ISSN: 2310-2799
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546,196 artículos
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Año:
2009
ISSN:
2395-8812, 0187-6236
LEMOYNE HERNÁNDEZ, LUIS; ÁLVAREZ CALDERÓN, JESÚS
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
The problem of weather forecasting based on the use of a priori information, from a first principles model, in conjunction with on-line measurements is addressed. Our derivation of an estimation algorithm evidences that understanding and exploitation of available estimation techniques require ingredients from physical knowledge of the process, tools to represent partial differential equations (as a reduced set of ordinary differential equations), numerical error propagation and conditional estimation in statistics. It is concluded that updating of the model error statistics and the number and location of measurements play an important role on the estimator performance. A suitable treatment of the preceding issues leads to an estimator whose accuracy, size, numerical treatment, computational effort and measurement mesh can be chosen so that performance is guaranteed while keeping simplicity and ease of implementation.
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Año:
2009
ISSN:
2395-8812, 0187-6236
FERNÁNDEZ, C.; CASTRO, M.
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
A two-dimesional hydrostatic mesometeorological model has been applied to analyze a typical atmospheric local circulation observed in anorthern zone of the iberian peninsula during the summer. by means of two model simulation with different land-use type distributions, the definitive influence of the aridity of the soils in the central plateau on the intensity and inland penetration of the sea-breeze and on the development of the cuasi-permanent iberian surface thermal low in the summer season is shown.
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Año:
2009
ISSN:
2395-8812, 0187-6236
CASTELLANOS ROMÁN, M. A.; SALAZAR, S.; GÓMEZ L., B.
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
The results of the study of the polycristallibe material composition in soil and its corresponding atmosphere in four differente zones of Mexico, are presented. the analyses were carroed out by x-ray diffraction. for the first time, the composition of the cristalline phase of backgrond aerosol in rural, maritime, suburban and urban atmosphere, was obtained. it was found out that the urban atmosphere is particularly rich in crystalline phases in comparison with the other areas.
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Año:
2009
ISSN:
2395-8812, 0187-6236
TEJEDA MARTÍNEZ, ADALBERTO; MARURI, J. M.; MARTÍNEZ, A.
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
Three statistical models for estimation of the mean monthly wet bulb air temperature (Tw) in Mexico are presented. They are multi-linear functions of climatic parameters such as temperature, precipitation and cloudiness. These variables are routinely observed in about 1,500 climatological stations in Mexico. The three propossed models give a fairy good estimate of Tw.
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Año:
2009
ISSN:
2395-8812, 0187-6236
KONDRATYEV, KIRILL YA.
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
Based on discussions at a Session of the Intergovernmental Committee on Climate Change Working Group 1 held during the period February 26 - March 2, 1990 in Great Britain, and in the context of the WG-1 Report, a review has been made of the state-of-the-art of studies on global climate change. A consensus has been reached on one of the most important conclusions that the causes of the climate warming observed during the last century remain still unclear. This determines the top urgency of studies and quantitative assessments of the internally forced variability of the climate system, without which the "filtering-out" of anthropogenic impacts on climate cannot be reliable. Such insufficiently studied factors of climate formation as ocean-atmosphere and cloud-radiation interactions are the most substantial aspects of the internal variability. The related unsolved problems have been discussed.
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Año:
2009
ISSN:
2395-8812, 0187-6236
TEJEDA MARTÍNEZ, ADALBERTO
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
An exponential model for the simulation of the monthly mean hourly shape of the air temperature curve is presented. Its accuracy was shown to be greater than the model of De Wit et at. (1978), which was shown to be one of the best methods according to a revision made by Reicosky et al. (1989).
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Año:
2009
ISSN:
2395-8812, 0187-6236
CRESS, ALEXANDER; SCHONWIESE, CHRISTIAN D.
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
In order to investigate the volcanic forcing of air temperature on a global scale five different volcanic activity parameter time series are used, two of them representing new modifications of earlier assessments. These parameter time series are compared with each other and with the observed tropospheric (1851-1984) and stratospheric (1964-1984) temperature variations whereby in case of the tropospheric temperature (near suface) 108 regional 'boxes' of seasonal data time series are available. In addition to a correlation analysis, including techniques moving in time, a multiple regression model is used which includes also solar, ENSO and anthropogenic COa forcing. From this model the seasonal and regional maximum air temperature signals are derived which may be due to volcanic forcing. These signals as well as the signal-to-noise ratios are presented in their hemispheric and zonal mean averages and in regional mapping all over the world.
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Año:
2009
ISSN:
2395-8812, 0187-6236
SALINAS ZAVALA, C. A.; LLUCH COTA, D. B.; HERNÁNDEZ VÁZQUEZ, S.; LLUCH BELDA, D.
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
During 1990, rainfall over baja california sur, mexico, reached very high values, accounting for the third highest record since 1950. the characterization of the seasonal precipitation patterns on that year was intended, by the anlysis of some rainfall temporal indicators: relative contribution of the summer and winter precipitation, interannual variation among both coasts and tropical hurricanes occurring over the area; as well as some spatial ones; like the modification of the average previously defined precipitation spatial distribution (regions) over the state. resuts are compared with those registered during 1983, a year with high precipitations derived from by a particulrly intense enso event. the comparative analysis of the selected indicators shows that the conditions originating high rainfall values during 1990 were quite different than the conditions on 1983.
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Año:
2009
ISSN:
2395-8812, 0187-6236
MIRANDA, JAVIER; MORALES, J. R.; CAHILL, THOMAS A.; ALDAPE, F.; FLORES M., J.
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
Samples of airborne particulate matter with sizes between 0 and 15 µm in Mexico City were analyzed in order to evaluate its elemental composition. Samples were collected during one week in August 1990, using a Stacking Filter Unit (SFU), resulting in the separation between particles having sizes 2.5 to 15 µm (coarse), and smaller than 2.5 µm (fine). The collection period was from 6:00 to 12:00 hrs. Analyses with proton Induced X-ray Emission (PIXE) allowed the quantification of elements with atomic number greater than 10; Proton Elastic Scattering Analysis (PESA) gave information on hydrogen contents; and elemental carbon (soot) was measured by means of the Laser Integrating Plate Method (LIPM). Also, the gravimetric mass of the deposited matter was measured. The results permit then the possible identification of sources of the measured elements, with the help of Cluster Analysis. Moreover, the comparison of the gravimetric mass with the mass reconstructed from the elemental analysis supports the values obtained in the latter.
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Año:
2009
ISSN:
2395-8812, 0187-6236
JAUREGUI, ERNESTO
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México
Resumen
It has been claimed that air temperature (averaged over all latitudes) has increased by about 0.5ºC during the last 100 years. Since models are not able to simulate regional variations, it is of interest to explore temperature trends, especially in tropical areas where the climate change signal is likely to be smaller than at higher latitudes and therefore, more difficult to be distinguished from natural variability. Using mean annual minimum temperatures, an attempt is made to examine climatic change in a tropical region over the past half century. The following are the main findings from this analysis. Urban warming is evident in stations located in tropical cities with rapidly growing populations like Leon and Mexico City. Temperature records from smaller cities (less than 50,000 inh.) tend to duplicate the global temperature changes (warming before the 1940's and cooling in the 1960-1970's). For rural stations, however, no appreciable warming trend is evident in the 1980's.
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