Maria OrtizBevia - Academia.edu (original) (raw)

Papers by Maria OrtizBevia

Research paper thumbnail of Evolution of heating and cooling degree-days in Spain: Trends and interannual variability

Global and Planetary Change, 2012

Weather-conditioned energy demand (degree-days) for indoor cooling in Spain has shown a significa... more Weather-conditioned energy demand (degree-days) for indoor cooling in Spain has shown a significant increase in recent decades. The North Atlantic Oscillation and the Southern Oscillation also influence the Spanish heating and cooling degree-days. Projections for the future from a set of coupled regional simulations are that towards the middle of the 21st century the summer demands for cooling in Spain will be increased by 50 % .

Research paper thumbnail of Spatial and temporal analysis of the seasonal and interannual variability in the tropical Pacific simulated with a coupled GCM

Annals of Geophysics, 2009

In the first part of this work, the dominant time scales that explain the tropical variability of... more In the first part of this work, the dominant time scales that explain the tropical variability of the first SINTEX simulation (ECHAM4(T30)-ORCA) are identified through a spectral analysis. Higher order spectral analysis is used to examine the interactions among these time scales. The time series analyzed are an average of sea surface temperature over the Niño3 region. The time scales obtained are compared with those identified in another coupled GCM simulation (ECHAM4(T42)-OPYC3). The higher importance of the biannual time scale in this last is explained partly by the strength of the coupling between the annual and the biannual time scales. There is no such strong coupling in the SINTEX simulation. Important differences among the generation of the simulated warm (or cold) event suggest the need of a systematic classification to isolate their relevant features. Therefore in the second part of this work, we address this problem. A space-time cluster analysis is performed on a data set built by collecting the values of the heat content anomalies in the tropical Pacific region, in the fifteen months previous to a peak in the Niño3 Index that has been identified as a 'warm' (or 'cold') event. In the case of the warm events, three types of generation schemes are found. In two of them, there are anomalies of heat content in the west, north and south of the equator, more than nine months before the events start. In the third case, the anomalies appear and grow in the central equatorial Pacific. Only two types are needed to classify the generation of cold events. Negative sea level height anomalies appear six months before the Niño3 Index reaches the (local) minimum. They are located north of the equator in one of the groups, and south of it in the other. Some of these characteristic traits also appear in observations of warm and cold events.

Research paper thumbnail of Sea ice concentration anomalies as long range predictors of anomalous conditions in the North Atlantic basin

Tellus A, 2002

Long-range empirical forecasts of North Atlantic anomalous conditions are issued, using sea ice c... more Long-range empirical forecasts of North Atlantic anomalous conditions are issued, using sea ice concentration anomalies in the same region as predictors. Conditions in the North Atlantic are characterized by anomalies of sea surface temperature, of 850 hPa air temperature and of sea level pressure. Using the Singular Value Decomposition of the cross-covariance matrix between the sea ice field (the predictor) and each of the predictand variables, empirical models are built, and forecasts at lead times from 3 to 18 months are presented. The forecasts of the air temperature anomalies score the highest levels of the skill, while forecasts of the sea level pressure anomalies are the less sucessful ones. To investigate the sources of the forecast skill, we analyze their spatial patterns. In addition, we investigate the influence of major climatic signals on the forecast skill. In the case of the air temperature anomalies, the spatial pattern of the skill may be connected to El Niñ o Southern Oscillation (ENSO) influences. The ENSO signature is present in the predictor field, as shown in the composite analysis. The composite pattern indicates a higher (lower) sea ice concentration in the Labrador Sea and the opposite situation in the Greenland-Barents Seas during the warm (cold) phase of ENSO. The forecasts issued under the El Niñ o conditions show improved skill in the Labrador region, the Iberian Peninsula and south of Greenland for the lead times considered in this paper. For the Great Lakes region the skill increases when the predictor is under the influence of a cold phase. Some features in the spatial structure of the skill of the forecasts issued in the period of the Great Salinity Anomaly present similarities with those found for forecasts made during the cold phase of ENSO. The strength of the dependence on the Great Salinity Anomaly makes it very difficult to determine the influence of the North Atlantic Oscillation.

Research paper thumbnail of Nonlinear estimation of El Niño impact on the North Atlantic winter

Journal of Geophysical Research, 2010

Research paper thumbnail of Impact of global warming on ENSO phase change

Advances in Geosciences, 2006

We compare the physical mechanisms involved in the generation and decay of ENSO events in a contr... more We compare the physical mechanisms involved in the generation and decay of ENSO events in a control (present day conditions) and Scenario (Is92a, IPCC 1996) simulations performed with the coupled ocean-atmosphere GCM ECHAM4-OPYC3. A clustering technique which objectively discriminates common features in the evolution of the Tropical Pacific Heat Content anomalies leading to the peak of ENSO events allows us to group into a few classes the ENSO events occurring in 240 years of data in the control and scenario runs. In both simulations, the composites of the groups show differences in the generation and development of ENSO. We present the changes in the statistics of the groups and explore the possible mechanisms involved.

Research paper thumbnail of Application of statistical techniques to the analysis and prediction of ENSO: Bayesian oscillation patterns as a prediction scheme

Dynamics of Atmospheres and Oceans, 1995

Here we study the low-frequency variability of the tropical Indian and Pacific basins with a new ... more Here we study the low-frequency variability of the tropical Indian and Pacific basins with a new statistical technique, Bayesian oscillation patterns (BOP). To describe the climatic system in this region, zonal wind and sea surface temperature (SST) are the selected variables. Their variability can be explained in terms of a reduced number of frequencies and spatial patterns. These are identified for each field by a statistical procedure. With the help of the patterns and the frequencies a predictive scheme is devised and applied in two forecast experiments. In the first, zonal wind anomalies are predicted using patterns and frequencies identified in the wind field. A more sophisticated scheme, a linear model which includes non-harmonic oscillations and interactions between patterns, is used when forecasting SST seasonal anomalies in the Nifio3 region. In this case, the predictors include the values of the frequencies identified in the BOP analysis of both wind and SST fields, and the corresponding patterns.

Research paper thumbnail of Dynamic modeling of air traffic emissions with a two variable system

International Journal of Sustainable Transportation, 2021

Greenhouse gases emissions modify the radiative balance of the Earth, causing changes in its clim... more Greenhouse gases emissions modify the radiative balance of the Earth, causing changes in its climate. Climate Change is considered one of the greatest threats to economic and social stability. Avia...

Research paper thumbnail of Empirical seasonal forecasts of the NAO

Research paper thumbnail of Linear and nonlinear links of winter European precipitation to Northern Hemisphere circulation patterns

Climate Dynamics

The connections between European rainfall variability in winter (from January to March) and North... more The connections between European rainfall variability in winter (from January to March) and Northern Hemisphere circulation patterns, as represented by 500-hPa geopotential height, are investigated in the period 1900–2014. Initially, three statistically significant pairs of linearly-related circulation and precipitation patterns, explaining 45% of the variance in the latter field, are identified. The first two essentially represent the North Atlantic Oscillation (NAO) and the East Atlantic (EA) patterns, while the third corresponds to a structure described in recent literature as a blend of the Pacific North America (PNA) pattern and the so-called Asia Bering North America (ABNA) pattern. The residual precipitation field is then examined for patterns that can introduce non-linear modulations into the circulation-precipitation links. It is so found that the NAO impact on European rainfall is modulated by North American and Pacific factors controlling cyclogenesis over Newfoundland. The positive-phase EA rainfall anomalies over Central Europe and the British Isles seem to be markedly affected by the NAO phase. Finally, a possible signature from the Circumglobal Teleconnection Pattern disrupting the NAO influence on East Mediterranean precipitation anomalies is detected.

Research paper thumbnail of Empirical seasonal forecasts of the NAO

Research paper thumbnail of Erratum to: An estimation of ENSO predictability from its seasonal teleconnections

Theoretical and Applied Climatology

Research paper thumbnail of A classification of ENSO events in a coupled ocean-atmosphere GCM

A clustering technique is designed in order to group into a few classes the ENSO events occurring... more A clustering technique is designed in order to group into a few classes the ENSO events occurring in 100 years of data from a coupled ocean-atmosphere GCM (ECHAM4-ORCA) simulation. Tropical Pacific heat content anomalies during the 15 months previous to the event's peak (as identified in the Niño3 SSTA Index) are compared in terms of two definitions of distance. A classification of ENSO events emerges which divides them into three classes. These are characterized by a composite built as the average of all members in a given group. Significant features in the composites are identified by means of tests on the class mean and median. In the first group, the warming occurs shortly after cold anomalies in the equatorial Pacific. Warm off-equatorial anomalies growing in the western ocean during this cold phase induce the transition to the warm one once they reach the equator. Though not immediately preceded by cold anomalies, anomalous heat in the western off-equator also leads the eq...

Research paper thumbnail of Trends in indices of climatic extremes in central-western Spain

Different indices of climate extremes have been computed from daily temperature and precipitation... more Different indices of climate extremes have been computed from daily temperature and precipitation data registered in meteorological stations in the central-western area of Spain. The data have been obtained from the SpanishMeteorological Office and cover the period from 1958 to 2001. Eight indicators, six of them for temperature (TX10P,TX90P,TN10P, TN90P, WSDI and CSDI) and two for the precipitation (R10mm and R20mm) extremes, have been computed. Their trends during the interval under consideration have been estimated and tested for statistical significance. In agreement with previous studies, our results indicate a generalized tendency towards warmer conditions, although there appear to exist remarkable disparities in the magnitude and significance of the trends even on this regional scale. Regarding the precipitation extremes, significant trends are detected in a minority of the stations under study.

Research paper thumbnail of Scale interactions in the tropical Atlanticvariability simulated with a coupled GCM

Warm and cold events in the Gulf of Guinea are an important feature in the interannual variabilit... more Warm and cold events in the Gulf of Guinea are an important feature in the interannual variability of the tropical Atlantic Ocean, and partly a manifestation of the equatorial Atlantic system's intrinsic variability. Due to the relatively reduced zonal extension of this ocean, the latter variability is comparatively weak and thus strongly modified by other factors at play, either local or remote, like the seasonal cycle or ENSO. We present here an analysis of the tropical Atlantic variability in a 100-year-long chunk of the output of a coupled GCM. Through it, we obtain a better understanding of this variability and of its interactions with the seasonal cycle and with the ENSO signal. Following hints in the observations, we separate warm or cold events of the simulation in a few types, according to their similarities and differences. This classification is carried out as a spatio-temporal cluster analysis of the values, from nine months before up to the peak of the event, of th...

Research paper thumbnail of ENSO-related quadriennial variations in European rainfall

Precipitation over Europe displays pronounced spectral peaks at quadriennial timescales. Part of ... more Precipitation over Europe displays pronounced spectral peaks at quadriennial timescales. Part of this variability is shown here to be connected with the El Niño - Southern Oscillation (ENSO). The characteristic pattern of precipitation anomalies, lagging the tropical Pacific sea surface temperature (SST) by about 6 months, consists of a wide band of anomalies of one sign across most of the

Research paper thumbnail of The influence of meteorological variability on the mid-term evolution of the electricity load

Research paper thumbnail of A cyclo-stationary model of sea surface temperatures in the Pacific Ocean

Tellus A, 1985

Sea surface temperature anomalies in mid-latitude north Pacific Ocean are compared with a cyclo-s... more Sea surface temperature anomalies in mid-latitude north Pacific Ocean are compared with a cyclo-stationary stochastic model in which the anomalies are forced by atmospheric "weather" disturbances. The results show that the model explains the observed two-time auto-covariances of the anomalies for almost all (98%) of the studied region.

Research paper thumbnail of Generation of equatorial Atlantic warm and cold events in a coupled general circulation model simulation

Tellus A, 2002

Warm and cold events in the Gulf of Guinea, characteristic of the tropical interannual variabilit... more Warm and cold events in the Gulf of Guinea, characteristic of the tropical interannual variability, can be generated in several ways. This emerges from a statistical analysis of 200 years of interannual variability simulated by a coupled ocean-atmosphere General Circulation Model. The application of a clustering technique to the anomalies of the thermal energy stored in the upper oceanic layers leads to the separation of the events, either warm or cold, into a number of classes, each of them distinguished by a particular generation scheme. The physical mechanisms involved are identified by examining the contributions of the various terms in the mixed layer tendency equation. Basically, those few classes can be sorted into two larger groups. In one of them, the onset stage is characterized by an eastward propagation of the anomalies. Atmospheric flows play a leading part in the generation of events within this group. In the second group, thermal energy anomalies are generated in situ in the Gulf of Guinea, and it is mixing that gives the most important contribution to the development of the events. The different classes are related to different seasonal signatures and also to differences in the influence of the El Nin o-Southern Oscillation (ENSO). While some of the classes are strongly influenced by ENSO, while in others this influence is not significant. This can explain the barely significant correlations between ENSO and the Atlantic warm events, a feature that the simulation analyzed here shares with the observations.

Research paper thumbnail of Empirical forecasts of tropical Atlantic sea surface temperature anomalies

Quarterly Journal of the Royal Meteorological Society, 2000

Research paper thumbnail of North Atlantic atmospheric regimes and winter extremes in the Iberian peninsula

Natural Hazards and Earth System Science, 2011

In this study, we assess the relationships between North Atlantic scale atmospheric regimes and e... more In this study, we assess the relationships between North Atlantic scale atmospheric regimes and extremes of precipitation and minimum temperature in the Iberian peninsula for an extended (DJFM) winter season. As found in previous studies, large scale atmospheric regimes are well represented in climate simulations while the extreme atmospheric variability is not. The relationship between some of these atmospheric regimes and the probability of occurrence of extreme values in simulations of present day climatic variability is validated here with daily observations at 68 meteorological stations all over the Iberian peninsula. Therefore, the possible changes in the probability of occurrence of winter extremes of minimum temperature and precipitation are obtained by projecting the changes in the probability of occurrence of the winter atmospheric regimes. The trends in the frequency of the observed large scale patterns give an indication of what can be expected in the next decades. For the long term (in a century), the changes are obtained directly from the comparison of the frequencies of the atmospheric regimes in the scenario simulations with those of the historical period. The projections obtained in this way are tested for consistency with the results obtained by comparing the changes in the extremes threshold values in the scenario with those of the historical simulations. The results point to a future with less precipitation extreme events and less minimum temperature extreme events in winter in the westerly central part of the Iberian peninsula.

Research paper thumbnail of Evolution of heating and cooling degree-days in Spain: Trends and interannual variability

Global and Planetary Change, 2012

Weather-conditioned energy demand (degree-days) for indoor cooling in Spain has shown a significa... more Weather-conditioned energy demand (degree-days) for indoor cooling in Spain has shown a significant increase in recent decades. The North Atlantic Oscillation and the Southern Oscillation also influence the Spanish heating and cooling degree-days. Projections for the future from a set of coupled regional simulations are that towards the middle of the 21st century the summer demands for cooling in Spain will be increased by 50 % .

Research paper thumbnail of Spatial and temporal analysis of the seasonal and interannual variability in the tropical Pacific simulated with a coupled GCM

Annals of Geophysics, 2009

In the first part of this work, the dominant time scales that explain the tropical variability of... more In the first part of this work, the dominant time scales that explain the tropical variability of the first SINTEX simulation (ECHAM4(T30)-ORCA) are identified through a spectral analysis. Higher order spectral analysis is used to examine the interactions among these time scales. The time series analyzed are an average of sea surface temperature over the Niño3 region. The time scales obtained are compared with those identified in another coupled GCM simulation (ECHAM4(T42)-OPYC3). The higher importance of the biannual time scale in this last is explained partly by the strength of the coupling between the annual and the biannual time scales. There is no such strong coupling in the SINTEX simulation. Important differences among the generation of the simulated warm (or cold) event suggest the need of a systematic classification to isolate their relevant features. Therefore in the second part of this work, we address this problem. A space-time cluster analysis is performed on a data set built by collecting the values of the heat content anomalies in the tropical Pacific region, in the fifteen months previous to a peak in the Niño3 Index that has been identified as a 'warm' (or 'cold') event. In the case of the warm events, three types of generation schemes are found. In two of them, there are anomalies of heat content in the west, north and south of the equator, more than nine months before the events start. In the third case, the anomalies appear and grow in the central equatorial Pacific. Only two types are needed to classify the generation of cold events. Negative sea level height anomalies appear six months before the Niño3 Index reaches the (local) minimum. They are located north of the equator in one of the groups, and south of it in the other. Some of these characteristic traits also appear in observations of warm and cold events.

Research paper thumbnail of Sea ice concentration anomalies as long range predictors of anomalous conditions in the North Atlantic basin

Tellus A, 2002

Long-range empirical forecasts of North Atlantic anomalous conditions are issued, using sea ice c... more Long-range empirical forecasts of North Atlantic anomalous conditions are issued, using sea ice concentration anomalies in the same region as predictors. Conditions in the North Atlantic are characterized by anomalies of sea surface temperature, of 850 hPa air temperature and of sea level pressure. Using the Singular Value Decomposition of the cross-covariance matrix between the sea ice field (the predictor) and each of the predictand variables, empirical models are built, and forecasts at lead times from 3 to 18 months are presented. The forecasts of the air temperature anomalies score the highest levels of the skill, while forecasts of the sea level pressure anomalies are the less sucessful ones. To investigate the sources of the forecast skill, we analyze their spatial patterns. In addition, we investigate the influence of major climatic signals on the forecast skill. In the case of the air temperature anomalies, the spatial pattern of the skill may be connected to El Niñ o Southern Oscillation (ENSO) influences. The ENSO signature is present in the predictor field, as shown in the composite analysis. The composite pattern indicates a higher (lower) sea ice concentration in the Labrador Sea and the opposite situation in the Greenland-Barents Seas during the warm (cold) phase of ENSO. The forecasts issued under the El Niñ o conditions show improved skill in the Labrador region, the Iberian Peninsula and south of Greenland for the lead times considered in this paper. For the Great Lakes region the skill increases when the predictor is under the influence of a cold phase. Some features in the spatial structure of the skill of the forecasts issued in the period of the Great Salinity Anomaly present similarities with those found for forecasts made during the cold phase of ENSO. The strength of the dependence on the Great Salinity Anomaly makes it very difficult to determine the influence of the North Atlantic Oscillation.

Research paper thumbnail of Nonlinear estimation of El Niño impact on the North Atlantic winter

Journal of Geophysical Research, 2010

Research paper thumbnail of Impact of global warming on ENSO phase change

Advances in Geosciences, 2006

We compare the physical mechanisms involved in the generation and decay of ENSO events in a contr... more We compare the physical mechanisms involved in the generation and decay of ENSO events in a control (present day conditions) and Scenario (Is92a, IPCC 1996) simulations performed with the coupled ocean-atmosphere GCM ECHAM4-OPYC3. A clustering technique which objectively discriminates common features in the evolution of the Tropical Pacific Heat Content anomalies leading to the peak of ENSO events allows us to group into a few classes the ENSO events occurring in 240 years of data in the control and scenario runs. In both simulations, the composites of the groups show differences in the generation and development of ENSO. We present the changes in the statistics of the groups and explore the possible mechanisms involved.

Research paper thumbnail of Application of statistical techniques to the analysis and prediction of ENSO: Bayesian oscillation patterns as a prediction scheme

Dynamics of Atmospheres and Oceans, 1995

Here we study the low-frequency variability of the tropical Indian and Pacific basins with a new ... more Here we study the low-frequency variability of the tropical Indian and Pacific basins with a new statistical technique, Bayesian oscillation patterns (BOP). To describe the climatic system in this region, zonal wind and sea surface temperature (SST) are the selected variables. Their variability can be explained in terms of a reduced number of frequencies and spatial patterns. These are identified for each field by a statistical procedure. With the help of the patterns and the frequencies a predictive scheme is devised and applied in two forecast experiments. In the first, zonal wind anomalies are predicted using patterns and frequencies identified in the wind field. A more sophisticated scheme, a linear model which includes non-harmonic oscillations and interactions between patterns, is used when forecasting SST seasonal anomalies in the Nifio3 region. In this case, the predictors include the values of the frequencies identified in the BOP analysis of both wind and SST fields, and the corresponding patterns.

Research paper thumbnail of Dynamic modeling of air traffic emissions with a two variable system

International Journal of Sustainable Transportation, 2021

Greenhouse gases emissions modify the radiative balance of the Earth, causing changes in its clim... more Greenhouse gases emissions modify the radiative balance of the Earth, causing changes in its climate. Climate Change is considered one of the greatest threats to economic and social stability. Avia...

Research paper thumbnail of Empirical seasonal forecasts of the NAO

Research paper thumbnail of Linear and nonlinear links of winter European precipitation to Northern Hemisphere circulation patterns

Climate Dynamics

The connections between European rainfall variability in winter (from January to March) and North... more The connections between European rainfall variability in winter (from January to March) and Northern Hemisphere circulation patterns, as represented by 500-hPa geopotential height, are investigated in the period 1900–2014. Initially, three statistically significant pairs of linearly-related circulation and precipitation patterns, explaining 45% of the variance in the latter field, are identified. The first two essentially represent the North Atlantic Oscillation (NAO) and the East Atlantic (EA) patterns, while the third corresponds to a structure described in recent literature as a blend of the Pacific North America (PNA) pattern and the so-called Asia Bering North America (ABNA) pattern. The residual precipitation field is then examined for patterns that can introduce non-linear modulations into the circulation-precipitation links. It is so found that the NAO impact on European rainfall is modulated by North American and Pacific factors controlling cyclogenesis over Newfoundland. The positive-phase EA rainfall anomalies over Central Europe and the British Isles seem to be markedly affected by the NAO phase. Finally, a possible signature from the Circumglobal Teleconnection Pattern disrupting the NAO influence on East Mediterranean precipitation anomalies is detected.

Research paper thumbnail of Empirical seasonal forecasts of the NAO

Research paper thumbnail of Erratum to: An estimation of ENSO predictability from its seasonal teleconnections

Theoretical and Applied Climatology

Research paper thumbnail of A classification of ENSO events in a coupled ocean-atmosphere GCM

A clustering technique is designed in order to group into a few classes the ENSO events occurring... more A clustering technique is designed in order to group into a few classes the ENSO events occurring in 100 years of data from a coupled ocean-atmosphere GCM (ECHAM4-ORCA) simulation. Tropical Pacific heat content anomalies during the 15 months previous to the event's peak (as identified in the Niño3 SSTA Index) are compared in terms of two definitions of distance. A classification of ENSO events emerges which divides them into three classes. These are characterized by a composite built as the average of all members in a given group. Significant features in the composites are identified by means of tests on the class mean and median. In the first group, the warming occurs shortly after cold anomalies in the equatorial Pacific. Warm off-equatorial anomalies growing in the western ocean during this cold phase induce the transition to the warm one once they reach the equator. Though not immediately preceded by cold anomalies, anomalous heat in the western off-equator also leads the eq...

Research paper thumbnail of Trends in indices of climatic extremes in central-western Spain

Different indices of climate extremes have been computed from daily temperature and precipitation... more Different indices of climate extremes have been computed from daily temperature and precipitation data registered in meteorological stations in the central-western area of Spain. The data have been obtained from the SpanishMeteorological Office and cover the period from 1958 to 2001. Eight indicators, six of them for temperature (TX10P,TX90P,TN10P, TN90P, WSDI and CSDI) and two for the precipitation (R10mm and R20mm) extremes, have been computed. Their trends during the interval under consideration have been estimated and tested for statistical significance. In agreement with previous studies, our results indicate a generalized tendency towards warmer conditions, although there appear to exist remarkable disparities in the magnitude and significance of the trends even on this regional scale. Regarding the precipitation extremes, significant trends are detected in a minority of the stations under study.

Research paper thumbnail of Scale interactions in the tropical Atlanticvariability simulated with a coupled GCM

Warm and cold events in the Gulf of Guinea are an important feature in the interannual variabilit... more Warm and cold events in the Gulf of Guinea are an important feature in the interannual variability of the tropical Atlantic Ocean, and partly a manifestation of the equatorial Atlantic system's intrinsic variability. Due to the relatively reduced zonal extension of this ocean, the latter variability is comparatively weak and thus strongly modified by other factors at play, either local or remote, like the seasonal cycle or ENSO. We present here an analysis of the tropical Atlantic variability in a 100-year-long chunk of the output of a coupled GCM. Through it, we obtain a better understanding of this variability and of its interactions with the seasonal cycle and with the ENSO signal. Following hints in the observations, we separate warm or cold events of the simulation in a few types, according to their similarities and differences. This classification is carried out as a spatio-temporal cluster analysis of the values, from nine months before up to the peak of the event, of th...

Research paper thumbnail of ENSO-related quadriennial variations in European rainfall

Precipitation over Europe displays pronounced spectral peaks at quadriennial timescales. Part of ... more Precipitation over Europe displays pronounced spectral peaks at quadriennial timescales. Part of this variability is shown here to be connected with the El Niño - Southern Oscillation (ENSO). The characteristic pattern of precipitation anomalies, lagging the tropical Pacific sea surface temperature (SST) by about 6 months, consists of a wide band of anomalies of one sign across most of the

Research paper thumbnail of The influence of meteorological variability on the mid-term evolution of the electricity load

Research paper thumbnail of A cyclo-stationary model of sea surface temperatures in the Pacific Ocean

Tellus A, 1985

Sea surface temperature anomalies in mid-latitude north Pacific Ocean are compared with a cyclo-s... more Sea surface temperature anomalies in mid-latitude north Pacific Ocean are compared with a cyclo-stationary stochastic model in which the anomalies are forced by atmospheric "weather" disturbances. The results show that the model explains the observed two-time auto-covariances of the anomalies for almost all (98%) of the studied region.

Research paper thumbnail of Generation of equatorial Atlantic warm and cold events in a coupled general circulation model simulation

Tellus A, 2002

Warm and cold events in the Gulf of Guinea, characteristic of the tropical interannual variabilit... more Warm and cold events in the Gulf of Guinea, characteristic of the tropical interannual variability, can be generated in several ways. This emerges from a statistical analysis of 200 years of interannual variability simulated by a coupled ocean-atmosphere General Circulation Model. The application of a clustering technique to the anomalies of the thermal energy stored in the upper oceanic layers leads to the separation of the events, either warm or cold, into a number of classes, each of them distinguished by a particular generation scheme. The physical mechanisms involved are identified by examining the contributions of the various terms in the mixed layer tendency equation. Basically, those few classes can be sorted into two larger groups. In one of them, the onset stage is characterized by an eastward propagation of the anomalies. Atmospheric flows play a leading part in the generation of events within this group. In the second group, thermal energy anomalies are generated in situ in the Gulf of Guinea, and it is mixing that gives the most important contribution to the development of the events. The different classes are related to different seasonal signatures and also to differences in the influence of the El Nin o-Southern Oscillation (ENSO). While some of the classes are strongly influenced by ENSO, while in others this influence is not significant. This can explain the barely significant correlations between ENSO and the Atlantic warm events, a feature that the simulation analyzed here shares with the observations.

Research paper thumbnail of Empirical forecasts of tropical Atlantic sea surface temperature anomalies

Quarterly Journal of the Royal Meteorological Society, 2000

Research paper thumbnail of North Atlantic atmospheric regimes and winter extremes in the Iberian peninsula

Natural Hazards and Earth System Science, 2011

In this study, we assess the relationships between North Atlantic scale atmospheric regimes and e... more In this study, we assess the relationships between North Atlantic scale atmospheric regimes and extremes of precipitation and minimum temperature in the Iberian peninsula for an extended (DJFM) winter season. As found in previous studies, large scale atmospheric regimes are well represented in climate simulations while the extreme atmospheric variability is not. The relationship between some of these atmospheric regimes and the probability of occurrence of extreme values in simulations of present day climatic variability is validated here with daily observations at 68 meteorological stations all over the Iberian peninsula. Therefore, the possible changes in the probability of occurrence of winter extremes of minimum temperature and precipitation are obtained by projecting the changes in the probability of occurrence of the winter atmospheric regimes. The trends in the frequency of the observed large scale patterns give an indication of what can be expected in the next decades. For the long term (in a century), the changes are obtained directly from the comparison of the frequencies of the atmospheric regimes in the scenario simulations with those of the historical period. The projections obtained in this way are tested for consistency with the results obtained by comparing the changes in the extremes threshold values in the scenario with those of the historical simulations. The results point to a future with less precipitation extreme events and less minimum temperature extreme events in winter in the westerly central part of the Iberian peninsula.