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Gualdi, Silvio
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Gualdi, Silvio
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silvio.gualdi@ingv.it
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staff
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Scopus Author ID
6603538344
Researcher ID
F-3061-2015
67 results
Now showing 1 - 10 of 67
- PublicationOpen AccessMulti-model assessment of the late-winter extra-tropical response to El Niño and La Niña(2022)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; El Niño-Southern Oscillation (ENSO) is known to affect the Northern Hemisphere tropospheric circulation in late-winter (January–March), but whether El Niño and La Niña lead to symmetric impacts and with the same underlying dynamics remains unclear, particularly in the North Atlantic. Three state-of-the-art atmospheric models forced by symmetric anomalous sea surface temperature (SST) patterns, mimicking strong ENSO events, are used to robustly diagnose symmetries and asymmetries in the extra-tropical ENSO response. Asymmetries arise in the sea-level pressure (SLP) response over the North Pacific and North Atlantic, as the response to La Niña tends to be weaker and shifted westward with respect to that of El Niño. The difference in amplitude can be traced back to the distinct energy available for the two ENSO phases associated with the non-linear diabatic heating response to the total SST field. The longitudinal shift is embedded into the large-scale Rossby wave train triggered from the tropical Pacific, as its anomalies in the upper troposphere show a similar westward displacement in La Niña compared to El Niño. To fully explain this shift, the response in tropical convection and the related anomalous upper-level divergence have to be considered together with the climatological vorticity gradient of the subtropical jet, i.e. diagnosing the tropical Rossby wave source. In the North Atlantic, the ENSO-forced SLP signal is a well-known dipole between middle and high latitudes, different from the North Atlantic Oscillation, whose asymmetry is not indicative of distinct mechanisms driving the teleconnection for El Niño and La Niña.66 33 - PublicationRestrictedA Multisystem View of Wintertime NAO Seasonal PredictionsSignificant predictive skill for the mean winter North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) has been recently reported for a number of different seasonal forecasting systems. These findings are important in exploring the predictability of the natural system, but they are also important from a socioeconomic point of view, since the ability to predict the wintertime atmospheric circulation anomalies over the North Atlantic well ahead in time will have significant benefits for North American and European countries. In contrast to the tropics, for the mid latitudes the predictive skill of many forecasting systems at the seasonal time scale has been shown to be low to moderate. The recent findings are promising in this regard, suggesting that better forecasts are possible, provided that key components of the climate system are initialized realistically and the coupled models are able to simulate adequately the dominant processes and teleconnections associated with low-frequency variability. It is shown that a multisystem approach has unprecedented high predictive skill for the NAO and AO, probably largely due to increasing the ensemble size and partly due to increasing model diversity. Predicting successfully the winter mean NAO does not ensure that the respective climate anomalies are also well predicted. The NAO has a strong impact on Europe and North America, yet it only explains part of the interannual and low-frequency variability over these areas. Here it is shown with a number of different diagnostics that the high predictive skill for the NAO/AO indeed translates to more accurate predictions of temperature, surface pressure, and precipitation in the areas of influence of this teleconnection.
68 4 - PublicationOpen AccessAnalysis of the mid-latitude weather regimes in the 200-year control integration of the SINTEX model(2003)
; ; ; ;Corti, S.; Istituto di Scienze dell 'Atmosfera e del Clima, CNR, Bologna, Italy ;Gualdi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Navarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; Recent results indicate that climate predictions require models which can simulate accurately natural circulation regimes and their associated variability. The main purpose of this study is to investigate whether (and how) a coupled model can simulate the real world weather regimes. A 200-year control integration of a coupled GCM (the «SINTEX model») is considered. The output analysed consists of monthly mean values of Northern Hemisphere extended winter (November to April) 500-hPa geopotential heights. An Empirical Orthogonal Function (EOF) analysis is first applied in order to define a reduced phase space based on the leading modes of variability. Therefore the principal component PDF in the reduced phase space spanned by two leading EOFs is computed. Based on a PDF analysis in the phase space spanned by the leading EOF1 and REOF2, substantial evidence of the nongaussian regime structure of the SINTEX northern winter circulation is found. The model Probability Density Function (PDF) exhibits three maxima. The 500-hPa height geographical patterns of these density maxima are strongly reminiscent of well-documented Northern Hemisphere weather regimes. This result indicates that the SINTEX model can not only simulate the non-gaussian structure of the climatic attractor, but is also able to reproduce the natural modes of variability of the system.190 335 - PublicationOpen AccessTROPICAL CYCLONE ACTIVITY IN A WARMER CLIMATE AS SIMULATED BY A HIGH RESOLUTION COUPLED GENERAL CIRCULATION MODEL:CHANGES IN FREQUENCY AND AIR-SEA INTERACTION(2010-05)
; ; ; ;Scoccimarro, Enrico; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Gualdi, Silvio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Navarra, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; This study investigates the possible changes that the greenhouse global warming might generate in the character- istics of the tropical cyclones (TCs). The analysis has been performed using climate scenario simulations carried out with a fully coupled high–resolution global general circulation model (INGV-SXG) with a T106 atmospheric resolution. The capability of the model to reproduce a reasonably realistic TC climatology has been assessed by comparing the model results from a simulation of the XX Century with observations. The model appears to be able to simulate tropical cyclone-like vortices with many features similar to the observed TCs. The simulated TC activity exhibits realistic geographical distribution, seasonal modulation and interannual variability, suggesting that the model is able to reproduce the major basic mechanisms that link the TC occurrence with the large scale circulation. The results from the climate scenarios reveal a substantial general reduction of the TC frequency when the atmospheric CO2 concentration is doubled and quadrupled. The reduction appears particularly evident for the tropical north west Pacific (NWP) and north Atlantic (ATL). In the NWP the weaker TC activity seems to be associated with a reduced amount of convective instabilities. In the ATL region the weaker TC activity seems to be due to both the increased stability of the atmosphere and a stronger vertical wind shear. Despite the generally reduced TC activity, there is evidence of increased rainfall associated with the simulated cyclones. Using the new fully coupled CMCC model (CMCC_MED), with a T159 atmospheric resolution, we found a significant modulation of the Ocean Heat Transport (OHT) induced by the TC activity. Thus the possible changes that greenhouse induced global warming during 21st century might generate in the characteristics of the TC-induced OHT have been analyzed.94 141 - PublicationOpen AccessA Diagnostic Study of the Indian Ocean Dipole Mode in El Nino and Non- El Nino Years(2007)
; ; ; ;Lee Drbohlav, H. K.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Gualdi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Navarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; The Indian Ocean Dipole Mode (IODM) is examined by comparing the characteristics of oceanic and atmospheric circulations, heat budgets, and possible mechanisms of IODM between El Nino and non-El Nino years. ERA-40 reanalysis data, Reynold SST, and ocean analysis from Modular Ocean Model with the assimilation of the temperature profile from World Ocean Dataset 1998 are used to form three-year composites of IODM during El Nino (72, 82, 97) and non-El Nino (61, 67, 94) years. In El Nino years, two off-equatorial, anti-cyclonic circulations develop as a Rossby-wave response to the increased pressure over the Indian Ocean. The resultant winds from easterlies to northeasterlies (from southerlies to southeasterlies) in the northwestern (southeastern) tropical Indian Ocean warms (cools) the mixed layer temperature by inducing an anomalous zonal (meridional and vertical) component in the ocean current that advects the basic-state mixed layer temperature. In non-El Nino years, a monsoon-like flow induces winds from westerlies to southwesterlies (from southerlies to southeasterlies) in the northwestern (southeastern) Indian Ocean. As a result, the cold advection by the anomalous eastward current (northward current) in the northwestern (southeastern) tropical Indian Ocean becomes dominant in non-El Nino years. In addition, the anomalous winds in these regions are the same sign as the climatological monthly mean winds. Hence the anomalous latent and sensible heat fluxes further contribute to the decrease of SST in the northwestern and the southeastern Indian Ocean. Consequently, the cooling of the eastern tropical Indian Ocean rather than the warming of western tropical Indian Ocean becomes the major feature of the IODM during non-El Nino years.147 1158 - PublicationOpen AccessEffect of Tropical Cyclones on Ocean Heat Transport as simulated by a High Resolution Coupled GCM(2010-05)
; ; ; ; ; ; ;Scoccimarro, Enrico; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Gualdi, Silvio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Bellucci, Alessio; CMCC ;Sanna, Antonella; CMCC ;Oddo, Paolo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Navarra, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; ; ; ; This study investigates the Tropical Cyclone (TC) effect on the northern hemisphere Ocean Heat Transport (OHT) and the possible changes that greenhouse induced global warming might generate in the characteristics of the TC-induced OHT (TCiOHT). The analysis has been performed using 20C3M (20th Century) and A1B (21st Century) IPCC scenario climate simulations obtained running a fully coupled high-resolution global general circulation model named CMCC_MED. The Atmospheric model component has a T159 horizontal resolution and 31 vertical levels. The Ocean model component has a horizontal resolution ranging from 2 degrees to 0.5 degrees near the equator and 31 vertical levels. The capability of the model to reproduce a reasonably realistic TC climatology has been assessed by comparing the model results from the simulation of the 20th Century with observations. TC detection method has been implemented thanks to the TC-MIP project. The model appears to be able to simulate tropical cyclone-like vortices with many features similar to the observed TCs. The simulated TC activity exhibits realistic structure, geographical distribution and interannual variability, suggesting that the model is able to reproduce the major basic mechanisms that link the TC activity with the large scale circulation. The TC-induced ocean cooling is well represented and the resulting column-integrated ocean heating makes the poleward OHT larger in the subtropics and decreases the poleward heat transport out of the deep tropics. This effect, investigated looking at the 100 most intense Northern Hemisphere TCs, is strongly correlated to the TC-induced momentum flux at the surface of the ocean: the winds associated to the TCs significantly weaken the trade winds in the 5-18N latitude belt and reinforce them in the 18-30N band. TCs frequency and intensity appear to be substantially stationary through the whole 1950-2069 period. The effect of the TCs on the OHT is overall less pronounced in the 21st century when compared to the 20th century.175 260 - PublicationOpen AccessThe impact of the AMV on Eurasian summer hydrological cycle(2020)
; ; ; ; ; ; ; ; ; Impact studies of the Atlantic Multidecadal Variability (AMV) on the climate system are severely limited by the lack of sufficiently long observational records. Relying on a model-based approach is therefore mandatory to overcome this limitation. Here, a novel experimental setup, designed in the framework of the CMIP6-endorsed Decadal Climate Prediction Project, is applied to the CMCC climate model to analyse the remote climate impact of the AMV on the Northern Eurasian continent. Model results show that, during Boreal summer, an enhanced warming associated to a positive phase of the AMV, induces a hemispheric-scale wave-train response in the atmospheric circulation, affecting vast portions of Northern Eurasia. The overall AMV-induced response consists in an upper-tropospheric anomalous flows leading to a rainfall increase over Scandinavia and Siberia and to an intensified river runoff by the major Siberian rivers. A strengthening of Eurasian shelves' stratification, broadly consistent with the anomalous river discharge, is found in the proximity of the river mouths during positive-AMV years. Considering that Siberian rivers (Ob', Yenisei and Lena) account for almost half of the Arctic freshwater input provided by terrestrial sources, the implications of these findings for decadal variability and predictability of the Arctic environment are also discussed.47 10 - PublicationOpen AccessSensitivity experiments to mountain representations in spectral models(2000-06)
; ; ; ; ; ; ;Navarra, A.; Istituto Nazionale di Geofisica, Roma, Italy ;Biasutti, M.; IMGA-CNR, Modena, Italy ;Gualdi, S.; IMGA-CNR, Modena, Italy ;Roeckner, E.; Max-Planck-Institut für Meteorologie, Hamburg, Germany ;Schlese, U.; Max-Planck-Institut für Meteorologie, Hamburg, Germany ;Shulzweida, U.; Max-Planck-Institut für Meteorologie, Hamburg, Germany; ; ; ; ; This paper describes a set of sensitivity experiments to several formulations of orography. Three sets are considered: a "Standard" orography consisting of an envelope orography produced originally for the ECMWF model, a"Navy" orography directly from the US Navy data and a "Scripps" orography based on the data set originally compiled several years ago at Scripps. The last two are mean orographies which do not use the envelope enhancement. A new filtering technique for handling the problem of Gibbs oscillations in spectral models has been used to produce the "Navy" and "Scripps" orographies, resulting in smoother fields than the "Standard" orography. The sensitivity experiments show that orography is still an important factor in controlling the model performance even in this class of models that use a semi-lagrangian formulation for water vapour, that in principle should be less sensitive to Gibbs oscillations than the Eulerian formulation. The largest impact can be seen in the stationary waves (asymmetric part of the geopotential at 500 mb) where the differences in total height and spatial pattern generate up to 60 m differences, and in the surface fields where the Gibbs removal procedure is successful in alleviating the appearance of unrealistic oscillations over the ocean. These results indicate that Gibbs oscillations also need to be treated in this class of models. The best overall result is obtained using the "Navy" data set, that achieves a good compromise between amplitude of the stationary waves and smoothness of the surface fields.107 279 - PublicationOpen AccessInfluences of the Atlantic and Pacific Oceans on Rainy Season Precipitation for the Southernmost Caribbean Small Island State, TrinidadSeasonal rainfall in the Caribbean Basin is known to be modulated by sea surface temperature anomalies (SSTAs) in the Atlantic and Pacific Oceans, and particularly those in the Equatorial Pacific and Atlantic and the Tropical North Atlantic. However, little is known about how these major oceans influence the seasonal precipitation of individual small island states within the region as climate variability at the island-scale may di er from the Caribbean as a whole. Correlation and composite analyses were determined using monthly rainfall data for the southernmost island of the Caribbean, Trinidad, and an extended area of global SSTAs. In addition to the subregions that are known to modulate Caribbean rainfall, our analyses show that sea surface temperatures (SSTs) located in the subtropical South Pacific, the South Atlantic, and the Gulf of Mexico also have weak (r2 < 0.5) yet significant influences on the islands’ early rainy season (ERS) and late rainy season (LRS) precipitation. Composite maps confirm that the South Pacific, South Atlantic, and the Gulf of Mexico show significant SSTAs in December–January–February (DJF) and March–April–May (MAM) prior to the ERS and the LRS. Statistical models for seasonal forecasting of rainfall at the island scale could be improved by using the SSTAs of the Pacific and Atlantic subregions identified in this study.
48 10 - PublicationOpen AccessThe INGV-CMCC Seasonal Prediction System: improved ocean initial conditions(2010)
; ; ; ; ; ; ; ;Alessandri, A.; Centro Euro-Mediterraneo per i cambiamenti Climatici, Bologna, Italy ;Borrelli, A.; Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna, Italy ;Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Cherchi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Gualdi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Navarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Di Pietro, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; ; ; ; ; The development of the INGV (Istituto Nazionale di Geofisica e Vulcanologia)-CMCC (Centro Euro-Mediterraneo per i Cambiamenti Climatici) Seasonal Prediction System (SPS) is documented. In this SPS the ocean initial conditions estimation includes a Reduced Order Optimal Interpolation procedure for the assimilation of temperature and salinity profiles at the global scale. Nine member ensemble forecasts have been produced for the period 1991-2003 for two starting dates per year in order to assess the impact of the subsurface assimilation in the ocean for initialization. Comparing the results with control simulations (i.e.: without assimilation of subsurface profiles during ocean initialization), we showed that the improved ocean initialization increases the skill in the prediction of tropical Pacific SSTs in our system for boreal winter forecasts. Considering the forecast of the El Ni˜no 1997-1998, the data assimilation in the ocean initial conditions leads to a considerable improvement in the representation of its onset and development. Our results indicate a better prediction of global scale surface climate anomalies for the forecasts started in November, probably due to the improvement in the tropical Pacific. For boreal winter, in both tropics and extra tropics, we show significant increases in the capability of the system to discriminate above normal and below normal temperature anomalies.401 498