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

An operational version of the Navy Layered Ocean Model is used to study the generation of a coastally trapped wave forced by a strong and intermittent wind event at the Northern Bight of Panamá. This study identifies the winds at the Northern Bight of Panamá as a new source for the generation of coastally trapped waves along the west coast of the North American continent. The results indicate that after its generation, the wave propagated poleward increasing the sea level > 10 cm, producing surface currents > 50 cm/s, and traveling > 1200 km. The generation and existence of the coastally trapped wave and the model results are validated with sea surface height coastal tide gauge observations.

A realistic three-dimensional distribution of moisture in the initial condition is essential for successful numerical weather prediction. The moisture profile serves as direct input to any forecast model. Since the ocean surrounding the Indian sub-continent is one of the enormous data sparse regions in the tropics, the remotely sensed data is an important source of meteorological information, used at various operational numerical weather prediction centers for preparing initial conditions. The temperature and moisture sounding data from the Television and Infrared Observation Satellite (TIROS) and the Operational Vertical Center (TOVS) onboard the National Oceanographic Atmospheric Administration (NOAA) polar orbiting satellite is being routinely received at National Centre for Medium Range Weather Forecasting (NCMRWF) through the Global Telecommunication System (GTS). Moisture information is available at three broad layers. In the present study an attempt has been made to derive a humidity profile from the NOAA polar orbiting satellite by the variable scale height algorithm. These profiles derived at standard pressure levels are validated with coinciding radiosonde observations, other humidity estimations, and analysis. The validation indicates that the percentage of root mean square (r.m.s) error is less than 10. The impact of these moisture profiles is examined in the NCMRWF analysis and forecast system for the June 1997 period. A positive impact of this TOVS derived moisture in the forecast of onset of monsoon-97 is noticed. Some of the results during the monsoon lows and depression arc also presented for the same period. In particular the rainfall forecast for 20th June, 1997 has improved.

Satellite-based quantitative precipitation estimates (QPE) offer the potential for global, near real-time monitoring of precipitation. Provided their accuracy, in terms of frequency and intensity structures, can be verified, such products would prove to be highly valuable for constraining uncertainty in land data assimilation, hydrological simulation and short-term prediction applications. Two gauge-corrected and three uncorrected satellite-based QPE products are assessed over México against a new composite gauge dataset developed from data collected during the 2004 North American Monsoon season. Analysis of daily averaged rain rates, rain-rate conditional biases, and frequency maps each show a tendency for uncorrected satellite QPE products to overestimate the frequency of moderate to heavy precipitation events (>25 mm/d) with respect to gauge-only analyses. While all products reasonably captured the large-scale distribution of rainfall, some uncorrected products, particularly those emphasizing infra-red based retrieval of rain rates, possessed comparatively low pattern correlation scores with the gauge composite. Although gauge-corrected products tended to somewhat underestimate rainfall at heavy event thresholds, significant value, in terms of overall bias correction, appears to be added to gauge-corrected QPE products versus uncorrected products. This added value, however, highlights ongoing challenges with regards to collecting and integrating surface gauge data in an operational QPE framework.  

This study explores the interannual variability in Mexico's warm season rainfall. It is based on historical rainfall data (1927-1997) from a grid of 130 long-term stations. The grid provides reasonable spatial coverage over most of the country. Using Principal Components Analysis, this study delimits five relatively large sub-areas of the country. Within each of these regions, monthly station rainfall exhibits high levels of spatial coherence. The regional structures are distinct and physically plausible with respect to the climatology of Mexico. The regional time series are expressed as departures from normal. In most of these series the intraseasonal, that is, month to month, persistence is minimal; in fact, only a few of the series display significant tendencies toward nonrandom serial behavior. This study evaluates the teleconnectivity between the regional rainfall series and several different indices of large-scale ocean and atmosphere variability. These indices include an El Nine-Southern Oscillation index, indices that describe the strength and position of the subtropical anticyclone belt, as well as local SSTs in the Eastern Pacific and the Gulf of Mexico. All of the teleconnection analyses consider the quasi-decadal mode of variability that is commonly referred to as the Pacific Decadal Oscillation (PDO). The study results generally agree with the findings of other researchers to the extent that they indicate differential teleconnectivity as a function of PDO phase. However, unlike other studies, we see no compelling evidence for non-linear behavior in the teleconnections within PDO phase. Instead, the more prominent feature of the teleconnections is simply that they tend to be both more spatially extensive and stronger in the positive PDO phase.  

The sensitivity of a bidimensional cloud model with an upgraded turbulence parameterization is tested. This model denoted as University of Buenos Aires model (UBA) has the ability to simulate a credible convective scenario in a real data case characterized by observed strong outflows. The main improvements have been made over the turbulence parameterization for the mixed phase microphysics using a first order turbulence closure. Four experiments were performed to accomplish this objective. Results show that the new turbulence parameterization affects the simulation of convection. The emphasis is in the representation of one of the significant features of the convective event used in this sensitivity test. Maximum surface wind speed corresponding to the strongest downdraft is better approached by the representation of a variable Km. In order to find out whether the sensitivity of the, UBA model to the turbulence parameterization is a peculiar characteristic of this model, the Advanced Regional Prediction System (ARPS) was also implemented to check results from the UBA model. ARPS model also shows sensitivity to the turbulence parameterization with a stronger impact. Compared with all 2-D experiments, the inclusion of the third dimension enhances the vertical motions but reduces the divergent outflows at the surface. The UBA model performance proves to be higher than the ARPS 2-D version in terms of convective outflow strength near the surface in this simulated case, at Resistencia airport. This result is encouraging and justifies future validation of the UBA model in other downburst cases in order to asses its capability as a prognostic tool in airport forecast activities.

The relationship between geographical latitude and longitude and cloud-to-ground lightning activity in the Iberian Peninsula is analyzed using data from 1992 until 1994. Three flash characteristics are considered: flash density, polarity and intensity. There is a strong dependence between flash density and both latitude and longitude, which may be explained as effect of altitude distribution and the Mediterranean sea respectively. The polarity also shows a strong dependence with latitude, which may be explained as effect of mesoscale convective systems (MCS) and temperature. The dependence between geographical longitude and polarity is weak and may be due to the higher intensity of the positive flashes together with the effect of MCSs. Peak-current amplitudes for both polarities show a clear relationship with latitude, which may be explained by orographic effects and the longer lightning channels at lower latitudes. A definite dependence between peak-current amplitudes and geographical longitude is not observed.

Some of well known F2 layer anomalies might have their origin in lower atmosphere and some have extra terrestrial sources. It has been suggested that the phenomena occurring below the ionosphere such as thunderstorms, lightning/sprites, volcanic eruptions and earthquakes and above the phenomena like corona mass ejection, solar flares and extra terrestrial events may produce F2 layer signatures. In the present paper we have tried to summarize the effect of some phenomena occurring below the ionosphere like thunderstorms, lightning/ sprites and seismic activity and the phenomena such as solar flares which occur above the ionosphere, on the ionospheric electron and ion temperatures. The paper also discusses possibilities. The ionospheric electron and ion temperatures were measured by the RPA payload aboard the Indian SROSS-C2 satellite. The normal day’s ion and electron temperatures have been compared to the temperatures recorded during the disturbed day. The satellite data corresponding to the disturbance period were analyzed in such way that the other possible effects were eliminated. The data used are from the period 1995-1998 in the altitude range 430-630 km over the Indian region. The data of thunderstorms activity have been obtained from IMD, Pune and details of seismic events during this period downloaded from the USGS website and existing literature. The data of solar flares have been obtained from NGDC, Boulder, Colorado, USA.

In this series of articles, complete NH3 and NOx emission inventories have been calculated for the first time for Galicia (NW Spain), a region in serious danger due to the eutrophication produced by these emissions. In this first part, NH3 emissions corresponding to main sources (from agricultural and non-agricultural activities) have been estimated and the associated uncertainties have been quantified. The results have shown that livestock emissions (particularly by broilers and cattle) are especially relevant in this region, representing almost 90% of the total, the use of fertilizers being the second source in importance, while all the non-agricultural sources as a whole contribute less than 4%. The study of uncertainties has shown that future research in the region has to focus on the development of more specific emission factors for agricultural sources (especially for cattle, broilers and urea) to reduce this uncertainty.  

Numerical solutions of the barotropic vorticity equation under forcing by wind stress, and mass transport between the basins of the Caribbean Sea and the Gulf of Mexico, are shown, in the first part of this study, the equation was solved for a steady flow with a flat bottom of 200m depth, realistic coastlines and horizontal resolution of 25 km. In the second part, we added the bottom bathymetry, and the equation was solved for the steady-state and non-steady-state. In the non-steady regime, we found that the Loop Current (LC) penetrates into the Gulf and bend westward into unstable configuration to give rise to a periodic eddy shedding regime, in which the anticyclonic eddies are shedded of the Loop Current and propagated westward as solitary Rossby waves. The lifetime of these anticyclonic eddies is about of 120 days; they have a size from 275 to 440 km and propagation speed of about 7.3 km day-1.

This paper is concerned with the development of the multiquadric interpolation scheme to produce gridded fields of meteorological variables. The results of the application of this method to real data is compared with analysis from Gandin's Optimum Interpolation scheme. Like the optimum interpolation scheme, which uses covariance functions as the basis functions, the multiquadric scheme uses hyperboloid radial basis function to fit the scattered data to a uniform grid. This scheme produces superior analysis compared to optimum interpolation analysis.