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ABSTRACT Sea surface temperature ( SST) is an important oceanic variable that impacts regional and global climate. This paper examines the relation of summer (June to August) surface air temperature ( SAT) variability over Saudi Arabia (1948-2013) with SST over the Atlantic, Pacific and Indian Oceans. The SAT over Saudi Arabia shows an abrupt increase around the 1980s (i.e. 1986). Partial correlations between SAT and different SST indices indicate that the Indo-Pacific warm pool ( IPWP) has a more significant effect on SAT than does the tropical North Atlantic ( TNA), tropical South Atlantic ( TSA) or Western Hemisphere warm pool ( WHWP). Hence, the change in IPWP SST can be considered as one of the factors linked to increase SAT over Saudi Arabia. The only significant relationship between El Niño and SAT is found in the Niño 4 region. Moreover, interactions between the tropical Atlantic meridional gradient mode and SAT are undetectable in the summer season, indicating that the TNA and TSA may have effectively independent roles on SAT over Saudi Arabia. The tropical Atlantic, through TNA and TSA, may influence the IPWP SST which modifies the strength of the Indian monsoon low, and in turn, has a strong influence on Saudi Arabia SAT variability. [ABSTRACT FROM AUTHOR]

A workshop was held in Casablanca, Morocco, in March 2012, to enhance knowledge of climate extremes and their changes in the Arab region. This workshop initiated intensive data compilation activities of daily observational weather station data from the Arab region. After conducting careful control processes to ensure the quality and homogeneity of the data, climate indices for extreme temperatures and precipitation were calculated. This study examines the temporal changes in climate extremes in the Arab region with regard to long-term trends and natural variability related to ENSO and NAO. We find consistent warming trends since the middle of the 20th Century across the region. This is evident in the increased frequencies of warm days and warm nights, higher extreme temperature values, fewer cold days and cold nights and shorter cold spell durations. The warming trends seem to be particularly strong since the early 1970s. Changes in precipitation are generally less consistent and characterised by a higher spatial and temporal variability; the trends are generally less significant. However, in the western part of the Arab region, there is a tendency towards wetter conditions. In contrast, in the eastern part, there are more drying trends, although, these are of low significance. We also find some relationships between climate extremes in the Arab region and certain prominent modes of variability, in particular El Niño-Southern Oscillation ( ENSO) and North Atlantic Oscillation ( NAO). The relationships of the climate extremes with NAO are stronger, in general, than those with ENSO, and are particularly strong in the western part of the Arab region (closer to the Atlantic Ocean). The relationships with ENSO are found to be more significant towards the eastern part of the area of study. © 2013 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The increasing trend of using agricultural wastes follows the concept of "waste to wealth" and is closely related to the themes of sustainable development goals (SDGs). Carbon-neutral technologies for waste management have not been critically reviewed yet. This paper reviews the technological trend of agricultural waste utilization, including composting, thermal conversion, and anaerobic digestion. Specifically, the effects of exogenous additives on the contents, fractionation, and fate of phosphorus (P) and potentially toxic elements (PTEs) during the composting process have been comprehensively reviewed in this article. The composting process can transform biomass-P and additive-born P into plant available forms. PTEs can be passivated during the composting process. Biochar can accelerate the passivation of PTEs in the composting process through different physiochemical interactions such as surface adsorption, precipitation, and cation exchange reactions. The addition of exogenous calcium, magnesium and phosphate in the compost can reduce the mobility of PTEs such as copper, cadmium, and zinc. Based on critical analysis, this paper recommends an eco-innovative perspective for the improvement and practical application of composting technology for the utilization of agricultural biowastes to meet the circular economy approach and achieve the SDGs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Fine particulate matter, with an aerodynamic diameter ≤ 2.5 μm (PM 2.5 ), is a severe problem in China. The lack of ground-based measurements and its sparse distribution obstruct long-term air pollution impact studies over China. Therefore, the present study used newly updated Global Estimates (V5. GL.02) of monthly PM 2.5 data from 2001 to 2020 based on Geographically Weighted Regression (GWR) by Washington University. The GWR PM 2.5 data were validated against ground-based measurements from 2014 to 2020, and the validation results demonstrated a good agreement between GWR and ground-based PM 2.5 with a higher correlation (r = 0.95), lower error (8.14), and lower bias (-3.10 %). The long-term (2001-2020) PM 2.5 data were used to identify pollution hotspots and sources across China using the potential source contribution function (PSCF). The results showed highly significant PM 2.5 pollution hotspots in central (Henan, Hubei), North China Plain (NCP), northwest (Taklimakan), and Sichuan Basin (Chongqing, Sichuan) in China, with the most severe pollution occurring in winter compared to other seasons. During the winter, PM 2.5 was in the range from 6.08 to 93.05 μg/m 3 in 33 provinces, which is 1.22 to 18.61 times higher than the World Health Organization (WHO) Air Quality Guidelines (AQG-2021; annual mean: 5 μg/m 3 ). In 26 provinces, the reported PM 2.5 was 1.07 to 2.66 times higher than the Chinese Ambient Air Quality Standard (AAQS; annual mean: 35 μg/m 3 ). Furthermore, provincial-level trend analysis shows that in most Chinese provinces, PM 2.5 increased significantly (3-43 %) from 2001 to 2012, whereas it decreased by 12-94 % from 2013 to 2020 due to the implementation of air pollution control policies. Finally, the PSCF analysis demonstrates that China's air quality is mainly affected by local PM 2.5 sources rather than by pollutants imported from outside China., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Countries depending on small-scale agriculture, such as Bangladesh, are susceptible to climate change and variability. Changes in the frequency and intensity of drought are a crucial aspect of this issue and the focus of this research. The goal of this work is to use SPI (standardized precipitation index) and SPEI (standardized precipitation evapotranspiration index) to investigate the differences in drought characteristics across different physiognomy types in Bangladesh and to highlight how drought characteristics change over time and spatial scales when considering different geomorphologies. This study used monthly precipitation and temperature data from 29 metrological stations for 39 years (1980-2018) for calculating SPI and SPEI values. To determine the significance of drought characteristic trends over different temporal and spatial scales, the modified Mann-Kendall trend test and multivariable linear regression (MLR) techniques were used. The results are as follows: (1) Overall, decreasing dry trend was found in Eastern hill regions, whereas an increasing drought trends were found in the in the rest of the regions in all time scaless (range is from - 0.08 decade -1  to - 0.15 decade -1  for 3-month time scale). However, except for the one-month time scale, the statistically significant trend was identified mostly in the north-central and northeast regions, indicating that drought patterns migrate from the northwest to the center region. (2) SPEI is anticipated to be better at capturing dry/wet cycles in more complex regions than SPI. (3) According to the MLR, longitude and maximum temperature can both influence precipitation. (4) Drought intensity increased gradually from the southern to the northern regions (1.26-1.56), and drought events occurred predominantly in the northwestern regions (27-30 times), indicating that drought meteorological hotspots were primarily concentrated in the Barind Tract and Tista River basin over time. Findings can be used to improve drought evaluation, hazard management, and application policymaking in Bangladesh. This has implications for agricultural catastrophe prevention and mitigation., (© 2022. The Author(s).)

Droughts are one of the most devastating and recurring natural disaster due to a multitude of reasons. Among the different drought studies, drought forecasting is one of the key aspects of effective drought management. The occurrence of droughts is related to a multitude of factors which is a combination of hydro-meteorological and climatic factors. These variables are non-linear in nature, and neural networks have been found to effectively forecast drought. However, classical neural nets often succumb to over-fitting due to various lag components among the variables and therefore, the emergence of new deep learning and explainable models can effectively solve this problem. The present study uses an Attention-based model to forecast meteorological droughts (Standard Precipitation Index) at short-term forecast range (1-3 months) for five sites situated in Eastern Australia. The main aim of the work is to interpret the model outcomes and examine how a deep neural network achieves the forecasting results. The plots show the importance of the variables along with its short-term and long-term dependencies at different lead times. The results indicate the importance of large-scale climatic indices at different sequence dependencies specific to the study site, thus providing an example of the necessity to build a spatio-temporal explainable AI model for drought forecasting. The use of such interpretable models would help the decision-makers and planners to use data-driven models as an effective measure to forecast droughts as they provide transparency and trust while using these models., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In this study, combined Dark Target and Deep Blue (DTB) aerosol optical depth at 550 nm (AOD 550 nm ) data the Moderate Resolution Imaging Spectroradiometer (MODIS) flying on the Terra and Aqua satellites during the years 2003-2020 are used as a reference to assess the performance of the Copernicus Atmosphere Monitoring Services (CAMS) and the second version of Modern-Era Retrospective analysis for Research and Applications (MERRA-2) AOD over Bangladesh. The study also investigates long-term spatiotemporal variations and trends in AOD, and determines the relative contributions from different aerosol species (black carbon: BC, dust, organic carbon: OC, sea salt: SS, and sulfate) and anthropogenic emissions to the total AOD. As the evaluations suggest higher accuracy for CAMS than for MERRA-2, CAMS is used for further analysis of AOD over Bangladesh. The annual mean AOD from both CAMS and MODIS DTB is high (>0.60) over most parts of Bangladesh except for the eastern areas of Chattogram and Sylhet. Higher AOD is observed in spring and winter than in summer and autumn, which is mainly due to higher local anthropogenic emissions during the winter to spring season. Annual trends from 2003-2020 show a significant increase in AOD (by 0.006-0.014 year -1 ) over Bangladesh, and this increase in AOD was more evident in winter and spring than in summer and autumn. The increasing total AOD is caused by rising anthropogenic emissions and accompanied by changes in aerosol species (with increased OC, sulfate, and BC). Overall, this study improves understanding of aerosol pollution in Bangladesh and can be considered as a supportive document for Bangladesh to improve air quality by reducing anthropogenic emissions., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Conversion of hazardous waste materials to value-added products is of great interest from both agro-environmental and economic points of view. Bone char (BC) has been used for the removal of potentially toxic elements (PTEs) from contaminated water, however, its potential BC for the immobilization of PTEs in contaminated water and soil compared to bone (BBC)- and plant (PBC)-derived biochars has not been reviewed yet. This review presents an elaboration for the potentials of BC for the remediation of PTEs-contaminated water and soil in comparison with PBC and BBC. This work critically reviews the preparation and characterization of BC, BBC, and PBC and their PTEs removal efficiency from water and soils. The mechanisms of PTE removal by BC, BBC, and PBC are also discussed in relation to their physicochemical characteristics. The review demonstrates the key opportunities for using bone waste as feedstock for producing BC and BBC as promising low-cost and effective materials for the remediation of PTEs-contaminated water and soils and also elucidates the possible combinations of BC and BBC aiming to effectively immobilize PTEs in water and soils., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Bioactive peptides derived from milk proteins are widely known to possess antibacterial activities. Even though the antibacterial effects of milk-derived peptides are widely characterized, not much focus is given to their antifungal characterization. Therefore, in this study, we investigated the antifungal properties of camel and cow whey and casein hydrolysates against various species of pathogenic Candida. The hydrolysates were produced using 2 enzymes (alcalase and protease) at differing hydrolysis durations (2, 4, and 6 h) and tested for their antifungal properties. The results showed that intact cow whey and casein proteins did not display any anti-Candida albicans properties, whereas the alcalase-derived 2 h camel casein hydrolysate (CA-C-A2) displayed a higher percentage of inhibition against Candida albicans (93.69 ± 0.26%) followed by the cow casein hydrolysate generated by protease-6 h (Co-C-P6; 81.66 ± 0.99%), which were significantly higher than that of fluconazole, a conventional antifungal agent (76.92 ± 4.72%). Interestingly, when tested again Candida krusei, camel casein alcalase 2 and 4 h (CA-C-A2 and CA-C-A4), and cow whey alcalase-6 h (CO-W-A6) hydrolysates showed higher antifungal potency than fluconazole. However, for Candida parapsilosis only camel casein alcalase-4 h (Ca-C-A4) and cow casein protease-6 h (Co-C-P6) hydrolysates were able to inhibit the growth of C. parapsilosis by 19.31 ± 0.84% and 23.82 ± 4.14%, respectively, which was lower than that shown by fluconazole (29.86 ± 1.11%). Overall, hydrolysis of milk proteins from both cow and camel enhanced their antifungal properties. Camel milk protein hydrolysates were more potent in inhibiting pathogenic Candida species as compared with cow milk protein hydrolysates. This is the first study that highlights the antifungal properties of camel milk protein hydrolysates., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Plastic pollution and its impact on marine ecosystems are major concerns globally, and the situation was exacerbated after the outbreak of COVID-19. Clean-up campaigns took place during the summer season (June-August 2020) in two coastal cities in Egypt (Alexandria and Hurghada) and Jeddah, Saudi Arabia to document the abundance of beach debris through public involvement, and then remove it. A total of 3673, 255, and 848 items were collected from Alexandria, Hurghada, and Jeddah daily, respectively. Gloves and face masks (personal protective equipment "PPE") represent represented 40-60% of the total plastic items collected from each of the three cities, while plastic bags represented 7-20% of the total plastics litter collected from the same cities. The results indicated the presence of 2.79, 0.29, and 0.86 PPE item m -2 in Alexandria, Hurghada and Jeddah, respectively. This short focus provides an assessment of the environmental impacts of single-use gloves and masks used for COVID-19 protection from June to August 2020. To the best of our knowledge, this study presents the first such information from the Middle East, specifically Egypt and Saudi Arabia. It highlights the need for further knowledge and action, such as safe, sustainable, and transparent waste management processes related to COVID-19 to reduce the negative impacts now, as well as in future events. Furthermore, this study helps in achieving key components of the United Nation's Sustainable Development Goals (SDGs). This short focus can serve as a multipurpose document, not only for scientists of different disciplines but for social media and citizens in general., Competing Interests: Declaration of competing interest We believe this subject is interesting and no data were published from Egypt or Saudi Arabia. We have the pleasure to submit this paper as a short communication. Having said that, I could not find a short communication option regarding the submission, so I have selected the nearest option. The authors declare no potential conflicts of interest concerning the research, authorship, and/or publication of this article., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This article evaluates the impact of upstream water withdrawal on downstream land use and livelihood changes in the Teesta River basin, using a combination of geospatial and social data. Results show that water bodies gradually decreased, indicating a low volume of water discharge from upstream of the Teesta River basin due to the construction of several barrages. During the study period, a significant change in the area of water bodies was observed between 2012 and 2016, from 881 to 1123 Ha, respectively. The cropland area increased because farmers changed their cropping practice due to water scarcity and floods. Trend analyses of riverbank erosion and accretion patterns suggest an increase in accretion rates compared to the rate of riverbank erosion. A household survey was conducted using a self-administered questionnaire where 450 respondents have participated (farmers: 200 and fishermen: 250). Survey results show that most of the farmers (65.5%) and fishermen (76.8%) think that the construction of upstream barrages caused harm to them. The majority of farmers and fishermen feel water scarcity, mainly in the dry season. We found that a large number of participants in the study area are willing to change their occupations. Furthermore, participants observed that many local people are migrating or willing to migrate to other places nowadays. Our study also found that farmers who face water scarcity in their area are more likely to change their location than their counterparts, while those who face problems in their cultivation are less likely to move. On the other hand, upstream barrages, fishing effects, and getting support in crisis significantly predict fishermen's occupation changes. We believe our results provide essential information on the significance of transboundary water-sharing treaties, sustainable water resource management, and planning., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The government of Saudi Arabia imposed a strict lockdown between March and July 2020 to stop the spread of the coronavirus disease (COVID-19), which has led to a sharp decline in economic activities. The daily temporal variations of PM 10 , PM 2.5 , carbon monoxide (CO), nitrogen dioxide (NO 2 ), and ozone (O 3 ) were used to investigate the changes in air quality in response to COVID-19 lockdown control measures from January to December 2020 in Jeddah, Saudi Arabia. Meteorological parameters (wind speed, direction, temperature, relative humidity) were also analyzed to understand the changes during the pandemic. As a result, significant reductions in the concentrations of NO 2 (- 44.5%), CO (- 41.5%), and PM 2.5 , PM 10 (- 29.5%, each) were measured in the capital city of Jeddah during the quarantine compared to the pre-lockdown average. In contrast, the lockdown caused a significant increase in O 3 by 41%. The changes in air quality during the COVID-19 outbreak by comparing the average pollutant concentration before lockdown (January 1-March 21, 2020) and the following 12 weeks during the partial lockdown (March 22-July 28, 2020), reveal a very significant decrease in pollutants, and consequently a significant improvement in air quality. Observed differences are attributable to changes in point source emissions associated with changes in localized activities, possibly related to decreased economic and industrial activity in response to the lockdown. The results of the present study show during the study period indicated a positive response to lockdown during the COVID-19 pandemic. Furthermore, the results can be used to establish future control measures and strategies to improve air quality., Competing Interests: Conflict of interestAuthors declare that there is no conflict of interest., (© King Abdulaziz University and Springer Nature Switzerland AG 2022, Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)

Dengue is an important global arboviral disease with expanding geographical range. It is a major public health concern in Western Saudi Arabia since its first detection in the city of Jeddah in 1994. In this retrospective study, we examined dengue incidence among febrile patients suspected for acute dengue infection at King Abdulaziz University Hospital, Jeddah from 2010 to 2014 and we tried to determine the effect of climate factors on dengue incidence in the city. Acute dengue incidence rates among clinically suspected patients showed annual variation with a range from 29.3% to 57%. Male gender and 11-30 years age range were found to be risk factors for dengue infection in Jeddah. While dengue infections can be detected throughout the year, most cases occurred between March and July with peaks in May and June. Seasonality of dengue was found to be significantly associated with the decrease in relative humidity and increase in temperature within the range of ∼25 °C to ∼33 °C but not extremely hot temperatures. Moreover, we found that rainfall during winter (November to February) has a significant lag effect on dengue infection among febrile patients in the city. Jeddah is the second largest city in Saudi Arabia and a major hub for pilgrims because of its close proximity to the holy sites in the Kingdom. The observed high rates of acute dengue infections clearly show the endemicity of dengue in Jeddah. The observed higher incidence rates at young age are expected to cause an increase in severe dengue cases in the future especially that multiple dengue serotypes are co-circulating in the city. Furthermore, the significant association between the different climate factors and dengue and their impact on the disease seasonality should help in the effort to implement effective control and management measures to reduce dengue burden in the Kingdom., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Unlabelled: Yanbu, on the Red Sea, is an affluent Saudi Arabian industrial city of modest size. Substantial effort has been spent to balance environmental quality, especially air pollution, and industrial development. We have analyzed six years of observations of criteria pollutants O3, SO2, particles (PM2.5 and PM10) and the known ozone precursors-volatile organic compounds (VOCs) and nitrogen oxides (NOx). The results suggest frequent VOC-limited conditions in which ozone concentrations increase with decreasing NOx and with increasing VOCs when NOx is plentiful. For the remaining circumstances ozone has a complex non-linear relationship with the VOCs. The interactions between these factors at Yanbu cause measurable impacts on air pollution including the weekend effect in which ozone concentrations stay the same or even increase despite significantly lower emissions of the precursors on the weekends. Air pollution was lower during the Eids (al-Fitr and al-Adha), Ramadan and the Hajj periods. During Ramadan, there were substantial night time emissions as the cycle everyday living is almost reversed between night and day. The exceedances of air pollution standards were evaluated using criteria from the U.S. Environmental Protection Agency (EPA), World Health Organization (WHO), the Saudi Presidency of Meteorology and Environment (PME) and the Royal Commission Environmental Regulations (RCER). The latter are stricter standards set just for Yanbu and Jubail. For the fine particles (PM2.5), an analysis of the winds showed a major impact from desert dust. This effect had to be taken into account but still left many occasions when standards were exceeded. Fewer exceedances were found for SO2, and fewer still for ozone. The paper presents a comprehensive view of air quality at this isolated desert urban environment., Implications: Frequent VOC-limited conditions are found at Yanbu in Saudi Arabia that increase ozone pollution if NOx is are reduced. In this desert environment, increased nightlife produces the highest levels of VOCs and NOx at night rather than the day. The effects increase during Ramadan. Fine particles peak twice a day-the morning peak is caused by traffic and increases with decreasing wind, potentially representing health concerns, but the larger afternoon peak is caused by the wind, and it increases with increasing wind speeds. These features suggest that exposure to pollutants must be redefined for such an environment.

Unlabelled: This paper presents a one-year record of in situ air-quality data from nine sites throughout Saudi Arabia. The data set is composed of hourly measurements of ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO) at six of the largest cities in Saudi Arabia (Riyadh, Jeddah, Makkah, Yanbu, Dammam, Hafouf) and two remote locations in the mountainous southwestern region of Alsodah for the year 2007. The authors found that international O3 and CO standards were routinely exceeded throughout the year at many sites, and that exceedances increased during Ramadan (Sep. 12-Oct. 13), the Islamic month of fasting when much of normal daily activity is shifted to nighttime hours. In general NO2 and CO levels were higher in Saudi cities compared to U.S. cities of comparable population, while O3 levels were lower. There was a general trend for O3 and NO2 to be negatively correlated in Saudi cities in contrast to U.S. cities where the correlation is positive, suggesting that ozone chemistry in Saudi Arabia is limited by volatile organic compound emissions. This may be caused by low biogenic emissions from vegetation. Pollutant levels were lower at most Saudi sites during the four day Hajj period (Dec. 18-21) but higher in Makkah which receives millions of visitors during Hajj. The authors also found that ozone levels were elevated during the weekend (Thursday & Friday) relative to weekday levels despite lower NO2, a phenomenon known as the "weekend effect." As little air quality data is available from Saudi Arabia in the English-language literature, this data set fills a knowledge gap and improves understanding of air quality in an important but under-reported region of the world., Implications: Air quality measurements at nine sites in Saudi Arabia provide a detailed look at spatial and temporal patterns of ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). NO2 and CO levels increased in most cities during the fasting month of Ramadan, whereas O3 levels decreased. This led to an increased frequency of CO exceedances based on international standards. NO2 and CO also increased in Makkah during the Hajj pilgrimage. In general, NO2 and O3 levels were anticorrelated at most sites, suggesting that O3 chemistry is limited by volatile organic compound emissions throughout much of Saudi Arabia.

Air pollution has been an increasing concern within the Kingdom of Saudi Arabia and other Middle Eastern countries. In this work the authors present an analysis of daily ozone (O3), nitrogen oxide (NO(x)), and particulate matter (< 10 miccrom aerodynamic diameter; PM10) concentrations for two years (2010 and 2011) at sites in and around the coastal city of Jeddah, as well as a remote background site for comparison. Monthly and weekly variations, along with their implications and consequences, were also examined. O3 within Jeddah was remarkably low, and exhibited the so-called weekend effect--elevated O3 levels on the weekends, despite reduced emissions of O3 precursors on those days. Weekend O3 increases averaged between 12% and 14% in the city, suggesting that NO(x)/volatile organic compound (VOC) ratios within cities such as Jeddah may be exceptionally high. Sites upwind or far removed from Jeddah did not display this weekend effect. Based on these results, emission control strategies in and around Jeddah must carefully address NO(x)/VOC ratios so as to reduce O3 at downwind locations without increasing it within urban locations themselves. PM10 concentrations within Jeddah were elevated compared with North American cites of similar climatology though comparable to other large cities within the Middle East. Implications: Daily concentrations of O3, PM10, and NO(x) in and around the city of Jeddah, Saudi Arabia, are analyzed and compared with those of other reference cities. Extremely low O3 levels, along with a significant urban weekend effect (higher weekend O3, despite reduced NO(x) concentrations), is apparent, along with high levels of PM10 within the city. Urban O3 in Jeddah was found to be lower than that of other comparable cities, but the strong weekend effect suggests that care must be taken to reduce downwind O3 levels without increasing them within the city itself. Further research into the emissions and chemistry contributing to the reduced O3 levels within the city is warranted.