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

Two cases of low-latitude snow with lightning are studied to determine their characteristics. Both cases had synoptic-scale origins, but also featured smaller-scale influences (e. g. orographic lift and elevated instability). The first event occurred in the Southern Hemisphere and was a late winter case that developed under the influence of underlying orography. Lightning was plentiful in that event (94 cloud-to-ground flashes in the region), but snow accumulations were not significant. Lightning flashes of negative polarity dominated this case, with a mean peak amplitude of -43.2 kA. The second event was a Northern Hemisphere case of elevated convection, with frontogenesis beneath an extended layer of potential instability. Appreciable lightning occurred with this event as well (706 cloud-to-ground flashes in the region), and snow accumulations were significant over a broad area. Lightning flashes of negative polarity dominated this case also, with a mean peak amplitude of -23.7 kA. Each of these events is worthy of further scrutiny, as studies of such storms do not appear often in the literature. Indeed, such warm, subtropical regions are often unprepared for the effects of just a little snow or ice accumulation. Future forecasters can anticipate better such anomalous events by looking for these broad features: 1) significant and well-defined synoptic-scale weather systems at low latitudes, 2) a strong baroclinic zone with a well-defined (≥60 ms-1) jet structure aloft, 3) cold air of appreciable depth and areal extent drawn much closer to the equator than is typical, and 4) a moist neutral to conditionally unstable layer above the frontal zone.

The water resource supply-demand relationship in the Sinú-Caribe Basin, Colombia, was analyzed based on current values and values projected for 2015 and 2025 by the Instituto de Hidrología, Meteorología y de Estudios Ambientales de Colombia ). The projections included estimated changes in the relationship based on general circulation climate change models under A2 greenhouse gas emission scenarios. The WEAP (Water Evaluation and Planning) System was applied to analyze and simulate different water systems and to guide management policies in order to provide tools, criteria and decision-making elements for devising adaptive strategies under adverse conditions.

An automated weather station was installed in January 2004 for the first time at the Destacamento Las Grutas of Gendarmería Nacional, Province of Catamarca (26°52’35”S, 68°18’37”W, 4000 masl). From April to December, meteorological conditions on the mountain were observed in order to better understand the high-altitude subtropical meteorology. This article documents the design, installation, and operation of the weather station, and presents a discussion of the collected measurements. The analyzed variables were air temperature, maxima and minima temperatures, humidity, precipitation, wind, as well as the occurence of snow, registered by the staff at Gendarmería. Large daily variability was recorded in most variables, which is not unexpected given the geographical location. Daily fields of the NCEP /NCAR Reanalysis relate the dates of large variability to cold surges affecting the region. Hourly wind direction measurements show preferential directions of SW-NW, with the largest variability occurring during November and December, indicating that moisture enters the region from different sources.  

In recent years, there has been an apparent alteration in tourists’ destination preferences. The reasons for this are, of course, very diverse. Due to discomforting environment of the coastal regions, people may prefer to spend their holidays in bioclimatologically more comfortable areas, such as mountain or plateau resorts. The aim of this study is to determine the effect of climate and weather on tourism and recreational activities via a questionnaire survey in the city of Erzurum, Turkey. It was found that although people who participated the survey live in a city, which is a well-known winter sports center and where extreme climatic features in winter are prevalent and have to experience, at least, an eight-month cold period (from late October to late May), they would still prefer summer season for recreation and tourism even if they were given full year recreation opportunities. This condition was thought to result from the lack of efficient winter recreation facilities and it was suggested that this kind of facilities should be constructed.

A spatial and temporal analysis of the air temperature in the boundary layer of Mexicali City, B.C. and rural surroundings was carried out. Several statistical tests were applied to a long-term database (1950-2000) to identify the temporal variability of the temperature; positive and statistically significant trends of the minimum temperature were observed, with a value of 0.66ºC/decade in the urban area, while in rural stations, smaller values were observed. Statistically significant results, but with a negative trend, were also observed with respect to the maximum temperature. When the spatial analysis was carried out, with a data base from a recent period (2000-2005), a nocturnal warm air mass in the urban atmosphere was present, and it was found that the maximum difference between the city and its surroundings occurs in winter with a value of 5.7ºC. These results suggest that urbanization, as well as in many other cities around the world, importantly affect the local climate and corroborate that in this city, an urban heat island has developed.

The Paraná river is the most important component of the La Plata basin, sustaining regional economies in three countries. In the last decades, significant regional changes such as deforestation and crop substitution have been taken place in the Paraná basin. This fact could have modified the basin response in terms of the Paraná streamflow. The main objective of this paper is to analyze the structure of the evapotranspiration (ET(t)) time series of the upper Paraná basin. We analyzed the relationship between the variables in the water balance equation, then we applied a singular spectral analysis (SSA) to learn more about the temporal structure of the ET(t) time series. The correlation study shows that ET(t) is correlated with precipitations in the northern sub-basins but it is not correlated at all in the southern basin. The time structure of ET(t)1, ET(t)3 and ET(t)4 exhibit low-frequency signals while the ENSO-range signals are statistically significant in ET(t)1 and ET(t)4 although it also appears in ET(t)2 and ET(t)3 as a weak signals. Looking at the whole basin, ET(t) would be affected either by changes in the basin physical properties or by the ENSO-range signals present in precipitation..

Measuring radar reflectivity as 10 log10 Z is inhomogeneous, since the argument of the logarithm is not dimensionless. Consequently, measurements in dBZ depend on the units used to measure Z. This study, in contrast, suggests an expression of the type 10 log10 (Z/Z0). An adequate selection of the constant Z0 (10-18 m3) will produce a redefinition that will not affect the measurements that have already been carried out and published up to now, since the result in dBZ will remain unchanged. A physical meaning has been searched for Z0 in relation with parameters typical for rain. It could be considered as an indicator of the minimum daily precipitation, but this cannot be extrapolated to all types of precipitation. However, it may be affirmed that for a specific distribution of hydrometeor sizes, Z0 provides a physical reference in terms of the number and volume of raindrops.

Individual tropospheric particles (0.03 to several um in diameter) were sampled using wire impactors on a DC-8 64 aircraft along and within Pacific Rim, from 125ºE to 120ºW and 70ºS to 70ºN, during the November 1989 and May 1990 Global Backscattering Experiment (GLOBE) deployments of NASA. A simple radiative balance model was used to determine the first order radiative effect of this aerosol layer at the surface. The results indicate that: (i) The background (optical thickness of ≈0.005) tropospheric aerosols between 2.4 - 12.2 km exert a warming tendency on surfaces with albedos > ≈0.02 in both the visible and infrared, (ii) There is an apparent increase in the coarse mode sulfur containing aerosol abundance compared to ≈15 years ago, suggesting that the background aerosol layer exerted a stronger tendency of planetary warming ≈15 years ago.

A multi-level, photochemical box model has been developed for the Mexico City metropolitan area (MCMA). A combination of in situ measurements and emission inventory estimates was used to obtain estimates of hydrocarbon speciation and emissions as well as NOx emissions. Preliminary results indicate that certain emissions estimates of NOx may be too high by a factor of two. This could cause the calculated, ozone isopleths to indicate that atmospheric O3 production in the MCMA could be hydrocarbon-limited. Hydrocarbon and/or NOx control strategies should not be implemented before a reliable emissions inventory is available.

In this study the surface layer fluxes for both the sensible heat and momentum have been estimated at a tropical location; Osu, Nigeria (7º26' N, 4º35' E), using profile measurements of mean wind and temperature realized within the pre-monsoon season (January - March). Due to the weak surface winds that commonly exist in the area (for the study period, U was 1.24 m.s-1) and strong insolation, the daytime SL was frequently found to be within the free convection regime. Typically in the daytime, the sensible heat flux H~200 W.m-2 and the friction velocity u* ~ 0.2 m.s-1. At nighttimes, the ground-based temperature inversion was very pronounced (>0.33ºC.m-1) and it is such that the intensity of the turbulence in the nocturnal SL was weaker, shallower, sporadic and unsustained (H~ -5.0 W.m-2; * < 0.2 m.s-1). The frequency distribution of these derived fluxes (and the mean variables) for the observation period is also discussed.