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

A mean monthly precipitation parameterization is given. It is developed by a multiple linear regression equation in terms of the temperature and the horizontal wind. Using a period of eleven years, from January 1982 to December 1992, for the anomalies of the mean monthly precipitation, temperature, zonal and meridional wind, and vorticity of the wind as variable data, we have obtained a skill above 80 in the estimation of the mean monthly precipitation anomalies in the Northern Hemisphere. The parameterization may be used to predict monthly precipitation anomalies with the Adem's Thermodynamic Model, or with any others energy balance or general circulation models, as well as to compute monthly precipitation anomalies from observed anomalies of temperature and horizontal wind data.

The stability of atmospheric waves with low wave numbers is investigated using a quasi-geostrophic model of the second kind. Such a model is based on the thermodynamic equation, the continuity equation and a rigorous use of the geostrophic relations. The boundary condition at the surface of the Earth is formulated in two ways. The effects of a boundary condition at 1000 hpa, where the vertical p-velocity is zero, is compared with the effects of a second condition, where w is zero. The two boundary conditions are used to determine the stability of the low wave number waves. The second condition introduces waves with large positive and negative phase velocities, especially in the low latitudes, but has also an influence on the stability of these waves. The main result of the comparative investigation is that the more correct boundary condition in general will produce stronger instabilities than the simpler boundary condition. The e-folding times obtained with the more general model is in closer agreement with the results obtained by observational studies.

We have established a relationship between net longwave radiation and planetary albedo at the surface and at the top of the atmosphere. It was found that there is an inverse relationship between the longwave radiation and the planetary albedo at both the surface and the top of the atmosphere. Latitudinal changes were also found to be a significant factor in addition to the seasonal one in the behavior of this relationship. This type of relationship can be helpful in understanding the climate cycle and explain many radiation budget problems.

The barotropic and the mixed barotropic-baroclinic stability problems are treated using a series expansion in trigonometric functions of the mean zonal velocity and the perturbation stream function. A two-level quasi-nondivergent model is used to handle the mixed stability problem, containing both horizontal and vertical wind shears in the basic state. In the present investigation the number of components in the series expansion is limited to four, because the most interesting meridional wind profiles may be simulated within this restriction. The models are formulated on the beta-plane.

In this work, several results are presented on the variability of monthly water inflow volumes (MIV) for the dams located on the rivers of the Gulf of California continental watershed. Monthly series of the Pacific Decadal Oscillation index PDO (1900 to 1999), rainfall (1921 to 1999), and MIV (1939 to 1999) were used for the analyses. Applying the Varimax Rotated Empirical Orthogonal Function analysis to MIV series, "Northern" and "Southern" regions were separated, being this result in agreement with the climatic characteristics of the study area. The rainfall-PDO relationship was found to be in-phase in winter for both regions during the entire analyzed period (1921-1999). In summer, the relationship was out-of-phase during 1956-1974 and in-phase in 1987-1991 for both regions. The results show a stable relationship in winter between the rainfall and the oceanic conditions, which agrees with the arid character of the study zone. In summer, the results imply a more remarkable influence of other than local factors of climate variability, like the mesoscale convective systems, the Mexican Monsoon and the Pacific tropical storms, the main sources of humidity in summer. The relationship between rainfall and PDO-index in winter suggests that during the next decade, in which the PDO seems to change to its cool phase, winters could continue to be dry and the inflow volumes for the dams could continue to be below normal.

In this paper the synoptic situation related to the intense rainfalls observed during summer 1997-1998 under strong El Niño conditions is studied. The mean synoptic situation of the summer 1997-1998 was characterized by a positive anomaly in the Pacific Ocean at 500 and 1000 hPa, approximately located at 55ºS,80ºW, northeast of that corresponding to El Niño event of 1982-1983. This phenomenon of blocking activity, along with a band of negative anomalies between 30 and 40ºS and 120 and 40ºW in 500 hPa and the intensification of the mass flux of air from the Amazonia to the northern limits of the Patagonia were the common characteristics of both cases. Then a comparison is performed between the rainfalls associated to El Niño events corresponding to the summer 1982-1983 and 1997-1998, in the south of South America. In both cases, intense rainfalls producing important flooding events within the Rio de la Plata basin have been recorded. During the first event, the maximum precipitation was observed in Paraguay and Misiones (Argentina), while a much larger area located to the south of the latter extending towards the center of Argentina was affected during the second event.

In recent years space instruments and remote sensing tools are allowing us to look at the Earth with new eyes; they have extended the scope of vision. India has the world's most gigantic monsoon system which is extremely important for the Indian agriculture. India gets most of its rain during four months (June to September) of the monsoon season. In July we get the highest number of tropical disturbances in the Indian oceanic region. During the month of July 1996, two low pressures and one depression formed over Indian region. The present study aims to derive the moisture profile for the period July 1996, by using remote sensing technique and their impact on the analysis-forecast system. The inclusion of satellite derived moisture in the numerical weather prediction (NWP) model results (i) the weakening monsoon flow pattern near Somalia region, (ii) the reduction of wind speeds in the south Bay of Bengal, (iii) the formation of a trough in the west coast of India, and (iv) the realistic rainfall prediction over the Orissa and Andhra Pradesh region, etc. All these effects are in contrast to the existing control and could help in better prediction of rainfall and flow pattern during the monsoon season.

The changes in the Hadley and Walker cells and their respective impacts on the South American rainfall during the ENSO episodes observed in the decade of 80, were investigated through cross-sections analyses of the atmospheric circulation in altitude, averaged in the zonal and meridional planes. Such large-scale cells almost inverted their climatological circulation pattern, during El Nino events (1982-83 and 1986-87). In these years, manifestation of the anomalous descending branch of the Hadley and Walker cells affects most of the north-northeast of South America, which inhibited the convective activity associated to ITCZ and caused drought conditions in the rainy seasons of the Guyana, Surinam, French Guiana, center-east of the Amazon and most of the Northeast Brazil. On the other hand, conditions of excess of precipitation observed in the south-southeast-of South America, were favored by the anomalous ascending branch of the Hadley cell. During La Nina events (1984-85 and 1988-89), it .was observed an intensification of the ascending and descending branches associated to the Walker and Hadley cells. The anomalous large-scale ascending movement associated to these cells, was extended to the Northeast of Brazil and equatorial South Atlantic, favoring ITCZ to become more active than the normal, which resulted in an above normal rainy season in these areas. An intense subsidence was noticed in the mid latitudes of South America, which inhibited the large-scale convection in the region, explaining the deficient rainy season observed in most of the south-southeast of South America.

The climate of a region is an environmental resource with important implications for things such as thermal comfort, health and productivity of the population. In this work the bioclimatic comfort was evaluated for seven seasonally warm/hot cities of Mexico by means of the following current indexes: Discomfort Index, Enthalpy Index and Heat Strain Index. Also, the periods during which it is necessary to use air conditioning in the studied cities were calculated from estimated global radiation and hourly data of temperature and relative humidity which made it possible to establish them with high precision. Finally, the useful of the Heat Strain Index is shown. It is a simple index needing available meteorological data to compare bioclimatic conditions of similar sites.

A description is made of ozone patterns as related to some meteorological variables (temperature, surface wind direction, speed, and global radiation). The observations are expressed in terms of eigenvectors and their associated coefficients in order to determine the gross features of the ozone city-wide patterns. By using concurrent 700 hPa prevailing upper winds and the observed converging surface winds induced by local and regional currents it was possible to provide a physical explanation for some characteristic ozone distributions observed in the MCMA. The present study attempts to provide additional basis to the knowledge of relationships between ozone distributions and meteorological parameters in the Mexico Basin.