropospheric O3 in relation to the Asian monsoon and El-Niño Southern Oscillation (ENSO). Fortnightly sonde measurements taken at Kuala Lumpur International Airport for the Southern Hemisphere Additional Ozonesondes network were used to obtain vertical O3 profiles for the period between 1998 and 2009. Daily O3 maxima between 1997 and 2011 at five locations were also analysed to determine influence of the cyclical changes on high ground level O3. Ground level O3 data was obtained from Department of Environment Malaysia. Exploratory data analysis methods such as Hierarchical Agglomerative Cluster Analysis (HACA) were employed to determine temporal variability at different altitudes. Spectral analysis was carried out to determine periodicity. The overall O3 concentration range for the soundings made during the two monsoon seasons showed less pronounced variability at altitudes between 2 km and 12 km during the southwest monsoon compared to the northeast monsoon season. HACA results for yearly average profile showed three distinct groups with strong ENSO event years clustered into a single group. Clustering the monthly average also gave three distinct groups. The two monsoons can be distinguished; however, the third group of months included both the inter-monsoon periods and months with high rainfall events. Correlation analysis of the vertical O3 profiles showed that near surface O3 concentration decoupled from the free troposphere at altitudes lower than 2 km ( < 0.05) indicating that the influence of downward intrusion of tropospheric O3 is minimal to near surface O3 concentrations. One-way ANOVA tests indicate that ENSO and monsoonal influence on tropospheric O3 was more prominent at higher altitudes. Daily maximum O3 concentrations did not show spatial consistency to ENSO and monsoonal modulation. Spectral analysis results showed a shift from annual to semi-annual cycle moving from north to south of the peninsula. A short term ground level O3 data set involving 22 stations was analysed to determine possible sources of O3 exceedance. Hourly average O3, nitrogen oxide (NO) and nitrogen dioxide (NO2) data from 2008 to 2010 for a total of seven stations located around the west coast of Peninsular Malaysia were analysed. O3 concentration at Cheras and Shah Alam monitoring stations consistently showed a high frequency of noncompliance to the Malaysian Air Quality Guideline value of 100 ppbv hourly O3. Analysis of the monthly average O3 and its precursor (NO and NO2) concentrations indicated a strong localised influence on the O3 exceedance patterns. HACA was performed on the daily maximum O3 concentration to analyse the spatial variability of the seven stations and the results gave three distinct clusters which can be explained primarily by local precursor emission and dispersion characteristics rather than monsoonal winds and geographical position. It can be concluded that only strong and sustained ENSO events had a significant impact on tropospheric O3 variability at lower altitudes. Although seasonal changes were an important cause of ground level O3 variability, high O3 episodes were strongly influenced by localized events. A simple tool is proposed to determine high ground level O3 exceedance period at stations that frequently show noncompliance. It was able to predict highest exceedance within a three month period.,Ph.D.
Pages:	131
Call Number:	QC881.2.T75F338 2016 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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