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

Heat fluxes between the atmosphere and the sea surface in the Gulf of Mexico are computed using the GOADS climatology, bulk formulae, radiation estimations from satellite, and a numerical model. 9 W m-2 is the estimated mean surface heat flux into the ocean, this is higher than previous studies due to different bulk formulae and data sources. The annual cycle has an amplitude of 168 W m-2. The contribution of each term in the heat equation is computed, analyzed and compared to previous studies. A numerical model with thermodynamics is used to study the relative importance of heat advection and entrainment on the sea surface temperature. The results indicate that the entrainment is important in the winter cooling of surface waters. When entrainment, which depends on the buoyancy loss and the wind induced turbulent kinetic energy, is not included, temperatures in winter stay higher than observations, with a root mean square (RMS) difference from observations of l.5ºC. Including entrainment and detrainment the RMS decreases to 1.0 ºC.

Series of ground-based measurements of cloud condensation nuclei (CCN) concentrations were performed at one-hour intervals near downtown Mexico City during nineteen days in the summer of-1985. The samplings were made with a cylindrical, thermal diffusion chamber operating at a fixed supersaturation of 0.75% and located 2 m above ground level. These data were analyzed in view of concurrent contaminant levels (NO, NO2, and SO2), aerosol particle concentrations and meteorological conditions, using information gathered by diverse agencies. The results indicate that the anthropogenic sources, along with the local meteorological conditions, determine the daily patterns of CCN concentrations in Mexico City.

The conditional instability of the second kind (CISK) is investigated. A quasi-geostrophic model with a variable static stability in the vertical direction is used to solve the CISK problem exactly. Due to the nature of the solution it cannot be calculated with any accuracy for small wavelenghts. Using vertical structure functions no numerical problems appear except for very small wavelenghts. The approximate solutions are in excellent agreement with the exact solution, when both of them can be evaluated with good accuracy. The frequency may be obtained by summing a series without solving the complete problem. The quasi-geostrophic case is generalized to the case of the primitive equations with a few vertical components. The existence of the gravity-inertia modes has an influence on the stability of the quasi-geostrophic mode. The long waves become more stable, but for short waves the difference between the two modes become very small. and in the limit where the wavelength goes to zero both of them will approach the so-called 'free-ride' solution. Large deviations from the quasi-geostrophic solution, as measured for example by the ratio of divergence to vorticity, are found for the short waves. A final result is that in using the primitive equations it is important to express the frictional vertical velocity in terms of the streamfunction, but not in terms of the geopotential. The latter procedure will lead to spurious modes due to an inconsistent use of the quasi-geostrophic equations. These spurious models have an e-doubling time which is a small fraction of a day.

A discrete-ordinate radiative transfer model is employed to develop a regional clear sky ultraviolet (UV) diagnosis system. The clear sky UV radiation, weighted by the spectral sensitivity of human skin is calculated using the Total Ozone Mapping Spectrometer (TOMS) data sets. Examples of the geographical clear sky UV Index distributions are presented and the model results are compared with surface UV measurements from the University of Colima for 1999.

The ground level concentration of an air pollutant is obtained using the Gaussian plume model. However, the effective height H of the pollutant has been considered as a function of the ground level coordinates x and y. Extreme radius of the stack is developed. The constancy of H has been studied as a special case for the problem. Interesting arguments about both maximum and worst concentrations have been derived.  

We have examined the possibility of symmetric instability using a set of zonally symmetric linear perturbation equations in the near equatorial monsoon region incorporating moist convection. In the dry model as well as moist model both unstable and neutral modes were obtained. The unstable modes have period of around 1 to 2 days and with doubling times of around 1 to 2 days. The amplitude structure of such unstable modes are mainly confined to the equatorial regions. Thus we have shown that zonal flows in the monsoon region exhibit symmetric instability.

Meteorological measurements were made from July through November 1990, at a field site 35 km north of the center of Lima, Peru, during a study designed to assess the quantity of fog water that could be collected The site was at an altitude of 430 m, on the summit of a low, flat topped, mountain 3.5 km from the coast The mean monthly wind speed at the site varied from 4.1 m s-1 in July to 5.4 m s-1 in October. The highest hourly and peak instantaneous wind speeds were 15.2 m s-1 and 16.6 m s-1, respectively and they occurred in October. The monthly average wind directions was almost constant at 197ºT. The mean monthly temperature increased from 13.1ºC in july to 15.5ºC in November and, when compared to the climatological values from the Lima airport (altitude 11 m), implied a lapse rate of 0.5ºC/100 m in the lower 400 m of the atmosphere. The mean relative humidity was near saturation from July through October and only dropped slightly in November with the coming of drier conditions in late spring. Measured precipitation was a minimal 10.5 mm yet this represented an increase over the climatological value of 5.9 mm for the same months at the Lima airport. These data provide the first comprehensive description of the meteorological conditions on a loma (hill with seasonal vegetation) on the coast of Peru. They further our understanding of how atmospheric water is made available to the plants and will be of great assistance in the designing and locating of large fog collectors, which can produce water for the afforestation and reforestation of the desert hills.  

Numerical experiments are carried out with a two-dimensional zonally averaged climate model in order to investigate the transient response of the climate of the Northern Hemisphere to the solar and greenhouse-gas forcings at the secular time scale. The atmospheric component of the model is based on the two-level quasi-geostrophic potential vorticity system of equations. At the surface, the model has land-sea resolution and incorporates detailed snow and sea-ice mass budgets. The upper ocean is represented by an integral mixed-layer model in which meridional convergence of heat is parameterized by a diffusive law. For the simulation of the transient response of climate to continuously changing forcings, the uptake of heat perturbations by the deep ocean is approximated as vertical diffusion. A comparison between the computed and observed present climates shows that the model does reasonably well in simulating the seasonal cycle of various climatic variables. In the experiments performed here, we consider the solar irradiance changes, parameterized from recent satellite observations using the Wolf number as a basis, as well as the variations in solar radiation caused by the changes in the Earth's orbital elements. The former induces in our model a warming of about 0.005 K between the time intervals 1765-1875 and 1876-1990, while the latter is responsible for a cooling of about 0.003 K. These changes appear weak compared to the greenhouse-gas-induced warming simulated by the model.

Stability of the Rossby-Haurwitz wave of subspace H1 Hn and two types of Verkley's modons is analyzed within the vorticity equation of an ideal incompressible fluid on a rotating sphere. Here Hn is the eigen subspace of the Laplace operator on a sphere corresponding to the eigenvalue n(n + 1). It is shown that arbitrary perturbations of the Rossby-Haurwitz wave can be divided into three invariant sets one of which contains a stable invariant subset Hn. Three invariant sets of small perturbations of the stationary Verkley modon are also found. The- separation of perturbations have been performed with the help of a conservation law for perturbations. Formulas for determining the distance between any two solutions from the whole set of modons and Rossby-Haurwitz waves are derived through the energy and enstrophy of the corresponding perturbation. Necessary and sufficient conditions for the distance between these solutions to be constant are obtained. It is shown that any super-rotation flow on a sphere (belonging to H1) is stable independently of choice of the rotation axis. Liapunov instability of any non-zonal Rossby-Haurwitz wave from H1 Hn where n ≥ 2 as well as of any dipole modon on a sphere is proved. It is shown that the Liapunov instability is caused by the algebraic growth of perturbations due to asynchronous oscillations of waves and has nothing in common with the orbital instability. It is proved that any monopole Verkley (1987) modon, as well as any Legendre polynomial, is linearly Liapunov stable with respect to invariant subsets of perturbations of sufficiently small scale.

This study discusses the climatological characteristics of sea/land breeze systems and their influence on meteorological parameters at Kalpakkam, Madras Atomic Power Project site on the east coast of India. Continuous data recorded at the meteorological laboratory at the site is used in the study. Wind speed and direction range, air temperature, relative and specific humidity are considered for the study. The change in the characteristics of the parameters was mainly governed by the onset time of sea/land flow. The change is more significant during the onset of sea breeze. Analysis of the data revealed that the change was due to advection and the regular diurnal variation of the parameters. Based on the variation in upper winds both the seasonal change in onset time for sea/land flows and its influence on meteorological parameters are discussed and explained qualitatively. The relative role of advection and diurnal variation of the parameters on the observed changes are also discussed.