An instrument based on the Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique was designed and constructed to measure scattered sunlight in the UV-visible region at different elevation angles. Slant column densities (SCDs) of specific gas absorbers such as nitrogen dioxide (NO2) and formaldehyde (HCHO) are derived from the measured spectra. In this contribution, the technical characteristics and performance of the instruments, their deployment in a newly formed observational network within the metropolitan area of Mexico City, and some results of the retrieved NO2 and HCHO SCDs are presented. These measurements provide more insight on the vertical and spatial distribution of these key atmospheric pollutants and their temporal variability, which also serve as a basis for present and future satellite validation studies.

The dynamics of the Loop Current (LC) and the release of its anticyclonic eddy (Loop Current eddy, LCE) are some of the most important features of the circulation in the Gulf of Mexico (GoM) and key aspects to gauge the validity of numerical simulations. Using a numerical model, we investigate the sensitivity of the LC and LCE detachments to three different mechanisms deemed to be relevant to their behavior: a) suppression of Caribbean vorticity perturbations entering the GoM; b) smoothness of the topography, and c) suppression of a deep canyon on the eastern Campeche Bank.The main results of these experiments in comparison to a reference run considered to be the more realistic one are:a. Suppression of Caribbean eddies reduces the number of LCE separations, but they are not the principal mechanism that triggers the separations. Locally generated instabilities over the northeastern Campeche Bank and the LC northward extension, appear to be the controlling factors.b. Smoothing the topography generates a wider and less intense LC and reduces the energy exchange terms related to flow instabilities. Nevertheless, the number of LCE separations is similar to the reference experiment. Extension of the LC controls the shedding that, in this case, tends to occur in the summer-fall season, when the LC is more extended, and the Yucatan transport abruptly weakens after its seasonal maximum.c. Removing the deep canyon in the eastern Campeche Bank, makes the LC extension more stable and reduces the number of LCE separations. The canyon appears to play an important role in spinning up cyclones generated over the LC eastern front that finally leads to an LCE release.The seasonal distribution of LCE separations in the experiments does not appear to be controlled by the strength of the barotropic and baroclinic instability source terms. Instead, a necessary but not sufficient condition for LCE separations is that the LC extends beyond 24º N. Our results indicate that caution should be exercised when interpreting LC statistics from a single numerical configuration.

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. 

Air pollution has been considered one of the major environmental challenges because of its effect on ecosystems and human health. The concentration levels and sources of heavy metals contamination were studied in road dust samples collected from various locations including four different activity areas: industrial, highways, residential and mixed use in Delhi, India. Metal content in road dust was analyzed by inductively coupled plasma atomic emission spectroscopy. The results showed high concentration levels of Ni, Cr and Pb in industrial areas. Pearson’s correlations coupled with principal component analysis revealed that Cd, Cr, Ni and Pb are associated with industrial sources whereas Zn and Cu are mainly contributed by vehicular traffic. Road dust contamination was assessed by various methods: degree of contamination, potential ecological index and pollution index. Contamination factor analysis showed that road dust samples are significantly contaminated by Zn and Pb. The potential ecological indices indicated high contamination of Cd and moderate contamination of Pb in road dust, but low contamination of Cr, Cu, Ni and Zn. The pollution index of most of the metals was higher than 1, indicating deterioration of road dust quality of Delhi city due to anthropogenic emissions. The degree of contamination, the potential ecological index and the integrated pollution index reveal that road dust from industrial, mixed use and highway areas are highly contaminated by heavy metals. The road dust from the residential area is also contaminated considerably. Evaluations by various methods indicated that all assessment methods are important for environmental quality evaluation.

Vehicle traffic and its effects on air quality were analyzed on the surroundings of provincial route No. 7 between the cities of Neuquén and Centenario. Concentration levels of carbon monoxide, nitrogen oxides and sulfur dioxide were estimated for a period of five years (2005-2009) through regular data of traffic flow, considering average speeds per sector, the characteristics of vehicles in circulation and meteorological data. Calculations were made by applying CALINE, a line source Gaussian dispersion model developed for predicting pollution levels near highways and arterial streets. In the cases analyzed within the area of study, critical concentrations of gases did not exceed the limits established by Argentinean regulations nor current international standards. The results describe the impacts on receptors located near the route in areas that comprise both industrial and agricultural activities. The route analyzed presents high vehicular traffic with more than 14 000 vehicles traveling daily during 2007. Within a five-yr period, daily traffic increased by 12%. The study revealed that the highest concentration of gases occurred during the winter season in morning hours, when vehicles decreased their velocity at a toll area. This situation may have been modified in behalf of air quality due to the removal of the toll station.

This paper presents an assessment on the behavior of plain carbon steel exposure to the atmosphere of Bogotá. The main climate and environmental parameters, including relative humidity (RH), temperature (T), sulphur dioxide deposition (DSO2) and particulate matter deposition (DPM) 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 Bogotá. 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 DPM and DSO2,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 Bogotá, based on RH, T and DSO2, was obtained.

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.

This paper conducts a day-by-day analysis of an intense Saharan dust storm that struck Athens (Greece) during April 2008 and consisted of two main dust waves (the first from 10/04/2008 to 14/04/2008 and the second from 19/04/2008 to 22/04/2008). Daily satellite data (1º × 1º resolution) of aerosol optical depth (AOD) were used, in order to follow the course of two dust plumes originated in North Africa through the eastern Mediterranean. Ground based measurements of particle concentrations (PM10 and PM2.5) and meteorological parameters (wind speed, air temperature, relative humidity and visibility) were also studied. The time intervals before and after each dust wave were taken under consideration, aiming to identify the atmospheric circulation that generated the dust storm and also the clearing mechanisms that removed the African dust from the Athenian atmosphere. Backward air mass trajectories isolated the source of the two dust plumes over Libya and Tunisia, where extreme daily AOD values were recorded. The transportation of dust in the Greek region, during both dust waves, was associated with south westerlies airflows attributed to the advent of low pressure systems from the Atlantic. The impact of both dust waves in Athens was interrupted by the prevalence of a strong north westerlies air stream, which carried the particles eastwards through Turkey, Cyprus and the Middle East. During this dust event, air quality in Athens was severely downgraded, but no thermal discomfort has occurred, according to the estimation of a Pollution Index (PI) and a Discomfort Index (DI), respectively. A drop in visibility was also reported. 

A fractal analysis from rainfall events registered in a semiarid region was carried out. The analysis was executed for Baja California, Mexico, a region that presents a high climatological variability. Rainfall data from 92 climate stations distributed along the region of study with at least 30 years of records were used. By studying the rainfall series patterns, the Hurst exponent values were obtained (both spatial and temporal) as well as their relation with the variables for annual average temperature, annual average rainfall, altitude and climatological distribution. The rescaled range method, box counting method, and multifractal detrended fluctuation analysis were successfully applied, having as a result the average value of the Hurst exponent for different time scales. Data showed that the daily rainfall series tend to present a persistent pattern; besides, the Hurst exponent values (Hu) were related to the type of climate, altitude, rainfall regime, and temperature of the studied area. The analysis of the Hurst exponent for different time scales showed that, at a smaller time scale, the Hurst value tends to increase; thus, the series present a stronger persistent behavior. Moreover, it can be confirmed that the fractal theory methodology allows analyzing the behaivor of a climate variable, in this case rainfall.

Homogeneity evaluations are usually performed on the total annual precipitation data, which often fails to detect non-homogeneity in seasonal precipitation. Furthermore, it is required to assess homogeneity using multiple methods as the performance of homogeneity testing methods depend on the distribution of the data. This is particularly important for the arid region where distributions of seasonal and annual rainfall are often non-normal. The homogeneity of annual and monthly precipitation datasets of 14 meteorological stations located in the arid region of Pakistan was assessed in this study using the Pettitt’s test, the standard normal homogeneity test (SNHT), the cumulative deviation test, the von Neumann’s ratio test, the Bayesian test, the Worsley’s likelihood ratio test, and Student’s t-test at a 95% confidence level. The rainfall series were categorized into three classes, namely “useful”, “doubtful” and “suspect” based on the results of different homogeneity tests. Results suggest that rainfall time series for most of the months in all the stations are useful. The rainfall time series are found doubtful for the month of June at two stations, for April at one station, and suspect for November at only one station. On the other hand, the annual series were found useful at 12 stations and suspect at two stations. Comparison of different homogeneity tests revealed that SNHT and Worsley’s tests are the most sensitive, and cumulative deviation test is the least sensitive to changes in monthly precipitation data. In the case of annual series, the von Neumann’s test was found most sensitive compared to other tests.

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/Tavg), 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 Hidrología, Meteorología 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.

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 Automática de Monitoreo Atmosférico (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.

Photosynthetic production in forest ecosystems occurs through the absorption of light and CO2. The present work deals with CO2 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 CO2 net absorption flux occurs during June-July (approximately 200 g C m–2 month–1).

Mundo Nano. Revista Interdisciplinaria en Nanociencias y Nanotecnología, es una publicación científica de acceso abierto que no cobra cuotas por procesamiento de artículos. Todos los textos que se postulan para su posible publicación son previamente revisados por pares, bajo la modalidad doble ciego. Está dirigida a especialistas en las nanociencias y la nanotecnología. Tiene como objetivo dar a conocer los principales resultados de investigación en el área, incluyendo sus implicaciones sociales, ambientales, éticas y legales. Por su naturaleza es una publicación de alcance internacional. Publica exclusivamente artículos de investigación y revisiones del campo de conocimiento de interés, escritos tanto en inglés como en español. La revista cuenta con un Código de Ética basado en los lineamientos del Committee of Publication Ethics (COPE) al cual se suscribe. Se publica dos veces al año (aparece los meses de enero y julio), en formato impreso y electrónico, editada y patrocinada desde 2008, de forma ininterrumpida, por la Universidad Nacional Autónoma de México.

Mundo Nano. Revista Interdisciplinaria en Nanociencias y Nanotecnología, es una publicación científica de acceso abierto que no cobra cuotas por procesamiento de artículos. Todos los textos que se postulan para su posible publicación son previamente revisados por pares, bajo la modalidad doble ciego. Está dirigida a especialistas en las nanociencias y la nanotecnología. Tiene como objetivo dar a conocer los principales resultados de investigación en el área, incluyendo sus implicaciones sociales, ambientales, éticas y legales. Por su naturaleza es una publicación de alcance internacional. Publica exclusivamente artículos de investigación y revisiones del campo de conocimiento de interés, escritos tanto en inglés como en español. La revista cuenta con un Código de Ética basado en los lineamientos del Committee of Publication Ethics (COPE) al cual se suscribe. Se publica dos veces al año (aparece los meses de enero y julio), en formato impreso y electrónico, editada y patrocinada desde 2008, de forma ininterrumpida, por la Universidad Nacional Autónoma de México.