Browsing by Author "Latif, M. T."
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Item Open Access Impact of the 2015 wildfires on Malaysian air quality and exposure: a comparative study of observed and modeled data(Institute of Physics, 2018-04-04) Mead, Mohammed Iqbal; Castruccio, S.; Latif, M. T.; Nadzir, M. S. M.; Dominick, D.; Thota, A.; Crippa, P.In September and October 2015, Equatorial Asia experienced the most intense biomass burning episodes over the past two decades. These events, mostly enhanced by the extremely dry weather associated with the occurrence of strong El Niño conditions, resulted in the transnational transport of hazardous pollutants from the originating sources in Indonesian Borneo and Sumatra to the highly populated Malaysian Peninsula. Quantifying the population exposure form this event is a major challenge, and only two model-based studies have been performed to date, with limited evaluation against measurements. This manuscript presents a new data set of 49 monitoring stations across Peninsular Malaysia and Malaysian Borneo active during the 2015 haze event, and performs the first comparative study of PM10 (particulate matter with diameter < 10 µm) and carbon monoxide (CO) against the output of a state-of-the-art regional model (WRF-Chem). WRF-Chem presents high skills in describing the spatio-temporal patterns of both PM10 and CO and thus was applied to estimate the impact of the 2015 wildfires on population exposure. This study showed that more than 60% of the population living in the highly populated region of the Greater Klang Valley was systematically exposed to unhealthy/hazardous air quality conditions associated with the increased pollutant concentrations from wildfires and that almost 40% of the Malaysian population was on average exposed to PM10 concentrations higher than 100 µg m−3 during September and October 2015.Item Open Access Influence of Northeast Monsoon cold surges on air quality in Southeast Asia(Elsevier, 2017-07-27) Ashfold, Matthew J.; Latif, M. T.; Samah, Azizan Abu; Mead, Mohammed Iqbal; Harris, Neil R. P.Ozone (O3) is an important ground-level pollutant. O3 levels and emissions of O3 precursors have increased significantly over recent decades in East Asia and export of this O3 eastward across the Pacific Ocean is well documented. Here we show that East Asian O3 is also transported southward to tropical Southeast (SE) Asia during the Northeast Monsoon (NEM) season (defined as November to February), and that this transport pathway is especially strong during ‘cold surges’. Our analysis employs reanalysis data and measurements from surface sites in Peninsular Malaysia, both covering 2003–2012, along with trajectory calculations. Using a cold surge index (northerly winds at 925 hPa averaged over 105–110°E, 5°N) to define sub-seasonal strengthening of the NEM winds, we find the largest changes in a region covering much of the Indochinese Peninsula and surrounding seas. Here, the levels of O3 and another key pollutant, carbon monoxide, calculated by the Monitoring Atmospheric Composition and Climate (MACC) Reanalysis are on average elevated by, respectively, >40% (∼15 ppb) and >60% (∼80 ppb) during cold surges. Further, in the broader region of SE Asia local afternoon exceedances of the World Health Organization's air quality guideline for O3 (100 μg m−3, or ∼50 ppb, averaged over 8 h) largely occur during these cold surges. Day-to-day variations in available O3 observations at surface sites on the east coast of Peninsular Malaysia and in corresponding parts of the MACC Reanalysis are similar, and are clearly linked to cold surges. However, observed O3 levels are typically ∼10–20 ppb lower than the MACC Reanalysis. We show that these observations are also subject to influence from local urban pollution. In agreement with past work, we find year-to-year variations in cold surge activity related to the El Nino-Southern Oscillation (ENSO), but this does not appear to be the dominant influence of ENSO on atmospheric composition in this region. Overall, our study indicates that the influence of East Asian pollution on air quality in SE Asia during the NEM could be at least as large as the corresponding, well-studied spring-time influence on North America. Both an enhanced regional observational capability and chemical modelling studies will be required to fully untangle the importance of this long-range influence relative to local processes.Item Open Access Isoprene hotspots at the Western Coast of Antarctic Peninsula during MASEC′16(Elsevier, 2018-12-28) Nadzir, M. S. M.; Cain, M.; Robinson, A. D.; Bolas, C.; Harris, Neil R. P.; Parnikoza, I.; Salimun, E.; Mustafa, E. M.; Alhasa, K. M.; Zainuddin, M. H. M.; Ghee, O. C.; Morris, K.; Khan, M. F.; Latif, M. T.; Wallis, B. M.; Cheah, W.; Zainudin, S. K.; Yusop, N.; Ahmad, M. R; Hussin, W. M. R. W.; Salleh, S. M.; Hamid, H. H. A.; Lai, G. T.; Uning, R.; Bakar, M. A. A.; Ariff, N. M.; Tuah, Z.; Wahab, M. I. A.; Foong, S. Y.; Samah, Azizan Abu; Chenoli, S. N.; Wan Johari, W. L.; Zain, C. R. C. M.; Rahman, N. A.; Rosenstiel, T. N.; Yusof, A. H.; Sabuti, A. A.; Alias, S. A.; Noor, A. Y. M.Isoprene (C5H8) plays an important role in the formation of surface ozone (O3) and the secondary organic aerosol (SOA) which contributed to the climate change. This study aims to determine hourly distribution of tropospheric isoprene over the Western Coast of Antarctic Peninsula (WCAP) during the Malaysian Antarctic Scientific Expedition Cruise 2016 (MASEC′16). In-situ measurements of isoprene were taken using a custom-built gas chromatography with photoionization detector, known as iDirac. Biological parameters such as chlorophyll a (chl-a) and particulate organic carbon (POC) were compared to the in-situ isoprene measurements. Significant positive correlation was observed between isoprene and POC concentrations (r2 = 0.67, p < 0.001), but not between isoprene and chl-a. The hotspots of isoprene over maritime Antarctic were then were investigated using NAME dispersion model reanalysis. Measurements showed that isoprene mixing ratio were the highest over region of King George Island, Deception Island and Booth Island with values of ∼5.0, ∼0.9 and ∼5.2 ppb, respectively. Backward trajectory analysis showed that air masses may have lifted the isoprene emitted by marine algae. We believe our findings provide valuable data set of isoprene estimation over the under sampled WCAP.