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

An objective analysis scheme to analyze daily maximum and minimum temperatures over Indian region has been developed. The daily data from 1970 to 1980 which are available with the India Meteorological Department have been used. The autocorrelation and structure functions of these two fields have been computed separately for every month of the year. Due to the strong anisotropy induced by the morphological characteristics of certain region, the observed autocorrelations have been modeled by a function which is not only a function of distance between two locations but also a function of their difference in elevation. The analysis scheme is optimum interpolation (using both types of correlation functions).  

In this study we investigate the time-scale at which NAO and ENSO are associated with the precipitation in Galicia (Northwestern of Spain), looking for possible climate predictors. The existence of preferred frequencies in all series was analyzed by using SSA (Singular Spectral Analysis), whereas the statistical significance of the results was checked by using the Monte-Carlo method. Results suggest that NAO and precipitation in Galicia could be related at a time scale of 8 years whereas the influence of ENSO is not significant.

The classic Stommel (1961) model of thermohaline circulation has predicted the existence of two modes of ocean motion for the pole-equator system. These are, one-cell thermal and one-cell saline modes. In contrast, the laboratory experiments conducted recently to duplicate this conceptual model have found three steady states in the control space of the model parameters: a two-layer thermal mode, a two-layer saline mode, and a three-layer hybrid state. A two-dimensional theoretical model is applied to investigate the multiple-cell formation. The lowest order solution is analysed using an expansion method and suggesting the aspect ratio as a small parameter. It is shown that asymmetry of vertical distribution between temperature and salinity is responsible for forming the multiple-cell thermohaline circulation.

Measurements of formaldehyde, acetaldehyde, acetone, propionaldehyde and butyraldehyde concentrations were made at five different forested regions in México. One set of two simultaneous samplings was performed at two sites located in the México State, one semi-rural area (Temascaltepec), and the other, a forested area (Rancho Viejo). A second set of two simultaneous samplings were made in southern Veracruz State, in one rural area (Monte Pío) and inside a tropical rainforest (at the Biology Station of the University of México). Finally, one sampling was performed in the Sierra of Puebla State (Cuetzalan). Propionaldehyde and butyraldehyde were not reported because their concentrations were always below or near the detection limit of the technique. The highest concentrations were found from 7:00 to 11:00 h and from 11:00 to 19:00 h in all the sampling sites. Arithmetic mean concentrations of acetone were the highest observed among the detected carbonyl compounds in almost all sites, ranging from 0.5 to 8.4 μg m-3. Arithmetic mean concentrations of formaldehyde and acetaldehyde ranged from 0.83 to 6 μg m-3 and 0.53 to 4.7 μg m-3, respectively. The Spearman’s correlations between formaldehyde and acetone, and between acetaldehyde and acetone were statistically significant at p < 0.05 in almost all sites. A significant correlation (p < 0.05) between formaldehyde and acetaldehyde was observed in México State at Rancho Viejo and Temascaltepec. The mean ratio HCHO/ CH3CHO of concentrations was 1.83 and 1.31 in the forested area of Rancho Viejo, first and second sampling periods, respectively; 1.71 and 1.62 in the semi-rural area of Temascaltepec, first and second sampling periods respectively; 1.70 in Cuetzalan; 2.90 in the rural area of Monte Pío; and 1.61 in the Biology Station tropical rainforest. These values show a greater influence of atmospheric pollutants transported from sites with anthropogenic activities, because HCHO/CH3CHO concentration ratios between 1 and 2 are typical values of urban air. During the onset of strong winds from the south (locally known as “surada”) a significant increase in carbonyl concentration was observed, in relation to the days before the “surada”, as a result of a possible transport of pollutants emitted by distant anthropogenic sources such as the highway near Catemaco town and industrial complexes near Coatzacoalcos city. The air mass back trajectories were calculated for Rancho Viejo, Temascaltepec and Cuetzalan, and average carbonyl concentrations in air were discussed according to the air mass origin.  

The behavior of temperatures in the region of Castilla-León in Spain was explored in a study of trend analyzes of the regional thermal anomalies in the zone. The work was developed in two steps: in the first, the working data series were refined, completed and homogenized. The variables addressed in these series were the maximum, minimum and mean temperatures corresponding to 38 weather observatories representative of the whole regional area and their length spanned the 1931-1996 period. Homogenization was carried out by applying the methodology established by Alexandersson and Moberg (1997). Once the homogeneous series had been constructed, in a second phase we analyzed their temporal behavior from regional anomaly series. To do so, the values of the anomalies were calculated at each of the selected stations −for the 1945-1996 period− from the mean monthly, seasonal and annual values of the 1961-1990 period. Then, following the methodology described by Jones et al. (1982) and Jones and Hulme (1996), the representative values for the whole region were determined. The results obtained for the whole period analyzed (1945-1996) indicated that, for a confidence interval of 95%, increasing trends are only seen for the maximum and mean winter values. Outside this threshold, the trend found was of the same sign in summer, whereas trends were decreasing for all the variables for their equinoctial seasons. By contrast, the behavior of temperatures in the 1972-1996 subperiod was striking; the annual maximum, minimum and mean temperatures displayed a certain increasing trend for that confidence interval. This was confirmed with the seasonal values, above all for spring and summer, and also (secondarily) those of winter and autumn. Thus, over the past 25 years analyzed there has been an increasing trend of about 0.05ºC/year in the values of the maximum, minimum and mean temperature anomalies, both annual and seasonal.

Using an integrated mixed layer model we carry out a simulation of the annual cycle of the sea surface temperature (SST) and of the mixed layer depth (MLD) in the Gulf of México. We also compute the annual cycle of the entrainment velocity in the deepest region of the Gulf of México. The model is based on the thermal energy equation and on an equation of mechanical and thermal energy balance based on the Kraus- Turner theory; both equations are coupled and are vertically integrated in the mixed layer. The model equations are solved in a uniform grid of 25 km in the Gulf of México, the northwestern region of the Caribbean Sea and the eastern coast of Florida. The surface ocean current velocity and the atmospheric variables are prescribed in the model using observed values. We show the importance of the Ekman pumping in the entrainment velocity. We found that the upwelling plays an important role in increasing the entrainment velocity, producing an important reduction in the SST and diminishing the depth of the mixed layer in the Campeche Bay. In the rest of the Gulf of México the downwelling tends to reduce the entrainment velocity, increasing the SST and the MLD. Comparison of the computed annual cycle of the SST and the MLD with the corresponding observations reported by Robinson (1973), shows a good agreement. In the deepest region of the Gulf of México, the photosynthetic pigment concentration data obtained from the Mexican Pacific CD-ROM of environmental analysis shows significative correlation with the computed annual cycle of the computed entrainment velocity only in January, April, May, June and September.

An annular denuder/filter-pack sampling technique has been employed to get an insight of the formaldehyde partitioning between gas phase and particles (PM2.5) in México City using short time sampling periods. Formaldehyde was trapped using DNPH derivatives and analyzed by HPLC/UV. One annular denuder was used to trap formaldehyde from the gas phase followed by a Teflon filter to trap PM2.5, and a second backup denuder was used to trap degassed formaldehyde from the filter. Just after finishing the sampling, filters were soaked in a DNPH solution to fix the PM2.5 formaldehyde, and the denuders where extracted with another DNPH solution. The sum of the concentrations in both phases ranged from 7.90 to 44.60 μg/m3 during the sampling periods from 8 a.m. to noon in several ocassions from 2000 to 2003. In average, the formaldehyde PM2.5/gas-phase ratio was about 0.15, one hundred times higher than previously observed. A large fraction of the formaldehyde in particles is easily lost by a combination of three processes: two of these, blow off from the trapped particles and displacement of the phase equilibrium, both well known and confirmed in other studies. A third process called extrussion of particles is described. Thus, PM2.5 may act as a temporal sink or a slow releasing source of formaldehyde in México City’s photochemical smog. This findings may have strong implications for air quality modeling.

Thirty years (1951-1980) of mean monthly thunderstorms days (TS) and rainfall (RF) amounts for 260 Indian observatories spread uniformly over the country were used to obtain their monthly, seasonal and zonal percentage of occurrence from all India totals. The study has revealed that there is a time lag of one month in the occurrence of peak activity of TS and RF. Seasonal analysis of these two parameters suggest that rainfall yield associated with postmonsoon season TS seems to be higher than the premonsoon season. Six zone analysis of TS and RF has suggested that there exists a wide range of variation in both parameters month after month in that zones, but the 30 year mean percentage of occurrence seems to be more or less equal in magnitude in each zone.

We study the accuracy of the finite differences discretization scheme for a 2-D simplified model of global tracer transport, in the case that the diffusion coefficients relating flux to the gradient of the mixing ratio have discontinuity jumps at the tropopause. We analyze the conventional box method for a typical downward flow with chemical reaction and for a typical upward flow, comparing the approximations of the solutions, for different discretization gridsizes. It turns out that the jumps may introduce remarkable errors in the discrete solutions, in the case of a typical downward flow; these errors propagate mainly into the troposphere. A noticeable improvement is achieved by reducing the gridsize. However, a typical upward flow is rather insensitive to the chosen gridsizes.

The goal of this contribution is to analyze the meteorological observations that the Spanish friar Antonio Llanos registered during the 1858-1865 period in the Philippines Isles. These records were published 140 years ago but have been ignored until now. The data published by Llanos are essentially information about precipitation. These data agree with the existence of an episode of El Niño during 1864 just as previous investigations based in proxy data have noted. Other early meteorological records of he Philippines Isles are presented, as well.