Atmósfera (Journal)
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Observed surface ozone trend in the year 2012 over Nairobi, Kenya
Get PDFClean air is a basic requirement for human health and wellbeing. The Kenya Meteorological Department has established air pollution monitoring activities in various sites in Nairobi, at Dagoretti Corner meteorological station and at Mount Kenya. Different pollutants are measured including ozone. The increased concentration of greenhouse gases in the atmosphere has influenced the weather and climate. This study examined the variations of surface ozone over Dagoretti Corner, Nairobi for a 12-month period ending July 2013, exactly one year after the start of data acquisition. The trend was studied using time series analysis of ozone concentration on both an hourly and monthly basis. The ozone data was then combined with meteorological data and temperature to find correlations between the two. Overall, the air quality of Nairobi, represented by Dagoretti Corner meteorological station is good as compared to the World Meteorological Organization ozone standards. The highest concentration of ozone is observed in the afternoon and the minimum at dawn on a daily basis. On seasonal scale, the highest levels are recorded in the cold months. This information helps to reduce exposure to the gas and thus to reduce its impacts on living things. The study recommends the reduction of exposure to the gas during the times when it has been observed to be highest in order to minimize its impactsEl aire limpio es un requerimiento básico para la salud y el bienestar humanos. El Servicio Meteorológico de Kenia ha iniciado acciones de medición de contaminación del aire en varios sitios de Nairobi, en el Centro Meteorológico de Dagoretti Corner y en el monte Kenia. Se miden diversos contaminantes, incluyendo el ozono. La concentración ascendente de gases de efecto invernadero en la atmósfera ha influido en el clima y el tiempo atmosférico. En el presente estudio se analizaron las variaciones de ozono superficial en Dagoretti Corner, Nairobi, durante un periodo de 12 meses que finalizó en julio de 2013, exactamente un año después del inicio de la obtención de datos. Para estudiar la tendencia se analizaron series de tiempo horarias y mensuales de la concentración de ozono. Los datos de ozono se correlacionaron con datos meteorológicos y de temperatura. En términos generales, se encontró que la calidad del aire en Nairobi (representada por la estación meteorológica de Dagoretti Corner) es buena de acuerdo con los estándares de la Organización Meteorológica Mundial. La mayor concentración de ozono se observó durante la tarde y la mínima al amanecer. En una escala estacional, los niveles más altos se observaron en los meses fríos. Esta información ayuda a reducir la exposición al gas y por lo tanto a disminuir sus efectos sobre los seres vivos. Se recomienda la reducción de la exposición al ozono en los tiempos en que se han observado mayores concentraciones para minimizar su impacto
A new methodology for building local climate change scenarios: A case study of monthly temperature projections for Mexico City
Get PDFThis paper proposes a new methodology for generating climate change scenarios at the local scale based on multivariate time series models and restricted forecasting techniques. This methodology offers considerable advantages over the current statistical downscaling techniques such as: (i) it provides a better representation of climate at the local scale; (ii) it avoids the occurrence of spurious relationships between the large and local scale variables; (iii) it offers a more appropriate representation of variability in the downscaled scenarios; and (iv) it allows for compatibility assessment and combination of the information contained in both observed and simulated climate variables. Furthermore, this methodology is useful for integrating scenarios of local scale factors that affect local climate. As such, the convenience of different public policies regarding, for example, land use change or atmospheric pollution control can be evaluated in terms of their effects for amplifying or reducing climate change impacts.Este trabajo propone una metodología para elaborar escenarios de cambio climático a escala local. Se usan modelos multivariados de series de tiempo para obtener pronósticos restringidos y se avanza en la literatura sobre métodos estadísticos de reducción de escala en varios aspectos. Así se logra: i) una mejor representación del clima a escala local; ii) evitar la posible ocurrencia de relaciones espurias entre variables de gran y pequeña escalas; iii) una representación apropiada de la variabilidad de las series en los escenarios de cambio climático, y iv) evaluar la compatibilidad y combinar la información de variables climáticas con las derivadas de los modelos de clima. La metodología propuesta es útil para integrar escenarios sobre la evolución de los factores de pequeña escala que influyen en el clima local. De esta forma, al escoger distintas evoluciones que representen, por ejemplo, distintas políticas públicas sobre uso del suelo o control de contaminantes, la metodología ofrece una manera de evaluar la conveniencia de dichas políticas en términos de sus efectos para amplificar o atenuar los impactos del cambio climático
UHF wind profiler observations of monsoon low-level jet (MLLJ) and its association with rainfall over a tropical Indian station
No full text High resolution data of horizontal winds profiles (zonal and meridional) in the lower troposphere, derived from a UHF wind profiler at a tropical Indian station, Pune (18o 32’ N, 73o 51’ E, 559 masl) during a 3-yr period (June 2003-May 2006) has been utilized to study seasonal and intra-seasonal variability of winds. Winds display a systematic seasonal evolution with behavior opposite in phase in the two altitude regimes below and above a height of 4-5 km. In the lower region, during the southwest monsoon months (June to September) winds are predominantly westerly with a peak in the 1.5-3.0 km range indicating the occurrence of the monsoon low-level jet (MLLJ). Soon after September, winds in this height region change from westerly to easterly and these easterlies continue in winter months (December to February). Above a height of 4 km, westerlies are observed during post-monsoon (October to November) and winter periods. The MLLJ is observed to be strong during normal/good monsoon years. On a day-to-day scale during southwest monsoon months, winds exhibit considerable intra-seasonal variability and periods of strong MLLJ seem to be associated with occurrence of spells of rainfall over the region
Solar absorption infrared spectroscopic measurements over Mexico City: Methane enhancements
Get PDFIn this contribution, the experiment for performing solar-absorption infrared measurements from UNAM's Atmospheric Observatory (Universidad Nacional Autononal de Mexico) located at the in the University campus in Mexico City is described. The Fourier Transform InfRared (FTIR) spectrometer and solar-tracker system are operating since June 2010 and from the recorded spectra, the total column amounts of several atmospheric gases can be derived. The current study presents the results obtained for methane (CH4), an important pollutant involved in ozone production and a rapid increasing greenhouse gas. The total column densities retrieved with high temporal resolution, present a large dispersion and day-to-day variability. A mean value of 2.92×1019 molecules/cm2 (1.825 ppm), with a 95% confidence interval between 2.66 and 3.19×1019 molecules/cm2, have been obtained for the period 06/2010 to 12/2011. No clear annual cycle can be determined from the monthly means due to the large variability in the measurements, suggesting a significant effect of the local emissions to the natural background concentrations. Some days with extraordinary enhancements are presented and a simple back trajectory analysis points to a predominant source direction from the Northeast of the measurement site. The methane contaminated air masses passing over the UNAM Atmospheric Observatory, however, originate presumably not from one but several dispersed sources. A more detailed analysis with modeling of the dynamics of these air masses is required
RE-ANALYSIS OF THE RAINFALL IN SOUTHERN BRAZIL
No full textThis study examined the precipitation in Southern Brazil, based on a data set provided by the Brazilian National Water Agency (ANA), covering the period from 1976 to 2010. Data were homogenized, using the software R and the subroutine Climatol, which allowed completing missing data. Isohyets were drawn using Geostatistics, to obtain semivariogram for each analysis. There was a remarkable variability from year to year in this region, with positive anomalies in ENSO episode (warm phase: El Niño) and negative anomalies in ENSO episode (negative phase: La Niña). Also, the responses of these variabilities were not uniform in the whole region, and there was variability from year to year and from event to event
INCIDENCE AND TREND OF BLOCKING ACTION SITUATIONS ON THE TEMPERATURE AND PRECIPITATION IN ARGENTINA
Get PDF Abstract: In southern South America and for the period 1960-2011, frequencies and trends of seasonal blocking situations (Bs) determined at 100º, 70º and 40ºW (B100, B70 and B40) are estimated. The effect of such situations on temperature and precipitation is also analyzed. The distribution of occurrences of B100, B70 and B40 peaks in spring and has minimum values in summer; trends are positive in summer and fall and negative in winter and spring.To the north of approximately 38ºS, B70 determine negative temperature anomalies (DT) over the entire country during the four seasons and B40 in spring and summer. Except for summer, rainfall is greater than normal when Bs occur at both longitudes.To the south of approximately 38ºS, B100 give place to negative DT. The frequencies and amounts of precipitation are greater in spring. This area is limited to the northernmost northern (southernmost southern) area in fall (summer).According to the signs of the trends of the Bs and to the associated values of temperature and precipitation, it is inferred the way in which they may have contributed to the change in both variables during 1960-2011
Black carbon and organic carbon emissions from wildfires in Mexico
Get PDFIn Mexico, approximately 7,650 wildfires occur annually, affecting 263,115 hectares of land. In addition to their impact on land degradation, wildfires cause deforestation, damage to ecosystems and promote land use change; apart from being the source of emissions of toxic substances to the environment (i.e., hydrogen cyanide, black carbon and organic carbon). Black carbon is a short-lived greenhouse pollutant that also promotes snow and ice melt and decreased rainfall; it has an estimated global warming potential close to 5000[1]. We present an estimate of the black carbon and organic carbon emissions from wildfires in Mexico from 2000 to 2012 using selected emission factors from the literature and activity data from local agencies. The results show average emissions of 5,955 Mg/year for black carbon and 62,085 Mg/year for organic carbon. Black carbon emissions are estimated to be 14,888 Gg CO2 equivalent (CO2 eq) per year on average. With proper management of wildfires, such emissions can be mitigated. Moreover, improved air quality, conservation of ecosystems, improvement of visibility and maintenance of land use are a subset of the related co-benefits. Mitigating organic carbon emissions, which are ten times higher than black carbon emissions, would also prevent the morbidity and mortality impacts of toxic organics in the environment. [1] The GWP is calculated as the ratio of the Absolute Global Warming Potential (AGWP) of a given gas to the AGWP of CO2. The AGWP has units of W-m-2 yr g-
RECENT TRENDS IN SEA SURFACE TEMPERATURE OFF MEXICO
Get PDFChanges in global mean sea surface temperature may have potential negative implications for natural and socioeconomic systems; however, measurements to predict trends in different regions have been limited and sometimes contradictory. In this study, an assessment of sea surface temperature change signals in the seas off Mexico is presented and compared to other regions and the world ocean, and to selected basin scale climatic indices of the North Pacific, the Atlantic and the tropical Pacific variability. We identified eight regions with different exposure to climate variability: In the Pacific, the west coast of the Baja California peninsula with mostly no trend, the Gulf of California with a modest cooling trend during the last 20 to 25 years, the oceanic area with the most intense recent cooling trend, the southern part showing an intense warming trend, and a band of no trend setting the boundary between North-Pacific and tropical-Pacific variability patterns; in the Atlantic, the northeast Gulf of Mexico shows cooling, while the western Gulf of Mexico and the Caribbean have been warming for more than three decades. Potential interactions with fisheries and coastal sensitive ecosystems are discussed.Los cambios de temperatura promedio del océano a nivel global tienen el potencial de afectar negativamente los sistemas naturales y socioeconómicos actuales; sin embargo, los registros para proyectar las tendencias de cambio a nivel regional son escasos y, en algunos casos, contradictorios. En este estudio se analizan las señales de cambio de la temperatura superficial en mares mexicanos, y se comparan con otras regiones del planeta y con indicadores climáticos clave, tanto del Pacífico Norte como de la franja tropical en el Atlántico y el Pacífico. Se identificaron ocho regiones con diferente exposición a la variabilidad climática: en el Pacífico, la costa occidental de la península de Baja California no muestra una tendencia clara, el Golfo de California exhibe una tendencia modesta de enfriamiento durante los últimos 20 a 25 años, en la parte más oceánica del Pacífico mexicano se nota una tendencia intensa de enfriamiento, la región más tropical muestra una tendencia intensa de calentamiento, y entre ambas regiones se forma una banda de transición sin tendencia; en el Atlántico, la parte noreste del Golfo de México muestra una tendencia de enfriamiento, en tanto que la parte oeste, junto con el Caribe, se han estado calentando por lo menos durante los últimos 30 años. Se analizan las interacciones potenciales de estas tendencias con algunas pesquerías principales y la presencia de ecosistemas costeros sensibles
DETECTION OF HAIL THROUGH THE THREE BODY SCATTERING SIGNATURES AND ITS EFFECTS ON RADAR ALGORITHMS OBSERVED IN ROMANIA
Get PDFThe Romanian National Meteorological Administration (NMA) radar network consists of five S-band and four C-band radars. Observation of convection in Romania through the Doppler radar network offered a new perspective in understanding the climatologic risk of certain regions and mesoscale environments. Highly organized convective systems, such as supercells, are better observed and their subsequent threat can be better anticipated during the nowcasting process using Doppler velocity fields and detection algorithmssuch as mesocyclones (MESO) and tornadic vortex signature (TVS). However, for warning purposes,these tools cannot be used without a subjective validation because of the associated errors and limitations of radar observations. In this paper several cases are presented where the presence of large hail inside the storm produced a radar artifact named three-body scatter signature (TBSS) that disturbed the Doppler velocity field. The cases presented were observed with S-band radars and were associated with hail reports on the ground. The first case shows a TBSS whose radial Doppler velocities are negative due to the falling hydrometeors. The second case is a less frequent event; there the Doppler velocities in the TBSS region are positive due to the updraft. The third case has both positive and negative values in the TBSS region; it is ocurred in a supercell that affected the city of Varna in Bulgaria with large hail. The positive values were associated with the overhang region in the rotational updraft at upper heights, while the negative values in the regions outside the rotational updraft at lower heights, were associated with the downdrafts. Features produced by the TBSS have perturbed the output of the MESO and TVS algorithms by introducing false strong values of wind shear that have been interpreted as rotation. Thus false mesocyclonic and tornadic vortex signatures were generated. In some of the cases large hail and weak tornadoes were reported, so the presence of a TBSS was a challenge for the nowcasters. In the last part of the paper we analyze the link between the TBSS appearance with reports of large hail at the ground in 2009 within the coverage area of the Romanian S-band radars, which also cover parts of Hungary, Bulgaria, the Republic of Moldova and Serbia. The results show that the TBSS artifact is a strong indicator of large size hail.La red de radares de la Administración Meteorológica Nacional de Rumania (NMA, por sus siglas en inglés) integra cinco radares de la banda S y cuatro radares de la banda C. La observación de procesos de convección en Rumania mediante la red de radares Doppler ofrece una nueva perspectiva para comprender el riesgo climatológico de ciertas regiones y entornos de mesoescala. Se observan mejor los sistemas convectivos altamente organizados, como las supercélulas, y su amenaza subsiguiente puede predecirse mejor durante el pronóstico a muy corto plazo (nowcasting) utilizando campos de velocidad Doppler y algoritmos de detección como mesociclones (MESO) y firmas de vórtice de tornados (TVS, por sus siglas en inglés). Sin embargo, para fines de prevención, estas herramientas no pueden utilizarse sin una validación subjetiva debido a los errores asociados y limitaciones de las observaciones de radar. En este trabajo se presentan varios casos en que la presencia de granizo de gran tamaño dentro de la tormenta produjo un artefacto de radar llamado “pico de granizo” (three-body scatter spike, TBSS) que alteró el campo de velocidad Doppler. Los casos presentados se observaron con radares de banda S y se compararon con informes de granizo sobre el terreno. El primer caso muestra un TBSS cuyas velocidades Doppler radiales son negativas debido a la presencia de hidrometeoros. El segundo exhibe una situación menos frecuente, cuando las velocidades Doppler en la región TBSS son positivas debido a la corriente ascendente. El tercer caso muestra valores positivos y negativos en la región TBSS; representa una supercélula con granizo de gran tamaño que afectó a la ciudad de Varna, en Bulgaria. Los valores positivos se asociaron con la región sobresaliente de la corriente rotacional ascendente a alturas superiores, en tanto que los valores negativos en las regiones externas de la corriente rotacional ascendente a alturas inferiores, se asociaron con las corrientes descendentes. Algunas anomalías producidas por el TBSS han alterado los resultados de los algoritmos TVS y MESO, introduciendo valores falsos de viento de gradiente fuerte que se han interpretado como rotación. De esta manera se generaron firmas falsas de mesociclones y vórtices de tornado. En algunos casos se reportaron tornados débiles y granizo de gran tamaño, por lo que la presencia de TBSS fue un reto para quienes realizan predicciones de muy corto plazo. En la parte final de este trabajo se analiza el vínculo entre la aparición de TBSS con informes de 2009 sobre granizo de gran tamaño en tierra en el área de cobertura de los radares de banda S en Rumania, que también abarcan zonas de Hungría, Bulgaria, Moldavia y Serbia. Los resultados muestran que la distorsión ocasionada por el TBSS es un fuerte indicador de granizo de gran tamaño
Multivariate delineation of rainfall homogeneous regions: A case study of Northwestern Mexico.
No full textLack of data in maximum daily rainfall frequency analysis can generate inefficient estimates for design purposes. An approach to diminish these errors is to apply regional estimation techniques, which require that all stations be located at the same homogeneous region. In this paper, a delineation of homogeneous precipitation regions was made based on the multivariate methods of principal component analysis and hierarchical ascending clustering. A region in northwestern Mexico was selected to apply this methodology. It was concluded that only the coefficients of variation of the L-moments, along with latitude, longitude and altitude at each climatological station are sufficient to define the homogeneous rainfall regions, and that either the inclusion or exclusion of information in the regional techniques has a direct impact on the estimation of events associated to different return periods.La escasez de información en el análisis de frecuencias de lluvias máximas diarias puede generar estimadores ineficientes para propósitos de diseño. Una forma de reducir estos errores es la aplicación de técnicas regionales, las cuales requieren que las estaciones involucradas pertenezcan a la misma región homogénea. En este trabajo se realiza una delimitación de regiones homogéneas de precipitación empleando un método multivariado basado en las técnicas de análisis de componentes principales y de agrupamiento jerárquico ascendente. La metodología propuesta se aplicó a una región del noroeste de México. Se concluyó que sólo se requieren los coeficientes de variación de los momentos-L y de la latitud, longitud y altitud de cada estación climatológica para definir las regiones homogéneas de precipitación, y que la inclusión o exclusión de información en las técnicas regionales tiene un impacto directo en la estimación de eventos asociados a diferentes periodos de retorno