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About

I studied Physics and Applied Mathematics / Astronomy (FCUP-UP, 1998) followed by a master degree in computational methods (FEUP-UP, 2000) and a PhD in Surveying Engineering (University of Porto, 2006, Thesis "Sea level change in the North Atlantic from tide gauges and satellite altimetry"). My  research is highly inter-disciplinary, with a strong emphasis on time series analysis and methodological approaches for the analysis of environmental data. A key aspect of my work on geophysical data analysis is the incorporation of problem-related knowledge into the data analysis process, which requires a very close interaction with experts from different fields (meteorology, oceanography, geology, physics, statistics,...) .

My current research interests span different fields in the general domain of geophysics, reflecting my strong interdisciplinary background, my interest in the earth system, planets in general, and space-earth interactions, and my expertise in data and time series analysis. My ongoing activities focus on the following topics:

- sea level variability from tide gauges, satellite altimetry, and synergy of sea level observations in a multivariate setting, including complementary observations (e.g. GPS), model outputs, in-situ measurements, remote sensing, and indirect proxys.

- radon variability in soils, air and water, and its use as a tracer and as a geophysical proxy, particularly in coastal and deep sea marine environments.

- environmental radioactivity, atmospheric electricity, and space-atmosphere-surface interactions.

I edited a book  "Nonlinear Time Series Analysis in the Geosciences - Applications in Climatology, Geodynamics and Solar-Terrestrial Physics" and three topical volumes. I'm the author of 3 book chapters and more than 40 papers in international peer-reviewed journals.

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Details

Details

  • Name

    Susana Alexandra Barbosa
  • Cluster

    Computer Science
  • Role

    Senior Researcher
  • Since

    12th January 2015
001
Publications

2017

Vertical land motion and sea level change in Macaronesia

Authors
Mendes, VB; Barbosa, SM; Romero, I; Madeira, J; da Silveira, AB;

Publication
GEOPHYSICAL JOURNAL INTERNATIONAL

Abstract
This study addresses long-term sea level variability in Macaronesia from a holistic perspective using all available instrumental records in the region, including a dense network of GPS continuous stations, tide gauges and satellite observations. A detailed assessment of vertical movement from GPS time series underlines the influence of the complex volcano-tectonic setting of the Macaronesian islands in local uplift/subsidence. Relative sea level for the region is spatially highly variable, ranging from -1.1 to 5.1 mm yr(-1). Absolute sea level from satellite altimetry exhibits consistent trends in the Macaronesia, with a mean value of 3.0 +/- 0.5 mm yr(-1). Typically, sea level trends from tide gauge records corrected for vertical movement using the estimates from GPS time series are lower than uncorrected estimates. The agreement between satellite altimetry and tide gauge trends corrected for vertical land varies substantially from island to island. Trends derived from the combination of GPS and tide gauge observations differ by less than 1 mm yr(-1) with respect to absolute sea level trends from satellite altimetry for 56 per cent of the stations, despite the heterogeneity in length of both GPS and tide gauge series, and the influence of volcanic-tectonic processes affecting the position of some GPS stations.

2017

Short-term variability of gamma radiation at the ARM Eastern North Atlantic facility (Azores)

Authors
Barbosa, SM; Miranda, P; Azevedo, EB;

Publication
Journal of Environmental Radioactivity

Abstract
This work addresses the short-term variability of gamma radiation measured continuously at the Eastern North Atlantic (ENA) facility located in the Graciosa island (Azores, 39N; 28W), a fixed site of the Atmospheric Radiation Measurement programme (ARM). The temporal variability of gamma radiation is characterized by occasional anomalies over a slowly-varying signal. Sharp peaks lasting typically 2–4 h are coincident with heavy precipitation and result from the scavenging effect of precipitation bringing radon progeny from the upper levels to the ground surface. However the connection between gamma variability and precipitation is not straightforward as a result of the complex interplay of factors such as the precipitation intensity, the PBL height, the cloud's base height and thickness, or the air mass origin and atmospheric concentration of sub-micron aerosols, which influence the scavenging processes and therefore the concentration of radon progeny. Convective precipitation associated with cumuliform clouds forming under conditions of warming of the ground relative to the air does not produce enhancements in gamma radiation, since the drop growing process is dominated by the fast accretion of liquid water, resulting in the reduction of the concentration of radionuclides by dilution. Events of convective precipitation further contribute to a reduction in gamma counts by inhibiting radon release from the soil surface and by attenuating gamma rays from all gamma-emitting elements on the ground. Anomalies occurring in the absence of precipitation are found to be associated with a diurnal cycle of maximum gamma counts before sunrise decreasing to a minimum in the evening, which are observed in conditions of thermal stability and very weak winds enabling the build-up of near surface radon progeny during the night. © 2017 Elsevier Ltd

2016

Trends in Extreme Mean Sea Level Quantiles from Satellite Altimetry

Authors
Barbosa, SM;

Publication
MARINE GEODESY

Abstract
Satellite altimetry allows the study of sea-level long-term variability on a global and spatially uniform basis. Here quantile regression is applied to derive robust median regression trends of mean sea level as well as trends in extreme quantiles from radar altimetry time series. In contrast with ordinary least squares regression, which only provides an estimate on the rate of change of the mean of data distribution, quantile regression allows the estimation of trends at different quantiles of the data distribution, yielding a more complete picture of long-term variability. Trends derived from basin-wide averaged regional mean sea level time series are robust and similar for all quantiles, indicating that all parts of the data distribution are changing at the same rate. In contrast, trends are not robust and diverge across quantiles in the case of local time series. Trends are under- (over-)estimated in the western (eastern) equatorial Pacific. Furthermore, trends in the lowermost quantile (0.05) are larger than the median trend in the western Pacific, while trends in the uppermost quantile (0.95) are lower than the median trend in the eastern Pacific. These differences in trends in extreme mean sea level quantiles are explained by the exceptional effect of the strong 1997-1998 El Nino-Southern Oscillation (ENSO) event.

2016

Wavelet-Based Clustering of Sea Level Records

Authors
Barbosa, SM; Gouveia, S; Scotto, MG; Alonso, AM;

Publication
MATHEMATICAL GEOSCIENCES

Abstract
The classification ofmultivariate time series in terms of their corresponding temporal dependence patterns is a common problem in geosciences, particularly for large datasets resulting from environmental monitoring networks. Here a wavelet-based clustering approach is applied to sea level and atmospheric pressure time series at tide gauge locations in the Baltic Sea. The resulting dendrogram discriminates three spatially-coherent groups of stations separating the southernmost tide gauges, reflecting mainly high-frequency variability driven by zonal wind, from the middle-basin stations and the northernmost stations dominated by lower-frequency variability and the response to atmospheric pressure.

2016

Long-term changes in the seasonality of Baltic sea level

Authors
Barbosa, SM; Donner, RV;

Publication
TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY

Abstract
The seasonal cycle accounts for about 40 % of the total sea level variability in the Baltic Sea. In a climate change context, changes are expected to occur, not only in mean levels but also in the seasonal characteristics of sea level. The present study addresses the quantification of changes in the seasonal cycle of sea level from a set of century-long tide gauge records in the Baltic Sea. In order to obtain robust estimates of the changes in amplitude and phase of the seasonal cycle, we apply different methods, including continuous wavelet filtering, multi-resolution decomposition based on the maximal overlap discrete wavelet transform, auto-regressive-based decomposition, singular spectrum analysis and empirical mode decomposition. The results show that all methods generally trace a similar long-term variability of the annual cycle amplitudes, and we focus on discrete wavelet analysis as the natural counterpart of classical moving Fourier analysis. In contrast to previous studies suggesting the existence of long-term changes in the seasonal cycle, in particular an increase of the annual amplitude, we find alternating periods of high and low amplitudes without any clear indication of systematic long-term trends. The derived seasonal patterns are spatially coherent, discriminating the stations in the Baltic entrance from the remaining stations in the Baltic basin, for which zonal wind accounts for typically more than 40 % of the variations in amplitude.

2015

Temporal variability of radon in a remediated tailing of uranium ore processing - the case of Urgeirica (central Portugal)

Authors
Barbosa, SM; Lopes, F; Correia, AD; Barbosa, S; Pereira, AC; Neves, LF;

Publication
JOURNAL OF ENVIRONMENTAL RADIOACTIVITY

Abstract
Radon monitoring at different levels of the cover of the Urgeirica tailings shows that the sealing is effective and performing as desired in terms of containing the strongly radioactive waste resulting from uranium ore processing. However, the analysis of the time series of radon concentration shows a very complex temporal structure, particularly at depth, including very large and fast variations from a few tens of kBq m(-3) to more than a million kBq m(-3) in less than one day. The diurnal variability is strongly asymmetric, peaking at 18 h/19 h and decreasing very fast around 21 h/22 h. The analysis is performed for summer and for a period with no rain in order to avoid the potential influence of precipitation and related environmental conditions on the radon variability. Analysis of ancillary measurements of temperature, relative humidity, wind speed and wind direction, as well as atmospheric pressure reanalysis data shows that the daily averaged radon concentration in the taillings material is anti-correlated with the atmospheric pressure and that the diurnal amplitude is associated with the magnitude of atmospheric pressure daily oscillations.

2015

Radon applications in geosciences - Progress & perspectives

Authors
Barbosa, SM; Donner, RV; Steinitz, G;

Publication
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS

Abstract
During the last decades, the radioactive noble gas radon has found a variety of geoscientific applications, ranging from its utilization as a potential earthquake precursor and proxy of tectonic stress over its specific role in volcanic environments to a wide range of applications as a tracer in marine and hydrological settings. This topical issue summarizes the current state of research as exemplified by some original research articles covering the aforementioned as well as other closely related aspects and points to some important future directions of radon application in geosciences. This editorial provides a more detailed overview of the contents of this volume, a brief summary of the rationale underlying the diverse applications, and outlines some important perspectives.