http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Wed, 08 May 2013 17:41:44 +0000 http://www.hindawi.com/journals/amet/2013/289284/ The Beijing 2008 Olympic and Paralympic Sailing Competitions (referred to as OPSC hereafter) were held at Qingdao during August 9–23 and September 7–13 2008, respectively. The Qingdao Meteorological Bureau was the official provider of weather support for the OPSC. Three-dimensional real-time information with high spatial-temporal resolution was obtained by the comprehensive observation system during the OPSC, which included weather radars, wind profile radars, buoys, automated weather stations, and other conventional observations. The refined forecasting system based on MM5, WRF, and statistical modules provided point-specific hourly wind forecasts for the five venues, and the severe weather monitoring and forecasting system was used in short-term forecasts and nowcasts for rainstorms, gales, and hailstones. Moreover, latest forecasting products, warnings, and weather information were communicated conveniently and timely through a synthetic, speedy, and digitalized network system to different customers. Daily weather information briefings, notice boards, websites, and community short messages were the main approaches for regatta organizers, athletes, and coaches to receive weather service products at 8:00 PM of each day and whenever new updates were available. During the period of OPSC, almost one hundred people were involved in the weather service with innovative service concept, and the weather support was found to be successful and helpful to the OPSC. Yan Ma, Rongzhen Gao, Yunchuan Xue, Yuqiang Yang, Xiaoyun Wang, Bin Liu, Xiaoliang Xu, Xuezhong Liu, Jianwei Hou, and Hang Lin Copyright © 2013 Yan Ma et al. All rights reserved. Wed, 08 May 2013 14:04:06 +0000 http://www.hindawi.com/journals/amet/2013/304321/ This study of a lee wave event over three-dimensional (3D) mountainous terrain in Lantau Island, Hong Kong, using a simulation combining mesoscale model and computational fluid dynamics (CFD) model has shown that (1) 3D steep mountainous terrain can trigger small scale lee waves under strong wind condition, and the horizontal extent of the wave structure is in a dimension of few kilometers and corresponds to the dimension of the horizontal cross-section of the mountain; (2) the life cycle of the lee wave is short, and the wave structures will continuously form roughly in the same location, then gradually move downstream, and dissipate over time; (3) the lee wave triggered by the mountainous terrain in this case can be categorized into “nonsymmetric vortex shedding” or “turbulent wake,” as defined before based on water tank experiments; (4) the magnitude of the wave is related to strength of wind shear. This study also shows that a simulation combining mesoscale model and CFD can capture complex wave structure in the boundary layer over realistic 3D steep terrain, and have a potential value for operational jobs on air traffic warning, wind energy utilization, and atmospheric environmental assessment. Lei Li, P. W. Chan, Lijie Zhang, and Fei Hu Copyright © 2013 Lei Li et al. All rights reserved. Tue, 30 Apr 2013 15:16:30 +0000 http://www.hindawi.com/journals/amet/2013/363029/ Relations between rainfall and the altitude of the terrain can have significant implications for rainfall-runoff studies in hydrology. The aim of this paper is to report on a study of relationships between annual and seasonal rainfall and the altitude of the terrain in Saudi Arabia (SA) using global ordinary least square (OLS) and local geographically weighted regression (GWR) methods. Results using the OLS method showed a significant correlation between altitude and spring rainfall, with a coefficient of determination of , but no significant correlation for the annual and other seasons’ rainfalls. The relationships were more pronounced when GWR local analysis was performed with coefficients of determination of , 0.64, 0.83, 0.82, and 0.71 for annual, winter, spring, summer, and fall rainfalls, respectively. There was some variation in the parameter estimates derived with GWR, but the majority of the estimates indicated a positive association. Results from this study corroborate those of selected other studies in which rainfall and altitude were found to be correlated spatially. The authors concluded that the use of a nonstationary local model such as GWR enabled them to provide a deeper explanation of relations between rainfall and the altitude of the terrain than a global model such as OLS in terms of spatial estimation and prediction. Khalid Al-Ahmadi and Sharaf Al-Ahmadi Copyright © 2013 Khalid Al-Ahmadi and Sharaf Al-Ahmadi. All rights reserved. Sun, 28 Apr 2013 08:54:54 +0000 http://www.hindawi.com/journals/amet/2013/272715/ Taking the Yarkand River as an example, this paper conducted an integrative approach combining the Durbin-Watson statistic test (DWST), multiple linear regression (MLR), wavelet analysis (WA), coefficient of determination (CD), and Akaike information criterion (AIC) to analyze the climatic-hydrological process of inland river, Northwest China from a multitime scale perspective. The main findings are as follows. (1) The hydrologic and climatic variables, that is, annual runoff (AR), annual average temperature, (AAT) and annual precipitation (AP), are stochastic and, no significant autocorrelation. (2) The variation patterns of runoff, temperature, and precipitation were scale dependent in time. AR, AAT, and AP basically present linear trends at 16-year and 32-year scales, but they show nonlinear fluctuations at 2-year and 4-year scales. (3) The relationship between AR with AAT and AP was simulated by the multiple linear regression equation (MLRE) based on wavelet analysis at each time scale. But the simulated effect at a larger time scale is better than that at a smaller time scale. Jianhua Xu, Yiwen Xu, and Chunan Song Copyright © 2013 Jianhua Xu et al. All rights reserved. Sun, 21 Apr 2013 14:49:26 +0000 http://www.hindawi.com/journals/amet/2013/705406/ The present paper investigates the role played by blocking high systems over Europe in abnormal weather over the Kingdom of Saudi Arabia (KSA) in summer 2010. The NCEP/NCAR Reanalysis data of several meteorological elements such as surface air temperature, wind, sea level pressure, relative humidity, outgoing long wave radiation, precipitation rate, and geopotential height at level 500 hpa) for summer seasons for the period 1948–2012 and in particular of summer 2010 have been used and analyzed through the present work. Furthermore, the corresponding daily and monthly mean values of climatic indices NAO index, SOI, and El-Nino3.4 have been analyzed. The results uncovered that air current in the upper atmosphere over Europe and NAO, SOI and El-Nino3.4 have impacts on the weather conditions over KSA through the study period 1948–2012. During the period of persistence of blocking system over Europe in summer 2010, results revealed that; weather in KSA was fully controlled by two abnormal weather regimes. The first one is the European blocking system and negative anomaly of NAO from the north. The second one is the positive anomaly of SOI and negative anomaly of El-Nino3.4. Y. Y. Hafez and M. Almazroui Copyright © 2013 Y. Y. Hafez and M. Almazroui. All rights reserved. Sun, 31 Mar 2013 11:08:41 +0000 http://www.hindawi.com/journals/amet/2013/410812/ This study considers a new hybrid three-dimensional variational (3D-Var) and ensemble Kalman filter (EnKF) data assimilation (DA) method in a non-perfect-model framework, named space-expanded ensemble localization Kalman filter (SELKF). In this method, the localization operation is directly applied to the ensemble anomalies with a Schur Product, rather than to the full error covariance of the state in the EnKF. Meanwhile, the correction space of analysis increment is expanded to a space with larger dimension, and the rank of the forecast error covariance is significantly increased. This scheme can reduce the spurious correlations in the covariance and approximate the full-rank background error covariance well. Furthermore, a deterministic scheme is used to generate the analysis anomalies. The results show that the SELKF outperforms the perturbed EnKF given a relatively small ensemble size, especially when the length scale is relatively long or the observation error covariance is relatively small. Hongze Leng, Junqiang Song, Fengshun Lu, and Xiaoqun Cao Copyright © 2013 Hongze Leng et al. All rights reserved. Mon, 25 Mar 2013 15:38:25 +0000 http://www.hindawi.com/journals/amet/2013/152875/ This study assesses the relationship between global sea surface temperature (SST) and a regional index of rainfall (NWPR) in Piura-Tumbes, a coastal region in northwestern Peru, over the period 1965–2008 by means of the Pearson product-moment correlation. The results show that this area is strongly influenced by three indices: El Niño-Southern Oscillation (ENSO) Niño3.4 region, the Indian Ocean Dipole (IOD), and the equatorial Atlantic Oscillation (ATL3). In particular, a positive correlation has been found with the two first indices (Niño3.4 and IOD) and a negative one with ATL3 with several months of delay. This allows developing a forecast regression model for monthly rainfall in NW Peru with months in advance. The results show that linear regression model is not enough to provide satisfactory results; however, a nonlinear regression model improves considerably the prediction of rainfall anomalies in NW Peru. Juan Bazo, María de las Nieves Lorenzo, and Rosmeri Porfirio da Rocha Copyright © 2013 Juan Bazo et al. All rights reserved. Thu, 21 Feb 2013 10:17:59 +0000 http://www.hindawi.com/journals/amet/2013/693541/ To protect humans from heat stress risks, thermal comfort and heat stress potential were evaluated under arid environment, which had never been made for such climate. The thermal indices THI, WBGT, PET, and UTCI were used to evaluate thermal comfort and heat stress. RayMan software model was used to estimate the PET, and the UTCI calculator was used for UTCI. Dry and wet bulb temperatures (, ), natural wet bulb temperature (), and globe temperature () were measured in a summer day to be used in the calculation. The results showed the following. (i) The thermal sensation and heat stress levels can be evaluated by either the PET or UTCI scales, and both are valid for extremely high temperature in the arid environment. (ii) In the comfort zone, around 75% of individuals would be satisfied with the surrounding environment and feel comfortable during the whole day. (iii) Persons are exposed to strong heat stress and would feel uncomfortable most of the daytime in summer. (iv) Heat fatigue is expected with prolonged exposure to sun light and activity. (v) During the daytime, humans should schedule their activities according to the highest permissible values of the WBGT to avoid thermal shock. A. M. Abdel-Ghany, I. M. Al-Helal, and M. R. Shady Copyright © 2013 A. M. Abdel-Ghany et al. All rights reserved. Thu, 17 Jan 2013 14:55:10 +0000 http://www.hindawi.com/journals/amet/2013/480210/ We study the potential value to stakeholders of probabilistic long-term forecasts, as quantified by the mean information gain of the forecast compared to climatology. We use as a case study the USA Climate Prediction Center (CPC) forecasts of 3-month temperature and precipitation anomalies made at 0.5-month lead time since 1995. Mean information gain was positive but low (about 2% and 0.5% of the maximum possible for temperature and precipitation forecasts, resp.) and has not increased over time. Information-based skill scores showed similar patterns to other, non-information-based, skill scores commonly used for evaluating seasonal forecasts but tended to be smaller, suggesting that information gain is a particularly stringent measure of forecast quality. We also present a new decomposition of forecast information gain into Confidence, Forecast Miscalibration, and Climatology Miscalibration components. Based on this decomposition, the CPC forecasts for temperature are on average underconfident while the precipitation forecasts are overconfident. We apply a probabilistic trend extrapolation method to provide an improved reference seasonal forecast, compared to the current CPC procedure which uses climatology from a recent 30-year period. We show that combining the CPC forecast with the probabilistic trend extrapolation more than doubles the mean information gain, providing one simple avenue for increasing forecast skill. Nir Y. Krakauer, Michael D. Grossberg, Irina Gladkova, and Hannah Aizenman Copyright © 2013 Nir Y. Krakauer et al. All rights reserved. Wed, 19 Dec 2012 11:00:40 +0000 http://www.hindawi.com/journals/amet/2012/579764/ We constructed a similarity model (based on Euclidean distance between rainfall and runoff) to study time-correlated characteristics of rainfall-runoff similar patterns in the upstream Red River Basin and presented a detailed evaluation of the time correlation of rainfall-runoff similarity. The rainfall-runoff similarity was used to determine the optimum similarity. The results showed that a time-correlated model was found to be capable of predicting the rainfall-runoff similarity in the upstream Red River Basin in a satisfactory way. Both noised and denoised time series by thresholding the wavelet coefficients were applied to verify the accuracy of model. And the corresponding optimum similar sets obtained as the equation solution conditions showed an interesting and stable trend. On the whole, the annual mean similarity presented a gradually rising trend, for quantitatively estimating comprehensive influence of climate change and of human activities on rainfall-runoff similarity. Xiuli Sang, Jianxin Xu, Kun Zhang, and Hua Wang Copyright © 2012 Xiuli Sang et al. All rights reserved. Mon, 17 Dec 2012 09:24:30 +0000 http://www.hindawi.com/journals/amet/2012/857831/ Youmin Tang, Soon-Il An, and Wansuo Duan Copyright © 2012 Youmin Tang et al. All rights reserved. Thu, 13 Dec 2012 15:40:06 +0000 http://www.hindawi.com/journals/amet/2012/213743/ Ocean temperature and ocean heat content change are analyzed based on four PMIP3 model results at the Last Glacial Maximum relative to the prehistorical run. Ocean cooling mostly occurs in the upper 1000 m depth and varies spatially in the tropical and temperate zones. The Atlantic Ocean experiences greater cooling than the rest of the ocean basins. Ocean cooling is closely related to the weakening of meridional overturning circulation and enhanced intrusion of Antarctic Bottom Water into the North Atlantic. Kelin Zhuang and John R. Giardino Copyright © 2012 Kelin Zhuang and John R. Giardino. All rights reserved. Thu, 22 Nov 2012 16:02:27 +0000 http://www.hindawi.com/journals/amet/2012/980816/ The present study investigates how changes in the Hadley Cell (HC) intensity impact the stationary Rossby waves energy propagation in the Southern Hemisphere (SH) extratropics. Composites for weak and strong HC Intensity Index (HCI) were used in this analysis. The results for weak HC cases showed a wave train emanating from the subtropical central-west Indian Ocean in an arc-like route, with zonal wavenumber three in the polar jet waveguide, and reaching the north of South America. For strong HC cases, the wave train is also trapped inside the polar jet waveguide with zonal wavenumber four, emanating from subtropical central-east Indian Ocean and reaching the subtropical west coast of Africa. A weaker zonally oriented wave train with zonal wavenumber five has been found in the subtropical region with opposite polarity for weak and strong HC cases. Over the South America, the results show that an HC weakening can lead to a very cold and rainy winter in the southwest of the continent and a mild warm and dry winter on Brazilian states of Minas Gerais and Bahia. A pattern almost opposite was observed when the CH strengthens. Ana Carolina Vasques Freitas and Tércio Ambrizzi Copyright © 2012 Ana Carolina Vasques Freitas and Tércio Ambrizzi. All rights reserved. Sun, 18 Nov 2012 15:50:31 +0000 http://www.hindawi.com/journals/amet/2012/178623/ Wind energy gains more attention day by day as one of the clean renewable energy resources. We predicted wind speed vertical extrapolation by using extended power law. In this study, an extended vertical wind velocity extrapolation formulation is derived on the basis of perturbation theory by considering power law and Weibull wind speed probability distribution function. In the proposed methodology not only the mean values of the wind speeds at different elevations but also their standard deviations and the cross-correlation coefficient between different elevations are taken into consideration. The application of the presented methodology is performed for wind speed measurements at Karaburun/Istanbul, Turkey. At this location, hourly wind speed measurements are available for three different heights above the earth surface. Zekai Şen, Abdüsselam Altunkaynak, and Tarkan Erdik Copyright © 2012 Zekai Şen et al. All rights reserved. Tue, 13 Nov 2012 13:35:32 +0000 http://www.hindawi.com/journals/amet/2012/818473/ Igor Esau, Stefania Argentini, Rajmund Przybylak, Irina Repina, and Anna Sjöblom Copyright © 2012 Igor Esau et al. All rights reserved. Tue, 13 Nov 2012 10:01:08 +0000 http://www.hindawi.com/journals/amet/2012/243603/ Tareq Hussein, Christer Johansson, and Lidia Morawska Copyright © 2012 Tareq Hussein et al. All rights reserved. Sun, 11 Nov 2012 13:23:03 +0000 http://www.hindawi.com/journals/amet/2012/483632/ Dimitris G. Kaskaoutis, Ralph A. Kahn, Pawan Gupta, Achuthan Jayaraman, and Aristides Bartzokas Copyright © 2012 Dimitris G. Kaskaoutis et al. All rights reserved. Wed, 07 Nov 2012 12:02:21 +0000 http://www.hindawi.com/journals/amet/2012/356265/ We provide an overview of light detection and ranging (lidar) capability for describing and characterizing desert dust. This paper summarizes lidar techniques, observations, and fallouts of desert dust lidar measurements. The main objective is to provide the scientific community, including nonpractitioners of lidar observations with a reference paper on dust lidar measurements. In particular, it will fill the current gap of communication between research-oriented lidar community and potential desert dust data users, such as air quality monitoring agencies and aviation advisory centers. The current capability of the different lidar techniques for the characterization of aerosol in general and desert dust in particular is presented. Technical aspects and required assumptions of these techniques are discussed, providing readers with the pros and cons of each technique. Information about desert dust collected up to date using lidar techniques is reviewed. Lidar techniques for aerosol characterization have a maturity level appropriate for addressing air quality and transportation issues, as demonstrated by some first results reported in this paper. L. Mona, Z. Liu, D. Müller, A. Omar, A. Papayannis, G. Pappalardo, N. Sugimoto, and M. Vaughan Copyright © 2012 L. Mona et al. All rights reserved. Mon, 05 Nov 2012 16:23:23 +0000 http://www.hindawi.com/journals/amet/2012/238589/ A parameterized method is developed to diagnose the air quality in Beijing and other cities with an index termed (parameters linking air-quality to meteorological elements PLAM) derived from a correlation between PM10 and relevant weather elements based on the data between 2000 and 2007. Key weather factors for diagnosing the air pollution intensity are identified and included in PLAM that include atmospheric condensation of water vapour, wet potential equivalent temperature, and wind velocity. It is found that the poor air quality days with elevated PM10 are usually associated with higher PLAM values, featuring higher temperature, humidity, lower wind velocity, and higher stability compared to the averaged values in the same period. Both 24 h and 72 h forecasts provided useful services for the day of the opening ceremony of the Beijing Olympic Games and subsequent sport events. A correlation coefficient of 0.82 was achieved between the forecasts and (air pollution index API) and 0.59 between the forecasts and observed PM10, all reaching the significant level of 0.001, for the summer period. A correction factor was also introduced to enable the PLAM to diagnose the observed PM10 concentrations all year round. J. Z. Wang, S. L. Gong, X. Y. Zhang, Y. Q. Yang, Q. Hou, C. H. Zhou, and Y. Q. Wang Copyright © 2012 J. Z. Wang et al. All rights reserved. Thu, 01 Nov 2012 15:40:59 +0000 http://www.hindawi.com/journals/amet/2012/953853/ The dynamics associated with drought in the Sahel have attracted considerable attention in the recent literature. This paper evaluates Sahel precipitation using the paradigm of the atmospheric centers of action, that is, the extended semipermanent highs and lows that dominate regional circulations and are evident in sea level pressure patterns. We find that Sahel precipitation is significantly influenced by changes in the Azores High and the South Asia Low. Specifically, about 50 percent of the variance of July to September rainfall over the Sahel is explained by changes in the Azores High Longitude position and South Asia Low pressure. In contrast, the contribution of the Southern Oscillation to Sahel precipitation is smaller in comparison. Results presented in this paper suggest that a key test for a climate model in simulating variability of Sahel rainfall is the accuracy with which the model simulates the dynamics of South Asia Low and the Azores High. Sultan Hameed and Nicole Riemer Copyright © 2012 Sultan Hameed and Nicole Riemer. All rights reserved. Wed, 31 Oct 2012 09:14:14 +0000 http://www.hindawi.com/journals/amet/2012/203682/ Rainfall is a complexity dynamics process. In this paper, our objective is to find the evidence of self-organized criticality (SOC) for rain datasets in China by employing the theory and method of SOC. For this reason, we analyzed the long-term rain records of five meteorological stations in Henan, a central province of China. Three concepts, that is, rain duration, drought duration, accumulated rain amount, are proposed to characterize these rain events processes. We investigate their dynamics property by using scale invariant and found that the long-term rain processes in central China indeed exhibit the feature of self-organized criticality. The proposed theory and method may be suitable to analyze other datasets from different climate zones in China. Zhiliang Wang and Chunyan Huang Copyright © 2012 Zhiliang Wang and Chunyan Huang. All rights reserved. Mon, 15 Oct 2012 15:44:17 +0000 http://www.hindawi.com/journals/amet/2012/584257/ During the summer of 2010, an unusually persistent blocking episode resulted in anomalously warm dry weather over the European part of Russia. The excessive heat resulted in forest and peat fires, impacted terrestrial ecosystems, greatly increased pollution in urban areas, and increased mortality rates in the region. Using the National Centers for Atmospheric Research (NCAR), National Centers for Environmental Prediction (NCEP) reanalysis datasets, the climatological and dynamic character of blocking events for summer 2010 and a precursor May blocking event were examined. We found that these events were stronger and longer lived than typical warm season events. Using dynamic methods, we demonstrate that the July 2010 event was a synoptic-scale dominant blocking event; unusual in the summer season. An analysis of phase diagrams demonstrated that the planetary-scale did not become stable until almost one week after block onset. For all other blocking events studied here and previously, the planetary-scale became stable around onset. Analysis using area integrated regional enstrophy (IRE) demonstrated that for the July 2010 event, synoptic-scale IRE increased at block onset. This was similar for the May 2010 event, but different from case studies examined previously that demonstrated the planetary-scale IRE was prominent at block onset. Anthony R. Lupo, Igor I. Mokhov, Merseid G. Akperov, Alexander V. Chernokulsky, and H. Athar Copyright © 2012 Anthony R. Lupo et al. All rights reserved. Mon, 15 Oct 2012 08:25:04 +0000 http://www.hindawi.com/journals/amet/2012/850704/ The lack of information on the vertical distribution of dust, in turn, results in large uncertainties when attempting to evaluate the impacts of dust on climate processes. We analyzed over two years of LIDAR measurements from NASA’s CALIPSO and CloudSat satellites to document the vertical pathways of transatlantic transport of Saharan dust. Our analysis overcomes the limitations of quantitative dust detections with passive satellite measurements over land and low clouds and provides the fine vertical resolved structures. The results show the strong seasonal shift in dust source regions and transportation pathways due to the meteorological and thermodynamical conditions, which also control the dust vertical distribution as well as the depth of the dust layer. The dust layer top descending rates of 35 m/degree in summer, 25 m/degree in autumn and spring, and 10 m/degree in winter are found, respectively, while the dust is being transported across the Atlantic. Comparison with the model simulation highlights the potentials of dust observations using CALIPSO LIDAR. The observed seasonal dependence of these pathways gives new insights into the transport of the Saharan dust and provides important guidance for simulations of the production and transport of the global dust aerosol. Dong Liu, Yingjian Wang, Zhien Wang, and Jun Zhou Copyright © 2012 Dong Liu et al. All rights reserved. Thu, 27 Sep 2012 16:47:29 +0000 http://www.hindawi.com/journals/amet/2012/529064/ Lake ice was simulated for the province of Quebec, Canada, for both contemporary and future climate conditions using a one-dimensional thermodynamic ice model. The model was forced with NARR data (32 km) and both the daily IMS product (4 km) and the MODIS snow product (500 m) were assessed for their utility at determining lake ice phenology at the subgrid cell level (based on the 32 km NARR grid). Both products were useful for detecting ice-off; however, the MODIS product was advantageous for detecting ice-on, mainly due to the finer resolution and resulting spatial detail. The subgrid cell variability in ice-on/off dates was typically less than 2% of the mean, although it ranged up to 10% for some grid cells. The simulations were found to be within the satellite-detected subgrid cell variability: 62% of the time for ice-off and 80% of the time for ice-on. Forcing the model with future climate scenarios from the Canadian Regional Climate Model predicts the regional ice cover durations will decrease by up to 50 days from the current 1981–2010 means to the 2041–2070 means and decrease from 15 to nearly 100 days shorter from the current means to the 2071–2100 means. Laura C. Brown and Claude R. Duguay Copyright © 2012 Laura C. Brown and Claude R. Duguay. All rights reserved. Thu, 20 Sep 2012 11:27:32 +0000 http://www.hindawi.com/journals/amet/2012/359164/ The Chaco plain region in Argentina is located in the north of the country and east of Los Andes where the main activity is the agriculture. As such activity is highly affected by interannual rainfall variability, the influence of some of the principal atmospheric and oceanic forcing is investigated in this paper. Results show that the factors which affect precipitation highly depend on the season and the subregion. The position of the South Atlantic Height and the sea surface temperature in the coast of southern Brazil and Buenos Aires seem to be the factors that affect rainfall, all over the year. The El Niño-Southern Oscillation phenomenon affects summer and spring rainfall and the Southern Annular Mode involves spring precipitation but both only in the east of the study region. Furthermore, enhanced convection in Central Brazil, mainly influences autumn and spring rainfall. Marcela Hebe González, María Laura Cariaga, and María de los Milagros Skansi Copyright © 2012 Marcela Hebe González et al. All rights reserved. Sun, 16 Sep 2012 09:39:15 +0000 http://www.hindawi.com/journals/amet/2012/246874/ Dust intrusions from African desert regions have an impact on the Mediterranean Basin (MB), as they cause an anomalous increase of aerosol concentrations in the tropospheric column and often an increase of particulate matter at the ground level. To estimate the Saharan dust contribution to PM10, a significant dust intrusion event that occurred in June 2006 is investigated, joining numerical simulations and specific measurements. As a first step, a synoptic analysis of this episode is performed. Such analysis, based only on meteorological and aerosol optical thickness observations, does not allow the assessment of exhaustive informations. In fact, it is not possible to distinguish dust outbreaks transported above the boundary layer without any impact at the ground level from those causing deposition. The approach proposed in this work applies an ad hoc model chain to describe emission, transport and deposition dynamics. Furthermore, physical and chemical analyses (PIXE analysis and ion chromatography) were used to measure the concentration of all soil-related elements to quantify the contribution of dust particles to PM10. The comparison between simulation results and in-situ measurements show a satisfying agreement, and supports the effectiveness of the model chain to estimate the Saharan dust contribution at ground level. F. Calastrini, F. Guarnieri, S. Becagli, C. Busillo, M. Chiari, U. Dayan, F. Lucarelli, S. Nava, M. Pasqui, R. Traversi, R. Udisti, and G. Zipoli Copyright © 2012 F. Calastrini et al. All rights reserved. Thu, 06 Sep 2012 16:35:27 +0000 http://www.hindawi.com/journals/amet/2012/649450/ A novel multimodel ensemble approach based on learning from data using the neural network (NN) technique is formulated and applied for improving 24-hour precipitation forecasts over the continental US. The developed nonlinear approach allowed us to account for nonlinear correlation between ensemble members and to produce “optimal” forecast represented by a nonlinear NN ensemble mean. The NN approach is compared with the conservative multi-model ensemble, with multiple linear regression ensemble approaches, and with results obtained by human forecasters. The NN multi-model ensemble improves upon conservative multi-model ensemble and multiple linear regression ensemble, it (1) significantly reduces high bias at low precipitation level, (2) significantly reduces low bias at high precipitation level, and (3) sharpens features making them closer to the observed ones. The NN multi-model ensemble performs at least as well as human forecasters supplied with the same information. The developed approach is a generic approach that can be applied to other multi-model ensemble fields as well as to single model ensembles. Vladimir M. Krasnopolsky and Ying Lin Copyright © 2012 Vladimir M. Krasnopolsky and Ying Lin. All rights reserved. Wed, 29 Aug 2012 09:26:29 +0000 http://www.hindawi.com/journals/amet/2012/240894/ We employ a nested system of global and regional climate models, linked to regional and urban air quality chemical transport models utilizing detailed inventories of present and future emissions, to study the relative impact of climate change and changing air pollutant emissions on air quality and population exposure in Stockholm, Sweden. We show that climate change only marginally affects air quality over the 20-year period studied. An exposure assessment reveals that the population of Stockholm can expect considerably lower NO2 exposure in the future, mainly due to reduced local NOx emissions. Ozone exposure will decrease only slightly, due to a combination of increased concentrations in the city centre and decreasing concentrations in the suburban areas. The increase in ozone concentration is a consequence of decreased local NOx emissions, which reduces the titration of the long-range transported ozone. Finally, we evaluate the consequences of a planned road transit project on future air quality in Stockholm. The construction of a very large bypass road (including one of the largest motorway road tunnels in Europe) will only marginally influence total population exposure, this since the improved air quality in the city centre will be complemented by deteriorated air quality in suburban, residential areas. Lars Gidhagen, Magnuz Engardt, Boel Lövenheim, and Christer Johansson Copyright © 2012 Lars Gidhagen et al. All rights reserved. Thu, 23 Aug 2012 09:11:43 +0000 http://www.hindawi.com/journals/amet/2012/725343/ We use a coupled model to estimate the natural variability of summertime rainfall over South America and to determine the time horizon when anthropogenic forcing will start having an effect on it. We use a combination of three experiments: preindustrial, 20th century, and the projected changes under A1B scenario. The first empirical orthogonal function of rainfall in December–February is used to characterize summertime variability. The model can display two different regimes of natural variability of this mode. In one regime, there is a strong coupling between the South Atlantic convergence zone (SACZ) and the Atlantic Ocean. In the other regime, the SACZ is dominated by internal atmospheric variability. The detection of the impact of anthropogenic forcing is calculated comparing the probability density functions (pdfs) of the preindustrial run with the one under the A1B scenario. We found that the detection strongly depends on the pdf used to characterize internal climate variability. If the pdf of the mode with coupling between the SACZ and the Atlantic Ocean is used, the anthropogenic influence is felt very early within the future scenario (in less than 30 years). On the contrary, with the pdf that characterizes an SACZ dominated by internal atmospheric variability, the forcing is detected only several (almost 50) years into the scenario. Stefanie Talento and Marcelo Barreiro Copyright © 2012 Stefanie Talento and Marcelo Barreiro. All rights reserved. Thu, 16 Aug 2012 07:35:52 +0000 http://www.hindawi.com/journals/amet/2012/505613/ Arctic climate has been changing rapidly since the 1980s. This work shows distinctly different patterns of change in winter, spring, and summer for cloud fraction and surface temperature. Satellite observations over 1982–2004 have shown that the Arctic has warmed up and become cloudier in spring and summer, but cooled down and become less cloudy in winter. The annual mean surface temperature has increased at a rate of 0.34°C per decade. The decadal rates of cloud fraction trends are −3.4%, 2.3%, and 0.5% in winter, spring, and summer, respectively. Correspondingly, annually averaged surface albedo has decreased at a decadal rate of −3.2%. On the annual average, the trend of cloud forcing at the surface is −2.11 W/m2 per decade, indicating a damping effect on the surface warming by clouds. The decreasing sea ice albedo and surface warming tend to modulate cloud radiative cooling effect in spring and summer. Arctic sea ice has also declined substantially with decadal rates of −8%, −5%, and −15% in sea ice extent, thickness, and volume, respectively. Significant correlations between surface temperature anomalies and climate indices, especially the Arctic Oscillation (AO) index, exist over some areas, implying linkages between global climate change and Arctic climate change. Xuanji Wang, Jeffrey Key, Yinghui Liu, Charles Fowler, James Maslanik, and Mark Tschudi Copyright © 2012 Xuanji Wang et al. All rights reserved.