Knowledge of solar radiation and its components in a particular area is crucial in studying solar energy and constructing solar energy devices due to the many advantages solar radiation has over ...fossil fuels. In this two-year study, conducted at a tropical site in Ile-Ife, Nigeria, from January 2016 to December 2017, twenty-one empirical models were proposed to estimate diffuse solar radiation using continuous solar radiation data. The models were divided into five groups and developed using relative sunshine duration and/or clearness index as input variables. The performance of five models from the literature was also examined and compared to measured data. The models' performance was evaluated using the Akaike Information Criteria (AIC), the Global Performance Index (GPI), and various statistical errors. Model 11, a quadratic model with clearness index as an input variable, had the lowest AIC (1.8098), AIC
C
(4.8099), ∆AIC
C
(0.0000), and GPI (− 2.1796) values and was the most accurate model for estimating diffuse solar radiation at the study site and other locations with similar climatic conditions. None of the models selected from the literature was suitable for estimating diffuse solar radiation at the study site; hence, the proposed models performed better.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Atmospheric turbidity exhibits substantial spatial–temporal variability due to factors such as aerosol emissions, seasonal changes, meteorology, and air mass transport. Investigating atmospheric ...turbidity is crucial for climatology, meteorology, and atmospheric pollution. This study investigates the variation in atmospheric turbidity over a tropical location in Nigeria, utilizing the Ångström exponent (α), the turbidity coefficient (β), the Linke turbidity factor (TL), the Ångström turbidity coefficient (βEST), the Unsworth–Monteith turbidity coefficient (KAUM), and the Schüepp turbidity coefficient (SCH). These parameters were estimated from a six-month uninterrupted aerosol optical depth dataset (January–June 2016) and a one-year dataset (January–December 2016) of solar radiation and meteorological data. An inverse correlation (R = −0.77) was obtained between α and β, which indicates different turbidity regimes based on particle size. TL and βEST exhibit pronounced seasonality, with higher turbidity during the dry season (TL = 9.62 and βEST = 0.60) compared to the rainy season (TL = 0.48 and βEST = 0.20) from May to October. Backward trajectories and wind patterns reveal that high-turbidity months align with north-easterly air flows from the Sahara Desert, transporting dust aerosols, while low-turbidity months coincide with humid maritime air masses originating from the Gulf of Guinea. Meteorological drivers like relative humidity and water vapor pressure are linked to turbidity levels, with an inverse exponential relationship observed between normalized turbidity coefficients and normalized water vapor pressure. This analysis provides insights into how air mass origin, wind patterns, and local climate factors impact atmospheric haze, particle characteristics, and solar attenuation variability in a tropical location across seasons. The findings can contribute to environmental studies and assist in modelling interactions between climate, weather, and atmospheric optical properties in the region.
Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals and are believed to favor ozone formation significantly. Traffic emission data for both compounds are scarce and ...mostly outdated. A better knowledge of today's HCHO and HONO emissions related to traffic is needed to refine air quality models. Here the authors report results from continuous ambient air measurements taken at a highway junction in Houston, Texas, from July 15 to October 15, 2009. The observational data were compared with emission estimates from currently available mobile emission models (MOBILE6; MOVES
MO
tor
V
ehicle
E
mission
S
imulator). Observations indicated a molar carbon monoxide (CO) versus nitrogen oxides (NO
x
) ratio of 6.01 ± 0.15 (r
2
= 0.91), which is in agreement with other field studies. Both MOBILE6 and MOVES overestimate this emission ratio by 92% and 24%, respectively. For HCHO/CO, an overall slope of 3.14 ± 0.14 g HCHO/kg CO was observed. Whereas MOBILE6 largely underestimates this ratio by 77%, MOVES calculates somewhat higher HCHO/CO ratios (1.87) than MOBILE6, but is still significantly lower than the observed ratio. MOVES shows high HCHO/CO ratios during the early morning hours due to heavy-duty diesel off-network emissions. The differences of the modeled CO/NO
x
and HCHO/CO ratios are largely due to higher NO
x
and HCHO emissions in MOVES (30% and 57%, respectively, increased from MOBILE6 for 2009), as CO emissions were about the same in both models. The observed HONO/NO
x
emission ratio is around 0.017 ± 0.0009 kg HONO/kg NO
x
which is twice as high as in MOVES. The observed NO
2
/NO
x
emission ratio is around 0.16 ± 0.01 kg NO
2
/kg NO
x
, which is a bit more than 50% higher than in MOVES. MOVES overestimates the CO/CO
2
emission ratio by a factor of 3 compared with the observations, which is 0.0033 ± 0.0002 kg CO/kg CO
2
. This as well as CO/NO
x
overestimation is coming from light-duty gasoline vehicles.
Implications:
Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals that ultimately contribute to ozone formation. There still exist uncertainties in emission sources of HONO and HCHO and thus regional air quality modeling still tend to underestimate concentrations of free radicals in the atmosphere. This paper demonstrates that the latest U.S. Environmental Protection Agency (EPA) traffic emission model MOVES still shows significant deviations from observed emission ratios, in particular underestimation of HCHO/CO and HONO/NO
x
ratios. Improving the performance of MOVES may improve regional air quality modeling.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Air quality policies based on scientific and technical information are effective for controlling air pollution and protecting public health. Analysis of observations from periodic intensive field ...studies combined with updated emission inventories, air quality monitoring and numerical modeling can be used to address the causes that trigger air pollution and catalyze the design of cost-effective emissions control policies.
Cutting-edge science is needed to address the air quality challenges posed by growing urbanization and climate change, emergent emission sources, and changes in emission profiles resulting from the implementation of advanced technology and regulatory measures.
Cities should work towards building robust infrastructure and air quality management tools and rely on scientific research to attain cleaner air. The impacts of changes in emissions profiles and atmospheric chemistry under a changing climate need to be better understood and incorporated in the design of air quality management programs.
•Locally derived scientific information is needed for effective air quality policies.•Intensive field campaigns generate scientific information to address air pollution.•Intensive field campaigns are useful to test new monitoring instrumentation.•Intensive field campaigns contribute to increase institutional capacity building.•Their cost is a minor fraction of the economic expenses associated to air pollution.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Temporally highly resolved speciated PM and VOC data used for source apportionment.•PMF analysis identified several cases of co-emission of VOCs and metals.•PMF results revealed day and nighttime ...isoprene emissions.
A commixture of gasphase compounds including carbon monoxide (CO), sulphur dioxide (SO2), volatile organic compounds (VOCs) and trace metals were collected at a site located at the urban/industrial interface in Houston, Texas. Positive Matrix Factorization (PMF) analysis yielded nine factors: gas/crude oil (21.3±5.5%), isoprene emission (17.0±7.1%), Si-rich (14.6±1.3%), liquefied petroleum gas (LPG) (11.2±4.0%), traffic (10.6±0.4%), Fluidized-bed Catalytic Cracking (FCC)/high temperature operations (7.2±4.3%), oil refinery (6.8±0.9%), soil and road dust (6.2±0.6%), and petrochemical industries (5.0±5.0%). Daytime and nighttime PMF runs were carried out to see potential differences among and within emission sources. Notable findings include: (1) Nocturnal isoprene emission was identified from traffic exhaust and industrial sources. (2) LPG emissions were higher during the day most likely due to temperature dependent evaporative processes. (3) V/Ni and SO2/V ratios reveal greater contribution from crude oil in the merged natural gas/crude oil emission factor. Corrosion might be responsible for emitting metals (i.e., Cr, Cu, Mo, Ni) from oil refineries during nighttime. (4) In the soil and road dust factor, metals relevant to plant physiological processes are mostly retained by the plants while the lanthanoids and other metals (i.e. Y, Pb, Mn, Ga, Ba) are more prone to physical removal during the day. (5) FCC/high temperature operations are dominated by metals at night. (6) The traffic factor increases during the day possibly due to the higher number of vehicles. Bivariate polar plots suggest the Houston Ship Channel area as the primary emission source for LPG, natural gas/crude oil, FCC/high temperature operations, and petrochemical industries.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Despite emission reductions, Houston continues to be designated as a nonattainment area for ozone (O3) by the Environmental Protection Agency. Upper‐level synoptic maps and information about the ...vertical structure of the lower troposphere obtained by in situ measurements were analyzed to characterize ozone exceedances in which peak 8‐h average concentration exceeded 85 ppb during the Texas Air Quality Study‐II in August–September 2006. Cluster analysis of meteorological conditions showed that the highest background surface O3 concentrations occurred under northerly or easterly flow regimes at 850 hPa, coinciding with the advection of dry continental air. Exceedance days in September 2006 occurred almost exclusively in postfrontal environments. These frontal passages are associated with shifts in wind direction and may lead to increases in background O3 from 30 ppbv (marine) to 60–70 ppbv (continental) throughout the lower troposphere. Several factors are identified to be important for 8‐h average ozone peaks in Houston under well‐developed land‐sea‐bay breeze conditions, including (1) the presence of easterly winds advecting industrial emissions from the Ship Channel, and (2) the presence of persistent large‐scale northerly flows aloft advecting elevated continental background ozone levels that are eventually entrained into lower layers through the growth of the convective planetary boundary layer.
Despite the central role of reactive organic carbon (ROC) in the formation of secondary species that impact global air quality and climate, our assessment of ROC abundance and impacts is challenged ...by the diversity of species that contribute to it. We revisit measurements of ROC species made during two field campaigns in the United States: the 2013 SOAS campaign in forested Centreville, AL, and the 2010 CalNex campaign in urban Pasadena, CA. We find that average measured ROC concentrations are about twice as high in Pasadena (73.8 μgCsm–3) than in Centreville (36.5 μgCsm–3). However, the OH reactivity (OHR) measured at these sites is similar (20.1 and 19.3 s–1). The shortfall in OHR when summing up measured contributions is 31%, at Pasadena and 14% at Centreville, suggesting that there may be a larger reservoir of unmeasured ROC at the former site. Estimated O3 production and SOA potential (defined as concentration × yield) are both higher during CalNex than SOAS. This analysis suggests that the ROC in urban California is less reactive, but due to higher concentrations of oxides of nitrogen and hydroxyl radicals, is more efficient in terms of O3 and SOA production, than in the forested southeastern U.S.
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IJS, KILJ, NUK, PNG, UL, UM
Gradients of HONO, NOx (NO + NO2) and O3 were measured during an early summer campaign on a high-rise building in downtown Santiago de Chile. Distinct gradients of decreasing concentrations with ...altitude were observed for HONO and NOx, while O3 concentrations were found to increase with altitude. From the observed daytime maximum of the HONO/NOx ratio the existence of a strong daytime source of HONO is proposed, thus confirming recent results from another measurement site in downtown Santiago, where a high contribution of HONO to the OH radical initiation sources of >50% was observed. Since the HONO/NOx ratio and its daytime maximum were found to be independent of the altitude, it is concluded that HONO is an important OH radical source in Santiago not only close to the ground surface, but also at higher altitudes of the boundary layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In August 2013, the Qatar Environment and Energy Research Institute (QEERI), was the first to launch temporally highly resolved ozonesondes in the Middle East region. The data from 20 launches ...consistently show changes in meteorological parameters at about 5.5 km above the surface, which are more pronounced following a change in synoptic conditions on 15 August 2013, including temperature inversions, corresponding change in potential temperatures, relative humidity, and significant wind shear. These changes are typically associated with a large scale subtropical subsidence layer in accordance with previous aircraft studies in this region. Below the inversion layer, the ozone follows typical patterns for lower tropospheric measurements, starting in the surface layer up to 0.5 km above the ground level around noon at about 66 ± 15 ppbv. However, above the subsidence inversion, ozone mixing ratios begin to increase to 80 ± 13 ppbv between 6 and 12 km with maximum values ∼100 ppbv around 8 km, then decreasing again before reaching the stratosphere.
Three-day HYSPLIT back trajectories indicate that ozone levels are typically about 17% lower in the 6–12 km range under wind flow conditions from the East than in cases when trajectories came from the Mediterranean. High pressure may lead to subsidence of ozone from the upper troposphere/lower stratosphere and eventually cause an increase of ozone mixing ratios by ∼18% above average between 6 and 7 km, i.e. slightly above subtropical subsidence layer. Under the impact of regional convective activity and associated lightning, ozone mixing ratios can increase by more than 35% averaged over the 9–12 km altitude range. In both cases maximum ozone in the mid to upper troposphere reached more than 100 ppbv.
•For the first time temporally highly resolved O3 sondes in the Middle East region.•Upper tropospheric ozone in the Arabian Gulf region is on average 80 ± 13 ppbv.•O3 in the 6–12 km range is higher when air masses came from the Mediterranean.•High pressure may cause subsidence of O3 from upper troposphere/lower stratosphere.•Convective activity and associated lightning can substantially increase O3.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Formaldehyde (HCHO) is the most important carcinogen in outdoor air among the 187 hazardous air pollutants (HAPs) identified by the U.S. Environmental Protection Agency (EPA), not including ozone and ...particulate matter. However, surface observations of HCHO are sparse and the EPA monitoring network could be prone to positive interferences. Here we use 2005–2016 summertime HCHO column data from the OMI satellite instrument, validated with high-quality aircraft data and oversampled on a 5 × 5 km2 grid, to map surface air HCHO concentrations across the contiguous U.S. OMI-derived summertime HCHO values are converted to annual averages using the GEOS-Chem chemical transport model. Results are in good agreement with high-quality summertime observations from urban sites (−2% bias, r = 0.95) but a factor of 1.9 lower than annual means from the EPA network. We thus estimate that up to 6600–12 500 people in the U.S. will develop cancer over their lifetimes by exposure to outdoor HCHO. The main HCHO source in the U.S. is atmospheric oxidation of biogenic isoprene, but the corresponding HCHO yield decreases as the concentration of nitrogen oxides (NO x ≡ NO + NO2) decreases. A GEOS-Chem sensitivity simulation indicates that HCHO levels would decrease by 20–30% in the absence of U.S. anthropogenic NO x emissions. Thus, NO x emission controls to improve ozone air quality have a significant cobenefit in reducing HCHO-related cancer risks.
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IJS, KILJ, NUK, PNG, UL, UM
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