Browsing by Author "Liew Juneng"

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    Current Circulation Pattern in Waters Around Pulau Tinggi, Johor
    (Penerbit UKM) Fredolin T. Tangang; Liew Juneng; Mohd Syamil Mohd Yussof
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    Factors influencing the variations of PM10 aerosol dust in Klang Valley, Malaysia during the summer
    (Elsevier, 2011) Liew Juneng; Mohd Talib Latif; Fredolin Tangang
    The associations between the variations of PM10 concentration during summer monsoon dry seasons over the Klang Valley, Malaysia and the local meteorological factors, synoptic weather conditions as well as the regional hotspots number were examined based on simple multiple linear regression analysis. The regressive relationships established, suggest that the variation of PM10 in Klang Valley was governed significantly by all of the examined factors. Local meteorological conditions are among those factors which governed the largest day-to-day variations of PM10 concentration in the Klang Valley areas during the dry season.
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    Impact of regional haze towards air quality in Malaysia: A review
    (Elsevier, 2018) Mohd Talib Latif; Murnira Othman; Nurfathehah Idris; Liew Juneng; Ahmad Makmom Abdullah; Wan Portia Hamzah; Md Firoz Khan; Nik Meriam Nik Sulaiman; Jegalakshimi Jewaratnam; Nasrin Aghamohammadi; Mazrura Sahani; Chung Jing Xiang; Fatimah Ahamad; Norhaniza Amil; Mashitah Darus; Helena Varkkey; Fredolin Tangang; Abu Bakar Jaafar
    Haze is a common phenomenon afflicting Southeast Asia (SEA), including Malaysia, and has occurred almost every year within the last few decades. Haze is associated with high level of air pollutants; it reduces visibility and affects human health in the affected SEA countries. This manuscript aims to review the potential origin, chemical compositions, impacts and mitigation strategies of haze in Malaysia.
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    Interaction of PM10 concentrations with local and synoptic meteorological conditions at different temporal scales
    (Elsevier, 2020) Hanashriah Hassan; Mohd Talib Latif; Liew Juneng; Norhaniza Amil; Md Firoz Khan; Diong Jeong Yik; Nur Aleesha Abdullah
    Changing meteorological conditions over short and long time scales are anticipated to affect the concentrations of particulate matter with aerodynamic diameter below than 10 μm (PM10) in the atmosphere. This study aims to identify the temporal characteristics of PM10 including its relationship with local and synoptic meteorological conditions in Petaling Jaya (PJ), Malaysia from 1996 to 2016.A high volume sampler (HVS), mounted on the rooftop of MetMalaysia, was used to monitor daily PM10 concentrations. The meteorological parameter data were obtained from the MetMalaysia PJ station.
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    Investigating the mechanisms of diurnal rainfall variability over Peninsular Malaysia using the non-hydrostatic regional climate model
    (Springer, 2017) Ahmad Fairudz Jamaluddin; Fredolin Tangang; Jing Xiang Chung; Liew Juneng; Hidetaka Sasaki; Izuru Takayabu
    This study aims to provide a basis for understanding the mechanisms of diurnal rainfall variability over Peninsular Malaysia by utilising the Non-Hydrostatic Regional Climate Model (NHRCM). The present day climate simulations at 5 km resolution over a period of 20 years, from 1st December 1989 to 31st January 2010 were conducted using the six-hourly Japanese re-analysis 55 years (JRA-55) data and monthly Centennial in situ Observation Based Estimates (COBE) of sea surface temperature as lateral and lower boundary conditions.
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    Long term assessment of air quality from a background station on the Malaysian Peninsula
    (Elsevier, 2014) Mohd Talib Latif; Doreena Dominick; Fatimah Ahamad; Md Firoz Khan; Liew Juneng; Firdaus Mohamad Hamzah; Mohd Shahrul Mohd Nadzir
    Rural background stations provide insight into seasonal variations in pollutant concentrations and allow for comparisons to be made with stations closer to anthropogenic emissions. In Malaysia, the designated background station is located in Jerantut, Pahang. A fifteen-year data set focusing on ten major air pollutants and four meteorological variables from this station were analysed. Diurnal, monthly and yearly pollutant concentrations were derived from hourly continuous monitoring data. Statistical methods employed included principal component regression (PCR) and sensitivity analysis.
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    Madden Julian oscillation modulation for surface ozone in Peninsular Malaysia
    (Elsevier, 2020) Mary Angelina Jud; Liew Juneng; Fredolin T. Tangang; Mohd Talib Latif; Jing Xiang Chung; Fatimah Ahamad
    This study investigates the modulation of Madden-Julian Oscillation (MJO) on surface ozone (O3) variability in Peninsular Malaysia. A 17-years (2000-2016) record of daily maximum surface ozone (O3Max) concentration from 24 air quality monitoring stations across Peninsular Malaysia were divided into six sub-regions namely R1, R2, R3, R4, R5 and R6. To investigate MJO modulation on O3Max, total cloud cover (TCC), surface air temperature (SAT) and surface wind from ERA Interim Reanalysis were also analyzed.
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    Overview of atmospheric aerosol studies in Malaysia: Known and unknown
    (Elsevier, 2016) Kasturi Devi Kanniah; Dimitris G. Kaskaoutis; Lim Hwee San; Mohd Talib Latif; Nurul Amalin Fatihah Kamarul Zaman; Liew Juneng
    In the present work, we summarize and discuss the results of previous studies that investigated the aerosol properties over Malaysia by means of various instrumentation and techniques, focusing on the use of remote sensing data to examine atmospheric aerosols. Furthermore, we identify gaps in this research field and recommend further studies to bridge these knowledge gaps.
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    Seasonal and long term variations of surface ozone concentrations in Malaysian Borneo
    (Elsevier, 2016) Mohd Talib Latif; Doreena Dominick; Fatimah Ahamad; Nur Shuhada Ahamad; Md Firoz Khan; Liew Juneng; Chung Jing Xiang; Mohd Shahrul Mohd Nadzir; Andrew D. Robinson; Marzuki Ismail; Mohammed Iqbal Mead; Neil R.P. Harris
    Malaysian Borneo has a lower population density and is an area known for its lush rainforests. However, changes in pollutant profiles are expected due to increasing urbanisation and commercial-industrial activities. This study aims to determine the variation of surface O3 concentration recorded at seven selected stations in Malaysian Borneo. Hourly surface O3 data covering the period 2002 to 2013, obtained from the Malaysian Department of Environment (DOE), were analysed using statistical methods.
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    Seasonal circulations in the Malay Peninsula Eastern continental shelf from a wave-tide-circulation coupled model
    (Springer, 2011) Fredolin T. Tangang; Changsui Xia; Fangli Qiao; Liew Juneng; Feng Shan
    A wave-tide-circulation coupled model based on Princeton Ocean Model is established to study the seasonal circulation in the Malay Peninsula Eastern Continental Shelf region. The model successfully reconstructs the observed seasonal variation of the circulation in the region, as well as the main currents. The simulated tidal harmonic constants, sea surface temperature, and sea surface height anomaly agree with the observations well.
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    SouthEast Asia HydrO-meteorological droughT (SEA-HOT) framework: A case study in the Kelantan River Basin, Malaysia
    (Elsevier, 2020) Mou Leong Tan; Liew Juneng; Fredolin T. Tangang; Narimah Samat; Ngai Weng Chan; Zulkifli Yusop; Sheau Tieh Ngai
    A holistic framework was introduced to project the potential hydro-meteorological droughts of the Kelantan River basin, Malaysia. The framework integrates the multi-model high-resolution climate projections of the Coordinated Regional Climate Downscaling Experiment – Southeast Asia (CORDEX-SEA) and the widely applied Soil and Water Assessment Tool (SWAT) model. The quantile mapping approach was used to reduce the biases in the CORDEX-SEA projections before applying into SWAT. The SWAT-simulated standardized streamflow index (SSI) was validated with observed data to check the capability of SWAT in drought estimation.
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    Spatio-temporal assessment of nocturnal surface ozone in Malaysia
    (Elsevier, 2019) Mohd Famey Yusoff; Mohd Talib Latifa; Liew Juneng; Md Firoz Khan; Fatimah Ahamad; Jing Xiang Chung; Anis Asma Ahmad Mohtar
    This study aims to determine the level and potential sources of nocturnal surface ozone (NSO) in different regions in Malaysia. Eleven-year (2005-2015) ozone data from 37 continuous air quality monitoring stations throughout Malaysia have been analysed to determine spatio-temporal variations in NSO concentrations. NSO daily maximum concentrations from different regions in Malaysia were used for seasonal variation analysis while linear regression and the Mann-Kendall trend test were used for the annual variation analysis.
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    Spatio-temporal characteristics of PM10 concentration across Malaysia
    (Elsevier, 2009) Liew Juneng; Mohd Talib Latif; Fredolin T. Tangang; Haslina Mansor
    The recurrence of forest fires in Southeast Asia and associated biomass burning, has contributed markedly to the problem of trans-boundary haze and the long-range movement of pollutants in the region. Air pollutants, specifically particulate matter in the atmosphere, have received extensive attention, mainly because of their adverse effect on people's health. In this study, the spatial and temporal variability of the PM10 concentration across Malaysia was analyzed by means of the rotated principal component analysis.
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    Trend and status of air quality at three different monitoring stations in the Klang Valley, Malaysia
    (Springer, 2010) Siti Zawiyah Azmi; Mohd Talib Latif; Aida Shafawati Ismail; Liew Juneng; Abdul Aziz Jemain
    Over the last decades, the development of the Klang Valley (Malaysia), as an urban commercial and industrial area, has elevated the risk of atmospheric pollutions. There are several significant sources of air pollutants which vary depending on the background of the location they originate from. The aim of this study is to determine the trend and status of air quality and their correlation with the meteorological factors at different air quality monitoring stations in the Klang Valley. The data of five major air pollutants (PM10, CO, SO2, O3, NO2) were recorded at the Alam Sekitar Sdn Bhd (ASMA) monitoring stations in the Klang Valley, namely Petaling Jaya (S1), Shah Alam (S2) and Gombak (S3). The data from these three stations were compared with the data recorded at Jerantut, Pahang (B), a background station established by the Malaysian Department of Environment.
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    Unjuran Perubahan Iklim Ekstrim Masa Depan di Malaysia
    (Penerbit UKM, 2013) Meng Sei Kwan; Fredolin T. Tangang; Liew Juneng
    Mitigating and adapting to the impacts of climate change at regional level require downscaled projection of future climate states. This paper examined the possible changes of future climate extremes over Malaysia based on the IPCC SRES A1B emission scenario. The projected changes at 17 stations were produced by bias correcting the UKMO PRECIS downscaling simulation output. The simulation expected higher probability of rainfall extreme occurrences over the west coast of Peninsular Malaysia during the autumn transitional monsoon period. In addition, possible early monsoon rainfall was projected for certain stations located over East Malaysia. The simulation also projected larger increase of warm temperature extremes but smaller decrease of cold extremes, suggesting asymmetric expansion of the temperature distribution. The impact of the elevated green house gases (GHG) is higher in the night time temperature extremes as compared to the day time temperature extremes. The larger increment of warm night frequencies as compared to the warm day suggests smaller diurnal temperature ranges under the influence of higher greenhouse gases. Stations located in East Malaysia were projected to experience the largest increase of warm night occurrence.
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    Variation of surface ozone exceedance around Klang Valley, Malaysia
    (Elsevier, 2014) Fatimah Ahamad; Mohd Talib Latif; Rosy Tang; Liew Juneng; Doreena Dominick; Hafizan Juahir
    The total hourly surface ozone (O3) exceedance from the 100 ppbv hourly O3 standard set by the Department of Environment Malaysia (DOE) was analysed, as elevated O3 concentrations pose health risks to humans and harms vegetation. Air quality data from 2008 to 2010 were obtained from a total of seven stations located around the west coast of Peninsular Malaysia.
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    Variations of surface ozone concentration across the Klang Valley, Malaysia
    (Elsevier, 2012) Mohd Talib Latif; Lim Shun Huey; Liew Juneng
    Hourly air quality data covering the period 2004-2008 was obtained from the Air Quality Division, the Department of Environment (DOE) through long-term monitoring by Alam Sekitar Sdn. Bhd. (ASMA) were analysed to investigate the variations of surface ozone (O3) in the Klang Valley, Malaysia. A total of nine monitoring stations were selected for analysis in this study and the results show that there are distinct seasonal patterns in the surface O3 across the Klang Valley. A high surface O3 concentration is usually observed between January and April, while a low surface O3 concentration is found between June and August.
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    Volatile organic compounds and their contribution to ground-level ozone formation in a tropical urban environment
    (Elsevier, 2022) Mohd Faizul Hilmi Zulkifli; Nor Syamimi Sufiera Limi Hawari; Mohd Talib Latif; Haris Hafizal Abd Hamid; Anis Asma Ahmad Mohtar; Wan Mohd Razi Wan Idris; Nur Ili Hamizah Mustaffa; Liew Juneng
    This study aims to determine the trends of volatile organic compound (VOC) concentrations and their potential contribution to O3 formation. The hourly data (August 2017 to July 2018) for 29 VOCs were obtained from three Malaysian Department of Environment continuous air quality monitoring stations with different urban backgrounds (Shah Alam, Cheras, Seremban). The Ozone Formation Potential (OFP) was calculated based on the individual Maximum Incremental Reactivity (MIR) and VOC concentrations.
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    Wavelet-based time series model to improve the forecast accuracy of PM10 concentrations in Peninsular Malaysia
    (Elsevier, 2015) Doreena Dominick; Mohd Talib Latif; Liew Juneng; Md Firoz Khan; Norhaniza Amil; Mohammed Iqbal Mead; Mohd Shahrul Mohd Nadzir; Phang Siew Moi; Azizan Abu Samah; Matthew J. Ashfold; William T. Sturges; Neil R.P. Harris; Andrew D. Robinson; John A. Pyle
    Particle mass concentrations (PM10, PM2.5 and PM1) and particle number concentration ((PNC); 0.27 μm ≤ Dp ≤ 34.00 μm) were measured in the tropical coastal environment of Bachok, Kelantan on the Malaysian Peninsula bordering the southern edge of the South China Sea. Statistical methods were applied on a three-month hourly data set (9th January to 24th March 2014) to study the influence of north-easterly winds on the patterns of particle mass and PNC size distributions.