Hourly Variation Research Articles

Implications of the timing of residential natural gas use for appliance electrification efforts

Current strategies for deep decarbonization of the residential building sector invoke the following three pillars of action: (1) radically improve the efficiency of end-use electricity consumption, (2) shift to 100% renewable generation of electrical grid power, and (3) move aggressively to electrify all remaining fossil fuel end-uses. Due to the previous unavailability of high temporal resolution natural gas consumption data, the pursuit of this policy agenda has largely occurred in the absence of a thorough understanding of hourly variations in the intensity of household natural gas use. These variations can have important downstream impacts on the electricity system once electrification has been achieved. This study presents a series of analyses which are based upon a novel dataset of hourly interval natural consumption data obtained for (N = 17,072) households located within a low-income portion of Southern California Gas Company’s service territory. Results indicate that diurnal patterns of hourly natural gas use largely coincide with the timing of daily peak electricity loads. These findings suggest that the aggressive electrification of residential end-use appliances has the potential to exacerbate daily peak electricity demand, increase total household expenditures on energy, and, in the absence of a fully decarbonized electrical grid, likely result in only limited greenhouse gas emissions abatement benefits.

Design, Fabrication and Characterization of a Solar Fish Dryer

Herein, a forced convection solar fish dryer is designed, constructed and characterized to yield a better main of drying fish. The designed dryer incorporated a heat storage unit which complimented the drying rate of the product during off sunshine hours. The device was characterized during raining and dry seasons and results clearly indicated the influence of seasonal variation on the performance of the device. Average hourly variation of the dryer and ambient temperatures measured on the selected days of the different months of measurement during the two seasons, clearly indicated that temperatures were significantly enhanced by the device. This was due to the high ability of the designed solar collector to trap large amount of long waves. Maximum dryer and ambient temperatures during raining season were measured to be (58.9±2) oC and (40±2) oC whereas, (73.5±1.3) oC and (45±1.8) oC respectively, were measured during the dry season. Average daily moisture loss from the drying fish was notably high, especially during dry season which was due to the high dryer temperatures and decrease in atmospheric humidity. The efficiency of the solar dryer was estimated to be 76 %. The fishes with initial moisture content of 87 % was dried to 13 %. This moisture content is in range with the United Nations Economic Commission for Europe (UNECE) Standard DDP-19 concerning the marketing and commercial quality control of dried fish.

Enhanced photochemical formation of secondary organic aerosols during the COVID-19 lockdown in Northern China

To eliminate the spread of a novel coronavirus breaking out in the end of 2019 (COVID-19), the Chinese government has implemented a nationwide lockdown policy after the Chinese lunar New Year of 2020, resulting in a sharp reduction in air pollutant emissions. To investigate the impact of the lockdown on aerosol chemistry, the number fraction, size distribution and formation process of oxalic acid (C2) containing particles and its precursors were studied using a single particle aerosol mass spectrometer (SPAMS) at the urban site of Liaocheng in the North China Plain (NCP). Our results showed that five air pollutants (i.e., PM2.5, PM10, SO2, NO2, and CO) decreased by 30.0–59.8% during the lockdown compared to those before the lockdown, while O3 increased by 63.9% during the lockdown mainly due to the inefficient titration effect of O3 via NO reduction. The increased O3 concentration can boost the atmospheric oxidizing capacity and further enhance the formation of secondary organic aerosols, thereby significantly enhancing the C2 particles and its precursors as observed during the lockdown. Before the lockdown, C2 particles were significantly originated from biomass burning emissions and their subsequent aqueous-phase oxidation. The hourly variation patterns and correlation analysis before the lockdown suggested that relative humidity (RH) and aerosol liquid water content (ALWC) played a key role in the formation of C2 particles and the increased aerosol acidity can promote the conversion of precursors such as glyoxal (Gly) and methyglyoxal (mGly) into C2 particles in the aqueous phase. RH and ALWC decreased sharply but O3 concentration and solar radiation increased remarkably during the lockdown, the O3-dominated photochemical pathways played an important role in the formation of C2 particles in which aerosol acidity was ineffective. Our study indicated that air pollution treatment sponges on a joint-control and balanced strategy for controlling numerous pollutants.

Development of a sustainable energy system utilizing a new molten-salt based hybrid thermal energy storage and electrochemical energy conversion technique

In the present study, an integrated solar and wind based cogeneration system is developed for power and ammonia production. A new molten-salt based thermal energy storage and electrochemical energy conversion technique is utilized, which includes electrochemical ammonia synthesis, direct ammonia fuel cell, and thermal energy storage system. A transient energy and exergy analyses is performed on the developed system considering the hourly variations in wind velocities as well as solar intensities. The energy efficiency of the overall system on monthly average days varies between a minimum value of 29.4% and a maximum value of 38.7% across the year. In addition, the exergy efficiency of the developed system is found to vary between 30.2% and 39.8%. Furthermore, the daily ammonia production is found to reach peak value of 4292.3 kmol/day during the year. Moreover, the maximum discharge capacity of the molten salt-based direct ammonia fuel cell system attains a value of 31.8 MWh across the year. Several parametric studies are also performed to assess the effects of varying operating conditions on the performance of the developed system as well as subsystem units.

Annual and Seasonal Surface Circulation Over the Mid‐Atlantic Bight Continental Shelf Derived From a Decade of High Frequency Radar Observations

AbstractA decade (2007–2016) of hourly 6‐km‐resolution maps of the surface currents across the Mid‐Atlantic Bight (MAB) generated by a regional‐scale High Frequency Radar network are used to reveal new insights into the spatial patterns of the annual and seasonal mean surface flows. Across the 10‐year time series, temporal means and interannual and intra‐annual variability are used to quantify the variability of spatial surface current patterns. The 10‐year annual mean surface flows are weaker and mostly cross‐shelf near the coast, increasing in speed and rotating to more alongshore directions near the shelfbreak, and increasing in speed and rotating to flow off‐shelf in the southern MAB. The annual mean surface current pattern is relatively stable year to year compared to the hourly variations within a year. The 10‐year seasonal means exhibit similar current patterns, with winter and summer more cross‐shore while spring and fall transitions are more alongshore. Fall and winter mean speeds are larger and correspond to when mean winds are stronger and cross‐shore. Summer mean currents are weakest and correspond to a time when the mean wind opposes the alongshore flow. Again, intra‐annual variability is much greater than interannual, with the fall season exhibiting the most interseasonal variability in the surface current patterns. The extreme fall seasons of 2009 and 2011 are related to extremes in the wind and river discharge events caused by different persistent synoptic meteorological conditions, resulting in more or less rapid fall transitions from stratified summer to well‐mixed winter conditions.

Reserve constrained dynamic economic dispatch in multi-area power systems: An improved fireworks algorithm

The multi-area economic dispatch (MAED) plays a major role in an interconnected power system to determine the generation dispatch strategy and satisfy the load demands as well as the technical constraints. Tie-line capacity between different areas, upper/lower generation limits, generator ramp rates, transmission losses, valve point effect, disjoint prohibited zones as well as spinning reserve are considered as the MAED problem constraints. Due to hourly load variations, the MAED problem should be solved dynamically to coincide the realistic conditions which build up the multi-area dynamic economic dispatch (MADED) problem. Considering these constraints besides the intertemporal constraints which depends to the optimal conditions of each hour with respect to other time steps may increase the problem complexity. In this regard, an improved version of fireworks algorithm which is equipped with two effective cross-generation mutation strategies is deployed to handle the non-linear, non-smooth, non-convex, multi-dimensional and multi-constraints MADED problem. Furthermore, a new constraint handling scheme is developed to correct the potential solutions in feasible search space. Finally, two small and large systems are used to investigate the capability of the developed algorithm in finding the global or near-global optima.

Wind Farming Feasibility Assessment in 16 Locations of Nepal

The paper assesses the feasibility of wind farming at the 16 sites scattered in different ecological regions of Nepal. The wind speed, the hourly and seasonal variation of wind, the wind-rose, the wind turbulence rate, the wind power density, the Weibull probability distribution and the frequency of the wind speed above cut in speed were computed. The average wind speed at all the sites was found to be higher during the dry season from March to May. The wind speed of the modern turbine for power generation at eight sites was found to be above cut-in speed. However, the wind power density was found to be good only at the two sites and fairly good at the six sites. More than 50 % time of a year at these eight sites had over 3.5 m/s wind speed. However, the turbulence rate at all the studied sites was found to be above the acceptance range of 25 %. Among the study sites, Kagbeni, Thini, Jumla, Ramechhap, Vorleni, Patan west, Hansapur and Baddanda were found to be technically feasible sites for wind energy generation in Nepal.

Evaluación fisicoquímica y biológica en sistemas de tratamiento comerciales en Costa Rica

En Costa Rica, el 70.9% de la población utiliza el tanque séptico como sistema de tratamiento individual a las aguas residuales domésticas. A pesar de que los tanques sépticos son la tecnología de tratamiento más utilizada en el país, no se cuenta con información detallada acerca de su funcionamiento y su eficiencia. Además, labores de mantenimiento, como lo es la remoción de lodos sépticos, son ejecutadas directamente por cada familia que usa este sistema y sin que exista un protocolo de limpieza unificado. La evaluación de estos sistemas se llevó a cabo en sistemas de tratamiento fabricados por una de las empresas privadas más importantes del país. Cada equipo evaluado consistía en un tanque séptico y un filtro anaerobio de flujo ascendente (FAFA) para el tratamiento de aguas residuales domésticas. La caracterización incluyó aspectos físicos, químicos y biológicos de la calidad y cantidad del agua residual producida en tres sistemas de tratamiento distintos, considerando variaciones horarias, así como la calidad y la cantidad de lodos acumulados en cada sistema. Los sistemas de tratamiento estaban instalados en dos edificios multifamiliares y una casa unifamiliar. Los resultados indicaron que los sistemas de tratamiento son muy sensibles en cuanto a cantidad y calidad del agua residual, presentando variaciones horarias significativas y además, afectadas por el tipo de uso de agua que se da en los hogares; lo cual está directamente relacionado al funcionamiento del tratamiento.

Generation expansion planning under correlated uncertainty of mass penetration renewable energy sources

This study presents a methodology for generation expansion planning (GEP) under the presence of uncertainty of multiple renewable energy sources (RES). Both long- and short-term uncertainties are represented and incorporated within the proposed GEP model. The long-term RES uncertainty is simulated by the annual variation of the capacity credit. The short-term uncertainty is modelled by means of the net power based on the hourly variation of RES output power and load curve. The proposed GEP model is solved through three steps. In the first step, the proposed robust GEP model is solved considering the long-term uncertainty of the multiple RES. Short-term uncertainty is considered when solving the GEP model in the second step. In the last step, the robustness of the obtained robust GEP model results is verified by checking the reliability criteria. A new correlated polyhedral uncertainty set is introduced considering the correlation between the different RES uncertain coefficients through its correlation matrix. Different GEP results are presented for different uncertainty scenarios. The results demonstrate that considering the correlation among uncertain coefficients provides insight for effects of correlation on investment strategies. Reserve margin is adapted to cope with uncertainty impact. Reliability criteria are verified by DIgSILENT generation adequacy tool.

Test investigation of operation performance of novel split-type ground source heat pump systems for clean heating of rural households in North China

Novel split-type ground source heat pump (ST-GSHP) is being used widely in coal-to-electricity clean heating projects for rural residential buildings in North China. Taking 20 rural households in Jinzhou and Xinji, Hebei province, as examples, the actual operation performance of ST-GSHP systems during the whole heating period was tested and analyzed. Firstly, in-situ thermal response tests were conducted to obtain the initial ground temperature, the ground’s thermal conductivity and the heat extraction capacity of ground heat exchanger (GHE). Then the hourly and monthly variations of main operating parameters were analyzed, including the indoor and outdoor temperature, the inlet and outlet temperature of GHE, the electricity consumption, the heat extraction of GHE and indoor heating energy consumption. Finally, the operation performance of ST-GSHP systems in 20 rural households was analyzed, and the seasonal coefficient of performance (COP) during the whole heating period was evaluated. The present results can provide an important basis for optimal design and theoretical modelling of ST-GSHP systems in future.

Transient risk of ambient fine particulate matter on hourly cardiovascular events in Tainan City, Taiwan.

The association between daily changes in ambient fine particulate matter (PM2.5) and cardiovascular diseases have been well established in mechanistic, epidemiologic and exposure studies. Only a few studies examined the effect of hourly variations in air pollution on triggering cardiovascular events. Whether the current PM2.5 standards can protect vulnerable individuals with chronic cardiovascular diseases remain uncertain. we conducted a time-stratified, case-crossover study to assess the associations between hourly changes in PM2.5 levels and the vascular disease onset in residents of Tainan City, Taiwan, visiting Emergency Room of Chi Mei Medical Center between January 2006 and December 2016. There were 26,749 cases including 10,310 females (38.5%) and 16,439 males (61.5%) identified. The time of emergency visit was identified as the onset for each case and control cases were selected as the same times on other days, on the same day of the week in the same month and year respectively. Residential address was used to identify the ambient air pollution exposure concentrations from the closest station. Conditional logistic regression with the stepwise selection method was used to estimate adjusted odds ratios (ORs) for the association. When we only included cases occurring at PM2.5>10 μg/m3 and PM2.5>25 μg/m3, very significant ORs could be observed for 10 μg/m3 increases in PM2.5 at 0 and 1 hour, implying fine particulate exposure could promptly trigger vascular disease events. Moreover, a very clear increase in risk could be observed with cumulative exposure from 0 to 48 hours, especially in those cases where PM2.5>25 μg/m3. Our study demonstrated that transient and low concentrations of ambient PM2.5 trigger adult vascular disease events, especially cerebrovascular disease, regardless of age, sex, and exposure timing. Warning and delivery systems should be setup to protect people from these prompt adverse health impacts.

Empirical orthogonal function modelling of total electron content over Nepal and comparison with global ionospheric models

This analysis uses 3 years hourly observations of total electron content (TEC) from 5 global positioning system (GPS) station across Nepal to analyze the spatial trend. For this purpose, empirical orthogonal function modeling is used to investigate the annual and monthly variation inside the country. Empirical orthogonal function base functions and associated coefficients of TEC variability over Nepal have been studied to establish the relationship between observed and modeled TEC values. Both the observed GPS TEC values and the empirical orthogonal function modeled TEC values are compared with the global ionospheric models (global ionospheric map and international reference ionosphere) TEC values. The study shows an hourly pattern of TEC variation in which the TEC rises from dawn, reaches the highest TEC values about 40 TEC units during the peak hours of the day, then decreases at evening at the lowest diurnal values about 5 TEC units. Monthly TEC values over all sites are higher during the march and April (about 38 TEC unit), while they are lower values during December and January (about 10 TEC unit). Although the correlation coefficients between the GPS TEC values and the global modeled TEC values are higher, while it becomes highest with empirical orthogonal function modeled TEC values for both cases of hourly and monthly variations. We examined the root mean square errors between observed and modeled TEC values at each site by using tailor correlation plots and found that they are lower in case of empirical orthogonal function model. Monthly residuals between observed and empirical orthogonal function modeled TEC values are always lower as compared to other global modeled TEC values. These kinds of comparative analysis in the present work indicate that empirical orthogonal function model by using global geomagnetic activity works very well and is capable of depicting TEC variations accurately.

Solar wind parameter and seasonal variation effects on the South Atlantic Anomaly using Tsyganenko Models

We studied the space weather effects on the South Atlantic Anomaly (SAA) magnetic response using Tsyganenko models. For the physical parameters characterizing the SAA, the study considered the minimum magnetic field, the location (longitude and latitude) of the SAA center, and the area of the SAA. Regarding the space weather parameters, we considered the solar wind dynamic pressure, the interplanetary magnetic field components, B_{yIMF} and B_{zIMF}, the Dst index, and the geodipole tilting angle. To study the magnetic field response of the SAA, several different versions of the Tsyganenko models, namely, T96, T01, and TS05, were used to describe the external magnetic field contributions. The main internal magnetic field was calculated by the International Geomagnetic Reference Field (IGRF-12). The magnetic field study of the SAA was realized in long- and short-term (seasonal and diurnal) variations. We found that the Dst index and the geodipole tilting angle were the strongest influencing parameters on the SAA magnetic field response at all altitudes. Moreover, it was revealed that both magnetic poles might be a possible cause of the SAA magnetic field response, resulting from the space weather conditions. Furthermore, the magnetic field behavior of the SAA was affected by hourly variations, where the largest changes occurred at dayside.

Simulating coliform transport and decay from 3D hydrodynamics model and in situ observation in Nice area

In coastal area, raw wastewater can be directly discharged in the sea during extreme rain events or failure of the sewage network. The highly urbanized and touristic area of Nice is directly exposed to this risk. In order to protect the bathing population and to apply the European regulation (DCE, 2000), Nice municipality has decided to work on a forecasting tool of transport and fate of fecal bacterial indicators such as Escherichia coli. This paper deals with the first step of this approach which consists in developing a three-dimensional hydrodynamic simulation coupled with water quality parameters. The model used is based on Reynolds-Averaged Navier–Stokes’s equations for the calculation of the velocities and water depth (TELEMAC3D), and wave energy balance equation to account for the wave induced current (TOMAWAC). Two field measurements were conducted on a real wastewater pollution coming from a sewage pipe located at −38 m depth. The first campaign has validated the vertical diffusion of the effluent through the water column by the means of variable depth samples and has stressed the hourly variability of sewage bacterial quality. Due to the lack of data regarding this last point, the model could not be fully validated. The second campaign has been designed to overcome this issue and to gather all the data needed to proceed to the validation of our hydro-ecological simulation. The comparison of the field measurements and the simulations has successfully demonstrated the accuracy of the model. But the uncertainty associated with the laboratory analysis (MPN) are high, making the calibration and validation processes a complex task. Nevertheless, further research needs to be done regarding the variability of microbial quality in order to develop an operational tool allowing the forecast of bacterial pollution. The next step of this study will be to establish the hourly variation of microbial quality in the wastewater during dry and raining periods.

Field investigation on rural domestic sewage discharge in a typical village of the Taihu Lake Basin

Rural sewage is an important non-point pollution that aggravates eutrophication of the Taihu Lake. Practically grasping the characteristics of local villages’ sewage treatment demand, sewage flow and sewage quality has far-reaching significance for constructing suitable and efficient rural sewage treatment systems, and ultimately improving the water environment of the lake basin. To this end, the study conducted a field investigation in a typical village of the Taihu Lake Basin in July and continuously monitored sewage flow and sewage quality in the mode of sewage classification. The sewage quality test included chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH3-N), and total phosphorus (TP). This paper reviewed the development status of the typical village and demonstrated the rules of rural domestic water consumption and sewage discharge. It was found that the total sewage discharge flow in summer was around 88.90 L/(cap . d) and the hourly variation coefficient was around 3.92. Kitchen sewage, washing sewage, and toilet sewage had significant differences in sewage quality. Particularly, the nitrogen and phosphorus nutrients in toilet sewage were quite rich, accounting for 84.42% and 61.90% of the corresponding total load, respectively. Thus, the ideas of properties-classified treatment and resource treatment were worth being introduced into the rural sewage treatment process.

A high-resolution spatial and temporal on-road vehicle emission inventory in an Iranian metropolitan area, Isfahan, based on detailed hourly traffic data

The present study is primarily aimed to establish a detailed exhaustive emission inventory of urban motor vehicles in a medium-sized city, i.e. Isfahan. The International Vehicle Emission (IVE) model was utilized to estimate the motor vehicle Emission Factors (EFs) in different areas of Isfahan. IVE was adjusted using the results obtained by on-board real-world EF measurements. A high resolution 1 km × 1 km vehicle emission inventory for the year 2018 was then developed in a bottom-up approach. The method was employed based on the influencing factors such as the collected hourly-data on road network, traffic flow, vehicle driving cycles, and the vehicle population in Isfahan. Moreover, the variations of EFs with vehicle speed were investigated for different vehicle categories to assess the emission rates through Isfahan transportation fleet. The results showed that EFs of all pollutants emitted from vehicle exhausts usually decrease with vehicle speed. Also, gasoline vehicles have larger CO and VOCs EFs than the others, whereas vehicles fueled by diesel have the largest NOx, SOx, and PM10 EFs. The established emission inventory revealed that the annual amount of CO, VOCs, NOx, SOx, and PM10 emitted from Isfahan on-road mobile sources in 2018 are 267.6, 12.6, 20.3, 0.3, and 2.3 kt, respectively. The gasoline vehicles including cars and motorcycles were the main sources of CO, VOCs, and SOx, whereas the heavy-duty vehicles and buses equipped with diesel engines were the main sources of NOx and PM10. The hourly variations of EFs ensure an acceptable consistency with the hourly variation of the traffic flow at different areas. Moreover, the high-resolution spatial distribution of vehicle emission inventory represented that emissions were concentrated on the downtown, esp. on underdeveloped historical area of the city, where the most of the governmental and administrative departments are concentrated.

A novel solar integrated distillation and cooling system – Design and analysis

To meet the high cooling and fresh water demands in hot and arid regions, a novel integrated solar cooling and solar distillation system is introduced. The system consists of a solar ejector cooling system integrated with single-slope solar still. The proposed novel system is the first study to integrate two solar systems for cooling and water production with outputs significantly higher than any existing system. A steady state thermodynamics model is developed based on the mass, momentum and energy conservations and the performance of the integrated system is investigated. Results showed that the productivity of the solar still is enhanced by increasing the evaporation rate (using heating coil) and by increasing the condensation rate (using cooling coil). Simultaneously, this improved the COP of the ejector system by enhancing its entrainment ratio with slight increase in the required solar collector area. The performance of the system is investigated further for four different scenarios of integration between the solar ejector cooling and solar distillation systems. Results showed that the productivity of the still is five times higher than that of the conventional solar still. The effects of the major operating parameters on the performance of the system with R134a as the working fluid are investigated and analyzed. At a solar radiation of 500 W/m2, generator pressure of 3.3 MPa, generator temperature of 365 K, evaporator temperature of 283 K, a cooling capacity of 10.4 kW and distilled water of 8.10 kg/day are obtained. The annual produced water considering the hourly variation of the radiant flux was 5067 kg/year, which is 5.7 times more than the conventional systems. The estimated cost of one liter distilled water per 1 m2 area of the present solar still is $0.04, which is only 18% of the water cost of other still technologies. Moreover, the performance of additional four working fluids is compared in terms of COP, cooling capacity, required solar collector area and still productivity, based on which, R134a working fluid was recommended for its overall performance.

Retrieval of Secchi Disk Depth in Turbid Lakes from GOCI Based on a New Semi-Analytical Algorithm

The accurate remote estimation of the Secchi disk depth (ZSD) in turbid waters is essential in the monitoring the ecological environment of lakes. Using the field measured ZSD and the remote sensing reflectance (Rrs(λ)) data, a new semi-analytical algorithm (denoted as ZSDZ) for retrieving ZSD was developed from Rrs(λ), and it was applied to Geostationary Ocean Color Imager (GOCI) images in extremely turbid waters. Our results are as follows: (1) the ZSDZ performs well in estimating ZSD in turbid water bodies (0.15 m < ZSD < 2.5 m). By validating with the field measured data that were collected in four turbid inland lakes, the determination coefficient (R2) is determined to be 0.89, with a mean absolute square percentage error (MAPE) of 22.39%, and root mean square error (RMSE) of 0.24 m. (2) The ZSDZ improved the retrieval accuracy of ZSD in turbid waters and outperformed the existing semi-analytical schemes. (3) The developed algorithm and GOCI data are in order to map the hourly variation of ZSD in turbid inland waters, the GOCI-derived results reveal a significant spatiotemporal variation in our study region, which are significantly driven by wind forcing. This study can provide a new approach for estimating water transparency in turbid waters, offering important support for the management of inland waters.

One-Year Measurements of Equivalent Black Carbon, Optical Properties, and Sources in the Urumqi River Valley, Tien Shan, China

Equivalent black carbon (EBC) was measured with a seven-wavelength Aethalometer (AE-31) in the Urumqi River Valley, eastern Tien Shan, China. This is the first high-resolution, online measurement of EBC conducted in the eastern Tien Shan allowing analysis of the seasonal and hourly variations of the light absorption properties of EBC. Results showed that the highest concentrations of EBC were in autumn, followed by those in summer. The hourly variations of EBC showed two plateaus during 8:00–9:00 h local time (LT) and 16:00–19:00 h LT, respectively. The contribution of biomass burning to EBC in winter and spring was higher than in summer and autumn. The planetary boundary layer height (PBLH) showed an inverse relationship with EBC concentrations, suggesting that the reduction of the PBLH leads to enhanced EBC. The aerosol optical depths (AOD) over the Urumqi River Valley, derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) data and back trajectory analysis, showed that the pollution from Central Asia was more likely to affect the atmosphere of Tien Shan in summer and autumn. This suggests that long-distance transported pollutants from Central Asia could also be potential contributors to EBC concentrations in the Urumqi River Valley, the same as local anthropogenic activities.

Impact of mobile source emission inventory adjustment on air pollution photochemical model performance

Coupled weather forecasting and chemical transport models are useful tools to evaluate air pollution episodes in big cities for the purpose of forecasting and air pollution abatement measures' evaluation. However, large set of accurate data of various sources and modeling calibrations are needed for such complex modeling system to be reliable. The problem becomes more obvious when the model is operated over a domain in which there is a general lack of accurate input data such as emission inventory data. The current study investigates the possibility of model tuning for more accurate prediction of air pollutant concentrations in the city of Tehran in an air pollution episode as a case study. In the last several years, Tehran has frequently experienced long episodes of air pollution, often resulted in forced holidays in the city. WRF/CAMx modeling system were used to simulate the spatial distribution of pollutants concentrations over the city of Tehran in a highly polluted episode during December 2017. In order to improve model performance, a methodology was developed and used to adjust the emission inventory of the system. Due to lack of national emission inventory and background data, effects of introducing a top-down national emission inventory to the modeling system was investigated. This emission inventory can also be used to prepare more accurate boundary concentrations for countries located near Iran. In addition, emission rates of the most dominant emission sources of the city of Tehran – mobile sources – were adjusted using the results from chassis dynamometer tests. Also, the hourly variations of emission were improved using measured ambient NO2 concentrations. Comparison of modeled and measured concentrations at air quality monitoring stations for various pollutant showed that emission adjustment was the most effective method which resulted in considerable model performance improvement over Tehran. Results showed that due to better and more realistic emission factors used in the model, bias error for CO, NO2, O3 and PM2.5 reduced by 0.36 ppm, 3.4 ppb, 0.19 ppb and 2.14 μg/m3, respectively and correlation coefficient for CO, O3 and PM2.5 increased by 0.13, 0.02 and 0.6. This proves the possibility of using such method to improve model performance when there is a general lack of accurate input data.