Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The climate affects the Earth at three levels: the relationships between the Sun-Earth energy interaction, the regional climate by the troposphere-Earth relationship (basins) and the local climate by the climatic gradients in endo and exorreic basins. The information on coastal lagoons provided by the last two is scarce and has only been used to define local descriptive frameworks for particular study areas. As a result of this, this paper aims to determine the qualitative and quantitative influence of regional climate on the three local climates defined in an exorreic basin in the northwestern Gulf of Mexico at the level of regional climate. The coastal lagoon of Tampamachoco is located in one of these local climates. The regional climate affects the local climate and defines the seasons in tropical latitudes (the Gulf of Mexico), in accordance with the origin and amount of the rain. The seasons are defined with respect to the rainfall regimes presented in Köppen's classification, later modified by Garcia (1964), and corroborated with the frequency and intensity of the prevailing winds from 1922 to 1994. These are: 1) the season of northers: from November to February with an average of 222 mm, 2) the dry season: in March and April with an average of 92 mm and 3) the rainy season: from May to October with an average of 1071 mm. Three local climates are defined in response to an orographical factor, as BS1, Aw1 and Aw2. Type Aw1 corresponds to 35% of the basin and is located over the whole coastal plain, type Aw2 makes up 55% over the leeward portion of the Sierra Madre Oriental and the Sierra de Tantima mountain ranges and type BS1 makes up 10% over the windward portion of the Sierra de Tantima. The spatial and temporal differences in the rainfall over the whole basin produce two waterways with multiple sources as a result of the regional climate over the local climate, that affect the shape and hydrological behaviour of the lagoon. The Tuxpam River originates in the most humid climatic area and is a permanent supply to the lagoon with changes in discharge related to the seasons (March 695 m3/s, July 965 m3/s and September 1825 m3/s). The Santiago River, of which the supply is registered only in the rainy season, has its origin in a dry climatic area.

Changes in the states of two groups of major earth climatic subsystems are investigated: (a) "thick" subsystems (atmosphere, and ocean), and (b), "thin" subsystems (vegetation, snow, and sea ice). These two groups are distinguished with respect to temporal variations of their spatial extent which is dynamic for the "thin" subsystems and stable for "thick" subsystems. Stochastic models governing monthly and longer-term anomalies of remotely sensed and in situ, globally averaged parameters of these layers (tropospheric temperature, sea surface temperature vegetation, snow and sea ice cover areas) are evaluated according to a new modification of the maximum entropy method with frequency truncation of normalized spectra. The analysis shows that global temporal variations of global thick subsystems are governed by the Bernoulli-Wiener type stochastic processes, while variabilities of the global "thin" subsystems are described by the first order Markov processes with intermediate values of coefficients. It is hypothesized that stochastic variations in global sea ice, snow, and vegetation covers depend on only a small number of independent regional variations and therefore still show the Markov characteristics of the latter. On the basis of the analysis of observational data and stochastic modeling, the authors propose a concept of mechanisms of climatic variations which takes into consideration different climatic subsystems as well as different temporal and spatial scales. The proposed hypothesis explains the stationarity of changes in the area of global "thin" covers, and the non-stationary, random walk (i.e. without deterministic trends) character of global temperature changes.

The impact of two radiation parameterization schemes (NASA/Goddard and GFDL) in NCMRWF T80 model on the simulation of June, 1995 is presented in this paper. Our main aim here is to understand the sensitivity of different radiation schemes on the simulation of Indian summer monsoon onset phase. At Earth's surface, the simulation using NASA/Goddard scheme produces more reasonable balance between incoming and outgoing fluxes (radiative and the turbulent heat fluxes) compared to GFDL scheme. The inclusion of cloud scattering and hence the treatment of direct and diffused radiation separately in NASA/Goddard radiation scheme resulted in changes in the net shortwave flux at surface and hence in the surface temperature. Results also indicate the high sensitivity of surface temperature in the monsoon onset simulation. Both models reasonably simulate the mean June 1995 flow patterns. Comparison between the two simulations shows that T80 model with NASA/Goddard has less forecast errors at 200 hPa, whereas in 850 hPa this simulation has slightly higher forecast errors east of 75ºE longitude over Indian latitudes.

Hemispheric, synoptic and regional-local scale metereological conditions associated with the occurrence in Chile of two debris flows with catastrophic consequences are described. in both events high intensities and large spacial variability were observed. in the antofagasta case, which occurred at dawn on June 18, 1991, the convective development of a frontal disturbance was produced by the release of potential instability. in the second debris flow, that affected especially the City of Santiago during the morning of may 3rd, 1993, the convection developed through the release of conditional instability. The regional-local elements that favored the release of instability in each case are described, including estimates of the return period of the most characteristic meteorological elements. In the hemispheric and regional scales it is shown that both episodes developed in the general context of anomalies associated with the El Niño-Southern Oscillation (ENSO) events. In the case of Antofagasta, the extraordinary extension ti the subtropics of the anomalous heating of the tropical troposphere, characteristic of the mature phase of ENSO events.

The results of mass concentration of atmospheric particles collected by low volume samplers in sixteen monitoring stations of the Environmental Radiological Monitoring Network from Laguna Verde Nucleoelectric Plant, from 1991 to 1993, are reported. The levels of the yearly average mass concentrations were in a range of 22.6 µg/m3 ± 5.0 µg/m3 to 107.8 µg /m3 ± 3.7 µg/m3. Spacial variability is explained through the location of the stations, anthropogenic and natural influences. There were no significant differences in the average concentration over time. Moreover, the preliminary results of the chemical composition obtained by X Ray Fluorescence analysis are presented.

Temperature trends in the three years following the volcanic eruptions of Agung, El Chichón and Pinatubo are studied, employing monthly mean temperature data from four meteorological stations of the Meteorological Poligon of Camaguey (PMC). A descendent tendency was found for monthly mean temperature following those eruptions In general the trends in the three years following the eruptions are different, at a significative level of 99.5% from the trends of the entire data periods, revealing the cooling effects of those eruptions. Also in the Agung and El Chichón case the trends were significatively different at a 90% level, from the null trends. Different cooling effects between Pinatubo eruption and Agung and El Chichon eruptions are explained by the particularities of the movement of the stratospheric aerosols plume of the first, occasioned by the different epochs of the year in wich Pinatubo erupted respect to Agung and El Chichón. The evaluation of the temperature anomalies registered in the PMC in the year following the eruptions show a most intense cooling than in the Northern Hemisphere as a whole, reinforcing the hypothesis of the particular acentuate response of the PMC and probably for an island as Cuba to the shadowing of solar radiation by stratospheric aerosols, as result of its particular thermal insulation occasioned by the notable difference between the thermal capacities of the land and sea.

A bidimensional numerical model is used to simulate and to establish the most important mechanism that controls Sebastian Vizcaino Bay B.C. barotropic circulation. The observed circulation patterns were reproduced by the model; in particular anticyclonic gyre located East Cedros Island is predicted. This gyre has been described by hydrographic observations and direct data as a bay semipermanent circulation characteritic. Our results indicate the the gyre is generated by local wind field spatial variations.

The investigation explores the possibility that the observed intermonthly variations in the atmosphere may be described by a nonlinear low-order model containing nine components. The model is formulated on a f-plane and contains only wave-wave interactions. It is based on the equivalent barotropic atmosphere formulated in such a way that it contains both heating and dissipations. The wave numbers vary from 1 to 3 in the zonal and the meridional direction. Most of the integrations of the model assume that the oscillations are a planetary phenomenon, and they have therefore been performed with a maximum wavelength of 28000 km. The results show that the observed periods (30-35, 45 and 70 days) may be reproduced by the model. Other periods are also found, but they are mainly of small amplitudes. The model permits a determination of the heating pattern necessary to produce the observed oscillations. It is required that the heating level is above the time-averaged heating in the atmosphere, and the heating is such that it displays a strong meridional heating gradient. The investigation is a continuation of an earlier attempt to model intermonthly oscillations using a very simple three-component model based on the first equation of motion with non-linear advection and momentum forcing and dissipation. The new model permits a more physical description of the phenomena.

A simple low-order nonlinear model with forcing and dissipation is used to demonstrate that inter-monthly oscillations may be caused by the nonlinear interaction. The length of the period depends on the intensity of the forcing. The model used for the integrations has three components. Another low-order model based on the barotropic vorticity equation with Newtonian forcing is used to show that similar oscillations appear also in this model. It is proposed that the models may describe the basic mechanism for the observed atmospheric intermonthly variations although the models are too simple to account for details in the spatial distributions of the variations.

A vertically integrated, non-linear numerical model in finite differences is used to analyze two forcing mechanisms of the mean barotropic circulation in the Gulf of California: topographic rectification due to tidal currents (M2) and wind stress. Under tidal forcing the nonlinearities of the momentum equations induce unorganized strong tidal induced residual currents (ue > 5 cm s-1) in the channels between the islands, and along-isobath anticyclonic circulation in the Northern Gulf, with speeds Ue < 2.5 cm s-1 over the edge of Delfín Basin. These numerical results are in agreement with analytical results, which indicate that the tidal-induced currents are mostly due to the advective terms, and that continuity and the Coriolis term (but regulated by bottom friction) are responsible for the along-isobath flow. The quadratic bottom friction plays a role in generating mean currents only in the very shallow area off the Colorado River Delta. The effect of wind stress was modeled by imposing upon the running M2 model a constant surface stress (r = 0.016 Pa), from the NW for winter conditions and from the SE for summer conditions. The wind-induced circulation was obtained by averaging over a tidal cycle and then subtracting the tidal residuals. The two wind directions produce almost identical circulation patterns, but with opposite directions. For the NW wind stress, the main features of the predicted circulation are: (a) In the Northern Gulf an anticyclonic circulation pattern, with the strongest currents (up to ~ 10 cm s-1) following the bathymetry of the rim of Delfín Basin, Wagner Basin and the mainland coast off Bahía Adair and Bahía San Jorge. There is also a southward flow along the peninsula coast, from the Colorado River to Bahía San Luis Gonzaga. (b) In the Southern Gulf, there is a strong flow (~ 10 to 15 cm s-1) to the SE over the continental shelf along the mainland coast. A somewhat less well-defined return flow (~ 5 cm s-1) from Santa Rosalía to Isla San Lorenzo complete an anticyclonic circulation in the area immediately to the SE of the islands. Some of the predicted features of the wind-driven flow in the Northern Gulf of California are in qualitative agreement with current meter observations, but the model underestimates them which may be attributable to baroclinity, not included in the model.