Showing papers in "Atmosfera in 2017"

Economic growth and carbon dioxide emissions: An analysis of Latin America and the Caribbean

Abstract: This paper analyzes the empirical relationship between carbon dioxide (CO 2 ) emissions per-capita and economic growth in a panel of 20 Latin American and Caribbean countries over the period 1971-2011. This empirical relationship, known in the economic literature as the Environmental Kuznets Curve (EKC) hypothesis, suggests that the relationship between these variables, in the long run, follows an inverse U-shape, that is, from a certain level of per-capita income, an increased economic growth would be accompanied by improvements in environmental quality. Although this hypothesis has been studied since the 1990s, its empirical validity has recently been questioned on the basis of, among other things, the lack of diagnosis of the stationarity properties of the variables, and in a panel data context, the presence of cross-sectional dependence. Taking into account both criticisms, we use recent unit root tests and cointegration techniques that are robust to the presence of cross-sectional dependence. We find contradictory results depending on the assumption of cross-dependence. Under the assumption of cross-independence, the existence of an EKC with a realistic turning point is confirmed. However, this assumption is subsequently rejected, and because of the presence of cross-dependence in the panel, a long-run equilibrium relationship between the variables cannot be established, and we reject the existence of an EKC.

Effects of soil heat storage and phase shift correction on energy balance closure of paddy fields

Abstract: The eddy covariance technique was used to measure the energy fluxes of a paddy field under water-saving irrigation in the South China Plain for the stage of rice growth in 2013. This study analyzed the energy balance components and evaluated the energy balance closure. The study also discussed the response of surface energy balance to the change in soil heat storage between the heat flux plates buried at a specific depth and the surface, and the phase shift correction of energy balance components, by using three different statistical methods, namely ordinary least squares (OLS), energy balance ratio (EBR), and energy balance residual (D). The results showed that the OLS slope increased by an average of 8.8%, and the mean daily EBR increased by 5.0% after considering the change in soil heat storage. The range of half-hourly D over a four-month period decreased from –129 - 260 W m −2 to –102 - 194 W m −2 , and the absolute value of D decreased by 9.9% on the average. Considering the phase correction, the increase in OLS regression coefficients with an average of 11.3% and the decrease in half-hourly D, ranging from –61 to 176 W m −2 , both indicated that phase shift correction improved the surface energy balance closure at the half-hourly scale, specifically in the period from sunrise to noon, but had no use in the daily scale. Thus, the two correction methods are useful in improving the degree of energy balance closure shown in different temporal scales with proper evaluation index. Moreover, further research should be given with more attention for other correction aspects.

Effects of El Niño in Mexico during rainy and dry seasons: an extended treatment

Abstract: The effect of El Nino-Southern Oscillation (ENSO) on precipitation in Mexico is analyzed. Unlike previous studies, the amount of data used is larger and the Mexican territory is more widely covered. In this paper, daily precipitation from the CLICOM database updated to 2015 was used. The studied period spans from 1961 to 2013 and was divided into two periods: 1961-1990 and 1991-2013. For the same periods two separated seasons were considered: the cold and dry (November-April), and the warm and wet (May-October). Thus, the number of stations that exceed the amount of continuous information criteria for a certain period increases considerably. The Pearson correlation coefficient with a significance of 5% was used in order to test for the existence of a relationship between precipitation and the Multivariate ENSO Index (MEI). The results are presented in maps where regions of precipitation above or below average are observed. During the summer/warm months, the northwestern region of Mexico is clearly identified with a direct relationship between MEI and precipitation, whereas an inverse relationship in the part that lies south of latitude 22o N is seen. In the winter/cold months, there is a general increase in precipitation with increasing MEI. Distributions of normal rainfall for both winter and summer are also shown.

Economic evaluation of climate risk adaptation strategies: Cost-benefit analysis of flood protection in Tabasco, Mexico

Abstract: Economic losses as a result of natural hazards have been rising over the past few decades due to socio-economic development and perhaps climate change. This upwards trend is projected to continue, highlighting the need for adequate adaptation strategies. This raises the question of how to determine which adaptation strategies are preferred to cope with uncertain climate change impacts. This study shows how a multi-disciplinary cascade of hazard modelling, risk modelling, and a cost-benefit analysis can be applied to provide a first indicator of economically efficient adaptation strategies. We apply this approach to an analysis of flood risk and the desirability of flood protection in the state of Tabasco in Mexico, which faces severe flooding on an almost yearly basis. The results show that expected annual damage caused by coastal flooding is expected to increase from 0.53 billion USD today up to 4.12 billion USD in 2080 due to socio-economic development and climate change. For river floods, expected annual damages are estimated to increase from 1.79 billion USD up to 10.6 billion USD in 2080 if no adaptation measures are taken. Based on the estimated risk and cost-benefit analysis of installing flood protection infrastructure, we determined the economically optimal protection standards for both river and coastal floods as at least 100 years, if we take into account climate change. Our main conclusions are robust to key uncertainties about climate change impacts on flood risks, indirect damage caused by floods, the width of the protected floodplains, and the adopted social discount rate. We discuss how our multi-disciplinary approach can assist policy-makers in decisions about flood risk management, and how future research can extend our method to more refined local analyses which are needed to guide local adaptation planning.

The impact of climate on farm inputs in developing countries agriculture

Abstract: The success of the green revolution has prompted some analysts to suggest it can be extended more broadly to all poor farmers. This paper argues that suitable natural endowments are an important precondition for high input farming. Examining production functions across China, we find that outcomes are very climate sensitive. It follows that we also find that input demand functions are climate sensitive. Efforts to intensify farming in undeveloped regions should focus on places with suitable soils and especially climate. The results also suggest that farmers will partially adapt to climate change by altering their input intensity.

Effect of different pavements on human thermal comfort conditions

Abstract: The urban heat island (UHI) phenomenon and outdoor human thermal comfort may be affected by several factors such as the size of the built environment, the rate of open and green spaces and different types of ground surface covers (e.g., grass and artificial covers) in urban areas. Depending on the types and structures of the pavement/covering materials, which can have effects on the albedo and surface heating, ground surfaces reflect solar radiation or heat the air above them. Pavements that can absorb more solar radiation may turn it into heat, thus warming the air, which in turn heats urban areas and make them uncomfortable for human beings. The present study investigates the effect of different materials on the UHI intensity by considering nine different types of materials (andesite, granite, basalt, travertine, impregnated wood, soil, asphalt, clinker powder and grass) in the Ata botanical garden located in the city center of Erzurum, in the Eastern Anatolia region of Turkey. Temperature data were measured on clear summer days during the month of July and compared in terms of thermal comfort. All measurements were taken 150 cm above the ground at 12:00 p.m. by using an infrared thermometer (CEM-DT-8812). In order to estimate the physiologically equivalent temperature (PET) for each soil type, data were analyzed using the RayMan 2.1 software, and the scores were statistically analyzed with analysis of variance (ANOVA). The differences in mean temperatures were evaluated with Fisher’s least significant difference (LSD) test. The results showed that mean PET scores ranged between 28.9 oC for impregnated wood and 25.9 oC for grass (a difference of 3.0 oC), while the other scores were 26.1, 26.7, 27.1, 27.5, 27.8, 28.5 and 28.5 oC for travertine, granite, andesite, soil, clinker powder, basalt, and asphalt, respectively. The analytical results indicated that all the studied materials create a slight heat stress (23.1-29.0 oC) according to their PET indices and their predetermined comfort intervals. However, the levels of heat stress for impregnated wood, asphalt, and basalt were higher than the others. It was determined that grass, travertine and cube granite are optimal surface materials, since they exhibited a level of heat stress that is close to the comfort range (18.1-23.0 oC).

Performance of cumulus parameterization schemes in the simulation of Indian Summer Monsoon using RegCM4

Abstract: The Indian Summer Monsoon (ISM) is driven by organized large-scale convection; hence, its simulation is expected to depend on an appropriate representation of cumulus convection in the model. In the present study, the performance of different cumulus parameterization schemes is examined towards simulations of the ISM. The Regional Climate Model (RegCM4) is coupled with the Community Land Model (CLM 3.5) at 30 km resolution for the period May 1-September 30 for seasonal simulation of the ISM in three consecutive years, 2007, 2008, and 2009. Five numerical experiments with five convection schemes (Kuo, Grell, MIT, GO_ML [Grell over ocean and MIT over land], GL_MO [Grell over land and MIT over ocean]) are conducted for each of these three years. Some important features of the ISM simulated by the model, viz. low level westerly jet, upper level easterly jet, heat low, Tibetan high, etc., are analyzed and compared with that of the National Center for Environmental Prediction (NCEP) reanalysis. We found that the heat low over northwest India and Pakistan in all the three years is better simulated by the model with the MIT convection scheme compared to other convection schemes, whereas spatial distribution and accuracy of surface temperature is better simulated using GL_MO rather than MIT. The low level westerly jet is well captured by the model with MIT with slightly weaker strength compared to the National Center for Environmental Prediction (NCEP) reanalysis. The location and strength of the tropical easterly jet is well predicted in each simulation with some uncertainty in strength, and are better simulated with MIT. The comparison of the model simulated rainfall with 0.5o × 0.5o datasets from the Climate Research Unit (CRU TS3.22) indicates that seasonal and monthly average rainfall are well simulated with MIT and GO_ML; however, the same over central and western India is significantly underestimated by the model with all the convection schemes. Comparatively, higher sensible heat flux and lower latent heat flux are noticed in the model simulation with all schemes. This change of fluxes affects surface temperature and rainfall simulation significantly. The statistical analysis indicates that surface temperature and rainfall are well reproduced by the model with GL_MO and GO_ML, but circulation is better simulated with MIT only. It is observed that although the bias in the model with MIT is slightly higher than that of the two mixed schemes, the spatial distribution and other synoptic features of surface temperature and rainfall during ISM are well simulated. Thus, considering overall performances, the RegCM4 with MIT the cumulus convection scheme provides better simulation of seasonal and monthly features of the monsoon.

High resolution satellite derived erodibility factors for WRF/Chem windblown dust simulations in Argentina

Abstract: A proper representation of dust sources is critical to accurately predict atmospheric particle concentration in regional windblown dust simulations. The Weather Research and Forecasting model with Chemistry (WRF/Chem) includes a topographic-based erodibility map originally conceived for global scale modeling, which fails to identify the geographical location of dust sources in many regions of Argentina. Therefore, this study aims at developing a method to obtain a high-resolution erodibility map suitable for regional or local scale modeling using WRF/Chem. We present two independent approaches based on global methods to estimate soil erodibility using satellite retrievals, i.e. topography from the Shuttle Radar Topography Mission (SRTM) and surface reflectance from the Moderate Resolution Imaging Spectroradiometer (MODIS). Simulation results of a severe Zonda wind episode in the arid central-west Argentina serve as bases for the analysis of these methods. Simulated dust concentration at surface level is compared with particulate matter measurements at one site in Mendoza city. In addition, we use satellite aerosol optical depth (AOD) retrievals to investigate model performance in reproducing spatial distribution of dust emissions. The erodibility map based on surface reflectance from MODIS improves the representation of small scale features, and increases the overall dust aerosol loading with respect to the standard map included by default. Simulated concentrations are in good agreement with measurements as well as satellite derived dust spatial distribution.

Seasonal changes in the PM1 chemical composition north of Mexico City

Abstract: An Aerodyne Aerosol Chemical Speciation Monitor (ACSM; Aerodyne Inc.) was deployed at a site north of Mexico City from November 13, 2013 to April 30, 2014 to investigate the seasonal variability of the chemical composition of submicron particles. The ACSM provides real time information on mass concentration of the non-refractory main species (nitrate, sulfate, ammonium, chloride and organic compounds) in particulate matter less than 1 μm (NR-PM 1 ) with a 30-min time resolution. Meteorological variables (temperature, relative humidity, and wind speed and direction), as well as concentrations of black carbon, PM 1 , PM 2.5 , CO, SO 2 , NO, NO 2 , and O 3 , were also measured. The total NR-PM 1 mass concentrations plus black carbon (which must be close to the PM 1 total mass) showed a good correlation with PM 1 mass concentration measured with a Tapered Element Oscillating Micro-Balance, an indication of the soundness of the ACSM data. In average, the composition of the aerosol as well as its diurnal variability were similar to observations in previous studies using similar instruments (MCMA-2003 and MILAGRO). However, it was observed that the aerosol was persistently acidic during November and December probably due to a higher relative humidity, lower temperature, and more frequent winds from the NW, where the Tula industrial complex is located. A lower concentration of ammonia (NH 3 ) in the gas phase might affect the PM acidity too. These results suggest a seasonal variability in the aerosol chemistry in Mexico City, which should be verified with more long-term studies.

Analysis of the water balance under regional scenarios of climate change for arid zones of Colombia.

Abstract: This workdiscusses in detail the parameters involved in water balance. The analysis is performed by considering the current conditions and climate change in a climatic zone that represents the arid regions of Colombia: The municipality of Uribia (desert) in the state of La Guajira. For this purpose, some climatological stations, which by their reported values of temperature and precipitation can be considered representative of the arid or desert climatic zones according to the Lang’s index (PCP/T avg ), were selected. Then, with historical temperature and precipitation values registered at the station of the area, the baseline was built and its behavior analyzed. The station data were obtained from the database of the Instituto de Hidrologia, Meteorologia y Estudios Ambientales (Institute of Hidrology, Meteorology and Environmental Studies) of Colombia. After estimating the baseline scenarios, the current water balance on the site was calculated by taking into account the original variables and including new parameters, if necessary, for the calculation of the simplified continuity equation. The analysis included parameters such as potential and actual evapotranspiration, moisture of soil, storage or recharge and their changes, water deficit and excess, runoff, periods of recharge, and water use. Anomalies in temperatures (oC) and precipitation were calculated by taking into account the new climate scenarios “representative concentration pathways” for different periods (short- and long-term). With the anomalies identified, the baseline for the above-mentioned variables was adjusted. Again, the associated parameters were analyzed and discussed in the context of water balance. In climate change scenarios, the water balance projects a prospective exacerbation of desert conditions in the Uribia-Guajira region, since a decrease in the Lang’s index from its current value of 18.7 (desert) to 17.0 in 2050 and 14.5 in 2070 is expected, as a consequence of a decrease in precipitation (2.4 and 11.0%) and an increase in annual temperature of about 1.7 oC with the HadGEM2-ES model for the period 2041-2060 and 3.7 oC with the GFDL-CM3 model for the period 2061-2080. This can be verified by means of the Thornthwaite climate classification, which categorizes the area of study as an arid zone with limited and no excess of water. This deficit could lead to serious environmental consequences, social problems and a decline in the industrial and agricultural productivity of the zone.

Modeling for insights not numbers: The long-term low-carbon transformation

Abstract: Limiting global warming to prevent dangerous climate change requires drastically reducing global greenhouse gases emissions and a transformation towards a low-carbon society. Existing energy- and climate-economic modeling approaches that are informing policy and decision makers in shaping the future net-zero emissions society are increasingly seen with skepticism regarding their ability to forecast the long-term evolution of highly complex, nonlinear social-ecological systems. We present a structured review of state-of-the-art modeling approaches, focusing on their ability and limitations to develop and assess pathways towards a low-carbon society. We find that existing methodological approaches have some fundamental deficiencies that limit their potential to understand the subtleties of long-term low-carbon transformation processes. We suggest that a useful methodological framework has to move beyond current state of the art techniques and has to simultaneously fulfill the following requirements: (1) representation of an inherent dynamic analysis, describing and investigating explicitly the path between different states of system variables, (2) specification of details in the energy cascade, in particular the central role of functionalities and services that are provided by the interaction of energy flows and corresponding stock variables, (3) reliance on a clear distinction between structures of the sociotechnical energy system and socioeconomic mechanisms to develop it and (4) ability to evaluate pathways along societal criteria. To that end we propose the development of a versatile multi-purpose integrated modeling framework, building on the specific strengths of the various modeling approaches available while at the same time omitting their weaknesses. This paper identifies respective strengths and weaknesses to guide such development.

Carbon fluxes above a deciduous forest in Greece

Abstract: Photosynthetic production in forest ecosystems occurs through the absorption of light and CO 2 . The present work deals with CO 2 and carbon flux densities above a deciduous forest in Greece, the southernmost monitoring site in Europe. Results show annual net carbon absorption of 7.6 t C ha –1 y –1 , indicating that this forest is a strong carbon sink compared to other European sites. However, absorbance may be reduced by 1 μmol m –2 s –1 for every 1.5 oC above-canopy air temperature increase or 0.015 cm3 cm–3 active root-zone moisture depletion, beyond estimated optimum values. The forest acts as a carbon sink from late April to early November and as a source of carbon in the remaining period of the year. The highest CO 2 net absorption flux occurs during June-July (approximately 200 g C m –2 month –1 ).

Mapping recession risk for cultural heritage stone in Mexico City due to dry and wet deposition of urban air pollutants

Abstract: Air pollution is a threat to cultural heritage because it accelerates the natural deterioration of monuments, palaces, churches, and archaeological ruins, which have an irreplaceable value. In the Mexico City Metropolitan Area (MCMA), there are 19 968 buildings registered as archaeological, historic, or artistic monuments. Some are built with calcareous rocks (limestone and marble) but many of them are made with andesite, tezontle and tuff stone. This paper reports for the first time the spatial distribution of the potential risk of deterioration on calcareous rocks in terms of surface recession with regard to Mexican cultural heritage in the MCMA for the base year 2007. The risk estimate was performed using Lipfert’s damage function, only applicable to carbonate stones of medium and low porosity. These include mainly medium/high density limestone and marble. Carrara white marble has a density of 2.69 g cm –3 and a porosity of 0.37%, and limestone has a density of 2.2-2.6 g cm –3 and a porosity of 5-20%. For high porosity (low density) limestone the function would be applicable with a potential under-estimation. In this function, annual recession rate is a function of annual averages of precipitation, pH, and dry deposition of SO 2 and HNO 3 . Data from several meteorological monitoring networks, the MCMA air quality and acid deposition monitoring networks, and a 3D air quality model (MCCM) were interpolated in a GIS in order to obtain map layers for these variables. These overlaid maps were used to apply the Lipfert functions at the specific coordinates of a small sample of relevant historic or artistic monuments. The complexity of climate gradients, wind patterns, and emissions distribution within the Mexico Megacity leads to gradients as large as 50% in estimated recession rates using the Lipfert function at nearby sites made of the same type of building materials. The Comision Ambiental de la Megalopolis (Environmental Commission of the Megacity) divides the MCMA into five sectors. Differences in recession rates between them were, in 1990, as large as those between estimated values for Oviedo, Paris, and Prague in Europe for the period 1980-2000. Recession rates decreased by about 50% from 1990 to 2007, the base year for this report, due to the success of air pollution control actions focused on the protection of public health. Nevertheless, strong recession gradients are still expected for carbonate stone within the MCMA. The recession values reported in this work must be taken as conservative estimates due to the not yet optimal performance of 3D air quality models in urban meteorology and the high degree of uncertainty in modeling emissions inventories. Most notable is the SO 2 emissions inventory. These maps call for a program of experimental determination of recession rates for building materials that comprise a very large part of Mexico’s unique cultural heritage. These maps should also be added to the critical level maps obtained for human exposure, crops, and ecosystems in order to properly estimate the actual cost of air pollution in the MCMA and the area under its influence.

Characterizing and attributing the warming trend in sea and land surface temperatures

Abstract: Because of low-frequency internal variability, the observed and underlying warming trends in temperature series can be markedly different. Important differences in the observed nonlinear trends in hemispheric temperature series suggest that the northern and southern hemispheres have responded differently to the changes in the radiative forcing. Using recent econometric techniques, we can reconcile such differences and show that all sea and land temperatures share similar time series properties and a common underlying warming trend having a dominant anthropogenic origin. We also investigate the interhemispheric temperature asymmetry (ITA) and show that the differences in warming between hemispheres are in part driven by anthropogenic forcing but that most of the observed rapid changes is likely due to natural variability. The attribution of changes in ITA is relevant since increases in the temperature contrast between hemispheres could potentially produce a shift in the Intertropical Convergence Zone and alter rainfall patterns. The existence of a current slowdown in the warming and its causes are also investigated. The results suggest that the slowdown is a common feature in global and hemispheric sea and land temperatures that can, at least partly, be attributed to changes in anthropogenic forcing.

Population and trends in the global mean temperature

Abstract: The Fisher ideal index, developed to measure price inflation, is applied to define a population-weighted temperature trend. This method has the advantages that the trend is representative for the population distribution throughout the sample but without conflating the trend in the population distribution and the trend in the temperature. I show that the trend in the global area-weighted average surface air temperature is different in key details from the population-weighted trend. I extend the index to include urbanization and the urban heat island effect. This substantially changes the trend again. I further extend the index to include international migration, but this has a minor impact on the trend.

Ozone climatology and variability over Irene, South Africa determined by ground based and satellite observations. Part 1: Vertical variations in the troposphere and stratosphere

Abstract: In this investigation, the climatological characteristics of ozone over Irene (25.5o S, 28.1o E) are studied with the aid of both ground-based and satellite observations. The principle aim of this work is therefore to examine the variability of vertical ozone distribution over Irene. Ozonesonde measurements and satellite measurements in the mesosphere-lower thermosphere region from the Microwave Limb Sounder (MLS) onboard the Aura satellite and it measures for the period 2004-2007 are employed in this study. The MLS satellite measurements are collected when it overpasses Irene. The vertical ozone profiles are obtained from ozonesondes and the MLS and are found to be in good agreement from a 15 km altitude and above. Maximum ozone concentration is found in the altitude between 23-27 km. The monthly variation of ozone concentration measured by ozonesondes and MLS show maximum and minimum concentrations during spring and autumn, respectively. During spring, the maximum ozone concentration measured by ozonesonde is 4.5 × 10 12 molecules cm –3 while that measured by the MLS instrument is ~4.1 × 10 12 molecules cm –3 . A difference in the range of 0.4 × 10 12 to 0.8 × 10 12 molecules cm –3 was obtained for all seasons except during winter, when the difference was in the range 0.6 × 10 12 to 0.9 × 10 12 molecules cm –3 .

Annual atmospheric corrosion rate and dose-response function for carbon steel in Bogotá

Abstract: This paper presents an assessment on the behavior of plain carbon steel exposure to the atmosphere of Bogota. The main climate and environmental parameters, including relative humidity (RH), temperature (T), sulphur dioxide deposition (D SO2 ) and particulate matter deposition (D PM ) were measured. Furthermore, mass loss of AISI/SAE 1006 plain carbon steel coupons was measured along one year. In this case, coupons were exposed in eight test sites located across the city of Bogota. Results show that the corrosion rate of carbon steel is less than 35 μm yr –1 after one year. It was found that the west part of the city has the greatest aggressivity, which has the highest levels of D PM and D SO2 ,related with the characteristics of the anthropogenic activities distribution across the city. A dose-response function of plain carbon steel exposure to the atmosphere of Bogota, based on RH, T and D SO2 , was obtained.

Climatic analysis linked to land vegetation cover of Mexico by applying multivariate statistical and clustering analysis

Abstract: The climate regions of Mexico are delimitated using hierarchical clustering analysis (HCA). The data used consists of monthly means of maximum and minimum temperatures and monthly-accumulated precipitation. The dataset was obtained from heterogeneously distributed climatic stations in Mexico for the period from 1961 to 2004. This cluster method assigns precipitation and temperature variables to groups of clusters based on similar statistical characteristics. We carried out a principal components analysis to obtain a standardized reduced matrix to be used in HCA. By applying two clustering criteria (K-means and Ward´s method) it was possible to define statistically groups of stations that delimit regions of similar climate. In addition, the applied methodology describes the dominant vegetation distribution for each climate region. This analysis may contribute to the generation of new climate scenarios, where the dynamics of land vegetation cover could be included as a biomarker of climate.

Efficient prediction of total column ozone based on support vector regression algorithms, numerical models and Suomi-satellite data

Abstract: This paper proposes a novel prediction method for Total Column Ozone (TCO), based on the combination of Support Vector Regression (SVR) algorithms and different predictive variables coming from satellite data (Suomi National Polar-orbiting Partnership satellite), numerical models (Global Forecasting System model, GFS) and direct measurements. Data from satellite consists of temperature and humidity profiles at different heights, and TCO measurements the days before the prediction. GFS model provides predictions of temperature and humidity for the day of prediction. Alternative data measured in situ, such as aerosol optical depth at different wavelengths, are also considered in the system. The SVR methodology is able to obtain an accurate TCO prediction from these predictive variables, outperforming other regression methodologies such as neural networks. Analysis on the best subset of features in TCO prediction is also carried out in this paper. The experimental part of the paper consists in the application of the SVR to real data collected at the radiometric observatory of Madrid, Spain, where ozone measurements obtained with a Brewer spectrophotometer are available, and allow the system’s training and the evaluation of its performance.

LIDAR ground-based velocity track display analyses and surface observations of a vortex shedding event observed at the Hong Kong International Airport on April 11, 2011

Abstract: Vortex shedding occurs downstream of Lantau Island over the Hong Kong International Airport and can be hazardous to aircraft operating from that airport. An in-depth analysis of a vortex shedding structure is conducted using surface observations and Ground-Based Velocity Track Display (GBVTD) analysis of the Doppler Light Detection and Ranging (LIDAR) data. This in-depth examination of the surface data indicates that brief wind anomalies were observed contemporaneously with the passage of the vortices. Winds simulated using an idealized vortex model constructed using LIDAR-estimated properties of each vortex fit reasonably well with the weather buoy wind and pressure observations. GBVTD retrievals indicate radial convergence and upward motion at most times throughout the lifecycle of the vortices. This paper aims to document the three-dimensional structure of such vortices shedded from the mountains, which may be useful for aviation safety involving wind shear detection, avoidance and recovery at airports with similar terrain features nearby.

Concentration of heavy metals in condensed atmospheric water vapor at three Mexican localities

Abstract: The condensation of water vapor is a very useful technique in mitigating the scarcity of water resources for human consumption; however, the quality of this water must meet the highest standards to avoid becoming a health hazard. The present study quantifies trace elements such as As, Ba, Cu, Cd, Cr, Fe, Hg, Mn, Pb, and Zn, as well as pH and electrical conductivity (EC), in condensed atmospheric water vapor at three localities in Mexico. Atmospheric water vapor was condensed with an atmospheric water generator prototype. A total of 108 samples were obtained from three survey sites over the course of two seasons (wet and dry) during day/night shifts. The concentration of heavy metals was analyzed using inductively coupled plasma mass spectrometry. The pH and EC parameters were measured with a potentiometer/conductometer. We found Pb, Fe, and Cd in 91.66, 58.33, and 33% of the samples, respectively, at concentrations exceeding those permitted by the World Health Organization (WHO) for water intended for human consumption. Both pH and EC were within the limits established by the Department of Water Affairs of Namibia. The concentrations of trace metals in condensed atmospheric water vapor samples were within the maximum permissible limits determined by WHO for most elements analyzed in this study.

Implementation of the Unified Post Processor (UPP) and the Model Evaluation Tools (MET) for WRF-chem evaluation performance

Abstract: This study focuses on a detailed description of several modifications made in both the Unified Post-Processor (UPP) and the Model Evaluation Tools (MET) release packages, which are necessary in order to incorporate relevant chemical species and meteorological parameters into the verification process. The changes made in UPP and MET are illustrated with a high ozone concentration episode, comparing the Weather Research and Forecasting-chemistry (WRF-chem) simulations against observational data from the Red Automatica de Monitoreo Atmosferico (Automatic Atmospheric Monitoring Network) during a weekend in the Mexico City Metropolitan Area. National Emission Inventory (2006) formatted data was supplied to the WRF-chem model. Examples of statistical results and plots contemplating the new chemical species added to the verification process are given, with the aim to illustrate the kind of verification measurements and plots that MET could provide now. Finally, The modifications made over different files in UPP and MET packages could be of particular interest for users and developers of the WRF-chem model concerned about the forecast of the analysis episodes related with poor urban air quality.

Characteristics of particulate matter collected at an urban background site and a roadside site in Birmingham, United Kingdom

Abstract: This study was conducted to investigate the compositional characteristics of particulate matter (PM) collected both at an urban background site (Elms Road observational site, EROS) and a roadside site (Bristol Road observational site, BROS). PM samples were collected at the receptor sites between March 28 and April 11, 2012. Observed parameters included water-soluble ions (Cl – , NO – 3 , SO 4 2– , Na + , NH 4 + , K + , Mg 2+ , Ca 2+ ) and trace metals (V, Al, Cr, Mn, Fe, Zn, Cu, Sb, Ba, Pb). Results showed higher concentrations of NO – 3 , NH 4 + , Al and Fe at BROS than EROS regarding PM 2.5 ; and Cl – , NO – 3 , Na + , K + and Fe regarding PM 2.5-10 , indicating roadside increments. The ionic and metal components of PM 2.5 at EROS constituted 44 and 7% of the total measured PM mass, respectively. The proportions of these species were 46 and 8% at BROS. For PM 2.5-10 , water-soluble ions and trace metal components represented 42 and 12% at EROS, and 56 and 11% at BROS.

Wind tunnel simulations to detect and quantify the turbulent effects of a propagating He-Ne laser beam in air

Abstract: In this paper, we ascertain the effectiveness of our experimental setup in detecting and quantifying the turbulent effects experienced by a He-Ne laser beam as it passes through a wind tunnel. The beam propagated through a series of optical components as well as the in-house designed and manufactured wind tunnel under controlled laboratory conditions. The wind tunnel was built to fit within an existing setup, which has previously proven to be successful in detecting the turbulent effects from other turbulence models. For various wind speeds and temperature settings, the setup has been successful as it was able to detect and measure the atmospheric conditions within the turbulent environment and fully quantify the characteristics of the laser beam. With the use of highly accurate measuring devices, we were able to successfully measure the refractive index structure function ( C n 2 ) and the coherence diameter (Fried’s parameter). Values for C n 2 ranged between 1.61 × 10 –16 m –2/3 and 6.77 × 10 –15 m –2/3 , which can be classified under the moderate to strong turbulence regime. These results tie in well with various published works for similar atmospheric scenarios hence this setup was successfully able to fully detect and quantify the thermal turbulence and wind velocity effects on the laser beam using a point diffraction interferometer.