Meteorological parameters are the critical factors affecting the transmission of infectious diseases such as Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS), and ...influenza. Consequently, infectious disease incidence rates are likely to be influenced by the weather change. This study investigates the role of Singapore's hot tropical weather in COVID-19 transmission by exploring the association between meteorological parameters and the COVID-19 pandemic cases in Singapore. This study uses the secondary data of COVID-19 daily cases from the webpage of Ministry of Health (MOH), Singapore. Spearman and Kendall rank correlation tests were used to investigate the correlation between COVID-19 and meteorological parameters. Temperature, dew point, relative humidity, absolute humidity, and water vapor showed positive significant correlation with COVID-19 pandemic. These results will help the epidemiologists to understand the behavior of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus against meteorological variables. This study finding would be also a useful supplement to help the local healthcare policymakers, Center for Disease Control (CDC), and the World Health Organization (WHO) in the process of strategy making to combat COVID-19 in Singapore.
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•COVID-19 is an emerging infectious disease and highly contagious in nature.•Temperature, dew point, and absolute humidity showed positive significant associations with SARS-CoV-2 transmission.•SARS-CoV-2 displayed negative associations with wind speed and ventilation coefficient.
Black carbon (BC) has been demonstrated to pose significant negative impacts on climate and human health. Equivalent BC (EBC) measurements were conducted using a 7-wavelength aethalometer, from March ...to May 2016, over an urban atmosphere, viz., Chiang Mai (98.957°E, 18.795°N, 373 m above sea level), Thailand in northern peninsular Southeast Asia. Daily variations in aerosol light absorption were mainly governed by open fire activities in the region. The mean mass-specific absorption cross-section (MAC) value of EBC at 880 nm was estimated to be 9.3 m2 g−1. The median EBC mass concentration was the highest in March (3.3 μg m−3) due to biomass-burning (comprised of forest fire and agricultural burning) emissions accompanied by urban air pollution within the planetary boundary layer under favorable meteorological conditions. Daily mean absorption Ångström exponent (AAE470/950) varied between 1.3 and 1.7 and could be due to variations in EBC emission sources and atmospheric mixing processes. EBC source apportionment results revealed that biomass-burning contributed significantly more to total EBC concentrations (34–92%) as compared to fossil-fuel (traffic emissions). Health risk estimates of EBC in relation to different health outcomes were assessed in terms of passive cigarette equivalence, highlighting the considerable health effects associated with exposure to EBC levels. As a necessary action, the reduction of EBC emissions would promote considerable climate and health co-benefits.
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•The MAC value of EBC is determined to be 9.3 ± 0.2 m2 g−1 at 880 nm.•Daily EBC mass ranges from 0.7 to 5.6 μg m−3 during dry season of 2016.•Biomass-burning contributes as high as 92% to daily EBC concentration.•Health risk estimate of EBC is estimated to be as high as 11 PSC per day in March.
The characteristics and health risks of atmospheric black carbon are investigated over an urban location in northern peninsular Southeast Asia.
This study aimed to characterize the PM2.5 (particulate matter ≤ 2.5 μm in aerodynamic diameter) chemical components obtained at Doi Ang Khang (DAK; high mountain and near-source of biomass-burning ...(BB) emissions) and Chiang Mai University (CMU; foothill site and an urban location) in northern peninsular Southeast Asia (PSEA) during dry BB season of 2015 through the analysis of water-soluble inorganic ions, organic carbon (OC), and elemental carbon (EC) contents. The 24-h average PM2.5 levels (μg m−3) at DAK (118 ± 36) and CMU (113 ± 45) were about 4 folds greater than the WHO health-based guideline (25 μg m−3). Major diagnostics ratios between selected ions and carbonaceous fractions showed the significant BB influence on ambient aerosols. Enriched tracers in collected aerosols, such as NO3−, OC3 (evolved at 280–480 °C), and EC1-OP (EC evolved at 580 °C minus the pyrolized OC) confirmed that the samples were influenced by significant BB emissions. OC was the most abundant component in PM2.5 and the contribution of BB to OC was estimated to be ~90%. For the first time, the conversion factor of OC to organic matter was estimated on the basis of mass closure approach to be 1.7 ± 0.3 and 1.6 ± 0.3 at DAK and CMU, respectively. Effective carbon ratio, which indicates an association between carbonaceous particles and climatic impact, at DAK revealed the significant atmospheric warming due to the presence of more absorbing aerosols attributed to near-source BB emissions at the high mountain site. The estimated inhalation dose of PM2.5 and EC indicated severe health risk for local inhabitants during their outdoor activities. This study enhances the knowledge of aerosol chemical characterization and also addresses exposure to fine aerosols for local inhabitants during intense BB emissions in northern PSEA.
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•Organic matter (OM) is the most abundant aerosol component in this area.•For the first time, OC (organic carbon) to OM conversion factor was quantified.•Effective carbon ratio reveals significant atmospheric warming over mountain site.•High PM2.5 and elemental carbon (EC) loadings can cause severe health impacts.
Long-range transport (LRT) of air pollutants from East Asia during the northeast monsoon season impacts several downwind locations. In 2020, the initial COVID-19 lockdowns in China overlapped with ...Week 3 of the Chinese New Year (CNY) holiday, and an Asian outflow event. Thus, movement of the Chinese populace from city to city was already greatly reduced by the time of the LRT episode, although the reductions in industrial output are less clear. We found NO2 column concentrations were reduced by 24% during the CNY Week 3 this year compared to previous years. The attenuated transport event arrived to northern Taiwan with a PM2.5 concentration <45 μg m−3 and most often <35 μg m−3, which is 2–3 times lower than LRT episodes of similar back-trajectory and synoptic patterns. The whole episode persisted for about 60 h, longer than most LRT episodes from China to Taiwan. CMAQ v5.2.1 modeling of the LRT event with 100% emission and reduced emission scenarios, revealed emissions in China were approximately 50% less than normal periods. Due to the length of the episode and the significant reduction in emissions, Taiwan avoided a PM2.5 surplus of 19.2 μg m−3 on average during the episode, equivalent to a 0.5 μg m−3 reduction for the whole 3-month winter season. Employing the 100% emission model scenario and scaling up to the average episode hours each winter, the PM2.5 surplus delivered via plumes on the northeast monsoon is equivalent to a 0.5 μg m−3 surplus for the whole year.
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•COVID-19 lockdown in China reduced long-range transport of air pollution to Taiwan.•OMI NO2 over central-north China reduced by 24% compared to previous years.•PM2.5 concentration in northern Taiwan 2 times lower compared to similar episode•CMAQ simulation with 50% reduced emission in China matches measured PM2.5 in Taiwan.•Avoided PM2.5 pollution equivalent to 0.5 μg m−3 reduction for entire winter season
Severe air pollution in the form of smoke haze in the northern part of Southeast Asia (SEA) occurs annually in the dry season due to huge open area burning. Molecular markers of biomass burning were ...investigated by characterization of fine particles (PM2.5) collected in the dry season (23 February–28 April 2016). The average PM2.5, organic carbon (OC) and elemental carbon (EC) concentrations were 64.3 ± 17.6 μg m−3, 23.6 ± 8.1 μg m−3 and 2.85 ± 0.98 μg m−3, respectively. SO42− was the dominant species (8.73 ± 2.88 μg m−3) of water-soluble ion, followed by NH4+ (3.32 ± 1.01 μg m−3) and NO3− (2.70 ± 0.51 μg m−3). High concentrations of the biomass burning tracers K+ (1.27 ± 0.38 μg m−3) and levoglucosan (1.22 ± 0.75 μg m−3) were observed. The ratios of levoglucosan/K+ (0.92 ± 0.35) and levoglucosan/mannosan (20.4 ± 4.1) identified forest and agricultural waste burning as major contributors to the aerosol. Strong correlations (r > 0.800) between levoglucosan and OC, K+, anhydrosugar isomer (mannosan and galactosan) and other saccharides (mannose, arabitol and mannitol) verified that combustion of biomass was the major source of organic compounds associated with PM2.5 aerosols. Oxalate was the most abundant (0.75 ± 0.17 μg m−3; 53%) of the carboxylates. The concentration of oxalate was strongly correlated to that of PM2.5 (r = 0.799) and levoglucosan (r = 0.615), indicating that oxalate originates mainly from primary emissions from biomass burning rather than secondary formation from photochemical processes. Backward trajectories indicated that long-range transport air masses influencing air quality in Northern Thailand originated to the west and southwest.
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•Combustion of biomass was the major source of organic compounds in the PM2.5 aerosols.•Forest and agri-waste burning were identified as major contributors to the aerosols.•Oxalate originated mainly from primary emissions from biomass burning.•Long-range transport of PM2.5 into Northern Thailand was from the west and southwest.
Light-absorbing organic carbon (or brown carbon, BrC) has been recognized as a critical driver in regional-to-global climate change on account of its significant contribution to light absorption. BrC ...sources vary from primary combustion processes (burning of biomass, biofuel, and fossil fuel) to secondary formation in the atmosphere. This paper investigated the light-absorbing properties of BrC such as site-specific mass absorption cross-section (MACBrC), absorption Ångström exponent (AAEBrC), and the absorbing component of the refractive index (kBrC) by using light absorption measurements from a 7-wavelength aethalometer over an urban environment of Chiang Mai, Thailand in northern peninsular Southeast Asia (PSEA), from March to April 2016. The contribution of BrC to total aerosol absorption (mean ± SD) was 46 ± 9%, 29 ± 7%, 24 ± 6%, 20 ± 4%, and 15 ± 3% at 370, 470, 520, 590, and 660 nm, respectively, highlighting the significant influence of BrC absorption on the radiative imbalance over northern PSEA. Strong and significant associations between BrC light absorption and biomass-burning (BB) organic tracers highlighted the influence of primary BB emissions. The median MACBrC and kBrC values at 370 nm were 2.4 m2 g−1 and 0.12, respectively. The fractional contribution of solar radiation absorbed by BrC relative to BC (mean ± SD) in the 370–950 nm range was estimated to be 34 ± 7%, which can significantly influence the regional radiation budget and consequently atmospheric photochemistry. This study provides valuable information to understand BrC absorption over northern PSEA and can be used in model simulations to reassess the regional climatic impact with greater accuracy.
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•Aerosol light absorption due to BC and BrC were partitioned based on the AÅE method.•BrC contributed about 46% to total light absorption at 370 nm.•The MAC value of BrC was 2.4 ± 0.3 m2 g−1at 370 nm.•Biomass burning was the significant source of BrC during the dry season.•Averaged contribution of direct radiative forcing of BrC to that of BC was 34 ± 7%.
This article introduces an international regional experiment, East Asian Regional Experiment 2005 (EAREX 2005), carried out in March–April 2005 in the east Asian region, as one of the first phase ...regional experiments under the UNEP Atmospheric Brown Cloud (ABC) project, and discusses some outstanding features of aerosol characteristics and its direct radiative forcing in the east Asian region, with some comparison with the results obtained in another ABC early phase regional experiment, ABC Maldives Monsoon Experiment (APMEX) conducted in the south Asian region. Time series of aerosol optical thickness (AOT), single scattering albedo (SSA), aerosol extinction cross section profile and CO concentration shows that air pollutants and mineral dust were transported every 5 to 7 days in the EAREX region to produce SSA values at wavelength of 700 nm from 0.86 to 0.96 and large clear‐sky shortwave forcing efficiency at 500 nm from 60 W m−2 to 90 W m−2, though there are some unexplained inconsistencies depending on the evaluation method. The simulated whole‐sky total forcing in the EAREX region is −1 to −2 W m−2 at TOA and −2 to −10 W m−2 at surface in March 2005 which is smaller in magnitude than in the APMEX region, mainly because of large cloud fraction in this region (0.70 at Gosan versus 0.51 at Hanimadhoo in the ISCCP total cloud fraction). We suggest there may be an underestimation of the forcing due to overestimation of the simulated cloudiness and aerosol scale height. On the other hand, the possible error in the simulated surface albedo may cause an overestimation of the magnitude of the forcing over the land area. We also propose simple formulae for shortwave radiative forcing to understand the role of aerosol parameters and surface condition to determine the aerosol forcing. Such simple formulae are useful to check the consistency among the observed quantities.
A large concentration of finer particulate matter (PM2.5), the primary air-quality concern in northern peninsular Southeast Asia (PSEA), is believed to be closely related to large amounts of biomass ...burning (BB) particularly in the dry season. In order to quantitatively estimate the contributions of BB to aerosol radiative effects, we thoroughly investigated the physical, chemical, and optical properties of BB aerosols through the integration of ground-based measurements, satellite retrievals, and modelling tools during the Seven South East Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment (7-SEAS/BASELInE) campaign in 2014. Clusters were made on the basis of measured BB tracers (Levoglucosan, nss-K+, and NO3−) to classify the degree of influence from BB over an urban atmosphere, viz., Chiang Mai (18.795°N, 98.957°E, 354m.s.l.), Thailand in northern PSEA. Cluster-wise contributions of BB to PM2.5, organic carbon, and elemental carbon were found to be 54–79%, 42–79%, and 39–77%, respectively. Moreover, the cluster-wise aerosol optical index (aerosol optical depth at 500nm≈0.98–2.45), absorption (single scattering albedo ≈0.87–0.85; absorption aerosol optical depth ≈0.15–0.38 at 440nm; absorption Ångström exponent ≈1.43–1.57), and radiative impacts (atmospheric heating rate ≈1.4–3.6Kd−1) displayed consistency with the degree of BB. PM2.5 during Extreme BB (EBB) was ≈4 times higher than during Low BB (LBB), whereas this factor was ≈2.5 for the magnitude of radiative effects. Severe haze (visibility≈4km) due to substantial BB loadings (BB to PM2.5≈79%) with favorable meteorology can significantly impact the local-to-regional air quality and the, daily life of local inhabitants as well as become a respiratory health threat. Additionally, such enhancements in atmospheric heating could potentially influence the regional hydrological cycle and crop productivity over Chiang Mai in northern PSEA.
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•Impacts of BB on aerosol properties were investigated over Chiang Mai's urban atmosphere during 7-SEAS/BASELInE 2014.•Detailed radiation budget over BB sway urban site was quantified for the first time using in-situ datasets.•Atmospheric heating rate was estimated as high as 3.6Kd−1.•Large surface cooling and atmosphere warming was due to enhanced atmospheric absorption.•Severe haze episode linked to BB in northern PSEA can cause severe health impacts and modify the regional climate.
By modulating the Earth-atmosphere energy, hydrological and biogeochemical cycles, and affecting regional-to-global weather and climate, biomass burning is recognized as one of the major factors ...affecting the global carbon cycle. However, few comprehensive and wide-ranging experiments have been conducted to characterize biomass-burning pollutants in Southeast Asia (SEA) or assess their regional impact on meteorology, the hydrological cycle, the radiative budget, or climate change. Recently, BASE-ASIA (Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment) and the 7-SEAS (7-South-East Asian Studies)/Dongsha Experiment were conducted during the spring seasons of 2006 and 2010 in northern SEA, respectively, to characterize the chemical, physical, and radiative properties of biomass-burning emissions near the source regions, and assess their effects. This paper provides an overview of results from these two campaigns and related studies collected in this special issue, entitled “Observation, modeling and impact studies of biomass burning and pollution in the SE Asian Environment”. This volume includes 28 papers, which provide a synopsis of the experiments, regional weather/climate, chemical characterization of biomass-burning aerosols and related pollutants in source and sink regions, the spatial distribution of air toxics (atmospheric mercury and dioxins) in source and remote areas, a characterization of aerosol physical, optical, and radiative properties, as well as modeling and impact studies. These studies, taken together, provide the first relatively complete dataset of aerosol chemistry and physical observations conducted in the source/sink region in the northern SEA, with particular emphasis on the marine boundary layer and lower free troposphere (LFT). The data, analysis and modeling included in these papers advance our present knowledge of source characterization of biomass-burning pollutants near the source regions as well as the physical and chemical processes along transport pathways. In addition, we raise key questions to be addressed by a coming deployment during springtime 2013 in northern SEA, named 7-SEAS/BASELInE (Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles and Interactions Experiment). This campaign will include a synergistic approach for further exploring many key atmospheric processes (e.g., complex aerosol–cloud interactions) and impacts of biomass burning on the surface–atmosphere energy budgets during the lifecycles of biomass-burning emissions.
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•First comprehensive field study of biomass burning conducted in the northern SEA.•First in-situ measurements of air chemistry and physics in South China Sea/East Sea.•A conceptual model of circulation flows constructed for transport of biomass burning.•Characterization of biomass-burning aerosols in source/sink region in northern SEA.•Spatial distribution of Hg and POPs over northern SEA is illustrated.
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