A cyclone over Saudi Arabia on 5 January 2002: A case study

Summary A shallow and short-lived subsynoptic cyclone is discussed as one of typical events causing natural disasters over Saudi Arabia on 5 January 2002 using the Japan Meteorological Agency global analysis dataset. The main cause for its formation was vorticity stretching. On the same day widespread rainfall over Saudi Arabia with enhanced precipitation over the mountainous Jeddah region was also observed using the Global Precipitation Climatology Project dataset. Owing to eastward-moving wintertime synoptic-scale Mediterranean disturbances, this rainfall was associated with frontal activity, modified by the local orography.     

Sensitivity of a regional climate model on the simulation of high intensity rainfall events over the Arabian Peninsula and around Jeddah (Saudi Arabia)

As a step towards the adoption and use of the regional climate model (RegCM3) for the simulation of intense rainfall events over the Arabian Peninsula, this study examines its sensitivity to domain size, boundary location, forcing fields, and resolution. In the climatological results, RegCM3 performs well in reproducing the annual and the seasonal mean precipitation as well as the contrast between wet and dry years in terms of the amounts and locations of the rainbands. In addition, simulations are performed for two cases of intense rainfall events in the Jeddah area and surroundings using a combination of three domains and two boundary forcings at 50?km. The results show that different combinations of these parameters provide different skills for the regional model. However, RegCM3 performs relatively better when ERA40 (NNRP2) is used at the boundaries in the smaller domain (larger domain), indicating the importance of the stronger (relatively weaker) influence of boundary forcing needed to capture these intense rainfall events around Jeddah. This may be explained by the fact that around that region, RegCM3 produces, in the smaller domain, higher relative humidity and stronger wind vectors closer to the reanalyses when nested within the ERA40, while it shows its best performance with the larger domain when driven by NNRP2. It is also shown that the use of high resolution does not systematically improve the simulation of such events, although some encouraging results were produced.     

A study of suspended particulate matter in Lahore (Pakistan)

The results obtained from an investigation of suspended particulate matter in the metropolitan city of Lahore (Pakistan) are reported and analysed in this paper. X-ray diffraction studies of the airborne matter collected from va-rious urban and suburban sites show that non-clay minerals such as quartz, calcite and albite are contained in most of the samples in almost comparable amounts. Chemical analysis of some samples was carried out for complementing the x-ray diffraction data. The amount of quartz in the samples of dusty areas was found to be an order of magnitude more than in the samples of relatively cleaner areas. As the dust particles of these compounds are poor substrate for promoting nucleation of ice in the atmospheric clouds, they are liable to stay steadily in the atmosphere as pollutants.A comparison of the results of the airborne particulates and the soil samples collected from various sites show that the sources of quartz, calcite and albite in the airborne matter are both local and remote.     

Remote sensing of aerosols over the Solar Village, Saudi Arabia

Aerosol optical properties over Solar Village, Saudi Arabia have been studied using ground-based remote sensing observations through the Aerosol Robotic Network (AERONET). Our analysis covered 8 recorded years of aerosol measurements, starting from February 1999 through January 2007. The seasonal mean values of aerosol optical thickness (AOT), the Ångström wavelength exponent α and the surface wind speed (V), exhibit a one year cyclical pattern. Seasonal variations are clearly found in the shape and magnitude of the volume size distribution (VSD) of the coarse size mode due to dust emission. The Spring is characterized by dusty aerosols as the modal value of the exponent α was low ~ 0.25 while that of AOT was high ~ 0.3. The modal value of wind speed was the highest ~ 3.6 m/s in spring. The increase in wind speed is responsible for increasing the concentration of dust particles during Spring. Spring of 2003 has the highest mean values of AOT, V and VSD and the lowest mean value for the exponent α. The seasonal mean values of the exponent α are anticorrelated with those of the wind speed (r = − 0.63). The annual mean values of the exponent α are well correlated (r = 0.77) with those of the difference between the maximum and minimum values of temperature ΔT. They are anticorrelated (r = − 0.74) with the annual mean values of the relative humidity. Large aerosol particles and high relative humidity increase the radiative forcing. This results in reduction of the values of the temperature difference ΔT.     

Relationships of surface ozone with its precursors,particulate matter and meteorology over Delhi

Journal of Atmospheric Chemistry - The paper presents the temporal variations of surface ozone (O3) and its precursors (oxides of nitrogen (NOX), carbon monoxide (CO), methane (CH4) and non-methane...     

Urbanization effects on the air temperature rise in Saudi Arabia

We study the possible effects of urbanization on the rise of air temperature in Saudi Arabia for the period 1981–2010. The effects of variations in elevation and marine temperature on the air temperature trend are also investigated. Surface air temperature data are analyzed for 24 sites which are mostly located at the airports across the country. The population data for the current (2010) and earlier (2004 and 1992) censuses are used for the nearest cities where the observation sites are located. A national average is calculated using two different approaches (simple averaging and weighted according to area for 1985–2010 when all stations are available) which gives trends of 0.60 and 0.51 °C/decade respectively, both significant at the 99 % level. We find no link between the temperature increase and population increase nor with elevation at the 24 sites which are mostly located in the urban effected area but not at the city centers. This suggests that the rise in air temperature is not likely due to urbanization changes resulting from the population increases.     

Role of atmospheric ammonia in the formation of inorganic secondary particulate matter: A study at Kanpur,India

Levels of fine Particulate Matter (PM_fine), SO₂ and NO_x are interlinked through atmospheric reactions to a large extent. NO_x, NH₃, SO₂, temperature and humidity are the important atmospheric constituents/conditions governing formation of fine particulate sulfates and nitrates. To understand the formation of inorganic secondary particles (nitrates and sulfates) in the atmosphere, a study was undertaken in Kanpur, India. Specifically, the study was designed to measure the atmospheric levels of covering winter and summer seasons and day and night samplings to capture the diurnal variations. Results showed are found to be significantly high in winter season compared to the summer season. In winter, the molar ratio of to was found to be greater than 2:1. This higher molar ratio suggests that in addition to (NH₄)₂SO₄, NH₄NO₃ will be formed because of excess quantity of present. In summer, the molar ratio was less than 2:1 indicating deficit of to produce NH₄NO₃. The nitrogen conversion ratio (NO₂ to NO₃) was found to be nearly 50% in the study area that suggested quick conversion of NO₂ into nitric acid. As an overall conclusion, this study finds that NH₃ plays a vital role in the formation of fine inorganic secondary particles particularly so in winter months and there is a need to identify and assess sources of ammonia emissions in India.     

The diffusion of particulate matter from an elevated source

Summary The problem of the diffusion of particulate matter from an elevated source is important to industry, to agriculture and to public health. On the experimental and theoretical side, simple ground measurements of this phenomenon offer very sensitive tests of diffusion theories.A theoretical solution to this problem, using theK-theory formulation byDeacon [1], but valid only for neutral stability, was given byRounds [2] in 1955 and has been extended by approximate methods to cover any stability by the present author. Calculations then show the dependence of down-wind distribution of deposited matter on stability, surface roughness, height of source, wind speed and particle size. The effects on the location and magnitude of maximum deposition produced by simultaneous variations in two or more of the above parameters are also portrayed.The formulation bySutton [3] of the statistical theory (theC-theory) has been applied to particulate diffusion by numerous authors, who give differing solutions largely as a result of inconsistent boundary assumptions. A formally correct solution is derived, but a fundamental reexamination of the turbulence mechanism described by theC-theory reveals that this theory is probably not applicable to diffusion from an elevated source near the ground (although it may give essentially the correct ground concentration for gaseous aerosols). In addition, theK-theory has a decided advantage for practical application in that all the parameters required are inherent in the vertical profile of wind speed.

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Zusammenfassung Das Problem der Diffusion suspendierter Partikel von einer Quelle in der Höhe besitzt Bedeutung für Industrie, Landwirtschaft und öffentliche Hygiene. Von experimenteller und theoretischer Seite biete schon einfache Bodenmessungen dieses Vorganges sehr empfindliche Prüfmöglichkeiten für Diffusionstheorien.Eine theoretische Lösung dieses Problems, die auf derK-Theorie-Formulierung vonDeacon [1] beruht, jedoch nur für neutrale Stabilität Gültigkeit besitzt, wurde vonRounds [2] 1955 angegeben und wurde vom Verfasser der vorliegenden Arbeit durch Näherungsmethoden auf beliebige Stabilitätsbedingungen ausgedehnt. Berechnungen haben ergeben, daß die Abhängigkeit der Verteilung der Abwärtsströmungen der abgelagerten Materie von der Stabilität, der Bodenrauheit, der Höhe des Ausgangspunktes, der Windgeschwindigkeit und der Partikelgröße abhängig ist. Die Wirkungen, die durch gleichzeitige Variation von zwei oder mehr der genannten Parameter auf die Lokalisierung und das Ausmaß der maximalen Ablagerung hervorgerufen werden, konnten ebenfalls dargestellt werden. Suttons [3] Formulierung der statistischen Theorie (C-Theorie) wurde von zahlreichen Forschern auf die Partikeldiffusion angewendet, die im wesentlichen infolge unvereinbarer Grenzvoraussetzungen zu verschiedenartigen Lösungen gekommen sind. Es wird eine formell korrekte Lösung aufgestellt; doch ergibt eine auf die Grundtatsachen zurückgehende Überprüfung des Turbulenzmechanismus, wie er von derC-Theorie formuliert wird, daß diese Theorie wahrscheinlich nicht auf den Vorgang der Diffusion von einem erhöhten Ausgangspunkt in der Nähe des Bodens anwendbar ist (wenn sie auch in den Grundzügen in der Lage ist, die korrekte Bodenkonzentration für gasförmiges Aerosol wiederzugeben). Zudem hat dieK-Theorie einen entschiedenen Vorzug für die praktische Anwendung durch den Umstand, daß alle erforderlichen Parameter im Vertikalprofil der Windgeschwindigkeit enthalten sind.

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Résumé Le problème de la diffusion de particules en suspension issues d'une source en altitude revêt une certaine importance pour l'industrie, l'agriculture et l'hygiène publique. Du point de vue expérimental et théorique, même des mesures au sol de ce phénomène offrent de fines possibilités de vérification des théories de la diffusion.La solution de ce problème fondée sur la théorie deDeacon [1], mais qui ne vaut que pour une stabilité neutre, a été donnée parRounds [2] en 1955 et a été étendue par l'auteur à d'autres conditions quelconques de stabilité par des méthodes d'approximation. Le calcul montre que les courants descendants de particules dépendent de la stabilité, de la rugosité du sol, de l'altitude de la source, de la vitesse du vent et de la grosseur des particules. L'auteur a pu aussi apprécier l'effet des paramètres variables mentionnés sur la localisation et le dépôt maximum.De nombreux chercheurs ont appliqué la théorie deSutton à la diffusion des particules et ont abouti à diverses solutions, en raison probablement de conditions aux limites incompatibles. L'auteur établit une formule correcte; mais l'examen du mécanisme de turbulence tel qu'il est formulé dans la théorie deSutton [3] montre que cette dernière n'est probablement pas applicable au voisinage du sol dans le cas d'une diffusion ayant sa source en un point élevé, bien qu'elle puisse fournir la concentration correcte dans le cas d'un aérosol gazéiforme. En outre la théorie deDeacon présente un net avantage pour les applications, du fait que tous les paramètres nécessaires sont contenus dans le profil vertical de la vitesse du vent.

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Published by permission of the Director, Meteorological Branch, Department of Transport, Canada, and dedicated to Dr.Anders K. Ångström on the occasion of his 70th birthday.     

A simplified calibrated model for estimating daily global solar radiation in Madinah, Saudi Arabia

Solar radiation is the most important parameter in defining the energy budget at the surface thereby influencing the hydroclimate. Several empirical models based on air temperature are developed and used in several decision-making needs such as agriculture and energy sector. However, a calibration against direct observations is a priori for implementing such models. A calibrated model is developed for Saudi Arabia (Madinah) based on observations during 2007–2011. The model $ \left( {\mathrm{Rs}=A+B\cdot \mathrm{R}{{\mathrm{s}}_0}{{{\left( {{T_{\max }}-{T_{\min }}} \right)}}^C}} \right) $ is used to estimate daily solar radiation and results show a correlation coefficient of 0.94. The calibrated model outperforms the uncalibrated model available for this location. To increase the confidence, the calibrated model is also compared with a simple artificial neural network.     

A study to discriminate local,urban and regional source contributions to the particulate matter concentrations in the city of Dresden,Germany

The fractions of local traffic (LT), urban background (UBG) and regional background (RBG) of the particle pollution at a traffic-influenced kerbside in Dresden, Germany, were determined by measurements of size-segregated mass concentration, chemical composition and particle size distributions in a network of five measurement stations partly existing and partly set up for this study. Besides the kerbside station, one urban background site and three rural sites were included in the study. Using data from these different sites, the LT, UBG, and RBG contributions were calculated, following the approach of Lenschow et al. (2001). At the kerbside site, 19% of the total number concentration (Dp_St = 10–600 nm) could be attributed to the RBG, 15% to the UBG, and 66% to the LT immediately nearby. Particle mass concentrations up to Dp_aer = 420 nm RBG amounts to 68%, UBG to 21%, and LT only to 11%. Highest mass concentrations were observed at all stations in autumn and winter during easterly inflow directions. The local traffic fraction of PM₁₀ mass at the kerbside station was found to be 30% for westerly inflow, but only 7% for southeasterly inflow due to the dominating transport fraction from up to 80% of the particle mass at this inflow direction. Size-resolved investigation showed the main fractions in both the particle size ranges of Dp_aer = 0.42 to 1.2 and 0.14 to 0.42 μm at all stations. The main components sulphate, ammonium and total carbon showed higher concentrations at south-eastern/eastern inflow in autumn at all stations, while nitrate at the kerbside and urban background site was higher during westerly inflow in winter. The chemical composition at the regional background site at westerly inflow (12% nitrate, 8% sulphate, 11% total carbon) was significantly different from that at easterly inflow (3% nitrate, 15% sulphate, 22% total carbon). The prevailing part of the ionic mass was always found in the fine particle range of Dp_aer = 0.14 to 1.2 μm at all stations. For all inflow directions highest total carbon concentrations were observed at the kerbside station, especially in the ultra-fine size range of Dp_aer = 0.05 to 0.14 μm with up to 30% of the whole carbon. PAH concentrations were always higher at south-eastern/eastern inflow especially during wintertime. Trace metal components and silicon were found mainly in the coarse mode fraction at the kerbside resulting from abrasion or resuspension.     

Cloud modification in Saudi Arabia: Statistical estimation of the results

The results of experiments to enhance precipitation in Saudi Arabia by Weather Modification Inc. (USA) are presented. Statistical analysis of radar measurements indicates that there are significant changes in cloud characteristics and an increase in precipitation due to seeding.     

Investigation of the impact of dynamic factors on Cb cloud development in Saudi Arabia

Changes are analyzed of a Cb cloud characteristics due to its merging with feeder clouds, on the data on a long-living Cb cloud in Saudi Arabia on July 4, 2008. Continuous radar and satellite observations of the cloud are carried out during 6 h. The Cb cloud development is also numerically simulated using a nonstationary 1½ model. It is found that the processes of Cb cloud merging with feeder clouds developing in its vicinities affect significantly the Cb cloud development. This impact demonstrates itself in longer duration of the Cb cloud life span, increasing top height, reflectivity, precipitation duration and intensity. Modification of the feeder clouds can accelerate their development, which eventually can affect notably the Cb cloud.     

Seasonal variability of the observed and the projected daily temperatures in northern Saudi Arabia

Variability in the observed daily temperature for the 31-year period (1978–2008) is studied for northern Saudi Arabia (nSA) by computing the probability distribution functions (PDFs) on a seasonal basis. The 31-year base period is divided into three decades and the results for the first (1978–1987) and the last decade (1999–2008) are presented. When averaged over all seasons, mean values of the observed decadal PDFs depict a positive shift from the first to last decade in the minimum, mean, and maximum temperature of 0.81 °C, 1.03 °C, and 1.25 °C, respectively. The daily temperature datasets from a regional climate model (RCM) and two versions of a coupled atmosphere-ocean general circulation model (AOGCM) are compared with the observed daily temperature datasets. The RCM is driven by re-analysis data for the historical period and by the HadCM3 model for the future, while the AOGCMs used are the GFDL CM2.0 and 2.1 models, with both HadCM3 and the GFDL simulations corresponding to the SRES A1B scenario. The average shifts from 1978–1987 to 1999–2008 in the mean value of the PDFs for the minimum, mean and maximum temperature are 0.63 °C, 0.54 °C and 0.45 °C, respectively, for the RCM, and 0.97 °C, 0.97 °C and 0.96 °C, respectively, for the AOGCM. Thus, the RCM shows a smaller shift in the mean of PDF for maximum temperature than for mean or minimum temperature, the AOGCM shows a comparable shift for all three, and the observations show a greater shift in the PDF for maximum temperature. For the period 2070–2099 relative to 1978–2008, the three average shifts are 4.11 °C, 3.87 °C and 3.44 °C for the RCM and 3.63 °C, 3.74 °C and 3.84 °C for the AOGCM.     

Annual and seasonal trends of cooling, heating, and industrial degree-days in coastal regions of Saudi Arabia

In this study, we systematically analyze the changing properties of reference evapotranspiration (ETref) across China using Penman?CMonteith (P-M) method, exploring the major sensitive meteorological variables for ETref, and investigating influences of human activities, mainly urbanization in this study, on ETref changes in both space and time. We obtain some important conclusions: (1) decreasing annual and seasonal ETref is observed in the east, south and northwest China. However, a long strip lying between these regions is identified to be characterized by increasing ETref; (2) in the regions east to 100°E, the net total solar radiation is the main cause behind the decreasing ETref. In northwest China, however, relative humidity is recognized as the most sensitive variable for the ETref; (3) in the east and south China, urbanization greatly influences the ETref by directly decreasing net solar radiation. The increased air pollution and aerosols in the highly urbanized regions are the main driving factors causing decreasing net radiation; and (4) this study reveals accelerating hydrological cycle from south to north China. Besides, increasing ETref in the source regions of large rivers in China may pose new challenges for the basin-scale water resource management. The results of this study highlight the integrated effects of climate changes and human activities on ETref changes in different regions of China, which will be of great scientific and practical merits in in-depth understanding of hydrological cycle alterations under the changing environment in China.     

An experimental investigation of a wind-generated suspension of particulate matter from a tailings disposal area

A wind tunnel investigation of the wind erosion of uranium mine-tailings material typical of a northern Ontario site has been carried out. The aim of the study was to measure the effects of various parameters, including mean and turbulent wind characteristics of the boundary layer and surface moisture content, upon the erosion process. The analysis of experimental data has yielded a mathematical model for predicting the net vertical mass fluxes. The results show that the dry vertical flux is proportional to u _* ^2.3and the wet flux to u _* ^5.0 Partical size analysis was also carried out.     

Origins of atmospheric particulate matter over the North Sea and the Atlantic Ocean

During the ANT VII/1 cruise of the RV Polarstern from Bremerhaven (Germany) to Rio Grande do Sul (Brazil), atmospheric particulate matter was collected by bulk filtration with a time step of 36 hours. Elemental analyses were performed in order to determine atmospheric aerosol concentrations of Al, Si, P, S, K, Ca, Ti, Mn, Fe, and Zn over the North Sea, the Channel, and the North and South Atlantic. The slight and continuous moving in latitude, associated with the large variability in concentration levels and chemical composition, allow us to point out the relative influence of the major sources of particulate matter: desert soil-dust in the tropical North Atlantic, anthropogenic emissions in the North Sea and the Channel, and biomass burning and continental biogenic activity in the tropical South Atlantic.     

香港能见度、大气悬浮粒子浓度与气象条件的关系

利用2005年赤鱲角能见度及东涌悬浮粒子 (PM2.5) 浓度的每小时数据,发现PM2.5 浓度与能见度 (撇除雨雾及相对湿度≥95%的个例) 呈倒数关系,相关系数约为0.8。此外,出现低能见度 (能见度低于8 km,而雨雾及相对湿度≥95%的个例不计) 的每月总时数与月平均PM2.5浓度都呈现相类似的季节趋势,即冬季较高,夏季较低。利用HYSPLIT作反轨迹图分析显示这现象跟影响香港的空气来源有关。来自内陆的轨迹中,出现低能见度的日平均时数及日平均PM2.5的浓度,分别远高于来自海洋的轨迹。文中还分析了一个有热带气旋接近本港的个例,论证气象条件对能见度及PM2.5浓度的重要性。     

Possible Effects of Global Warming on Agriculture and Water Resources in Saudi Arabia: Impacts and Responses

This study assesses the possible impact of climatic change on Saudi Arabia's agriculture and water supplies using climatic change scenarios from GCMs (General Circulation Models) and related research. The resulting assessment indicates that an increase in temperature and decrease in precipitation could have a major negative impact on agriculture and water supplies in Saudi Arabia. To find signs of climatic change in Saudi Arabia a preliminaryassessment of systematic changes in temperature and precipitation was made, based on the records of four Saudi weather stations. The analysis of this data, which dates back to 1961, shows no discernable signs of climatic change during the study period. Such data is, however, limited both spatially and temporally and cannot provide conclusive evidence to confirm climatic changes projected by GCMs. Nevertheless, in the light of recent climatic conditions and rapid population growth, Saudi decision-makers are urged to adopt a `no regret' policy. Ideally, such a policy would include measures to avoid future environmental or socioeconomic problems that may occur in the event of significant climatic change.