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

Auroral observations of equatorward extent of the rayed auroral displays are researched. Ground-based observations at Belgrano Station (78.0º S; 38.8º W) during the southern winter months of 1981 are considered. Four hourly sequences of geomagnetic indices AE, AL, AU and PC, the interplanetary magnetic field (IMF) and relevant solar wind parameters are superposed for 18 substorms. The present work confirms (during the 240 minute intervals centered at the sudden equatorward shift event) the relationships existing between the southward interplanetary magnetic field component (Bz), and the auroral occurrence of substorms and the westward auroral electrojet intensity.

The thermo-oxy-haline structure down to 100 m depth was determined in September 1987 through eight selected stations obtained from a transect of 340 km long across offshore waters near Manzanillo, between 104 W and 108 W at 19 N The waters in the first 20 m were relatively warm, from 26.4 C to 33.1 C. The average at 5 m depth was 30 C. That means a positive surface anomaly of 1.5 C. Salinity was between 0.1-0.4 o/oo higher than normal at the surface and it showed to be increased in the whole water column. Oxygen was considered normal at the surface. From 20 m to 100 m depth it was found a subsurface warming. The largest temperature deviations from Eastropac 1967 is at 75 m depth (> 2σ). The 15 C thermocline was found depressed at depths as down to 100 m. At the same depths, and about 150 km from the coast, salinity attained its largest values, between 35.1 o/oo to 35.2 o/oo. Near the coast the oxygen minimum concentration was 0.7 ml/l whereas 200 km seaward it was 0.4 ml/l. The Oxygen Minimun Layer (1.07 ml/l) was found near the coast depressed to 100 m depth. These results indicate advection of subsurface warmer waters northwards, perhaps due to an strengthening or northward displacement of the Equatorial Countercurrent. The onset of ENSO 1986-87 episode was between October and November 1986 at Tumaco (1.8 N) and Acapuico (16 8 N) respectively. While at Ensenada (31.9 N) the largest anomalies of SST and sea level did not appear until December 1986 In spite that surface warming was observed in the Galapagos Islands in November 1986, however the onset of ENSO 1986.1987 at Chicama (7.9 S) on the South American coast occurred five months later, in April 1987. Positive anomalies of SST and sea level remained in December 1987 along the west coast of Central America and Mexico However there is a decaying trend toward normal.

An analytical theory of two-level, moist, quasi-geostrophic baroclinic waves with meridional variation, but without the fl-effect, is developed. The formulation is similar to that of Tang and Fichtl (1983) except that the meridional variation of the waves isallowed. The basic parameters are a rotational Froude number F = (where f is the Coriolis parameter, Sd the static stability in descending portion of the wave, p2 the pressure at the middle level, kd the zonal wave number in the descending portion of the wave, ℓ(=π/D) the meridional wave number and D the meridional extent of the wave) and a heating parameter e which is proportional to the midlevel vertical gradient of the mean flow saturation mixing ratio. For ε ≠ 0 the disturbances are characterized by an unequal zonal length of the ascending or wet portion of the wave (a) and zonal length of the descending or dry portion of the wave (b). The first mode has a small region of strong ascending motion and a large region of weak descending motion (a/b < 1) with the reverse for the second mode (a/b > 1). These features are similar to those obtained by Tang and Fichtl (1983). In the present paper a meridional-scale equation is derived, expressing three possibilities: (i) FORMULA = 0 (no meridional variation of baroclinic waves, discussed in Tang and Fichtl, 1983); (ii) ε = 0 (dry model, discussed in Phillips, 1954, with β-effect ignored, ℓ being arbitrary); and (iii) a biquadratic equation in ℓ/kd. This latter equation essentially contains the information of the influence of latent heat release on the meridional scale of baroclinic waves. The model of meridionally uniform baroclinic waves (ε = 0) and the dry model (e = 0) are singular in that the characteristics of these two models cannot be deduced by setting ℓ/kd → 0 or ε → 0 in this biquadratic equation. For ε < 0.464, the ratio of the meridional extent D of the zonal domain, a + b, is less than 0.7. For a given e and a given F, this ratio is larger for the first mode than for the second mode. The growth rate in the ascending region is equal to that in the descending region. The growth rate depends on both F and ℓ/kd. For a given F, the larger the heating parameter e, the larger the growth rate.  .

Measurements of CO2 concentrations in the atmosphere of Mexico City were carried out through the years 1981-1982, during daylight hours. The results indicate that 82 of the CO2 levels were above 330 ppmv, which is the reported approximate atmospheric background. During daylight hours CO2 concentrations show three maxima: the first between 9:30 and 10:30 h, the second between 12:00 h and 13:00 and the third between 15:00 and 16:00 h local time. The peaks coincide with the rush hours in the city. The annual curves of CO2 show a seasonal variation with low values during the winter and a maximum in spring, the lowest values corresponding to the middle of the rainy season. Since natural sources during the daylight hours are probably negligible, the applicability of CO2 data as an indicator of air pollution in Mexico seems to be feasible.

In order to study the temperature and precipitation variations for the state of Aguascalientes, Mexico (22º, 2' N Lat, 102ºW Long), seven meteorological stations data are analyzed. The recorded data are for periods between 1921 to 1985. The possible local effects associated to these variations are studied by the aridity index and productivity (biomass) behavior. The results show an average increase of temperature in the state of T = 0.4ºC. This increase coincides with the general global warming trend reported by Jones et al. (1986). We also found an increase in the aridity index and a reduction of the productivity (gr/m2 year) of the state.

The solitary disturbances and wave motions of various scales are the peculiarities which appear on the general east flow in the tropical atmosphere. Relatively simple systems of the hydrothermodynamic equations permit the modeling of these peculiarities A nonlinear system allows to find a solition's type solution in a limited area. Such solution is called "modon". A linear system contains almost all wave motions in the low latitudes including the equatorial belt. Three parts of the spectrum are revealed especially clear-the first part corresponds to the period interval of some dozen minutes, the second one to the order one to ten days, and the third part corresponds to the quasi-biennial oscillation of the zonal wind.

Based on 20 years of daily data the precipitation patterns of Baja California Sur, Mexico are studied as well as the precipitation during the passage of the cyclones which came within 250 km of its coast. the 30 cyclones here treated have a moderate average contribution (20%) to the annual precipitation and show a different precipitation pattern from the annual values. however the recharge to the acquifers may still benefit from the observed heavy localized rains during the passage of some cyclones or at times like in 1967 and 1977 when the cyclones contributed to about 45 and 69% of the annual precipitation.

The structure of baroclinic waves on a zonal current is investigated. Using a two level, quasi-nondivergent model it is possible to derive two nonlinear equations describing the changes in time of the ratio of the amplitudes and the phase angle difference between the vertically averaged wave and the thermal wave. All steady states and their linear stability properties are found. It turns out that one stable steady state describes a westward sloping wave increasing in amplitude with height This state corresponds to the asymptotic state of the amplifying baroclinc wave. Another steady state with the opposite slope is unstable Four additional steady states are found for sufficiently small windshears. They are stable, but of an oscillatory nature and are either vertical or sloping half a wave length.  

The photo-oxidation of n-butane and trans-but-2-ene is simulated under conditions of constant irradiation (normal incidence zero zenith angle) at sea level and at the altitude of Mexico City (2234 m). The object is to understand step by step the effect of changes in irradiation and atmospheric pressure on the production of ozone in a contaminated atmosphere, the individual and combined effects of irradiation and pressure were explored.

A one-dimensional stable nocturnal boundary layer model of two-layers is constructed, which includes various meteorological processes: turbulence, radiation, interaction boundary layer - soil and boundary layer - synoptic flux. The model predicts the thermodynamic profiles; and two heights. One is born the boundary layer, and the other from the turbulent surface sublayer. The boundary layer evolves as. a system in contraction at night and expansion during the day, influenced mainly by strong radiative cooling or heating and soil type. Predictions agree with the profiles obtained by other authors.