Atmósfera (Journal)
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ANALYSIS OF THE LATIN AMERICAN WEST COAST RAINFALL PREDICTABILITY USING AN ENSO INDEX
Get PDFThe objective of this study was to determine the probability of occurrence of wet or dry season events, by means of estimating latitudinal profiles for the association between El Niño Southern-Oscillation and the rainfall along the west coast of Central and South America. The analysis was performed using multinomial linear regression and multinomial logit regression models. We used monthly time series of the Pacific equatorial sea surface temperature (SST), the Niño 3.4 index, a sea level pressure index (SOI) and rainfall anomalies over a 2.5 × 2.5º grid along the west coast of Central and South America, for latitudes starting at 25º N through 45º S, from 1951 to 2011. We defined an ENSO index (NSO) as predictor and rainfall as response. Data was grouped into seasons and then categorized into terciles to construct 3 × 3 non-symmetrical three way contingency tables. As results, we generated latitudinal profiles of the predictability (association) of rainfall for the west coast of Central and South America, using the ENSO phases as predictor.
ON THE DISTINCT INTERANNUAL VARIABILITY OF TROPICAL CYCLONE ACTIVITY OVER THE EASTERN NORTH PACIFIC
No full textThe tropical eastern North Pacific (ENP) basin exhibits very large interannual variability in the frequency of occurrence of tropical cyclones, presenting very active (more than 20 tropical cyclones per season) and very inactive years (only eigth tropical cyclones). The large-scale factors that may influence the distinct interannual variability are investigated in this study, by analyzing the composites of seven years of high activity and 10 years of low activity from 1965 to 2013. The results of composite analyses indicate that the low-level vorticity and mid-tropospheric relative humidity are mostly unfavorable for tropical cyclogenesis during active years. The sea surface temperature (SST) may play a small role modulating the occurrence of tropical cyclones, but the reduced vertical shear of the horizontal wind between 850 and 200 hPa is the main contributor to cyclogenesis during the active years, confirming earlier results by Camargo et al. (2007). We use an intensity model (Emanuel et al., 2006, 2008) to further investigate the key environmental factors affecting TC intensity, exploring the relative roles of changes in SST, vertical wind shear and TC tracks. The results indicate that the interannual variability in the frequency of major hurricanes (categories 3 through 5) is best simulated when the effects of both SST and vertical wind shear are combined. Furthermore, changes in TC tracks may play an important role in the intensity achieved. In particular, during the years with high activity, the location for cyclogenesis shifts eastward and more TCs have west-northwestward tracks, leading to longer lifetime and higher intensity, compared to years with low TC activity in the basin.
Rapid deepening of tropical cyclones in the northeastern Tropical Pacific: The relationship with oceanic eddies
No full text The National Hurricane Center best track archive data for the northeastern Tropical Pacific includes tropical cyclones (TC) that exhibited rapid and/or explosive deepening during the period 1993-2009. Concurrently, satellite altimeter observations show the northeastern Tropical Pacific populated by cyclonic and anticyclonic oceanic eddies. These two sources of data are used to study the role of oceanic eddies in the spatial distribution of the oceanic heat content and the rapid and/or explosive deepening of TCs in the northeastern Tropical Pacific. Analysis of the results demonstrates that: (1) Interaction between TCs and anticyclonic eddies occurred in ~ 73% of the TCs within the analyzed period; (2) 90% of the TCs that reached major hurricane category had experienced an interaction with anticyclonic eddies; (3) ~ 18% (3%) of the TCs were characterized by rapid (explosive) deepening and 74% of these TCs reached the deepening status after direct and/or indirect interaction with anticyclonic eddies; moreover, 86% of them reached a major hurricane category. Analysis of the atmospheric conditions demonstrates the important role of dry air intrusion along the vertical profile ofthe lower atmosphere as an inhibitor of tropical cyclone deepening
EXPERIMENTAL VERIFICATION OF THE TURBULENT EFFECTS ON LASER BEAM PROPAGATION IN SPACE
No full textIn this work, we have modified an existing experimental setup to fully classify the thermal effects on a laser beam propagating in air. Improvements made to the setup include a new, more powerful laser, a precision designed turbulence delivery system, an imbedded pressure sensor, and a platform for height adjustability between the laser beam and the turbulence model. The setup was not only able to reproduce previous results exactly but also allowed new data for the turbulence strength C2n, the Rytov variance (scintillation) and the coherence diameter (Fried’s parameter) to be successfully measured. Analysis of the produced interferograms has been discussed using fast Fourier transforms. The results confirm, within the Kolmogorov regime, that phase and intensity fluctuations increase relative to temperature. The turbulent region exhibited very strong disturbances, in the range of 1.1 × 10–12 m–2/3 to 2.7 × 10–12 m–2/3. In spite of the strong turbulence strength, scintillation proved otherwise, since the condition for a weak turbulence environment was determined in the laboratory and a low scintillation index was to be expected. This is as a result of the relatively short propagation distances achieved in the laboratory. In the open atmosphere, path lengths extend over vast distances and in order for turbulent effects to be realized, the turbulence model must generate stronger turbulence. The model was, therefore, able to demonstrate its ability to fully quantify and determine the thermal turbulence effects on a propagating laser beam.En este trabajo se modificó un diseño experimental preexistente para clasificar íntegramente los efectos térmicos de un rayo láser que se propaga en el aire. Las mejoras incorporadas al diseño previo incluyeron un láser más potente, un sistema de formación de turbulencias de alta precisión, un sensor de presión integrado, y una plataforma para ajustar la altura entre el rayo láser y el modelo de turbulencia. Este diseño no sólo puede reproducir resultados previos con exactitud, sino que además permitió la medición exitosa de nuevos datos sobre la intensidad de la turbulencia C2n, la varianza de Rytov (cintilación) y el diámetro de coherencia (parámetro de Fried). Los interferogramas resultantes se analizaron utilizando transformadas rápidas de Fourier. Los resultados confirman, dentro del régimen de Kolmogorov, que las fluctuaciones en fase e intensidad se incrementan en relación con la temperatura. La región turbulenta mostró perturbaciones muy intensas, en el rango de 1.1 × 10–12 m–2/3 a 2.7 × 10–12 m–2/3. A pesar de la intensidad de la turbulencia, con relación a la cintilación se demostró algo diferente, ya que la condición para un entorno de turbulencia débil se determinó en el laboratorio y se esperaba un bajo índice de cintilación. Esto es resultado de las distancias de propagación relativamente cortas obtenidas en el laboratorio. En la atmósfera abierta las trayectorias cubren grandes distancias y, para determinar los efectos de la turbulencia, el modelo debe generar turbulencias de mayor intensidad. De esta manera, el modelo demostró su capacidad para cuantificar y determinar plenamente los efectos térmicos de la turbulencia en un rayo láser en propagación
RECENT WARMING IN THE BALEARIC SEA AND SPANISH MEDITERRANEAN COAST. TOWARDS AN EARLIER AND LONGER SUMMER
Get PDFThis paper analyses recent changes in the temperature of the Balearic Sea and surrounding coastal areas. Monthly temperature data from several weather stations located around the Balearic basin have been used to obtain land temperatures during the period 1960-2010, and monthly thermal satellite images from the Physical Oceanography Distributed Active Archive Center (PO.DAAC) covering the period 1985-2009 have been processed to obtain sea surface temperatures (SSTs) in the Balearic Sea. A rise in temperature has been observed since 1980 and increasingly in the last 25 years, with an average warming trend of 0.039 ºC/year on land for the period 1960-2010 and 0.026 ºC/year in SSTs for 1985-2009. The seasonal analysis showed that, in the last 25 years, higher trends were registered during the transition from spring to summer, with the highest warming rates in June (0.12 ºC/year on land and 0.08 ºC/year in SSTs). Results show a recent tendency towards earlier and longer summers both on land and sea.
Studies regarding the quality of numerical weather forecasts of the WRF model integrated at high-resolutions for the Romanian territory
Get PDFThe aim of this paper is to evaluate the quality of high-resolution weather forecasts from the Weather Research and Forecasting (WRF) numerical weather prediction model. The lateral and boundary conditions were obtained from the numerical output of the Consortium for Small-scale Modeling (COSMO) model at 7 kmhorizontal resolution. The WRF model was run for January and July 2013 at two horizontal resolutions(3 and 1 km). The numerical forecasts of the WRF model were evaluated using different statistical scores for 2 m temperature and 10 m wind speed. Results showed a tendency of the WRF model to overestimate the values of the analyzed parameters in comparison to observations
The impact of nitrogen fertilizer use on greenhouse gas emissions in an oil palm plantation associated with land use change
Get PDFThe emissions of greenhouse gases (GHGs) in an oil palm plantation associated with land use change have been evaluated on a site-specific basis. Nitrous oxide (N₂O) emissions from the application of nitrogen fertilizers during the growth stages of the palm oil were analyzed for palms of different ages within the plantation. The N₂O release ranges between 19.11-22.17 kg of N2O-N/ha, resulting in the emission of 1052.26-1209.51 kg of CO2-eq/ha. However, there is no clear relationship between the emissions of N2O or CO2-eq and the age of the oil palms. On the other hand, the impact from land use change for the development of the site was also evaluated by assessing the emissions from carbon stock changes within the plantation. The transformation of a rubber estate into an oil palm plantation loses the soil carbon content (i.e., release of carbon emissions). However, this phenomenon has been anticipated in literature. Overall, fertilizer-related emissions and fuel emissions during the growth stages contribute to about 79 and 21%, respectively, of the total GHG emissions from the plantation. Therefore, it is likely that the application of nitrogen fertilizer may increase the existing carbon emission from the conversion of rubber to oil palm plantation, but the values are within the estimated for a Malaysian oil palm plantation
The influence of the Tula, Hidalgo complex on the air quality of the Mexico City Metropolitan Area
Get PDFUsing an air quality model, this study shows how emissions from the “Miguel Hidalgo” refinery of Petróleos Mexicanos (Pemex) and the thermoelectric plant “Francisco Pérez Ríos” of the Comisión Federal de Electricidad (CFE, Federal Electricity Commission) in Tula, Hidalgo influence the atmosphere of the Mexico City Metropolitan Area (MCMA). The model couples meteorology and chemistry. The weather scenario encompasses the period from October 20-28, 2005. Two scenarios are compared: the first assumes a 40% reduction in emissions of NOx, SO2, and volatile organic compounds (VOCs) from the Tula complex (reduction scenario), and the second considers the scenario without reduction (baseline scenario). The model is compared with measurements of the Red Automática de Monitoreo Atmosférico (Automatic Environmental Monitoring Network). We observe that under certain weather conditions, the energy sector of Tula, Hidalgo affects the air quality in the MCMA. The reduction scenario is effective in reducing SO2 concentrations; however, despite a 40% decrease in the emissions of ozone precursors, their concentrations in the MCMA did not decrease.Se utilizó un modelo de calidad del aire para analizar las emisiones provenientes de la refinería de Petróleos Mexicanos (Pemex) “Miguel Hidalgo” y la planta termoeléctrica “Francisco Pérez Ríos” de la Comisión Federal de Electricidad (CFE) localizadas en la ciudad de Tula, Hidalgo. La finalidad fue identificar la influencia de estas emisiones en la composición atmosférica de la Zona Metropolitana del Valle de México (ZMVM). El modelo utilizado acopla la meteorología y la química necesarias para la realización del estudio de impacto. Se llevó a cabo la simulación de dos escenarios que comprenden el periodo del 20 al 28 de octubre de 2008: un “escenario base” con las emisiones reales del complejo industrial y un “escenario de reducción” alternativo que supone una disminución del 40% en las emisiones de NOx, SO2 y compuestos orgánicos volátiles (COV) del complejo industrial. Los resultados del modelo se cotejaron con mediciones en superficie de la Red Automática de Monitoreo Atmosférico y se observó que en ciertas condiciones meteorológicas las emisiones del sector industrial sí influyen en la calidad del aire de la ZMVM. El escenario de reducción fue efectivo para simular una disminución en la concentración de SO2 en las inmediaciones de la zona industrial e igualmente para el Valle de México; sin embargo, esta misma reducción en COV y NOx no logró disminuir la concentración de ozono en la ZMVM
Regional climate change scenarios over southern South America for future climate (2080-2099) using the MM5 Model. Mean, interannual variability and uncertainties
Get PDF Atmósfera 29(1), 35-60 (2016)This work focuses on evaluating the climate change projected by the end of the 21st century under the SRES A2 emission scenario over southern South America using the regional model MM5. The model projects: (i) an increase of precipitation over central Argentina, Uruguay and southern Brazil during summer and fall; (ii) a decrease in precipitation over most of the study domain during winter and spring; (iii) an important decrease in precipitation over central and southern Chile, through the year. In general, the projected temperature increase depends on the season and the examined area; particularly, it is highest over tropical and subtropical latitudes in spring and over high latitudes in summer. The MM5 model projects: (i) an increase of the interannual precipitation variability of precipitation over central Argentina and Uruguay regardless the season; (ii) a slight decrease in interannual temperature variability over large extents of Argentina for summer and winter; (iii) a slight increase in interannual temperature variability at transition seasons; with highest values over central Chile in autumn and over north central Argentina in spring. From the reliability assessment of regional climate projections, it can be concluded that signal-to-noise ratio is high for temperature and low for precipitation. Therefore, the MM5 model is a useful tool in the generation of regional climate change scenarios of high resolution over southern South America, particularly for temperature, and is a starting point to perform studies related to impacts of climate change
Evaluation of ensemble NWP models for dynamical downscaling of air temperature over complex topography in a hot climate: A case study from the Sultanate of Oman
Get PDFThis paper evaluates the use of ensemble numerical weather prediction (NWP) models for dynamical downscaling of temperature over a complex, hot region. This approach delivers information about the uncertainty of the NWP models and provides probabilistic information for comparison with the currently used single NWP model. An ensemble system was constructed using four members with a 7 km resolution over Oman. Two limited-area models (LAMs), the high-resolution model (HRM) and the model from the Consortium for Small-Scale Modeling (COSMO) formed the ensemble members. The two LAMs were derived and initialized using the general circulation model (GCM) data from the German Global Model (GME), which runs at 40 km resolution, using two different initial atmospheric states. The first initial state was provided by the 3Dvar data assimilation system at the German Weather Service (Deutscher Wetterdienst, DWD),and the second initial state was provided from the reanalysis data (ERA-Interim) from the European Centre for Medium-Range Weather Forecasts (ECMWF). The results reveal the uncertainty in temperature prediction related to the uncertainty of the NWP models that were used and indicate that there is no best model for the entire domain. On average, the ensemble mean performed better than individual members