- Home
- Conferences
- Conference Proceedings
- Conferences
6th International Congress of the Brazilian Geophysical Society
- Conference date: 15 Aug 1999 - 19 Aug 1999
- Location: Rio de Janeiro, Brazil
- Published: 15 August 1999
1 - 50 of 399 results
-
-
Survey Design For Vertical-Cable Seismic Acquisition
Authors Carlos Rodriguez-Suarez and Robert R. StewartThe vertical cable recording geometry has shown considerable promise as a seismic acquisition technique. It is
especially suitable for marine areas where any of the following are present: 1) obstacles (e.g. platforms or buoys) for a
vessel towing streamers, 2) deep to very deep water, 3) a complex subsurface geology, 4) pipelines on the sea bottom,
and 5) a hard (e.g., carbonate or basalt) sea floor. The last two situations may prohibit the use of ocean bottom cables
(OBC). On land, it can be seen as a 3D-VSP with one or more wells (cables).
If we are to acquire vertical cable data, we need to be able to design the surveys to best image the target geology in the
most economic way. Thus, we are interested in questions of source and receiver distribution and the resultant target
coverage.
Analysis of fold for regular grids of bins in vertical-cable acquisition was done for a straightforward, still realistic, 2.5-D
synthetic case. It describes a passive continental margin environment in a Mesozoic basin. Acquisition geometries with a
different numbers of vertical cables, hydrophones per cable, numbers of shot points and water depths were analyzed.
Three-dimensional ray tracing was used to obtain the reflection point from a target layer. Converted (P- to S-) waves, and
a land case were also analyzed.
The results show that good coverage can be obtained using only a single cable, a reasonable number of hydrophones
per cable and a fair shot point spacing. Deeper water acquisition shows better fold homogeneity than shallow water when
several cables are used on an optimized configuration.
-
-
-
Viabilidade Da Sísmica 4D Em Um Campo Terrestre Brasileiro: Enfoque De Rochas
We made a feasibility study for the application of the time lapse seismic technique on a shallow onshore Brazilian field, at
the Potiguar Basin, Rio Grande do Norte. This anonymous but real fluvial reservoir are now being subjected to vapor
injection, which is a good production technique for seismic monitoring. Seismic velocities measurements on core
samples and reservoir fluids, as well as fluid substitution on the available well log data, were used at the preliminary
stage of the feasibility study in order to quantify the velocities and impedance changes that the reservoir would
experience as a function of temperature, fluid saturation and pore pressure. Biot-Gassmann equations were combined
with the reservoir thermal simulation in order to construct a velocity and impedance model for the seismic modeling. It
was found that acoustic impedance changes as large as 40% would occur and that it should be resolved by the high
resolution 3D seismic. The initial and final seismic models and it’s updated versions shall help the reservoir geophysicists
on the interpretation of the real time lapse seismic data, which may provide insights on the fluid flow behavior and
reservoir heterogeneities.
-
-
-
High Precision/Fast Adaptive Step Size Ray-Tracing By Curvature Criteria
More LessHere I present one version of Hamilton based ray-tracing equations solution (Cerveny, 1987) (Popov,
1996) aiming at increasing precision as well as reducing and controling the computation’s effort. The
errors in numerical evaluating the differential ray-tracing equation can be classified in two kinds. First
the error in interpolating the velocity field and its derivatives. Second the error in evaluating the next
ray’s coordinates and slowness vector by the Runge-Kutta method. The first one has well-known solutions
like fourth order precision Bi-cubic spline interpolation (William et al., 1994). The second, the
fourth order precision Runge-Kutta method, needs the time step. If we apply a constant time step, it
requires the use of a high-density coordinate’s sampling when used for a non-homogeneous medium.
The reason is that the precision of ray-tracing is directly related to the curvature radio of the ray and the
last with the gradient of the square slowness. Then to obtain a high precision ray-tracing we need to decrease
the size of the time step in regions where there are large variations of the square slowness field
or on the other hand increase where there are no such variations. The result is an adaptive algorithm,
which automatically adapts the size of the ray coordinates interval to the necessity of the medium by
geophysical control. Despite the existence of the “adaptive control for Runge-Kutta method” (William
et al., 1994) it’s based in numerical considerations. Here I developed an alternative based on solid
physical arguments most properly useful for wave propagation purposes which can easily control the
accuracy of ray’s coordinates and in consequence the ray’s amplitudes (Lambaré, G. and Lucio, P.S.
and Hanyga A., 1996) and time of processing by just changing a parameter.
-
-
-
Um Algoritmo Prático De Modelagem 3-D Baseado Na Solução Da Equação Acústica Completa Da Onda
More LessEste trabalho apresenta a versão 3-D de um algoritmo para solução da equação acústica completa da onda,
baseado no método das diferenças finitas. Este algoritmo foi idealizado para requerer um mínimo de operações
extra para levar em conta as variações de densidade no meio. Também são exploradas técnicas de programação
capazes de reduzir sencivelmente os custos computacionais de tal aplicação. Com isto, a modelagempor solução
da equação da onda, que é uma poderosa ferramenta, pode se tornar mais prática para as aplições da indústria
do petróleo.
-
-
-
Contribuição Da Gravimetria Na Prospecção De Água Subterrânea No Litoral Norte Do Ceará, Brasil
More LessA gravity investigation is conducted in a coastal area in the northeastern Ceará State (Brazil). The objective of the survey is the detection of the regional geological structures which control the accumulation of underground water. This investigation consists of 1668 gravity stations, including previous surveys both in land and marine areas. The Bouguer gravity map is dominated by regional effect caused by the mantle uplift in the continental passive margin. To display more clearly the gravity anomalies caused by upper crustal heterogeneities, the local regional gravity field is removed by using a polynomial surface fitting. The resulting residual gravity anomaly map permits us to associate the gravity anomalies with known precambrian geologic units, granitic batholiths and surface structural features. The gravity lineaments are concordant with the NE-SW structural trends. In the northwestern of the studied area an elongated relative gravity low, visible in the residual map, indicates a NWSE secundary deformation trend, underlying of the sedimentary cover. These results will be prioritized and will be used to guide a more detailed geophysical survey.
-
-
-
Primeiros Resultados Do Sonar De Varredura Lateral Em Águas Profundas Rebocado Próximo Ao Fundo Marinho
More LessHigh resolution geophysical data has provided important results for petroleum industries facilities. Petrobras has been
acquiring deep towed sonar data since 1997 in all brazilian basins to obtain further detailed information of the sea floor to
support pipeline instalation. The seafloor imaging system (SIS-3000) described here uses the CHIRP technology to
provided high resolution sonar images and CHIRP subbottom data profiles. The SIS 3000 system is composed by two
subsystems as follow: tow vehicle and shipboard eletronics. This paper will present an overview of the deep towed
CHIRP sonar and some initial results in the Campos Basin.
-
-
-
A Rede De Detectores De Radiação Ultravioleta Solar Do Inpe
Nas duas últimas décadas verificou-se uma significativa redução do ozônio atmosférico global, criando uma
preocupação sobre o possível aumento da radiação UV-B na superfície terrestre. Entretanto, poucas medidas
de UV na superfície estavam disponíveis até meados de 1980, e a maioria destas concentrava-se no hemisfério
norte. Descreve-se neste trabalho a rede de detectores de UV do INPE e alguns resultados. O INPE vem
operando desde o início da década de noventa, vários detectores UV dos tipos radiômetros UV-Biometer, GUV e
Espectrofotômetros Brewer no Brasil, Bolívia, Chile e Antártica, constituindo uma base de dados com uma
significativa distribuição geográfica, de latitudes equatoriais, médias e polares. Esta distribuição espacial é
importante para o estudo do comportamento da radiação ultravioleta solar face ao quadro de mudanças
atmosféricas associado aos fenômenos da redução global do ozônio.
-
-
-
Medidas Da Radiação Uv-B Difusa Em Banda Larga E Estreita
Authors Abel A. Silva, Ezequiel Echer and Volker W.J.H. KirchhoffMesmo em dias de céu encoberto pode-se notar o bronzeamento da pele humana nas pessoas em atividade ao ar livre.
Esse fenômeno é devido a ação da componente difusa da radiação solar global UV-B. Estudos anteriores mostram que
essa radiação é importante para ângulos solares zenitais elevados, mais comuns nas latitudes altas. Neste trabalho é
feito um estudo da relação entre a radiação solar global UV e a sua componente difusa. As atividades foram conduzidas
em Cachoeira Paulista (23.1o S, 45.0o W) com radiômetros de banda larga e estreita em dias de céu limpo, tendo sido
verificado que a radiação difusa representa pelo menos 40% da global na faixa do UVB.
-
-
-
Topographic Effect Of Transient Electromagnetic Responses
Authors Wenbao Hu, Liangjun Yan and Xingong TangA three dimensional body is designed to simulate the valley shaped topography. Transient responses are
calculated for topography at source location and at receiver location respectively. Modeling results are shown
by relative anomalies in contours. The behavior of the topographic effect to transient eletromagnetic field
responses can be characterized by local anomaly for topography at receiver location, and by equivalently an
extra source with strong high frequency excitation for topography at source location. Learning from the
modeling results, it is emphasized that the ground wire source shall be set up at place as uniform as possible
for reliable deep sounding measurements.
-
-
-
Large Scale Multi-2D Prestack Depht Migration:A Gulf Of Mexico Deep Water Case Study
More LessThe attraction of the deep water Gulf has increased over recent years due to the advancement of several core
technologies. Foremost within these new applications is the use of pre-stack depth migration for illuminating
the sub-salt structure, at water depths in excess of 3300 meters. Large scale 2D depth migration projects (e.g. >
3000 miles) provide a cost effect way of ascertaining the regional sub-salt geology and highlighting areas for
prospect evaluation. The results from three large multi-2D, prestack depth migration projects are presented.
The unique problems associated with depth migrating in the deep water province are highlighted in terms of
acquisition, time processing and specifically the application of depth imaging technology for imaging of the
sub-salt. It is shown that a combination of long streamer acquisition with prestack depth imaging can provide
an adequate image of the sub-salt, suitable for prospect evaluation in a short period of time.
-
-
-
2D Seismic Data Images A Fold And Thrust Belt In Noerthwestern Venezuela
Authors R.C. Ahlborn and J.W. PowellOlder 2D seismic data in the Falc6n basin, Zulia and Falcon states, northwestern Venezuela, indicates the
probable existence of a fold and thrust belt in northwestern Venezuela. This belt is likely the result of the collision of
the Caribbean Plate with the South American Plate during the Paleogene. A second pulse during the Lower Miocene
is also recorded on 2D seismic profiles near the coast of Falcbn. Southwest vergent thrusts are evidenced in the
Cocuiza basin, on the Dabajuro high and the Coro platform. Younger south vergent thrusts with large fault
propagated folds are seen within the Urumaco trough. Although some of the low-angle thrusting is due to wrench
movements along the Oca fault system, much of the thrusting can be attributed to compression rather than
transpression during plate collision.
-
-
-
About Of The Digital Geomagnetic Records Processing With Noice
Authors Julio C. Gianibelli and Iris R. CabassiDigital records of the Total Intensity of the Earth Magnetic Field, realized by means of protonic precession
sensors per one minute, shows erratic pulses. The criterions of analysis and filtering of these pulses for
magnetically quiet days are studied. The more adequates methods had been the one of comparisson of
succesive samples, and the filtered method by means of a windows of the median determination.
In this paper, the results for records with ramdom spikes of the Trelew Magnetic Observatory (ϕ = 43°2683 S;
λ = 294°6183) are analyzed.
-
-
-
Different Styles Of Canyon Infill Related To Gravity And Bottom Current Processes : Examples From The Upper Slope Of The Se Brazilian Margin
Authors A.R. Viana, W. Almeida Jr. and L.C. MachadoA series of modern submarine canyons were examined in the south-eastern Brazilian margin in order to identify
the different styles of canyon filling and their relationship with sedimentary processes and sea-level changes.
Such study should be considered as a predictive tool in order to estimate the presence of reservoir-like
deposits. Four seismic facies related to intra-canyon depositional patterns were individualised in this study:
clinoform prograding lateral accretion (Cp), cahotic fill (Ch), parallel-to-divergent aggradation (Pd) and
horizontal strata (Pl). Relationship between these styles and sea-level changes was attempted and results
indicate a complex interaction between hydrodynamic conditions, position of sediment source and sediment
availability. Coriolis Effect seems to play a minor role in controlling the downcanyon flow/erosion processes.
Lateral accretion is mainly related to the southward flowing Brazil Current. Aggradation and horizontal strata are
related to a relative decrease in the Brazil Current action and to an increase in gravity flows activity.
-
-
-
Un Geoide De Precisión Para Uruguay Informe Del Proyecto Urugeoide 2000
More LessSe presenta el proyecto UruGeoide 2000, cuyo objetivo es la determinación de un modelo geoidal con precisión
centimétrica para Uruguay. La metodología propuesta, está basada en la combinación de un modelo geopotencial,
anomalias gravimétricas y un modelo numérico de terreno, a través de la técnica "remove-restore", usando
Transformada Rápida de Fourier. Los datos disponibles, así como las investigaciones realizadas en modelos
geopotenciales de alto grado y ultra alto grado, son presentados en este informe.
-
-
-
Influência Transiente Da Temperatura Poço-Formação Em Perfis De Resistividade(Com Invasão)
More LessThe principal aim here is show a transient thermal-resistivity log dependence. The induction devices (ILM and
6ff40), common used in log interpretation, may have some errors and new corrections will be needed. This
features are presented when multilayer transient temperature is evaluated and applied to resistivity model. A
simple eight meters deep formation is simulated with 2d-thermal and resistivity model, composed by shale and
sandstone reservoir, where multiphase radial fluid flow was performed. Due mud circulation, temperature
dependence of apparent resistivity formation are evaluated and compared with the resistivity when wellformation
temperatures are the same (150oC). Errors into 1% to 12% are expected to medium and deep induction
log information with this model.
-
-
-
Using Seismic Data To Verify 3D Geometry - Some New Approaches To Field Qc
More LessIn today’s 3D surveys, the volume of data can be overwhelming. It is essential to have methods that quickly identify
errors and/or bad data. Modern field QC uses seismic trace attributes (energy levels within specified windows, energy
decay factors, first arrival times) in combination with survey information (shot and receiver positions) to create new
quality control measurements and displays, Such QC displays can quickly pinpoint location and other errors at both
shot and receiver positions. Examples of verifying 3D geometry, energy decay maps, and finding posrtron errors will
illustrate the latest QC methods.
-
-
-
Equatorial Spread-F And Plasma Bubbles: A Step Towards Prediction
Authors Inez S. Batista, M.A. Abdu, R.T. de Medeiros and J.H.A. SobralEquatorial spread F (ESF) and plasma bubbles are plasma irregularity phenomena that are known to occur in the
equatorial- and low-latitude ionospheric F region at evening and nighttime. Those irregularities cause
scintillation that disrupts trans ionospheric radio propagation, up to the GHz frequency range interfering on
communication systems including the Global Positioning System - GPS. Although the general characteristics of
spread F and bubbles, concerning their variation with season, solar cycle, and magnetic activity, are fairly well
understood, we do not know much about the cause of the day-to-day variability, a crucial point when prediction
is concerned. In this paper, we analyze ionospheric data from two low latitude stations in Brazil, in either
presence or absence of bubbles, in order to try to establish the conditions under which bubbles shall occur. We
conclude that the F layer critical frequency (foF2) in the afternoon-sunset hours (or equivalently the F layer
maximum density, NmF2) is a useful parameter to predict the occurrence of the bubble.
-
-
-
The Role Of The Stike-Slip Tectonics In The Evolution Of The Alboran Sea, Western Mediterranean
Authors José Rodriguez-Fernandez and Menchu ComasThe Alboran Basin is a Neogene extensional basin which originated and evolved since the early Miocene within a plate
tectonic setting of convergence between Iberia and Africa. The basin has been identified as formed by crustal stretching
and extensional tectonic from the early to the late Miocene. However, the current organization of the Alboran Sea basin
has resulted mainly from post-Miocene contractional tectonics superimposed on earlier extensional structures. The
present structural framework indicates that two sets of conjugate strike-slip systems (left-lateral faults with a NE-SW
trending, and right-lateral faults with a NW-SE trending; being 120• -130• the angle between the two strands) accounted
for a significant post-Messinian deformation of the Alboran Sea basin. The stress field evidenced by the wrench-tectonic
structures is consistent with the latest Neogene to Present Africa-Eurasie roughly N-S convergence plate kinematics in
the westernmost Mediterranean.
-
-
-
Efeito Da Profundidade Dos Eletrodos Em Levantamentos De Eletrorresistividade
Authors H.K. Sato and F.A.F. OliveiraThe influence of electrode depths in electroresistivity
survey is studied. Generally, the investigators don’t care
about this detail but it can introduce significant departures
on the apparent resistivity values obtained with
small electrode spacings. To check the influences, theoretical
analysis is performed using simulated vertical
electrical sounding with undergrounded Wenner array.
Field data using Schlumberger array are collected to
demonstrate the existence of such effects. Computed
apparent resistivity values obtained with the same field
array parameters, separations and depths, are successfully
fitted to the field data, and a horizontally layered
model is obtained. The studies with two layer models,
shown that the effects of undergrounded electrodes are
more expressivewhen the second layer is more conductive
than the first one. Ambiguities arise in the reversed situations.
-
-
-
Electromagnetic Waves Generation By The Hybrid Modulational Instability
More LessAn improved model of the fundamental plasma emission of type III solar radio bursts is presented. It is shown
that nonlinear conversion of a traveling Langmuir pump wave into an electromagnetic wave can occur via either
convective or absolute hybrid modulational instabilities, resulting from the coupling of two wave triplets, with
the Langmuir pump wave and ion-acoustic daughter wave common to both wave triplets. The properties of
these four-wave hybrid modulational instabilities are studied using the observed interplanetary parameters.
-
-
-
Atividade Solar Nos Anéis De Crescimento De Árvores Em Canela
Authors Nivaor Rodolfo Rigozo and Daniel Jean Roger NordemannTree ring studies are usually used to determine or verify climatic factors which prevail at a given place or region
and may cause tree ring width variations. Few studies are dedicated to the geophysical phenomena which may
underlie these tree ring width variations. Furthermore, it is known that some trrestrial phenomena suffer
influence from short and long time scale solar variability. So, a study on solar activity records in tree rings at
short time scales was developed. In order to determine a tree growth ring width mean chronology, an optical
and computational method was set up and applied to tree samples (araucaria and pine trees) from Canela-RS,
Brasil. Spectral analysis by maximum entropy method and iterative regression was applied to the search of
periodicities related to solar activity phenomena. The results obtained have shown periodicities related to 11 yr
and 22 yr solar cycle influence on tree growth rings.
-
-
-
Diurnal Variation Of Summertime Cloud-To-Ground Lightinig Activityactivityin The Southeastern Brazil
This paper reports the results of an analysis of 300,000 cloud-to-ground flashes recorded in the southeastern
Brazil in the summer season of 1993 in terms of the local time dependence of their characteristics. Whereas the
lightning activity of negative and positive cloud-to-ground flashes exhibit a diurnal cycle with a well-defined
time of maximum frequency in the afternoon, the flash multiplicity and peak current intensity do not exhibit such
a local time variation. The local time dependence and geographic distribution of the lightning activity are in
agreement with what is expected from isolated thunderstorms. In turn, the peak current intensity and the flash
multiplicity did not show any dependence on local time. The results are compared with similar data obtained in
the western and eastern U.S. in the period 1995-97.
-
-
-
Uma Análise Do Modelo De Madden&Marshall Para Descrever A Polarização Elétrica Observada Em Rochas Contendo Argila Disseminada
Authors Alexandre Nunes Barreto and Carlos Alberto DiasThe impedance function associated to the Madden & Marshall model proposed to describe membrane polarization,
was rewriten using five new parameters with clear petrophysicalmeaning. The behavior of this function was
analyzed together with its new parameters when varying the electrochemical parameters of the originalmodel and
some limitations were shown.
-
-
-
Long Term Variation Of The Lightning Flash Characteristics In The Southeastern Brazil:1988-1995
The long-term variation of the cloud-to-ground lightning flash density in terms of its geographical, monthly and
diurnal distribution is presented, based on the longest lightning data set ever obtained in the tropics. The
results are based on 12.8 millions cloud-to-ground lightning flashes recorded in the southeastern Brazil from
1988 to 1995 with a lightning network consisting of four LPATS sensors located in Minas Gerais. They should be
considered as reference for future studies in this region.
-
-
-
Estudo Geofísico Preliminar Com Os Métodos Tem/Fem Na Planície Costeira Norte Fluminense
More LessIn 1998, ON/CNPq and LENEP/UENF undertook a geophysical pilot study in the Northern Coastal Plain of Rio de Janeiro State, near Rio das Ostras town. The region is characterised by both the scarcity of drinking water for human consumption and the existence of saline intrusions; this last caused mainly by the presence of a complex quaternary geology and the excessive exploitation of the aquifers. The research was performed by employing the time (TEM) and frequency (FEM) domains electromagnetic methods to evaluate the effectiveness of both methods in these geological conditions in order to be able to formulate a more comprehensive hidrogeological research in the region in near future. The FEM profiles and the uni-dimensional interpretation of the TEM were able to depict the different geological formations, to locate the main aquifers and to reveal the salty water- fresh water contact. Our results evince a promising future for using eletromagnetic geophysical methods in the region as well as it confirmed that a regional survey is essential in the indication of most suitable places to locate productive fresh-water wells.
-
-
-
Mesospheric Reduction Of The Chemical Heating Rates By Nightglow Emissions At 23Os And 4Os
Authors P.R. Fagundes, D. Gobbi, H. Takahashi and Y. SahaiSimultaneous observations of several nightglow emissions have been carried out at Fortaleza (40S, 380W) and
Cachoeira Paulista (23oS, 45o W), Brazil, since 1987. Using the OH Meinel (9,4) and O2 atmospheric b(0,1) bands
observed at these two stations during the period from 1987 to 1994, we present and discuss the night-time
reduction in chemical heating rates by these mesospheric airglow emissions. The total emission rates of the OH
Meinel bands and O2 atmospheric b(0,0) and O2 infrared atmospheric (1Δg) bands were calculated using the
reported data for the relative band intensities I(ν/,ν//)/I(9,4), I(O2b(0,0))/I(O2 b(0,1)) and I(O2 (1Δg))/ I(O2b(0,1)). This
study showed that the reduction in chemical heating rates (RCH) by the OH Meinel bands, at both the locations,
has seasonal variations with monthly mean values varying from 0.4 K/day* to 0.9 K/day* (where day* means
averaged over the night). However, the RCH rates due to the radiation in the Meinel bands at Cachoeira Paulista
presented a weak ter-annual variations, whereas at Fortaleza semi-annual variations were observed. Also, the
RCH rates by O2* showed semi-annual variations at both locations, presenting values from 0.05 K/day* to 0.25
K/day*.
-
-
-
Comparison Between The Mesopause Temperature+D57 Profiles Measured With A Sodium Temperature Lidar And The Oh (6,2) And 02A (0,1) Rotational Temperatures 23Os
Authors P.P. Batista, B.R. Clemesha, D. Gobbi, M.P.P.M. Jorge, D.M. Simonich, H. Takahashi and I. VaselovskiiThe mesopause temperature profile has been measured at São José dos Campos (23.2o S, 45.9o W) for a total of 15
nights from July to October 1998. The technique used is the measurement of the Doppler temperature of the sodium
atoms present in the atmospheric sodium layer with a Lidar. During 7 of the 15 days of Lidar temperature data,
simultaneous measurements of the rotational temperature of the OH(6,2) band at 843.0 nm and the O2 (0,1)
Atmospheric band at 864.5 nm were obtained at a nearby station, Cachoeira Paulista (22.7o S , 45.2o W), with a tilting
filter photometer. There is a fair agreement between the OH temperature and the Gaussian weighted temperature
calculated using the Lidar temperatures centered on 84.7 km and with a half-width of 4.5 km, consistent with rocket
measurements for the OH emission profile, for most of the days. But no consistent combination of height and half-width
can reproduce the absolute value and variation of the O2 (0,1) temperature for most of the days, suggesting that the
transition probabilities used for determining the latter may need to be revised.
-
-
-
Study Of The Space Variations Of The Energetic He Ions At Low Altitudes In Brazilian And South Atlantic Magnetic Anomaly Region
Authors G. Pugacheva, A. Gusev, T. Kohno, I. Martin and W. SpjeldvikThe L distribution of 1 - 9 MeV/nuc helium ion flux observed with the low altitude Japanese OHZORA satellite
has a multipeak structure, different from one flux maximum of proton radiation belt and two flux maxima of
electron radiation belt. The peak fluxes of 1 - 3 MeV/nuc He ions are located at L=1.35-1.6, L ~ 1.8 - 2.3 (only in
1984), and L = 2.8 - 3.2. Recently, two low altitude satellite SAMPEX (1992 – up to now) and MIDORI (1996-97)
missions reported new observations of energetic He flux peaked at L ~ 2 and show the existence of stable (at
least with lifetime of several years) flux there at higher energies above 10 MeV/nuc in contrast to the lower
energies. To analyze the nature of the multipeak structure and the origin of the L=2 helium flux we studied
magnetic local time dependence of the peak helium fluxes observed by OHZORA. The 1 - 3 MeV/nuc helium ion
flux exhibits strong local-time variation at L ~ 3 having several times greater flux at the evening side at MLT =
17-21 hours than at the other MLT sides. The one of possible explanation of the flux variation with MLT is that ~
1 MeV/nuc helium ions do not drift around the Earth and are located at L about 3 due to the ion interactions
with the Earth's electric morning-evening field.
-
-
-
A 2D Simulation Of The Proton Radiaton Belt With Pellpack Code
Authors A. Gusev, I. Martin, G. Pugacheva, A. Christy and W. SpjeldvikThe numerical solution of diffusion equation for geomagnetically trapped protons taking into account
deceleration of protons by Coulomb interactions with free and bounded electrons, the charge exchange
process, the cosmic ray albedo neutron decay (CRAND) source and electric and magnetic radial diffusion was
obtained using the PELLPACK code based on the finite element method. The advantage of the method in
comparison with the traditional finite differences method is a several order greater speed of computation at the
same precision. When boundary conditions at L=7 are given with the distribution function extracted from
proton spectrum obtained on board of ATS 6 satellite, the PELLPACK code produces 2D unidirectional proton
flux at the top of geomagnetic lines from L=1 up to L=7 that satisfactory agrees with the AP8 model proton flux
for all proton energies more than ~ 300 - 500 keV. For less proton energies AP8 model predicts the trapped
proton fluxes on several orders of magnitude greater than PELLPACK code at L < 4 that possibly could be
explained by uncertainty of very low energy proton flux data at L=7. The detailed fitness of observational model
proton fluxes by numerical theoretical solution of transport equation is still not attained.
-
-
-
Fast 3-D Modeling And Inversion Of Surface Em Data
More LessThis work presents an algorithm for three-dimensional modeling and inversion of electromagnetic field data. In recent
years, there has been an increase in use of electromagnetic techniques for mineral, oil and geothermal exploration.
Since most of the targets are of three-dimensional nature, it is important to consider the full dimensionality of the problem
in the interpretation. The forward code is based on a finite difference approximation while the sensitivities needed in the
inversion are obtained from the forward problem based on the reciprocity principle. A parametric functional is constructed
using the data misfit and a model misfit to an a priori earth model, weighted by a regularization parameter. This functional
is then minimized using the conjugate gradient method. The most time consuming parts of an inversion algorithm are the
forward problem and calculation of the sensitivities. Also, in the 3-D problem, storage becomes another important issue.
First results will be presented, along with methods that will help improve both speed and storage on the way to make the
3-D problem tractable.
-
-
-
Sound Velocity Of Drilling Mud Saturated With Reservoir Gas
Authors José M. Carcione and Flávio PolettoDrillings muds are used to balance subsurface pressures, lubricate the drillstring, clean the
bottom of the hole, remove cuttings and aid formation evaluation. During drilling, the mud
is pumped down the drill pipe and returns via the annulus between the drill string and the
formations. If the pore-fluid formation pressure exceeds that of the mud column, reservoir gas
can enter the wellbore? creating a kick and causing severe damage. Knowledge of the in-situ
sound velocity of drilhng mud can be useful for evaluating the presence and amount of gas
invasion in the drilling fluid. Technologies such as mud pulse acoustic telemetry require this
information. In the following sections, we propose a model for calculating the in-situ density
and sound velocity of water-based and oil-based drilling muds containing formation gas.
-
-
-
A Study About The Occurrence Of Days With High Activity Of Cloud-To-Ground Lightning Flashes In The Southeastern Brazil In The Years 1992 To 1994
Authors Heloisa H. Faria, Osmar Pinto Junior, André M. Carvalho and Armando C. FilhoThe occurrence of days with high activity of cloud-to-ground lightning flashes in the southeastern Brazil in the
years 1992 to 1994 was investigated. The high activity days were arbitrarily defined as those with more than
20,000 cloud-to-ground flashes. The meteorological conditions and flash characteristics during these days were
determined. The lightning data were obtained through a lightning location system (LPATS), and the flash
characteristic studied were the polarity, the peak current intensity and the diurnal distribution.
-
-
-
Signal To Noise Ratio Enhancement By Adaptive Filtering
Authors Enrique D. Mercerat and Alberto H. CominguezAn adaptive filtering techniquewas implemented in order to remove random noise from seismic data. The operator
was calculated in the frequency-offset domain (FX), and it could enhance the lateral coherence of seismic events.
For each frequency an optimum Wiener filter was designed following the classical approach using the complete
seismic section. After that, an adaptive algorithm was implemented to actualize the filter coefficients in order to
reduce the output error. This automatic actualization avoided us the use of predetermined design windows. The
adaptive filter was based on a generalized expression of the least-mean square (LMS) filter dealing with complex
frequency input signal. The performance was evaluated on synthetic seismic data contaminated with additive
gaussian noise.
-
-
-
Seismic Imaging Of The Crust In The Aconquija And Adjacent Regions; Catamarca, Tucuman And Santiago Del Estero, Argentina
More LessDeep Seismic Study, in eastern and western foothills of Sierra de Aconquija, northwestern Sierras Pampeanas, Argentina, shows the deep structure of the range and the deep geometry of the Andean foreland basin. "Self-truncating" extended correlation algorithm was applied to compute cross-correlation between the sweep and the records of Vibroseis lines. Special procedures, such as finite difference migration, FX deconvolution, FMED processing and complex demodulation, were applied in order to improve the interpretation. On the eastern side of Sierra de Aconquija, the structure is characterized by reverse faulting with eastward vergence, with the Guasayán and El Rosario faults exhibiting the most deformation. To the south, the Guasayán fault produces the uplift of the Guasayán basement range over tertiary deposits, and can be identified in the seismic reflection record down to 40 km depth. On the western side of Sierra de Aconquija, the deep structure of Campo del Arenal is characterized by westward vergent structures controlled by the anisotropy of the Sierra de Aconquija basement. Further to the west, the deformation style changes to eastward vergence. Conspicuous sub-horizontal acoustic-reflectors at about 18, 30, 40 and 50 km depth, are interpreted as present or past brittle-ductile transitions.
-
-
-
Log-Derived Rock Strength Evaluation
Authors José Agnelo Soares and Lucia Duarte DillonSeveral oil industry operations, like borehole stability, pore collapse analysis and hydraulic fracturing, demand
rock mechanical knowledge that sometimes is unavailable or is only poorly known. Statistical relationships
defined through dynamic and static rock properties, simultaneously determined in lab tests, yield a novel
approach to continuously evaluate rock strength over whole depth well intervals.
-
-
-
Métodos Geoelétricos Aplicados No Estudo Do Lençol Freático Em Área De Disposição De Resíduos Industriais
Ensaios geofísicos pelo método da eletrorresistividade, utilizando as técnicas de campo da sondagem elétrica vertical –
SEV (arranjo Schlumberger) e caminhamento elétrico - CE (arranjo dipolo-dipolo), foram executados em áreas de
disposição de resíduos industriais no município de Iracemápolis-SP. Os estudos geofísicos visaram obter um
diagnóstico prévio dos materiais em subsuperfície frente à possível contaminação por resíduos industriais. Foram
executadas três SEV´s, as quais caracterizaram a litologia dos materiais em subsuperfície em solo superficial seco
(resistividade variando de 13 a 14.353 ohm.m), solo de alteração de diabásio (resistividade variando de 25 a 83 ohm.m)
e diabásio (resistividade de 617 ohm.m). A profundidade do nível d´água obtido apresentou uma variação de 9,3 (SEV-
01) a 13,5 (SEV-03) metros. Para o CE, foram levantadas cinco linhas, a partir das quais, pode-se delimitar a área de
disposição de resíduos, avaliar as condições da pluma de contaminação e determinar as direções preferenciais do fluxo
d´água subterrâneo. Mapas referentes a três níveis de investigação (profundidades teóricas de 10, 20 e 30 metros)
evidenciam que a pluma tende a diminuir sua faixa de contaminação em função da profundidade, restringindo-se a
locais isolados. Duas direções preferenciais do fluxo subterrâneo d´água foram identificadas, acompanhando, de um
modo geral, a topografia do local estudado.
-
-
-
Estudos Morfológicos Das Depleções Do Plasma Ionosférico Por Imagens Digitalizadas
Authors Daniela Cristina Santana, J.H.A. Sobral and H. TakahashiA ionosfera, ambiente natural de propagação dos sinais de comunicação, foi descoberta inicialmente devido a
observação de variações periódicas nas medições do campo geomagnético que combinadas com a alta condutividade
elétrica da ionosfera, podem alterar a trajetória desses sinais de comunicação. É uma região rica em fenômenos
naturais de importância direta para o homem e o para meio ambiente. É justamente um desses fenômenos, denominado
de depleções do plasma ionosférico, exclusivo das regiões equatoriais, que queremos enfatizar. Para o seu estudo, há
várias técnicas desenvolvidas, das quais podemos citar a luminescência atmosférica, ou o airglow. O acompanhamento
constante do airglow noturno permite realizar um estudo morfológico e dinâmico da ionosfera noturna. As imagens
digitalizadas do airglow noturno são obtidas pelo imageador all-sky 180º que é um equipamento recém desenvolvido
pelo grupo de pesquisa Luminescência Atmosférica - LUME, da área de Ciências Espaciais e Atmosféricas - CEA, do
Instituto Nacional de Pesquisas Espaciais – INPE e encontra-se em operação desde outubro de 1997 no laboratório do
LUME em Cachoeira Paulista(22.7ºS, 45.0ºW) – SP. O airglow noturno existe em vários comprimentos de onda sendo
que para o registro das depleções do plasma ionosférico é necessário a emissão do OI 6300 Å (λ = 630 nm), uma luz
vermelha de muita baixa intensidade, que está presente na termosfera. As depleções do plasma ionosférico variam a
intensidade da emissão do OI 630 nm de acordo com o cotidiano e a estação do ano. Os nossos estudos focalizam as
depleções do plasma ionosférico que ocorrem sobre a região de Cachoeira Paulista(22.7ºS, 45.0ºW) – SP,
principalmente as fortíssimas ocorrências nas noites de 30/01/1998 e 26/08/1998. As imagens digitalizadas das
depleções do plasma ionosférico via OI 630 nm obtidas pelo imageador all-sky 180º são analisadas e processadas por
aplicativos computacionais em desenvolvimento na linguagem computacional Interactive Data Language – IDL,
seguindo os padrões básicos para o desenvolvimento de um aplicativo computacional. Esses aplicativos computacionais
introduzem uma nova técnica fotométrica para o estudo das depleções do plasma ionosférico.
-
-
-
About The Seasonal Distribution Of Geomagnetic Activity
The annual distribution of geomagnetic activity is studied through the geomagnetic indices aa, Dst and AE,
according to different levels of intensity for each of the indices. For thresholds that correspond to moderate to
fairly intense storms, the distribution follows the well-known pattern of a seasonal variation, with maxima
around the equinoxes and minima near the solstices. However, the observed pattern deviates from this behavior
as the distribution refers to levels associated to the occurrence of more intense storms. For the latter type of
storms, the geomagnetic index aa shows the occurrence of a peak in July (but not in January, as a seasonal
symmetry would suggest). The contribution of very intense storms to the July peak seems to be evenly
distributed along the 11 solar cycles covered by this index. Furthermore, although the records for the indices
Dst and AE are restricted to shorter time intervals as compared to aa, they also show the possible existence of
this peak for July.
The present analysis gives also some indications for the existence of a peak in November in the distribution of
very intense storms. This peak shows up particularly for the indices Dst and AE, whose records go back only to
1957. Therefore, its real existence is more questionable than that of the peak for July.
-
-
-
Phase Relationship Between F-Region Electron Density And Electric Field Fluctuations-Some New Observations
Authors P. Muralikrishna, M.G.S. Aquino, S.M. Soares and M.C. De FariaIn-situ measurements of the height variation of the ionospheric electric field and electron density variations were made
with a rocket-borne electric field double probe and two different types of electron density probes. A Brazilian made
SONDA III rocket carrying these experiments in addition to other airglow experiments was launched on 18-th December,
1995 at 2117 hrs (LT) from the equatorial rocket launching station, Alcantara. The rocket reached an apogee altitude of
557km and covered a horizontal range of 589km. Several ground equipments were operated during the launch campaign
with the specific objective of knowing the ionospheric conditions at the time of launch and thereby to launch the rocket
into an F-region prone to the presence of large plasma bubbles. The rocket in fact passed through several medium scale
plasma bubbles and the electric field double probe and the electron density probes detected the presence of a wide
spectrum of electric field and electron density irregularities. In the base of the F-region the electric field double probe
measurements clearly indicated the presence of large amplitude fluctuations, closely associated with large amplitude
electron density irregularities But in the height region close to the rocket apogee though the electron density profile
showed the presence of large scale spatial structures, the electric field measurements did not show fluctuations of similar
amplitude. Being a nighttime launch one would expect the electron density irregularities, if generated by the well-known
cross-field instability mechanism, in height regions where the electron density gradient is downward, i.e in the same
direction as the ambient Hall electric field. An FFT algorithm was then used to estimate the spectral distribution of the
electric field and electron density fluctuations, thus estimating the height variation of the spectral variation. Some new
results on the phase relationship between the electric field and electron density fluctuations are presented here.
-
-
-
Ionospheric Experiments On Board The Brazilian Scientific Applications Satellites Saci-1 And Saci-2
Authors P. Muralikrishna, M.A. Abdu, S. Domingos, J.A.C.F. Neri and L.P. VieiraA set of three plasma diagnostic experiments, known as PLASMEX, are developed for launch on board the
Brazilian Scientific Applications Satellites SACI-1 and SACI-2. The main objective of the experiments is to
investigate the phenomenon of ionospheric plasma bubbles, known to exist in the ionospheric region over a
wide range of latitudes. It is intended to make measurements of the density, temperature and spectral
distribution of the irregularities in the ionospheric plasma using (1) a High Frequency Capacitance Probe for
measuring the plasma density, (2) a fixed-bias Langmuir Probe for measuring the electron density profile and
the spectral distribution of plasma irregularities, and (3) an Electron Temperature Probe for measuring the
kinetic temperature of the ionospheric electrons. While the satellite SACI-1, is to be launched this year from
China on board a LONG MARCH rocket SACI-2 is also expected to be launched this year on board a Brazilian
satellite launch vehicle VLS from Alcantara-MA. In the High Frequency Capacitance Probe a metallic sensor in
the form of a sphere of about 60mm diameter is used as a capacitance element in the tank circuit of a "Clapp"
type oscillator. In the fixed bias Langmuir Probe a metallic sensor, similar to that used in the HFC experiment, is
used to collect the elctron or ion currents from the ambient plasma. The sensor potential is selected using
telecommands, from four predetermined values namely -1V, 0V, +1V and +2V. In the Electron Temperature Probe
two semicircular metallic sensors in the form of a circular disc, is used to determine the kinetic temperature of
the ionospheric electrons. On board SACI-1 the HFC, LP and ETP sensors are mounted at the extremities of
three of the four solar panels, while on board SACI-2 they are mounted at the extremities of three deployable
booms about 1m long. The PLASMEX experiments will be operated by commands from an onboard Microcontroller.
While SACI-1 has a near polar sun synchronous orbit, SACI-2 has a low inclination orbit. Thus SACI-1
can give a complete global coverage for the measurement of plasma parameters, while SACI-2 can give detailed
information on the behaviour of these parameters in the low latitude and equatorial regions. A brief summary of
the experiments PLASMEX along with details of the data acquisition system, on board processing of the LP ac
data etc. is presented here.
-
-
-
Equatorial Spread-F Irregularities As Observed By Three Different Rocket-Borne Plasma Density Probes
Authors P. Muralikrishna, M.A. Abdu, M.G.S. Aquino and M.C. De FariaSome new results obtained from in-situ measurements of the height variation of the ionospheric electron density made
with rocket-borne electron density probes during a campaign conducted from Alcantara (2.31oS; 35.2oW) in Brazil are
presented here. The campaign designated Guará was conducted in collaboration with NASA. In addition to several
plasma diagnostic instruments provided by other participating institutes the Aeronomy Division in the Instiuto Nacional de
Pesquisas Espaciais in Brazil provided a High Frequency Capacitance probe that measured the height profile of the
electron density. During the Guara campaign, a Black Brant X sounding rocket was launched on 14-th October 1994 at
1955hrs (LT) to investigate into the phenomenon of high-altitude equatorial spread-F events. The rocket, as expected
passed through an active topside spread-F event, monitored simultaneously by several ground-based instruments. The
electron density height profile and the amplitude of the electron density fluctuations were measured simultaneously by
three different plasma density probes; a High Frequency Capacitance (HFC) probe, a conventional Langmuir Probe (LP)
and a Plasma Frequency Probe (PFP). While the PFP provided the absolute electron density, the LP gave the relative
variation in the electron density. The electron density profile obtained from the HFC probe measurements is practically
absolute except for a plasma sheath factor. But this technique does not provide the small scale electron density
fluctuation amplitude. The three experiments provided data, which could be used not only to obtain reliable electron
density data, but also to arrive at some of the inherent difficulties associated with each of these techniques. For example
the elctron density profiles estimated from the HFC and PFP experiments are almost identical except for a small factor
varying with altitude. The amplitude of large scale fluctuations provided by the LP measurements is considerably less
than that provided by HFC and PFP. The k-spectra of the plasma irregularities were obtained by the spectral analysis of
the electron density fluctuation data. The electron density irregularites associated with the plasma bubbles were seen to
have rather sharp lines in their k-spectra extending over a wide range of altitude. What one would expect from the
existing theories on the generation of small scale irregularities by the cascading process is a flat k-spectrum. Present
results may be indicative of the presence of preferred wave modes in developing plasma bubbles.
-
-
-
Obtencion De Parametros Fisicos Y Elasticos Mediante Tomografia De Transmision "Cross-Hole
More LessEn este trabajo presentamos los resultados de emplear una técnica tomográfica de inversión sísmica para la
reconstrucción de imágenes del subsuelo, en términos de las velocidades de las ondas P y S, así como una
técnica para la representación de parámetros sísmicos, tal como la relación de velocidades de la onda P y onda
S, la densidad, las constantes elásticas, y la porosidad, a partir de observaciones del tiempo de tránsito.
La metodología se aplicó a datos reales obtenidos de un experimento realizado en un campo petrolero ubicado
en el Estado de Texas, E.U.A., del cual se tenían algunos datos geológicos. Se obtuvieron los tomogramas de
los parámetros sísmicos, los cuales permitieron corroborar los datos litológicos, y así mismo inferir otros
detalles de la estructura interna del subsuelo.
Finalmente, hacemos énfasis de la importancia de aplicar la Tecnología descrita, en los campos petroleros de
México, ya que nos permitirá conocer las características físicas y elásticas de los yacimientos y analizar su
comportamiento lateral, etapas importantes que se realizan durante la caracterización de yacimientos.
-
-
-
Disturbances On Magnetotelluric Data Due To Electrified Railway
More LessMagnetotelluric (MT) soundings were made on two transverse profiles to the Campos do Jordão Railway (CJR) in the
period range of 4 to 3000s. The profiles are located in two adjacent regions of the São Paulo State with contrasting
conductivity: the conductive sedimentary region of Taubaté Basin and the resistive crystalline region of Serra da
Mantiqueira. The data were collected during diurnal and nocturnal periods, when the CJR operates with DC current and
when it is turned off, respectively. The objective of this study is to attempt to eliminate the electromagnetic noise
produced by the CJR in the diurnal data. To achieve this goal we plan to use some techniques based on the MT
response function estimation and then to estimate the resistivity profile of the region. This profile will be compared with
the results obtained from nocturnal data, not contaminated with the noise of the CJR, to verify the relative efficacy of the
methods employed to filter out the electromagnetic noise. The preliminary results indicate that the Serra da Mantiqueira
region is 177.8 times more resistive than the Basin and that the skin depth in the Basin is of 2.7 km.
-
-
-
On The Role Of Cosmic Rays In The Atmospheric Processes
Authors Yuri I. Stozhkov, V.I. Ermankov, I.M. Martin, P.E. Pokrevsky and M.G.S. MelloThe role of charged particles in processes in the atmosphere is considered. It is shown that these particles play the
important role in the global electric circuit provided the conductivity of air. The steady state equation describing ion
production rate and their recombination is analyzed on the base of experimental data on cosmic ray fluxes and ions
concentrations. These data were obtained at polar, middle and equatorial latitudes in the atmosphere from the ground
level up to 30-35 km. The influence of charged particle fluxes on rainfall values during Forbush decrease and powerful
solar proton events is demonstrated. Also, the mechanism of thunderstorm electricity production, separation of opposite
sign charges, and lightning production is discussed.
-
-
-
Participação Da Unicamp Com Experimentos Na Estação Espacial Internacional
A collaborative project to study Solar-Earth relationship using International Space Station (ISS), prepared by Institute of
Space Research (IKI) of Rusian Academy of Science and State University of Campinas (Unicamp) will be described. The
main objective will be identify phenomena relating solar influences in climatology variations on Earth, mainly intensity of
rains in Brazil. Infrared, visible and X-ray detectors will be installed on board of ISS russian segment to realize monitoring
on Brazilian territory.
-
-
-
Structure And Development Of The Powell Basin (Ne Antarctic Peninsula)
More LessPowell Basin is one of the few present-day examples of a small ocean basin largely surrounded by blocks of
continental crust. The western and eastern margins are conjugate passive margins having a transitional crust in the
continent-ocean boundary. The distinct characteristics of these two margins suggest a degree of asymmetry in their
development. A possible origin of asymmetrical extension during the initial rifting stage may be the occurrence of a
shear zone with an eastwards dipping component. A spreading ridge, located in the central part of the basin, split
into two crests that may be interpreted as two segments of an overlapping spreading centre (OSC). The rifting
episode could have begun about 35-40 Ma. A maximum age of Early Oligocene (29 Ma latest Early Oligocene) is
proposed for the ocean basin spreading, that appears to have ceased during the Early Miocene (23 Ma). The
eastward motion of the South Orkney Microcontinent relative to the Antarctic Peninsula created this basin. A pullapart
origin, related to a dextral fault system, has been proposed for the basin development. However, a possible
alternative is to consider that the transcurrent fault bounding the basin has opposite kinematics (sinistral the
northern one and dextral the southern one). In this model, the continental crust at the north of the Powell Basin
remains fixed in relation to the Antarctic Peninsula.
-
-
-
Resultados Preliminares De La Campaña De Ozonosondeo En Una Localidad De Altura (La Paz, Bolivia)
Authors Francesco Zaratti, Marcos Andrade and Ricardo FornoSe analizan los datos de once lanzamientos de sondas de ozono realizados en la región de La Paz ( 3400 m
snm) en el mes de Junio de 1998. Se estudia el comportamiento de variables como la temperatura, la altura de la
tropopausa, el contenido troposférico de ozono, la distribución estratosférica del ozono y el valor integral del
mismo. Se comparan los resultados obtenidos en esa campaña con los datos de un trabajo similar realizado en
1963 en la misma localidad con el fin de poner en evidencia eventuales modificaciones en la atmósfera local. Se
discute también un posible origen de la disminución del ozono total sobre las tierras altas tropicales.
-
-
-
Impactos Sócio-Ambientais Provocados Por Emanações Radiogênicas De Rochas “Graníticas” Utilizadas Em Ambientes Internos
More LessSão avaliados fatos referentes ao estudo das emanações radiogênicas produzidas por rochas “graníticas”
utilizadas em ambientes internos, relativos aos impactos sociais, ambientais, de segurança no trabalho,na
indústria e na comercialização desses materiais, observados durante o desenvolvimento das medições.
-
-
-
Applicability Of Eudo-Rotation Technique For Land Vsp With Difference In Surface Conditions At The Source Locations In Anisotropy Study
Authors Sergei Gorshkalev and Wladimir KarstenPseudo-rotation technique may be applied in marine VSP study of azìmuthal anisotropy of horizontally layered
media. lt uses multicomponent downhole registration of downgoing converted PS-waves from two symmetrical
sources with small offsets because directed sources of S-waves can not be used on sea. Land symmetrícal
sources are more widely used than directed sources, so we would like to estimate efficiency of this technique
for land VSP. The land survey conditions involve variations of near-surface properties and altitudes, which
cause the travel times of identical waves to differ. The technique of equalization of these travel times before the
pseudo-rotation was suggested. lt was tested on synthetical data of full wavefield. The model used was based
on the VSP surveys in the Yurubchen-Tokhomo oilfield zone in Eastern Siberia.
-
-
-
Estudo Das Estruturas Coerentes Na Cla Clara Por Radar Doppler
More LessThe evaluation of the respective role played by the coherent structures and the turbulence in the vertical transport within
the atmospheric boundary layer was the scientific objective of the TRAC experiment, the experimental framework of this
study, that made use in June 1993 of coordinated aircraft-radar measurements. The analyzed cases of ABL showed that
the radar was able to provide a coherent and continuous representation of the meteorological fields over a horizontal
range of several tens of kilometers and vertically up to 2.5 km, i.e., well beyond the top of ABL. Coherent structures
appeared as a common feature of the ABL under study and not as an exception. From radar measurements we found in
particular that turbulent scales of the inertial sub-range were modulated by the coherent structures. The capability of the
detection of weather cumulis located at the top of the ABL show that the radar is able to provide a description of the
entire ABL including the processes in the entrainement zone.
-