Haze Conditions Research Articles

Variability of winter haze over the Beijing-Tianjin-Hebei region tied to wind speed in the lower troposphere and particulate sources

This study analyzes the variability of winter haze days and visibility in the Beijing-Tianjin-Hebei (BTH) region, in relation to the regional average wind speed changes in the lower troposphere and emissions for 1961–2014. Winter mean surface meteorological data, NCEP/NCAR atmospheric reanalysis data, and fossil fuel emission data are used. The results reveal a significant increase in the haze days of +0.8 days decade−1 (p < .01), and a subsequent decline in visibility of −1.56 km decade−1 (p < .01). Most interestingly, an accelerated increase in the number of haze days was observed for the last 11-year period (+8.3 days decade−1, p < .01) of the study period (2004–2014). Regression analysis indicates that the increase of haze occurrence and decrease in visibility are partly due to the significant (p < .01) declining trend of the mean wind speed in the lower troposphere (−0.19 m s−1 decade−1 at 10 m, (−0.23 m s−1 decade−1 at 925 hPa), and − 0.21 m s−1 decade−1 at 850 hPa), and partly due to the declining (dust storm frequency as a proxy, −0.41 days dec−1) surrounding particulate sources and increasing fossil fuel emissions (total carbon emission as a proxy, +48,206.8 thousand metric tons dec−1). Specifically, wind speed changes in the lower troposphere explain 41.3% of the interannual varation of the winter haze days and 71.2% of the visibility variance. These are extended to 51.7% and 81.6% respectively when combined with information about the natural (dust storm frequency) and anthropogenic (fossil fuel emissions) particulate sources. Therefore, the analyses show that wind speed changes in the lower troposphere, together with the varied natural and anthropogenic sources of particulates, play a key role in modulating winter haze and visibility conditions in the BTH area.

Performance analysis of chaotic FSO communication system under different weather conditions

AbstractFree space optics (FSO) is a competent technology for wireless communication providing solutions to bandwidth, cost, and portability challenges in radio frequency communication. This paper presents a numerical approach for securing information in free space by using chaos produced through semiconductor lasers. Laser rate equations are applied to model chaos generated by semiconductor laser, followed by chaos masking scheme to hide the message signal inside the generated chaos before transmission. As FSO communication link availability and efficiency is a major concern in different atmospheric conditions, therefore fog, rain, and haze conditions are analyzed and compared for FSO communication‐based on Q‐factor and eye diagram patterns. The results are further studied for both FSO communication models, ie, with and without applying chaos masking scheme.

Decomposition Analysis of Carbon Emissions from Energy Consumption in Beijing-Tianjin-Hebei, China: A Weighted-Combination Model Based on Logarithmic Mean Divisia Index and Shapley Value

The Beijing-Tianjin-Hebei (B-T-H) region, who captures the national strategic highland in China, has drawn a great deal of attention due to the fog and haze condition and other environmental problems. Further, the high carbon emissions generated by energy consumption has restricted its further coordinated development seriously. In order to accurately analyze the potential influencing factors that contribute to the growth of energy consumption carbon emissions in the B-T-H region, this paper uses the carbon emission coefficient method to measure the carbon emissions of energy consumption in the B-T-H region, using a weighted combination based on Logarithmic Mean Divisia Index (LMDI) and Shapley Value (SV). The effects affecting carbon emissions during 2001–2013 caused from five aspects, including energy consumption structure, energy consumption intensity, industrial structure, economic development and population size, are quantitatively analyzed. The results indicated that: (1) The carbon emissions had shown a sustained growth trend in the B-T-H region on the whole, while the growth rates varied in the three areas. In detail, Hebei Province got the first place in carbon emissions growth, followed by Tianjin and Beijing; (2) economic development was the main driving force for the carbon emissions growth of energy consumption in B-T-H region. Energy consumption structure, population size and industrial structure promoted carbon emissions growth as well, but their effects weakened in turn and were less obvious than that of economic development; (3) energy consumption intensity had played a significant inhibitory role on the carbon emissions growth; (4) it was of great significance to ease the carbon emission-reduction pressure of the B-T-H region from the four aspects of upgrading industrial structure adjustment, making technological progress, optimizing the energy structure and building long-term carbon-emission-reduction mechanisms, so as to promote the coordinated low-carbon development.

Research and application of image enhancement technology in traffic scene of fog and haze

The images captured under fog and haze conditions, due to the scattering of the atmosphere, lead to blurred content and lower contrast, which brings serious impact on the application of traffic system and outdoor vision system. Based on the improved multi-scale Retinex algorithm MSR (Multi-Scale Retinex), a new fog removal method is proposed. This method estimates the luminance component according to the bootstrap filter, and then processes the image according to the adaptive histogram equalization method with limited contrast. Experiments show that the method can effectively remove the fog effect and realize the restoration of color degraded images.

Time effects of high particulate events on the critical conversion point of ground-level ozone

Particulate matter (PM), especially those with an aerodynamic particle size of less than 10 μm (PM10), is typically emitted from transboundary forest fires. A large-scale forest fire may contribute to a haze condition known as a high particulate event (HPE), which has affected Southeast Asia, particularly Peninsular Malaysia, for a long time. Such event can alter the photochemical reactions of secondary pollutants. This work investigates the influence of PM on ground-level ozone (O3) formation during HPE. Five continuous air quality monitoring stations from different site categories (i.e., industrial, urban and background) located across Peninsular Malaysia were selected in this study during the HPEs in 2013 and 2014. Result clearly indicated that O3 concentrations were significantly higher during HPE than during non-HPE in all the sites. The O3 diurnal variation in each site exhibited a similar pattern, whereas the magnitudes of variation during HPE and non-HPE differed. Light scattering and atmospheric attenuation were proven to be associated with HPE, which possibly affected O3 photochemical reactions during HPE. Critical conversion time was used as the main determining factor when comparing HPE and non-HPE conditions. A possible screening effect that resulted in the shifting of the critical transformation point caused a delay of approximately of 15–30 min. The shifting was possibly influenced by the attenuation of sunlight in the morning during HPE. A negative correlation between O3 and PM10 was observed during the HPE in Klang in 2013 and 2014, with −0.87. Essentially, HPE with a high PM concentration altered ground-level O3 formation.

Microscopic morphology and seasonal variation of health effect arising from heavy metals in PM2.5 and PM10: One-year measurement in a densely populated area of urban Beijing

In order to study the sustained impact of particulate matter on urban residents, 572 PM2.5 and PM10 samples in all were attained simultaneously from a densely populated area of Beijing from September 2015 to August 2016. 11 types of heavy metals were determined as to better ascertain the seasonal variation characteristics of particle composition. In the course of the year, the mean concentrations of PM2.5 and PM10 were detected to be 102.45 μg m−3 and 144.75 μg m−3, respectively. From general perspective, winter turned out to be the longest in haze day quantity and the highest in particle concentration, followed by spring, autumn and summer, successively. The mass concentrations of numerous PM2.5 elements fluctuated evidently in the decreasing order of Ba, Zn, Mn, Sr, Cu, Pb, Cr, V, Ni, Cd and Sb. In contrast with other seasons, winter displayed the most evident increase of metal content in particulates, especially under the condition of haze. Relationship between different size particles was also reckoned with in this study. High concentration ratio of PM2.5 and PM10 (0.76–0.84) was detected during haze period, and PM2.5 was accounted as a primary pollutant during haze-fog day in Beijing. Moreover, the carcinogenic and non-carcinogenic risk posed by detected heavy metals was investigated. Cr posed the highest carcinogenic risk, and in the meantime, as compared with other non-carcinogenic metals, value of Pb was the highest in Hazard Quotient. Risk arising from Cr and Cd in winter shall be noteworthy, and accordingly it may pose danger or potential risk to adults in haze days. Eventually, a large amount of fly ash and soot particles in winter samples were indicated from SEM-EDX analysis results, whereas those are rarely detected in summer samples.

Study of Literatures for the Impact on PM2.5 Purification by Architectural Design under Haze Conditions

This paper focuses on literatures reviewing with key words of architectural and PM2.5 based on the China Academic Journal Network Publishing Database (CKNI) and Elsevier SD database. Statistical analysis on the searched 184 related literatures show the following results. (1) 20.6% of the all targeted literatures showed that PM2.5 concentration was one of the important impact parameters of indoor & outside air quality. (2) 16.3% of the literatures illustrated that the architecture designing contributed significantly to indoor and outdoor fine particulate pollution by controlling particle generation and diffusion. It can be concluded that the three-dimensional architectural design, the total layout of the building designing strategy and the architectural space design based on green building-oriented architectural designing concept will be the future focused research and the frontier question.

Estimation of Direct Radiative Effects of Background and Smoke Aerosol in the IR Spectral Region for Siberian Summer Conditions

We present estimates of direct radiative effects (DRE) for background and smoke aerosol in the IR spectral region. The estimates are obtained using an original Monte Carlo algorithm and OPAC models for typical summer conditions and smoke haze conditions on the territory of Siberia in 2012. It is shown that the DRE value at the atmospheric boundaries in the thermal spectral region is approximately 3% of the daily mean radiation effect in the solar spectral region under background conditions, and 10–15% under conditions of strong turbidity.

Image dehazing based on dark channel prior and brightness enhancement for agricultural monitoring

Obtaining clear and true images is a basic requirement for agricultural monitoring. However, under the influence of fog, haze and other adverse weather conditions, captured images are usually blurred and distorted, resulting in the difficulty of target extraction. Traditional image dehazing methods based on image enhancement technology can cause the loss of image information and image distortion. In order to address the above-mentioned problems caused by traditional image dehazing methods, an improved image dehazing method based on dark channel prior (DCP) was proposed. By enhancing the brightness of the hazed image and processing the sky area, the dim and un-natural problems caused by traditional image dehazing algorithms were resolved. Ten different test groups were selected from different weather conditions to verify the effectiveness of the proposed algorithm, and the algorithm was compared with the commonly-used histogram equalization algorithm and the DCP method. Three image evaluation indicators including mean square error (MSE), peak signal to noise ratio (PSNR), and entropy were used to evaluate the dehazing performance. Results showed that the PSNR and entropy with the proposed method increased by 21.81% and 5.71%, and MSE decreased by 40.07% compared with the original DCP method. It performed much better than the histogram equalization dehazing method with an increase of PSNR by 38.95% and entropy by 2.04% and a decrease of MSE by 84.78%. The results from this study can provide a reference for agricultural field monitoring. Keywords: agricultural monitoring, image dehazing, monitoring image, dark channel prior (DCP), brightness promoting DOI: 10.25165/j.ijabe.20181102.3357 Citation: Wang X Y, Yang C H, Zhang J, Song H B. Image dehazing based on dark channel prior and brightness enhancement for agricultural monitoring. Int J Agric & Biol Eng, 2018; 11(2): 170–176.

Evaluation of FSO System Availability in Haze Condition

In this paper, we proposed the evaluation of FSO system availability in haze condition. The atmospheric attenuation by weather conditions in the atmosphere as the most challenging problem of FSO system as the system performance is severely degraded and causing the signal optic to be transmitted poorly. The effects of haze condition on the performance of FSO system is stressed out and focused in this paper. From the evaluation of the analysis, designs of FSO system are proposed to obtain a system with improved link performance in haze conditions. The scattering coefficient and the atmospheric attenuation are determined using Beer’s Lambert equation. From the research, the link performance of the system is greatly improved using Design 2 with minimum BER of 10-127127 and maximu m Q Factor of 23.98. The FSO system using Design 2 has better performance compared to Design 1 in haze condition as the optical signals could penetrate the dense haze better without losing much optical power during the transmission to the scattering.

Partial differential equation-based hazy image contrast enhancement

This study describes a modified partial differential equation (PDE)-based algorithm for contrast enhancement of hazy images. The formulation is supported by similarities between haze and low light conditions. The proposed approach employs multi-scale, local-global enhancement of inverted log reflectance and illumination components. These multiple processes are combined in a suitable PDE framework for improved effectiveness. Furthermore, the de-hazing process is automated via gradient-based optimization, eliminating the manual determination of PDE stopping time. Solutions are also devised for visual halo effect, over-enhancement and colour distortion. Based on subjective and quantitative analysis, the proposed technique consistently outperforms several de-hazing algorithms from the literature.

Acidity of Aerosols during Winter Heavy Haze Events in Beijing and Gucheng, China

We investigated the acidity and concentrations of water-soluble ions in PM2.5 aerosol samples collected from an urban site in Beijing and a rural site in Gucheng, Hebei Province from November 2016 to January 2017 to gain an insight into the formation of secondary inorganic species. The average SO42–, NO3–, and NH4+ concentrations were 8.3, 12.5, and 14.1 μg m–3, respectively, at the urban site and 14.0, 14.2, and 24.2 μg m–3, respectively, at the rural site. The nitrogen and sulfur oxidation ratios in urban Beijing were correlated with relative humidity (with correlation coefficient r = 0.79 and 0.67, respectively) and the aerosol loadings. Based on a parameterization model, we found that the rate constant of the heterogeneous reactions for SO2 on polluted days was about 10 times higher than that on clear days, suggesting that the heterogeneous reactions in the aerosol water played an essential role in haze events. The ISORROPIA II model was used to predict the aerosol pH, which had a mean (range) of 5.0 (4.9–5.2) and 5.3 (4.6–6.3) at the urban and rural site, respectively. Under the conditions with this predicted pH value, oxidation by dissolved NO2 and the hydrolysis of N2O5 may be the major heterogeneous reactions forming SO42– and NO3– in haze. We also analyzed the sensitivity of the aerosol pH to changes in the concentrations of SO42–, NO3–, and NH4+ under haze conditions. The aerosol pH was more sensitive to the SO42– and NH4+ concentrations with opposing trends, than to the NO3– concentrations. The sensitivity of the pH was relatively weak overall, which was attributed to the buffering effect of NH3 partitioning.

Characteristics of Turbulent Transfer during Episodes of Heavy Haze Pollution in Beijing in Winter 2016/17

We analyzed the structure and evolution of turbulent transfer and the wind profile in the atmospheric boundary layer in relation to aerosol concentrations during an episode of heavy haze pollution from 6 December 2016 to 9 January 2017. The turbulence data were recorded at Peking University’s atmospheric science and environment observation station. The results showed a negative correlation between the wind speed and the PM2.5 concentration. The turbulence kinetic energy was large and showed obvious diurnal variations during unpolluted (clean) weather, but was small during episodes of heavy haze pollution. Under both clean and heavy haze conditions, the relation between the non-dimensional wind components and the stability parameter z/L followed a 1/3 power law, but the normalized standard deviations of the wind speed were smaller during heavy pollution events than during clean periods under near-neutral conditions. Under unstable conditions, the normalized standard deviation of the potential temperature σ θ /|θ*| was related to z/L, roughly following a –1/3 power law, and the ratio during pollution days was greater than that during clean days. The three-dimensional turbulence energy spectra satisfied a –2/3 power exponent rate in the high-frequency band. In the low-frequency band, the wind velocity spectrum curve was related to the stability parameters under clear conditions, but was not related to atmospheric stratification under polluted conditions. In the dissipation stage of the heavy pollution episode, the horizontal wind speed first started to increase at high altitudes and then gradually decreased at lower altitudes. The strong upward motion during this stage was an important dynamic factor in the dissipation of the heavy haze.

Determination of carbonyl pollutants adsorbed on ambient particulate matter of type PM2.5 by using magnetic molecularly imprinted microspheres for sample pretreatment and capillary electrophoresis for separation and quantitation.

The authors describe a method for the determination of carbonyl pollutants adsorbed on ambient particulate matter (diameter < 2.5μm; PM2.5). 2,4-Dinitrophenylhydrazine (DNPH) was used to derivatize carbonyl compounds. Magnetic molecularly imprinted polymers (MMIPs) selective for 2,4-DNPH were synthesized to remove excess of the derivatization reagent 2,4-DNPH. Micellar electrokinetic chromatography (MEKC) was then applied to the separation of DNPH-derivatized carbonyl compounds. The increased sensitivity of MEKC with UV detection and the sample cleanup resulted in drastically reduced sampling times (15min) with detection limits ranging from 0.005-0.068μg·m-3 for different carbonyls. The method was applied to continuous monitoring of carbonyl compounds on ambient PM 2.5 for two consecutive months. The concentrations and gas-to-particle ratios of carbonyls were determined, and a statistical method was used to evaluate the correlation among different carbonyls. It was observed that the total concentration of carbonyls, especially of multi-carbon carbonyls, increases with the level of air pollution. The level of isovaleraldehyde rises sharply and accounts for 37% of total carbonyls on days with extremely humid haze. The ratio of acetaldehyde to propionaldehyde (C2/C3) decreases with the duration and heaviness of haze conditions. Results indicate that anthropogenic emissions and the characteristics of the atmosphere (e.g. temperature, sunlight, and relative humidity) are the main factors that lead to abnormally high levels of isovaleraldehyde and other carbonyls in ambient PM 2.5. Graphical abstract Schematic of a method for the determination of carbonyl pollutants adsorbed on ambient fine particle of type PM2.5. Magnetic molecularly imprinted polymers (MMIPs) were synthesized to remove the excess derivatization reagent (2,4-DNPH) in air sample prior to CE separation.

Image dehazing based on dark channel prior and brightness enhancement for agricultural monitoring

Obtaining clear and true images is a basic requirement for agricultural monitoring. However, under the influence of fog, haze and other adverse weather conditions, captured images are usually blurred and distorted, resulting in the difficulty of target extraction. Traditional image dehazing methods based on image enhancement technology can cause the loss of image information and image distortion. In order to address the above-mentioned problems caused by traditional image dehazing methods, an improved image dehazing method based on dark channel prior (DCP) was proposed. By enhancing the brightness of the hazed image and processing the sky area, the dim and un-natural problems caused by traditional image dehazing algorithms were resolved. Ten different test groups were selected from different weather conditions to verify the effectiveness of the proposed algorithm, and the algorithm was compared with the commonly-used histogram equalization algorithm and the DCP method. Three image evaluation indicators including mean square error (MSE), peak signal to noise ratio (PSNR), and entropy were used to evaluate the dehazing performance. Results showed that the PSNR and entropy with the proposed method increased by 21.81% and 5.71%, and MSE decreased by 40.07% compared with the original DCP method. It performed much better than the histogram equalization dehazing method with an increase of PSNR by 38.95% and entropy by 2.04% and a decrease of MSE by 84.78%. The results from this study can provide a reference for agricultural field monitoring. Keywords: agricultural monitoring, image dehazing, monitoring image, dark channel prior (DCP), brightness promoting DOI: 10.25165/j.ijabe.20181102.3357 Citation: Wang X Y, Yang C H, Zhang J, Song H B. Image dehazing based on dark channel prior and brightness enhancement for agricultural monitoring. Int J Agric & Biol Eng, 2018; 11(2): 170–176.

A multi-scale fusion scheme based on haze-relevant features for single image dehazing

Abstract Outdoor images are often degraded by aerosols suspending in atmosphere in bad weather conditions like haze. To cope with this phenomenon, researchers have proposed many approaches and single image based techniques draw attention mostly. Recently, a fusion-based strategy achieves good results, which derives two enhanced images from single image and blends them to recover haze-free image. However, there are still some deficiencies in the fusion-input images and weight maps, which leads their restoration less natural. In this paper, we propose a multi-scale fusion scheme for single image dehazing. We first use an adaptive color normalization to eliminate a common phenomenon, color distortion, in haze condition. Then two enhanced images, including our newly presented local detail enhanced image, are derived to be blended. Thereafter, five haze-relevant features of dark channel, clarity, saliency, luminance and chromatic are investigated since those can serve as weight maps for fusion. Dark channel, clarity and saliency features are finally selected due to their expression abilities and less interconnection. The fusion is processed with a pyramid strategy layer-by-layer. The multi-scale blended images are combined in a bottom-up manner. At last quantitative experiments demonstrate that our approach is effectiveness and yields better results than other methods.

Availability analysis of terrestrial free space optical (FSO) link using visibility data measured in tropical region

Haze and rain are the most impairments factors to free space optical (FSO) links. These weather conditions limit the visibility, and thereby causes high attenuation of the optical signal. This high attenuation reduces the availability performance of the FSO link. This study evaluates the performance of a terrestrial FSO link under tropical climate conditions. The performance analysis is evaluate over 5 km link distance. The cumulative distribution function (CDF) of the received signal to noise ratio (SNR) is used to study the outage performance of the FSO link under haze conditions. The performance analysis is based on three years measured visibility data in Malaysia. Based on the statistical analysis, link availability of 99.99% can be achieved for 37.44 dB SNR over 1 km link distance. Carrier class availability “five nine” can be achieved for 20 dBm transmission power using 1550 nm wavelength.

Haze Removal Based on a Fully Automated and Improved Haze Optimized Transformation for Landsat Imagery over Land

Optical satellite imagery is often contaminated by the persistent presence of clouds and atmospheric haze. Without an effective method for removing this contamination, most optical remote sensing applications are less reliable. In this research, a methodology has been developed to fully automate and improve the Haze Optimized Transformation (HOT)-based haze removal. The method is referred to as AutoHOT and characterized with three notable features: a fully automated HOT process, a novel HOT image post-processing tool and a class-based HOT radiometric adjustment method. The performances of AutoHOT in haze detection and compensation were evaluated through three experiments with one Landsat-5 TM, one Landsat-7 ETM+ and eight Landsat-8 OLI scenes that encompass diverse landscapes and atmospheric haze conditions. The first experiment confirms that AutoHOT is robust and effective for haze detection. The average overall, user’s and producer’s accuracies of AutoHOT in haze detection can reach 96.4%, 97.6% and 97.5%, respectively. The second and third experiments demonstrate that AutoHOT can not only accurately characterize the haze intensities but also improve dehazed results, especially for brighter targets, compared to traditional HOT radiometric adjustment.

Factors Contributing to Haze Pollution: Evidence from Macao, China

Haze is a major environmental concern in many cities because it adversely affects people’s physiological and psychological well-being. This paper examines the extent of haze in Macao during the period 1986–2016. It identifies the relationships between haze, energy use, and meteorological conditions directly. The haze in Macao changed over the period 1986–2016 with air pollution getting worse and then improving after 2007. Specifically, the number of haze hours increased from 3 in 1986 to 766 in 2007, and then dropped to 57 in 2016, while the total energy use increased from 12,246 TJ in 1986 to 37,144 TJ in 2007, and then to 42,405 TJ in 2016. As per primary energy, Macao used 12,096 TJ in 1986, 21,388 TJ in 2007, and 16,647 TJ in 2016 excluding aviation kerosene. Bivariate correlations show that haze was most positively and significantly associated with annual primary energy use. Multiple regression analysis indicates that the number of hours with haze was significantly, positively related to the consumption of gas oil/diesel, fuel oil, and natural gas in Macao and aviation kerosene. Nevertheless, the improvement in Macao could come at a cost to areas in downwind of Zhuhai’s coal power stations supplying Macao’s electricity energy.

A campaign for investigating aerosol optical properties during winter hazes over Shijiazhuang, China

As the capital of the most air-polluted Hebei province in China, Shijiazhuang has been suffering serious haze pollutions especially during wintertime. An integrated campaign for investigating aerosol optical properties under haze conditions over Shijiazhuang were carried out using a sunphotometer, an aethalometer and a lidar in the winter from late 2013 to early 2014. The results indicated that the haze episodes during the measurement period were severer and more frequent over Shijiazhuang than Beijing. Under heavy pollution conditions (PM2.5>150μg/m3) over Shijiazhuang, fine-mode fractions of AOD500nm were larger than 0.80 with more dispersive angstrom exponent due to hygroscopic growth. The mean values of SSA over Shijiazhuang were smaller than those over Beijing both in this study and the severe haze episodes in January 2013, suggesting that there were more fine-mode absorbing particles over Shijiazhuang. More significant spectrally-dependence of imaginary part of refractive index over Shijiazhuang implies larger relative magnitude of brown carbon (BrC) as compared to Beijing. The black carbon (BC) measurement displayed extremely high records with a larger ratio of BC to PM2.5 (12.11% in average) comparing with other cities in China. The high carbonaceous aerosols (BC and BrC) should be attributed to large amounts of coal consumption. During the hazes with high BC concentrations, the daily maximal planetary boundary layer (PBL) heights were consistently lower than 500m, implying the impacts of BC aerosols on the PBL development and hence enhance the surface haze pollution.