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The impact of model resolution on simulated ambient air quality and associated human exposure
Get PDFA simple numerical experiment to evaluate the influence of model resolution on estimates of ambient air quality and associated human exposure is presented. This is done based on annual mean NO2 concentration fields for the agglomeration of Brussels and surroundings, simulated by the deterministic urban/regional-scale AURORA model at a resolution of 1 km. These NO2 concentration fields were used to calculate domain-wide exposure, which is defined here as the population density-weighted concentration. It was found that exposure decreased by 38% when degrading the resolution of the model from 1 to 64 km. A straightforward analysis revealed that this exposure reduction could be explained by the covariance between the concentration and population density patterns.Se presenta un experimento numérico sencillo cuyo objetivo es evaluar la influencia de la resolución de los modelos en estimaciones de la calidad del aire ambiente y la exposición humana asociada. Para ello se tomaron como base los promedios anuales de concentración de NO2 para la aglomeración urbana de Bruselas y sus alrededores, usando campos simulados mediante el modelo determinístico de escala urbana/regional AURORA con resolución de 1 km. Estas concentraciones de NO2 se utilizaron para calcular la exposición humana, que se define aquí como la concentración ponderada por la densidad de población. Se encontró que la exposición disminuyó en 38% cuando la resolución del modelo se redujo de 1 a 64 km. Un análisis sencillo reveló que esta reducción de la exposición puede explicarse por la covarianza entre la concentración y los patrones de densidad de población
ENSO index teleconnection with seasonal precipitation in a temperate ecosystem of northern Mexico
Get PDFEl Niño Southern Oscillation (ENSO) is the most important large-scale circulatory phenomenon that causes climatic variability in northern Mexico. The current challenge is to understand its consequences for both local climate and ecological processes of ecosystems. Within this context, we compared the degree of association of three different ENSO indices with local seasonal precipitation (P) in northern Mexico, and used dendrochronological series (tree-ring chronologies [TRI]) of Pinus cooperi to assess the impact of forest growth. The results showed a strong association between ENSO, previous winter precipitation and TRI (r > 0.5, p = 0.05), indicating a positive relationship between warm ENSO phases and subsequent tree growth. The multivariate ENSO index was slightly better at explaining the connection between P and radial growth than other indices. These results could be used to support further research on the effects of ENSO on local climate and forest ecosystems
Definition and temporal evolution of the heat and cold waves over the Spanish Central Plateau from 1961 to 2010
Get PDFThe temporal behavior of the annual frequency of heat and cold waves observed between 1961 and 2010is established for the Spanish Central Plateau and for the two sub-areas in it. The series of daily maximumand minimum temperature anomalies for the working areas were calculated from the daily data concerningtemperature anomalies. The thresholds of these series of anomalies, determined by the P10 and P90 percentilesvalues, were obtained. Heat waves occur when there are two or more consecutive days on which the maximumand minimum temperature anomalies are simultaneously greater than the values of the thresholds obtainedfor the P90 percentile. The heat waves that affected the Spanish Central Plateau and the two sub-areas duringthe period of time considered were identified and their monthly and annual frequencies were obtained. Likewise,a cold wave is considered to have occurred when there are two or more consecutive days on which themaximum and minimum temperature anomalies are simultaneously lower than the thresholds establishedby the corresponding P10 percentiles. The cold waves occurring in the study area were identified and theirmonthly and annual frequencies in the study period were established. According to the results, the monthswith highest number of heat waves between 1961 and 2010 were May (25 waves) and June (23 waves).Trend analysis of the series of annual frequencies indicates that there was an increasing trend towards theoccurrence of heat waves, with a confidence level greater than 99%. The linear model established indicatesthat an increase had occurred in the frequency of heat waves in the Spanish plateau of the order of 0.6 wavesevery 10 years. Regarding cold waves, these were detected in each month of the year and their frequencyranged between eight and 16 events per year. The months with lowest number of cold waves were April(nine), July (eight) and August (nine), and the months with the highest number were March, May, June andOctober, with 16 cold waves. The years with the highest number of cold waves were 1969, 1971 and 1977,with seven cases. In the other years the annual rate was between one and six. Trend analysis of the series ofannual frequencies indicated that there was a decreasing frequency of cold waves, at the confidence levelof 99%. When a linear model was considered for the Spanish Central Plateau a decreasing frequency of thecold waves of the order of 0.54 waves in every 10 years was observed from 1961 to 2010.Se establece el comportamiento temporal de las frecuencias anuales de olas de calor y frío observadas entre 1961 y 2010 en la Meseta Central española y en las dos zonas que se pueden diferenciar en ella. A partir de los datos diarios de anomalías de temperatura se determinan las series de anomalías diarias de temperaturas máxima y mínima para las áreas de trabajo. Se obtienen los valores umbrales de dichas series de anomalías, determinados por los percentiles P10 y P90. Se establece la existencia de ola de calor cuando se observan dos o más días consecutivos en los que las anomalías de temperatura máxima y de temperatura mínima superan, simultáneamente, los valores de los umbrales establecidos por el P90. Se identifican las olas de calor que han afectado a la Meseta Central española, y a las dos subzonas durante el periodo de estudio y se establecen sus frecuencias mensuales y anuales. Asimismo, considerando que existe una ola de frío cuando hay dos o más días consecutivos en que los valores de temperaturas máximas y mínimas diarias son inferiores, simultáneamente, a los umbrales establecidos por el P10, se identifican las olas de frío y se establecen sus frecuencias mensuales y anuales en el periodo de estudio. Los resultados indican que los meses con mayor número de olas de calor entre 1961 y 2010 son mayo (25 olas) y junio (23 olas). El análisis de tendencia de las series de frecuencias anuales obtenidas indica que existe una tendencia creciente de olas de calor a un nivel de confianza mayor del 99%. El modelo lineal establece que se ha producido un aumento en la frecuencia de olas de calor en la Meseta Central española del orden de 0.6 olas cada 10 años. En cuanto a las olas de frío, se detectan olas de frío todos los meses del año en número que oscila entre ocho y 16 olas. Los meses con menor número son abril (nueve), julio (ocho) y agosto (nueve), y los meses con mayor número son marzo, mayo, junio y octubre con 16 olas. Los años con mayor número de olas de frío son 1969, 1971 y 1977 con siete casos; en el resto de los años la frecuencia anual está comprendida entre uno y seis. El análisis de tendencia de la serie de frecuencias anuales indica que existe una tendencia decreciente de las olas de frío a un nivel de confianza del 99%. Si se considera un modelo lineal, en la Meseta Central española se ha producido, entre 1961 y 2010, una disminución de olas de frío del orden de 0.54 olas cada 10 años
The response of the Gulf of Mexico to wind and heat flux forcing: What has been learned in recent years?
Get PDFThe Loop Current and its shed eddies dominate the circulation and dynamics of the Gulf of Mexico (GoM) basin. Those eddies are strongly energetic and are the cause of intense currents that may penetrate several hundred meters deep. However, there are regions in the GoM and periods of time in which the local atmospheric forcing plays an important role in its dynamics and thermodynamics. The circulation on theshelves, and particularly on the inner shelf, is mainly wind-driven with seasonality, changing direction duringthe year with periods of favorable upwelling/downwelling conditions. The wind-driven circulation is associatedwith the transport of waters with different temperature and salinity characteristics from one region toanother. The interannual variability of the circulation on the shelves is linked to the atmospheric variability.Intraseasonal variability of the wind patterns considerably affects the likelihood and magnitude of upwellingand downwelling. The geometry of the GoM is such that large-scale winds may drive opposing upcoast/downcoast currents along different parts of the curving coast, resulting in convergence or divergence zones.The width of the shelves in the GoM is variable;while the West Florida Shelf, the Texas-Louisiana shelfand the Campeche Bank are more than 200 km wide, they are narrower near Veracruz and Tabasco. Anotherconsequence of the GoM physiography and the wind forcing is the development of cross-shelf transports inthe southern Bay of Campeche, the southern Texas shelf and southeast of the Mississippi river, which in turnvary during the year. During autumn-winter (from September to April), the GoM is affected by cold frontscoming from the northwest United States, which are associated with strong, dry, and cold winds that mixits waters and generate large sensible and latent heat fluxes from the ocean to the atmosphere. These frontalpassages also cool the GoM surface waters due to mixing with lower temperature subsurface waters. Duringsummer, tropical cyclones crossing the GoM can dramatically affect circulation and coastal upwelling.La dinámica del Golfo de México (GoM) se asocia frecuentemente con la Corriente del Lazo y los remolinos que se desprenden de ésta, los cuales son altamente energéticos y ocasionan corrientes intensas que pueden penetrar varios cientos de metros en la columna de agua. Sin embargo, hay regiones en el GoM y periodos de tiempo en que el forzamiento atmosférico local juega un papel importante en su dinámica y termodinámica. La circulación en las plataformas, particularmente en la interna, es generada principalmente por viento y tiene estacionalidad, ya que cambia de dirección a lo largo del año y tiene algunos periodos de condiciones favorables para el afloramiento/hundimiento. La circulación generada por el viento se vincula con el transporte de aguas con diferentes características de temperatura y salinidad. La variabilidad interanual de la circulación en las plataformas está asociada con la variabilidad interanual de la circulación atmosférica. Se ha identificado que la variabilidad intraestacional de los patrones de viento modifica considerablemente la ocurrencia de afloramientos y hundimientos. Debido a la forma y tamaño del GoM, cuando la circulación en una plataforma ocurre en sentido horario, puede darse en sentido opuesto en otras plataformas. El ancho de las plataformas en el GoM es variable: la plataforma oeste de Florida, la de Texas-Louisiana y el Banco de Campeche miden más de 200 km, en tanto que las más angostas son las de Veracruz y Tabasco. Otra consecuencia de la fisiografía del GoM y el forzamiento del viento es el desarrollo de transportes perpendiculares a la plataforma en el sur de la Bahía de Campeche, el sur de la plataforma de Texas y al sureste del Mississippi, los cuales a su vez varían a lo largo del año. El GoM es afectado durante el otoño-invierno (desde septiembre hasta abril) por frentes fríos provenientes del noroeste de Estados Unidos, los cuales tienen asociados vientos fuertes, secos y fríos que mezclan sus aguas y generan intensos flujos de calor sensible y latente del mar hacia la atmósfera. Estos vientos también enfrían el GoM debido a la mezcla de aguas cálidas de la superficie con aguas subsuperficiales de menor temperatura. Durante el verano, los ciclones tropicales que cruzan el GoM afectan su circulación y los afloramientos costeros
Dust emission from different soil types in the northwest and the Indo-Gangetic Plains of India
Get PDFDust emission is a main source of aerosol in the atmosphere and is highly sensitive to wind velocity. Surface feature characteristics, soil properties and meteorological parameters also influence dust emission. Thus far, no study has referred to dust flux over the Indian subcontinent; therefore, we estimated dust flux using empirical equations and land cover data for seven locations in the northwest and the Indo-Gangetic Plains (IGP) having different soil types. Our study indicates differences in dust flux among locations. In the northwest, dust emission was initiated at a friction velocity of 0.23 to 0.27 m s–1 and dust flux was lesser than the IGP. In the IGP, dust emission was initiated at a friction velocity ranging from 0.22 to 0. 35 m s–1. Dust flux ranged from 0.073 to 0.084 kg m–1 s–1 at a given friction velocity (0.6 m s–1). It was observed that at low friction velocity, dust flux was low at locations with high clay content (> 20%) and sandy soils, compared to sandy loam and silt loam soil types. A reverse trend was observed at a higher friction velocity. Our study clearly indicates the effect of soil texture in dust emission
THE ROLE OF URBAN VEGETATION IN TEMPERATURE AND HEAT ISLAND EFFECTS IN QUERÉTARO CITY, MEXICO
Get PDFAlteration of climatic conditions and the urban heat island effect (UHI) are consequences of increased human population and activities in urban zones. Determining the magnitude of the UHI is important to improve urban planning in medium-size cities like Querétaro. Increase and conservation of vegetated areas is a mitigation option for UHI. Here we characterized both the UHI and the role of vegetation cover over temperature regularization in urban zones. Four local climatic zones were defined: three urban and one rural, each with two plots with low and high canopy cover defined by their average leaf area index (0.5 and 2.0, respectively). Air temperature and relative humidity were measured with data loggers at a 30 min time step from June 2012 to May 2013. Climatic data from six weather stations was also analyzed. Daily mean temperature increased at a rate of 0.75 ºC per decade (r2 = 0.38, P < 0.0001), and this was related to population dynamics (r2 = 0.52, P < 0.0001). Patterns of air temperature defined a cold and a warm season: July to March and April to June for maximum temperature, and November to March and April to October for minimum temperature. The difference between cold and warm seasons was 5 ºC (P < 0.0001). The minimum temperature was similar between canopy cover levels. However, relative humidity was higher in high canopy cover plots. The relationship between UHI and the pervious surface fraction of the city was inversely proportional. The UHI ranged from 0.1 to 5 ºC and this magnitude was similar between the warm and cold seasons. Vegetation with high canopy cover had lower temperature at 17:00 LT and higher at 9:00 to 10:00 LT during the warm season. Increasing the urban zone canopy cover by 50% would reduce the UHI by 2.05 ºC. In conclusion, vegetation with higher canopy cover improved environmental conditions in terms of relative humidity and regularization of extreme temperatures during the warm season.
Assessment of potential human health and environmental impacts of a nuclear power plant (NPP) based on atmospheric dispersion modeling
Get PDFThe United States Environmental Protection Agency (US-EPA) short-range atmospheric dispersion model (AERMOD, v. 12345) is a good candidate for the calculation of offsite radiation doses to the general public, and its advanced capability should provide better confidence in the accuracy of offsite public doses assessment. In this paper the AERMOD code has been used to assess the impact of routine and accidental atmospheric radioactive discharges from a new nuclear power plant (NPP) site in Geregu, Nigeria (7˚ 33ˈ N, 6˚ 41ˈ E) on the four major settlements (Ajakuta, Lokoja, Idah and Okene) that lay within the emergency planning zones of the NPP. The code has produced values of the scaling factors for ground level air concentrations and depositions of radionuclides (from the passing plume) over our areas of interest. The scaling factors have been used to assess the potential radiological impact on the offsite human and non-human biota. While the authorities, an integrated approach to the assessment and management of environmental risks from ionizing radiation (D-ERICA) was adopted for the non-human biota. The results of this work indicate that, under normal operations, the NPP does not pose any significant public health and environmental impacts. However, accidental conditions characterized by precipitation will lead to discernible radiological risks within the NPP sites emergency planning zone
MEXICO'S CONTRIBUTION TO GLOBAL RADIATIVE FORCING BY MAJOR ANTHROPOGENIC GREENHOUSE GASES: CO2, CH4 AND N2O
Get PDFThe IPCC (2013) gives simplified formulas to compute the radiative forcing (RF) resulting from the increase in anthropogenic greenhouse gases (AGG): carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and halocarbons. These formulas allow to compute the global RF of these gases relative to their pre-industrial (1750 A.D.) concentrations, and are used in this work to estimate the contribution of Mexico to the global RF by its emissions of CO2 (the most significant of the AGG), CH4 and N2O during the period 1990-2011, which are reported in the Inventario Nacional de Emisiones de Gases de Efecto Invernadero (National Inventory of Greenhouse Gases Emissions, INEGEI) (INECC, 2013). In comparison, by 2010 the national emissions per capita of Argentina, Spain and the United States were 108.8, 110.8 and 327.0% of the Mexican emissions, respectively, in units of equivalent CO2. Mexico’s CO2 emissions retained in the atmosphere during 1990-2011 amount to 4 624 457 Gg; they are higher than those of Spain and Argentina together, and represent 1/12 of the USA contribution. Mexico’s contribution is 1.47% of the global RF due to CO2, with a similar proportion than Spain and Argentina, but a smaller fraction compared to that of the USA (1/15). The main uncertainties of our computations for Mexico’s contribution to the global RF come from national emissions; the INEGEI indicates that the emissions considered for the calculation of uncertainties represent 89% of the total emissions of the inventory, resulting in a total uncertainty of ±5.6%. We are aware that, as a consequence, the concentration increase of CH4 and N2O due to Mexico’s emissions retained in the atmosphere during 1990-2011 is lower than their respective uncertainties for global concentrations: 1.72 vs. 2 ppbv and 0.13 vs. 1 ppbv
Characteristics of fog in an aerodrome in a tropical lowland area in northwestern Amazonia
Get PDFAn analysis of meteorological terminal aviation routine weather reports (METAR) generated at the “Ernesto Esguerra Cubides” (EEC) aerodrome (Tres Esquinas Airbase) is shown. The aerodrome is located in the municipality of Solano in the Colombian Amazonia. Reports covering the period January 1, 2009 to December 31, 2012 helped to identify and analyze the characteristics of the occurrence of fog events at the EEC aerodrome. The results show that fog is a frequent meteorological phenomenon at the EEC aerodrome. On average, one in five days of the study period had at least one report of fog. At the EEC, fog is the meteorological phenomenon that causes the most weather-related aerodrome closures; it caused 45.26% of the closures of the EEC aerodrome. The high percentage of episodes of fog with calm wind (95%) and its high occurrence between 22:00 and 08:00 LT suggest that fog at the EEC aerodrome is basically radiative-type. Fog appears in every month of the year. In addition, three episodes of dense fog over the EEC aerodrome were analyzed from METAR and aviation special weather reports (SPECI), images from the GOES-13 satellite, NOAA surface analysis charts and radio soundings made at the EEC aerodrome. The analysis of these data allowed us to establish the weather conditions in which three fog events were presented. It was found that in times when the North Atlantic anticyclone is farthest from the Colombian territory and the Intertropical Convergence Zone is located north of the territory, subsidence is generated in the lower and middle levels by inhibiting convection over the northwestern part of the Colombian Amazonia and favoring the occurrence of fog or mist in the area. Subsidence over the area is also related to convective activity in the departments of Guainía, Vaupés and Guaviare. This, together with sky conditions with few clouds and calm winds favor radiative cooling, increasing the likelihood of fog and mist
Role of forcing in large-time behavior of vorticity equation solutions on a sphere
Get PDFThe nonlinear barotropic vorticity equation (BVE) describing the vortex dynamics of viscous incompressible and forced fluid on a rotating sphere is considered. The asymptotic behavior of solutions of nonstationary BVE as t → ∞ is studied. Particular forms of the external vorticity source are given that guarantee the existence of a bounded attractive set in the phase space of solutions. The asymptotic behavior of the BVE solutions is shown to depend on both the structure and the smoothness of external forcing. Three types of sufficient conditions for global asymptotic stability of smooth and weak BVE solutions are also given. Simple attractive sets of a viscous incompressible fluid on a sphere under quasi-periodic polynomial forcing are considered. Each attractive set represents a BVE quasi-periodic solution of the complex (2n + 1)-dimensional subspace Hn of homogeneous spherical polynomials of degree n. The Hausdorff dimension of its trajectory, being an open spiral densely wound around a 2n-dimensional torus in Hn, equals to 2n. As the generalized Grashof number G becomes small enough then the domain of attraction of such spiral solution is expanded from Hn to the entire BVE phase space. It is shown that for a given G, there exists an integer nG such that each spiral solution generated by a forcing of Hn with n ≥ nG is globally asymptotically stable. Thus we demonstrate the difference in the asymptotic behavior of solutions in the cases, then Grashof number G is fixed and bounded, but the forcing is stationary or non-stationary. Whereas the dimension of the fluid attractor under a stationary forcing is limited above by G, the dimension of the spiral attractive solution (equal to 2n) may become arbitrarily large as the degree n of the quasi-periodic polynomial forcing grows. Since the small-scale quasi-periodic functions, unlike the stationary ones, more adequately depict the forcing in the barotropic atmosphere, this result is of meteorological interest and shows that the dimension of attractive sets depends not only on the forcing amplitude, but also on its spatial and temporal structure. This example also shows that the search of a finite-dimensional global attractor in the barotropic atmosphere is not well justified