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

In this study, trends of the precipitation day classes in the warm period (May-September) were investigated for Ankara. Data collected by Ankara Meteorology Station (AMS) which has urban characters, and Esenboga Meteorology Station (EMS) which has rural characters, were statistically analyzed to understand the trends of the precipitation day classes. At both, the urban and rural stations, an increase was observed in the number of precipitation days and light precipitation days within years. However, the number of heavy precipitation days increased at the station with urban character (AMS), while it decreased at the station with rural character (EMS). A 50% increase was observed in the number of heavy precipitation days at the urban station (AMS) in comparison with that of the rural station (EMS). The increasing trend in the precipitation and light precipitation days at both stations may be related to the changes in climate. However, the increase in the number of heavy precipitation days only at the station with urban character (AMS) may be due to urbanization.

A weekly cycle has been detected in the surface temperature field of the NCAR-NCEP reanalysis for the North Atlantic area. This cycle consists of a minimum in the weekend for most of the studied area and a minimum in the mid-week for areas with important snow or ice cover.

On the average, during boreal winter (December through February), the occurrence of El Niño/Southern Oscillation (ENSO) results in enhanced or diminished precipitation in various regions of the Americas. Anomalous convective activity in the central-eastern Pacific forces quasi-stationary Rossby waves that follow paths to the Northern and Southern hemispheres. The so-called Pacific-North American (PNA) pattern results in ascending motion and enhanced precipitation over California and the Gulf of Mexico. The PNA also affects the Caribbean Sea by inhibiting winter tropical convection due to subsidence. In the Southern Hemisphere (SH), a weak quasi-stationary wave train is observed over southeast South America that results in enhanced ascending motion and precipitation. Over the equatorial region, the descending branch of a stationary Kelvin wave inhibits convective activity over northeastern Brazil and other parts of northern South America. However, there are well known differences in the El Niño signal from one event to another in what is known as inter-ENSO variability. Through quasi-geostrophic analyses, the anomalous vertical motions associated with the quasi-stationary Rossby waves may be separated from those associated with the stationary equatorial Kelvin wave. Ray tracing analyses show that quasi-stationary Rossby waves with wavenumbers 3, 4 and 5 explain part of the spatial structure of the circulation anomalies over the subtropical Americas related to the upward and downward vertical motions. The phase and amplitude of these waves depend on the structure of the mean zonal flow and the location of the anomalous convective forcing, as concluded from sensitivity experiments with a baroclinic model. An error in the simulated intensity of the mean zonal flow may result in phase shifts of the vertical motions and consequently, on errors in the simulated precipitation anomalies over the subtropical Americas. Some General Circulation Models, such as the NCAR Community Climate Model (CCM3) have this problem. Even more, a systematic bias is found in the CCM3, with weaker (stronger) than observed anomalies in extratropical (tropical) vertical motions, and consequently, in weaker (stronger) than observed precipitation anomalies. The implication of these analyses for seasonal climate predictions at a regional level in the subtropical Americas is discussed.  

We examined the possible relationships between pollutant concentrations and mortality at seven different locations of Castilla-León, Spain, and the relationships between such concentration levels and emergency admissions (morbidity) at four hospitals in the region, taking into account the possible masking effect of other atmospheric variables. The study was based on daily mortality and morbidity data from 1995 to 1997 (ICD-9 codes: 390-459 cardiovascular; 460-519 respiratory; 520-579 digestive causes); moreover, data for meteorological variables (air temperature, relative humidity, solar radiation, atmospheric pressure and wind velocity) and air pollution data (SO2, O3, NO, NO2 and CO) were used. A minimum set of weather and pollutant predictors was selected using forward inclusion stepwise linear regression methods and these were used to produce a multivariate model of the different causes of mortality and morbidity. For the whole period, the mortality attributable to cardiovascular causes had an incidence higher than the mortality due to respiratory and digestive causes. The frequency distributions corresponding to the different diseases as classified by ages revealed that the population older than 69 is the most affected, the proportion of cardiovascular diseaserelated deaths in this age sector being 7-fold higher than for the rest of the groups. Mortality and morbidity due to respiratory and cardiovascular-related diseases showed a high correlation coefficient with temperature, solar radiation and ozone, and in general significant correlations were also seen with SO2.

A model for the mixed layer of the Gulf of México has been used to determine the effect that an idealized cyclonic vortex has in the sea surface temperature. The model consists of the equations of conservation of thermal energy and this of balance between mechanical energy and thermal energy, last based on the Kraus- Turner theory; both equations are vertically integrated in the mixed layer. As atmospheric forcing, we prescribe the surface wind associated with an axially-symmetric cyclonic vortex characterized by two parameters: the maximum tangential velocity and the radius at which that velocity is reached. The values of these two parameters, which depend on the position of the vortex, correspond to two cases: hurricane Hilda, which crossed the central part of the Gulf of México between September 29 and October 3, 1964 and hurricane Gilbert whose trajectory between 11 and 17 September, 1988 crossed the Caribbean Sea, the Yucatán Peninsula and the southwest Gulf of México. The results show that a cyclonic vortex with such characteristics, produce during its passage by the sea vertical turbulent water transport through the thermocline (entrainment) that is able to cool down the mixed layer in several degrees and increases the thermocline depth in several meters, in agreement with the observations.  

Urbanization has been the dominant demographic trend during the second half of the 20th century in México. In 2000 there were 69 cities with more than 100,000 inhabitants of which 9 of them exceeded one million population, totalizing 53.4 million. Using time series of mean monthly temperature for about a dozen available stations, this paper sets out to examine temperature changes occurring during the late 20th century. Since it is well established that urban warming is mainly a nocturnal phenomenon minimum temperature series were selected after a test for homogeneity. Trend analysis was applied to the minimum temperature series and a linear regression coefficient was obtained. Tests of significance were performed. Most of the positive trends proved to be significant (>90%). Although temperature trend variability amongst the individual ities was large (from 0.02ºC/decade to 0.74 ºC/decade) average temperature increase in large (≥106 inhabitants) cities was (0.57 ºC/decade) considerably higher than that orresponding to medium size urban centers where on the average temperature increase was 0.37 ºC/decade. These temperature increases express not only the urbanization effect but also that due to global climate change (of the order of 0.07 ºC/decade) and natural variability. In concluding it may be said that increasing urbanization in México has originated a positive trend in urban temperatures which has implications for human comfort and health.

An objective analysis of daily rainfall over Maharashtra (India) by distance weighting function on a mesoscale grid is described. The Barnes scheme is applied to interpolate irregularly distributed daily rainfall data on to a regular grid. The spatial resolution of the interpolated arrays is 0.25 degrees of latitude by 0.25 degrees of longitude. Some objectively determined constraints are employed in this study: (i) weights are determined as a function of data spacing, (ii) in order to achieve convergence of the analyzed values, two passes through the data are considered, (iii) grid spacing is objectively determined from the data spacing. The case of a typical westward moving monsoon depression during the 1994 monsoon season is chosen for this study. Objective analyses of six days (16 to 21 August 1994) have been carried out using variable length scale two pass (V2P) and fixed length scale two pass (F2P) Barnes scheme. A length scale of 80 km for the outer pass and 40 km for the inner pass are considered. Analyses show moderate improvement of V2P scheme over F2P scheme. The bias of the analysis based on V2P is 2% lower than that of analysis based on F2P.  

Three minimum extreme temperature series from meteorological stations located in or near the Mexican Pacific coast, Acapulco, Comitán and Manzanillo, are spectrally analyzed. The series cover a period from 1941 to 1981. The spectral analysis indicates that a significant quasiquinquenial periodicity (~5 yrs) is present in Comitán and Manzanillo, even more, Acapulco also shows a frequency ~5yr if the uncertainties are taken into account. This spectral peak can be considered either as related to solar activity or to strong El Niño events. The remaining periodicities can be associated to meteorological phenomena like El Niño and the quasi-biennial oscillation or to some solar activity phenomena. Furthermore, the behavior deduced from a coherence spectra analysis between the temperature and the Southern Oscillation Index, considered as a proxy of El Niño, and sunspot number, considered as a proxy of solar activity, indicates that the stations closer to the ocean might be more influenced by El Niño than by solar activity, while the station inland has both influences.

Recently developed theory of Lithosphere-Atmosphere-Ionosphere (LAI) coupling pays attention to the processes taking place within the near ground layer of atmosphere. Air ionization produced by radon emanating from the earth’s crust launches the chain of physico-chemical processes which change significantly the composition of air molecules, as well as air temperature and humidity. All these changes, as it was detected earlier, take place one-two weeks before strong earthquakes occur within the area of earthquake preparation. The present paper is an attempt to track these changes using meteorological data collected at meteorological stations close to the epicenters (less than 200 km) of strong earthquakes in México. The atmospheric anomalies were detected both on long term intervals (several tens of years) and within one-two weeks before the earthquakes occur. The long term variations reveal the anomaly for the year of earthquake, while the shortterm anomalies demonstrate the changing dynamics of air temperature and humidity before the earthquake.

Ionospheric anomalies related to the seismic events have been analyzed in the present paper. The ionospheric ion temperature data recorded by RPA payload aboard the Indian SROSS-C2 satellite are used for the period from January 1995 to December 1996. Earthquake events recorded in the region of interest by USGS were used to define the ionospheric ion temperature anomalies associated with the earthquake preparation, occurrence and relaxation. Ionospheric ion temperature data were analyzed in such a way that the anomalies due to other phenomena will not be masked over the temperature anomalies due to earthquakes. Ion temperature enhancements in the ionosphere were observed during earthquake events and few pre-post days to the events. The seismogenic vertical electric field propagation up to ionospheric height induces the Joule heating that may cause the ion temperature enhancement.