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The main purpose of the present study, conducted in the Piedemonte Llanero of Colombia, was to identify the role of covariates that influence soil properties under different land uses by analyzing the dynamics of selected soil properties in natural and agricultural areas. Soil samples were collected from 90 different sites throughout the region, 45 from areas with agricultural activities and 45 natural areas or areas with low anthropic intervention. The studied soils were strongly acidic (pH < 5.5), had low organic matter contents (1.73% and 2.34% on average in agricultural soils and natural areas, respectively) and, in general, represented poor conditions for agricultural production. The use of multivariate analysis showed that altitude was an important influence on soil properties. Moreover, it was found that land use influenced soil properties, which may limit productive capacity. The results presented here help to clarify the relationships between soils, climate, and landforms in an equatorial climate. [ABSTRACT FROM AUTHOR]

The methodical principles of the analysis of biogenic silica accumulation in the pelagic zones of the Pacific and Indian oceans are considered. Two quantitative approaches of lithological analysis are compared: method of absolute mass by A.D. Arkhangel'skii and volumetric method by A.B. Ronov. It is established that the concept of 'two oceans' ('ice' and 'non-ice') may be applied to both the oceans. Differences in the evolution of the silica accumulation rate in the Pleistocene between high- and low-latitude oceans are revealed. [ABSTRACT FROM AUTHOR]

Abstract: We test the feasibility of two scenarios that may drive the broad, prograde, equatorial jets in the Jovian atmosphere within the shallow “weather layer”. The first idea attempts to explain the flat-headed jet as a consequence of a hydrodynamic instability along an equatorially trapped primarily jet. The strong primary jet is induced by a 300ms−1 Kelvin wave. The second idea is a bridging of a pair of off-equatorial jets due to horizontal eddy diffusion (the so-called Gierasch mechanism). The primary jets can be induced by a Hadley circulation, and might then be interconnected by subsequent hydrodynamic instabilities between them. We test the two scenarios using a general circulation model, but have so far been unable to obtain an equatorial jet that resembles observations. It appears, therefore, that the previously proposed model of combining Kelvin and Hadley forcing, is more plausible under the shallow hypothesis. [Copyright &y& Elsevier]

The structure of the copepod community from the San Lorenzo Channel,Gulf of California, is described for 1990 and the 1992- 93 ENSO. Themain difference between sampling periods was the decrease of the calanoid Nannocalanus minor. This ocean species, distributed mainly in the equatorial zone, was one of the dominant in the plankton of the channel from February to August 1990. During the 1992-93 ENSO it appeared to be partially displaced by another equatorial but smaller species, Clausocalanus arcuicornis, and the tropical coastal species, Undinula vulgaris. Among the carnivores, Euchaeta marina decreased during ENSO, while the incidence of Candacia truncata and Candacia catula was observed. The mesh size of the net used noticeably affected the community structure observed, due to the escape of organisms through thenet. With the net of 300 pm mesh size, 30% more species were collected than with the net of 500 pm, and the abundances of the smaller species presented high escape percentages with the latter. [ABSTRACT FROM AUTHOR]

L'auteur présente les résultats des mesures des intensités de pluie et des affaiblissements dus à la pluie effectuées au Congo à la fréquence de 7 GHz. Il propose une relation empirique permettant de calculer la distribution des intensités de pluie en zone équatoriale et tropicale qui est bien vérifiée par les données expérimentales, tant pour les faibles que pour les fortes intensités de pluie. Il utilise certaines des méthodes de prévision dont on dispose actuellement pour établir les statistiques des affaiblissements dus à la pluie, notamment celles de S. H. Lin, F. Fedi, R. Crane. Les affaiblissements calculés avec chacune de ces méthodes sont comparés aux valeurs expérimentales. Measurements of rainfall rates and of attenuations due to rain at 7 GHz have been carried out in Congo. An empirical relationship for the prediction of rainfall rates in equatorial and tropical climates has been derived, and reveals good agreement with experimental data. Some rain attenuation prediction models (S. H. Lin, F. Fedi, R. Crane) are checked with our experimental data. [ABSTRACT FROM AUTHOR]

Resumo La estabilidad atmosférica en la capa superficial, influye en muchos de los procesos dinámicos que se dan en la atmósfera, afectan los fenómenos de difusión y transporte de energía y materia, razón por lo que se ha estudiado ampliamente en latitudes medias; sin embargo, existen muy pocos trabajos en condiciones típicas del altiplano ecuatoriano (latitud cero y altura media respecto al nivel del mar de alrededor de 2500 m). En el presente trabajo se desarrolla un estudio de la variación de la estabilidad atmosférica en dichas condiciones, usado datos de la estación meteorológica de la Universidad Nacional de Chimborazo del año 2015. Los resultados obtenidos en este estudio muestran un predominio del estado muy estable durante la noche y entre muy inestable e inestable durante el día según la clasificación de Pasquill, con un comportamiento medio mensual regular a lo largo del año.