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  • 1
    Electronic Resource
    Electronic Resource
    The interannual variability of the Madden–Julian Oscillation in an ensemble of GCM simulations (1999)
    Springer
    Climate dynamics 15 (1999), S. 643-658 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract  The interannual variability of the Madden– Julian Oscillation (MJO) is investigated in an ensemble of 15 experiments performed with the ECHAM4 T30 general circulation model (GCM). The model experiments have been performed with AMIP conditions from January 1979 to December 1993. The MJO signal has been identified applying a principal oscillation pattern (POP) analysis to the 200-mb tropical velocity potential. The results obtained from the model ensemble are compared with 15 y of ECMWF re-analysis and OLR observations. The results suggest that the warm and cold phases of El Niño have some influence on the spatial propagation of the oscillation. Both in the re-analysis and in the model ensemble, the results indicate that during La Niña conditions the MJO is mostly confined west of the date line, with the largest activity located over the Indian Ocean and the western Pacific. In warm El Niño conditions, the convective anomalies associated with the oscillation appear to penetrate farther into the central Pacific. These changes in the MJO convective forcing seem to affect the zonal mean of the rotational component of the flow anomaly, which tends to weaken during warm El Niño periods. Some weak reproducibility of the interannual variability of the MJO activity is found. The results obtained from four-member and eight-member subsamples of the ensemble indicate that the reproducibility of the interannual behaviour of the MJO can be detected by choosing an ensemble of a larger size. Corresponding to the emergence of reproducibility with the increasing size of the sample, the correlation between the MJO activity and the Niño-3 SST anomaly appears to in-tensify.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050307
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  • 2
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    Changes in Tropical Cyclone Activity due to Global Warming: Results from a High-Resolution Coupled General Circulation Model (2008)
    American Meteorological Society
    Details
    Publication Date: 2008-10-15
    Description: This study investigates the possible changes that greenhouse global warming might generate in the characteristics of tropical cyclones (TCs). The analysis has been performed using scenario climate simulations carried out with a fully coupled high-resolution global general circulation model. 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 twentieth 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 TC occurrence with large-scale circulation. The results from the climate scenarios reveal a substantial general reduction of TC frequency when the atmospheric CO2 concentration is doubled and quadrupled. The reduction appears particularly evident for the tropical western North Pacific (WNP) and North Atlantic (ATL). In the NWP the weaker TC activity seems to be associated with reduced 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. Finally, the action of the TCs remains well confined to the tropical region and the peak of TC number remains equatorward of 20° latitude in both hemispheres, notwithstanding the overall warming of the tropical upper ocean and the expansion poleward of warm SSTs.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 3
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    Atmospheric Horizontal Resolution Affects Tropical Climate Variability in Coupled Models (2008)
    American Meteorological Society
    Details
    Publication Date: 2008-02-15
    Description: The effect of atmospheric horizontal resolution on tropical variability is investigated within the modified Scale Interaction Experiment (SINTEX) coupled model, SINTEX-Frontier (SINTEX-F), developed jointly at Istituto Nazionale di Geofisica e Vulcanologia (INGV), L’Institut Pierre-Simon Laplace (IPSL), and the Frontier Research System. The ocean resolution is not changed as the atmospheric model resolution is modified from spectral resolution 30 (T30) to spectral resolution 106 (T106). The horizontal resolutions of the atmospheric model T30 and T106 are investigated in terms of the coupling characteristics, frequency, and variability of the tropical ocean–atmosphere interactions. It appears that the T106 resolution is generally beneficial even if it does not eliminate all the major systematic errors of the coupled model. There is an excessive shift west of the cold tongue and ENSO variability, and high resolution also has a somewhat negative impact on the variability in the east Indian Ocean. A dominant 2-yr peak for the Niño-3 variability in the T30 model is moderated in the T106 as it shifts to a longer time scale. At high resolution, new processes come into play, such as the coupling of tropical instability waves, the resolution of coastal flows at the Pacific–Mexican coasts, and improved coastal forcing along the coast of South America. The delayed oscillator seems to be the main mechanism that generates the interannual variability in both models, but the models realize it in different ways. In the T30 model it is confined close to the equator, involving relatively fast equatorial and near-equatorial modes, and in the high-resolution model, it involves a wider latitudinal region and slower waves. It is speculated that the extent of the region that is involved in the interannual variability may be linked to the time scale of the variability itself.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 4
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    NAO–ocean circulation interactions in a coupled general circulation model (2008)
    Springer
    Details
    Publication Date: 2008-04-18
    Print ISSN: 0930-7575
    Electronic ISSN: 1432-0894
    Topics: Geosciences , Physics
    Published by Springer
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  • 5
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    Impact of barrier layer on winter-spring variability of the southeastern Arabian Sea (2005)
    American Geophysical Union
    Details
    Publication Date: 2005-04-01
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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  • 6
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    Impact of increased vertical resolution on simulation of tropical climate (2006)
    Springer
    Details
    Publication Date: 2006-03-01
    Print ISSN: 0177-798X
    Electronic ISSN: 1434-4483
    Topics: Geosciences , Physics
    Published by Springer
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  • 7
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    The interannual variability of the Madden-Julian Oscillation in an ensemble of GCM simulations (1999)
    Springer
    Details
    Publication Date: 1999-09-03
    Print ISSN: 0930-7575
    Electronic ISSN: 1432-0894
    Topics: Geosciences , Physics
    Published by Springer
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  • 8
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    SINTA - SImulations of climate chaNge in the mediTerranean Area - Final scientific report (2008)
    Details
    Publication Date: 2020-12-21
    Description: This SINTA Project establish a scientific cooperation between the Italian Scientific Institution INGV (National Institute of Geophysics and Volcanology) and the Serbian Scientific Institutions such as the Republic HydroMeteorological Service (RHMSS) and the University of Belgrade (UB). INGV contributes the global models, University of Belgrade and RHMSS contribute their expertise on regional models, parameterization ofphysical processes and numerical schemes. In particular, the main objectives of this Project are: 1) Perform a set of global simulations with a Global Climate Model (GCM) available at INGV; 2) Perform a set of regional simulations with the UB Regional Climate Model (RCM) forced by boundary conditions from the GCM simulations; 3) Test the convection parameterization developed at UB in the INGV global model; 4) Training and visit exchanges of Serbian scientists in Italy.
    Description: INGV
    Description: Unpublished
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: open
    Keywords: Climate ; Mediterranean Area ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: report
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  • 9
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    Effects of Land-Surface-Vegetation on theboreal summer surface climate of a GCM (2007)
    American Meteorological Society
    Details
    Publication Date: 2020-11-19
    Description: A land surface model (LSM) has been included in the ECMWF Hamburg version 4 (ECHAM4) atmospheric general circulation model (AGCM). The LSM is an early version of the Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) and it replaces the simple land surface scheme previously included in ECHAM4. The purpose of this paper is to document how a more exhaustive consideration of the land surface–vegetation processes affects the simulated boreal summer surface climate. To investigate the impacts on the simulated climate, different sets of Atmospheric Model Intercomparison Project (AMIP)-type simulations have been performed with ECHAM4 alone and with the AGCM coupled with ORCHIDEE. Furthermore, to assess the effects of the increase in horizontal resolution the coupling of ECHAM4 with the LSM has been implemented at different horizontal resolutions. The analysis reveals that the LSM has large effects on the simulated boreal summer surface climate of the atmospheric model. Considerable impacts are found in the surface energy balance due to changes in the surface latent heat fluxes over tropical and midlatitude areas covered with vegetation. Rainfall and atmospheric circulation are substantially affected by these changes. In particular, increased precipitation is found over evergreen and summergreen vegetated areas. Because of the socioeconomical relevance, particular attention has been devoted to the Indian summer monsoon (ISM) region. The results of this study indicate that precipitation over the Indian subcontinent is better simulated with the coupled ECHAM4–ORCHIDEE model compared to the atmospheric model alone.
    Description: Published
    Description: 255–278
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: partially_open
    Keywords: Land Atmosphere interactions ; Global climate models ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    A Diagnostic Study of the Indian Ocean Dipole Mode in El Nino and Non- El Nino Years (2007)
    Details
    Publication Date: 2020-11-30
    Description: 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.
    Description: Published
    Description: 2961–2977
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Description: open
    Keywords: Indian Ocean Dipole ; El Nino ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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