The Experts below are selected from a list of 15768 Experts worldwide ranked by ideXlab platform
Michel Déqué - One of the best experts on this subject based on the ideXlab platform.
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Teleconnection-based evaluation of seasonal forecast quality
Climate Dynamics, 2020Co-Authors: Danila Volpi, Lauriane Batté, Jean-françois Guérémy, Michel DéquéAbstract:In response to the high demand for more skillful climate forecasts at the seasonal timescale, innovative climate prediction systems are developed with improved physics and increased spatial resolution. Alongside the model development process, seasonal predictions need to be evaluated on past years to provide robust information on the forecast performance. This work presents the quality assessment of the Météo-France coupled climate prediction system, taking advantage of an experiment performed with 90 ensemble members over a 37-year re-forecast period from 1979 to 2015. We focus on the boreal winter season initialised in November. Beyond typical skill measures we evaluate the model capability in reproducing ENSO and NAO Teleconnections on precipitation and near surface temperature respectively. Such an assessment is carried out first through a composite analysis, and shows that the model succeeds in reproducing the main patterns for near surface temperature and precipitation. A covariance method leads to consistent results. Finally we find that the Teleconnection representation of the model is not affected by shortening the verification period and reducing the ensemble size and therefore can be used to evaluate operational seasonal forecast systems.
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Teleconnection based evaluation of seasonal forecast quality
Climate Dynamics, 2020Co-Authors: Danila Volpi, Lauriane Batté, Jean-françois Guérémy, Michel DéquéAbstract:In response to the high demand for more skillful climate forecasts at the seasonal timescale, innovative climate prediction systems are developed with improved physics and increased spatial resolution. Alongside the model development process, seasonal predictions need to be evaluated on past years to provide robust information on the forecast performance. This work presents the quality assessment of the Meteo-France coupled climate prediction system, taking advantage of an experiment performed with 90 ensemble members over a 37-year re-forecast period from 1979 to 2015. We focus on the boreal winter season initialised in November. Beyond typical skill measures we evaluate the model capability in reproducing ENSO and NAO Teleconnections on precipitation and near surface temperature respectively. Such an assessment is carried out first through a composite analysis, and shows that the model succeeds in reproducing the main patterns for near surface temperature and precipitation. A covariance method leads to consistent results. Finally we find that the Teleconnection representation of the model is not affected by shortening the verification period and reducing the ensemble size and therefore can be used to evaluate operational seasonal forecast systems.
Ben B B Booth - One of the best experts on this subject based on the ideXlab platform.
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the multidecadal atlantic sst sahel rainfall Teleconnection in cmip5 simulations
Journal of Climate, 2014Co-Authors: Elinor R Martin, Chris D Thorncroft, Ben B B BoothAbstract:AbstractThis study uses models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to evaluate and investigate Sahel rainfall multidecadal variability and Teleconnections with global sea surface temperatures (SSTs). Multidecadal variability is lower than observed in all historical simulations evaluated. Focus is on Teleconnections with North Atlantic SST [Atlantic multidecadal variability (AMV)] as it is more successfully simulated than the Indian Ocean Teleconnection. To investigate why some models successfully simulated this Teleconnection and others did not, despite having similarly large AMV, two groups of models were selected. Models with large AMV were highlighted as good (or poor) by their ability to simulate relatively high (low) Sahel multidecadal variability and have significant (not significant) correlation between multidecadal Sahel rainfall and an AMV index. Poor models fail to capture the Teleconnection between the AMV and Sahel rainfall because the spatial distribution of SST ...
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The Multidecadal Atlantic SST—Sahel Rainfall Teleconnection in CMIP5 Simulations
Journal of Climate, 2014Co-Authors: Elinor R Martin, Chris D Thorncroft, Ben B B BoothAbstract:AbstractThis study uses models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to evaluate and investigate Sahel rainfall multidecadal variability and Teleconnections with global sea surface temperatures (SSTs). Multidecadal variability is lower than observed in all historical simulations evaluated. Focus is on Teleconnections with North Atlantic SST [Atlantic multidecadal variability (AMV)] as it is more successfully simulated than the Indian Ocean Teleconnection. To investigate why some models successfully simulated this Teleconnection and others did not, despite having similarly large AMV, two groups of models were selected. Models with large AMV were highlighted as good (or poor) by their ability to simulate relatively high (low) Sahel multidecadal variability and have significant (not significant) correlation between multidecadal Sahel rainfall and an AMV index. Poor models fail to capture the Teleconnection between the AMV and Sahel rainfall because the spatial distribution of SST ...
Danila Volpi - One of the best experts on this subject based on the ideXlab platform.
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Teleconnection-based evaluation of seasonal forecast quality
Climate Dynamics, 2020Co-Authors: Danila Volpi, Lauriane Batté, Jean-françois Guérémy, Michel DéquéAbstract:In response to the high demand for more skillful climate forecasts at the seasonal timescale, innovative climate prediction systems are developed with improved physics and increased spatial resolution. Alongside the model development process, seasonal predictions need to be evaluated on past years to provide robust information on the forecast performance. This work presents the quality assessment of the Météo-France coupled climate prediction system, taking advantage of an experiment performed with 90 ensemble members over a 37-year re-forecast period from 1979 to 2015. We focus on the boreal winter season initialised in November. Beyond typical skill measures we evaluate the model capability in reproducing ENSO and NAO Teleconnections on precipitation and near surface temperature respectively. Such an assessment is carried out first through a composite analysis, and shows that the model succeeds in reproducing the main patterns for near surface temperature and precipitation. A covariance method leads to consistent results. Finally we find that the Teleconnection representation of the model is not affected by shortening the verification period and reducing the ensemble size and therefore can be used to evaluate operational seasonal forecast systems.
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Teleconnection based evaluation of seasonal forecast quality
Climate Dynamics, 2020Co-Authors: Danila Volpi, Lauriane Batté, Jean-françois Guérémy, Michel DéquéAbstract:In response to the high demand for more skillful climate forecasts at the seasonal timescale, innovative climate prediction systems are developed with improved physics and increased spatial resolution. Alongside the model development process, seasonal predictions need to be evaluated on past years to provide robust information on the forecast performance. This work presents the quality assessment of the Meteo-France coupled climate prediction system, taking advantage of an experiment performed with 90 ensemble members over a 37-year re-forecast period from 1979 to 2015. We focus on the boreal winter season initialised in November. Beyond typical skill measures we evaluate the model capability in reproducing ENSO and NAO Teleconnections on precipitation and near surface temperature respectively. Such an assessment is carried out first through a composite analysis, and shows that the model succeeds in reproducing the main patterns for near surface temperature and precipitation. A covariance method leads to consistent results. Finally we find that the Teleconnection representation of the model is not affected by shortening the verification period and reducing the ensemble size and therefore can be used to evaluate operational seasonal forecast systems.
Kyungja Ha - One of the best experts on this subject based on the ideXlab platform.
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future change of northern hemisphere summer tropical extratropical Teleconnection in cmip5 models
Journal of Climate, 2014Co-Authors: Bin Wang, Yongsang Choi, Yu Kosaka, Kyungja HaAbstract:Two dominant global-scale Teleconnections in the Northern Hemisphere (NH) extratropics during boreal summer season (June‐August) have been identified: the western North Pacific‐North America (WPNA) and circumglobal Teleconnection (CGT) patterns. These Teleconnection patterns are of critical importance for the NH summer seasonal climate prediction. Here, how these Teleconnections will change under anthropogenic global warming is investigated using representative concentration pathway 4.5 (RCP4.5) experiments by 20 coupled models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). The six best models are selected based on their performance in simulation of the two Teleconnection patterns and climatological means and variances of atmospheric circulation, precipitation, and sea surface temperature. The selected models capture the CGT and its relationship with the Indian summer monsoon (ISM) reasonably well. The models can also capture the WPNA circulation pattern but with striking deficiencies in reproducing its associated rainfall anomalies due to poor simulation of the western North Pacific summer monsoon rainfall. The following changes are anticipatedin thelatterhalf of twenty-first centuryundertheRCP4.5scenario:1)significant weakening of year-to-year variability of the upper-level circulation due to increased atmospheric stability, although the moderate increase in convective heating over the tropics may act to strengthen the variability; 2) intensification of the WPNA pattern and major spectral peaks, particularly over the eastern Pacific‐North America and North Atlantic‐Europe sectors, which is attributed to the strengthening of its relationship with the preceding mature phase of El Ni~ Oscillation (ENSO); and 3) weakening of the CGT due to atmospheric stabilization and decreasing relationship with ISM as well as weakening of the ISM‐ ENSO relationship.
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Teleconnections associated with Northern Hemisphere summer monsoon intraseasonal oscillation
Climate Dynamics, 2013Co-Authors: Jayeon Moon, Bin Wang, Kyungja HaAbstract:The boreal summer intraseasonal oscillation (BSISO) has strong convective activity centers in Indian (I), Western North Pacific (WNP), and North American (NA) summer monsoon (SM) regions. The present study attempts to reveal BSISO Teleconnection patterns associated with these dominant intraseasonal variability centers. During the active phase of ISM, a zonally elongated band of enhanced convection extends from India via the Bay of Bengal and Philippine Sea to tropical central Pacific with suppressed convection over the eastern Pacific near Mexico. The corresponding extratropical circulation anomalies occur along the waveguides generated by the North African-Asian jet and North Atlantic-North European jet. When the tropical convection strengthens over the WNPSM sector, a distinct great circle-like Rossby wave train emanates from the WNP to the western coast of United States (US) with an eastward shift of enhanced meridional circulation. In the active phase of NASM, large anticyclonic anomalies anchor over the western coast of US and eastern Canada and the global Teleconnection pattern is similar to that during a break phase of the ISM. Examination of the evolution of the BSISO Teleconnection reveals quasi-stationary patterns with preferred centers of Teleconnection located at Europe, Russia, central Asia, East Asia, western US, and eastern US and Canada, respectively. Most centers are embedded in the waveguide along the westerly jet stream, but the centers at Europe and Russia occur to the north of the jet-induced waveguide. Eastward propagation of the ISO Teleconnection is evident over the Pacific-North America sector. The rainfall anomalies over the elongated band near the monsoon domain over the Indo-western Pacific sector have an opposite tendency with that over the central and southern China, Mexico and southern US, providing a source of intraseasonal predictability to extratropical regions. The BSISO Teleconnection along and to the north of the subtropical jet provides a good indication of the surface sir temperature anomalies in the NH extratropics.
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enso regulation of mjo Teleconnection
Climate Dynamics, 2011Co-Authors: Jayeon Moon, Bin Wang, Kyungja HaAbstract:The extratropical Teleconnections associated with Madden–Julian Oscillation (MJO) are shown to have an action center in the North Pacific where the pressure anomalies have opposite polarities between the Phase 3 (convective Indian Ocean) and Phase 7 (convective western Pacific) of the MJO. The Teleconnection in the same phase of MJO may induce opposite anomalies over East Asia and North America between El Nino and La Nina years. During MJO Phase 3, a gigantic North Pacific anticyclonic anomaly occurs during La Nina, making coastal northeast Asia warmer/wetter than normal, but the west US colder/drier; whereas during El Nino the anticyclonic anomaly is confined to the central North Pacific, hence the northwest US experiences warmer than normal weather under influence of a downstream cyclonic anomaly. During Phase 7, an extratropical cyclonic anomaly forms over the northwest Pacific during La Nina due to convective enhancement over the Philippine Sea, causing bitter winter monsoon over Japan; whereas during El Nino, the corresponding cyclonic anomaly shifts to the northeast Pacific due to enhanced convection over the equatorial central Pacific, which causes warm and wet conditions along the west coast of US and Canada. Further, the presence of ENSO-induced seasonal anomalies can significantly modify MJO Teleconnection, but the aforementioned MJO Teleconnection can still be well identified. During Phase 3, the MJO Teleconnection pattern over North Pacific will be counterbalanced (enhanced) by El Nino (La Nina)-induced seasonal mean anomalies. During Phase 7, on the other hand, the MJO Teleconnection anomalies in the northeastern Pacific will be enhanced during El Nino but reduced during La Nina; thereby the impacts of MJO Teleconnection on the North America is expected to be stronger during El Nino than during La Nina.
Francisco J. Doblas-reyes - One of the best experts on this subject based on the ideXlab platform.
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Boreal winter stratospheric variability in EC-EARTH: High-Top versus Low-Top
Climate Dynamics, 2020Co-Authors: Froila M. Palmeiro, Javier García-serrano, Omar Bellprat, Pierre-antoine Bretonnière, Francisco J. Doblas-reyesAbstract:The European Consortium EC-EARTH climate model version 3.1 is used to assess the role of a well-resolved stratosphere on stratospheric Teleconnections in the Northern Hemisphere winter. Two simulations of 100 years with constant radiative forcing, one with top at 0.01 hPa (L91, High-Top) and other with top at 5 hPa (L62, Low-Top) are compared. Results show how High-Top is able to generate a realistic Quasi-Biennial Oscillation in the tropical stratosphere, and to capture its Teleconnection to the extratropics. On the other hand, EC-EARTH properly simulates the leading modes of variability (EOFs) of the polar stratosphere in both High-Top and Low-Top configurations, although the El Niño-related wave-like Teleconnection dominates the signal of EOF3 (wavenumber 1 at 50 hPa) in High-Top, as in reanalysis, while the tropics-unrelated Pacific/North America pattern does it in Low-Top. At subseasonal time-scale, High-Top shows larger sudden stratospheric warming (SSW) occurrence in mid-winter, which is close to the documented in observational records, while SSW occurrence peaks by late-winter in Low-Top, despite both show a similar SSW decadal frequency (i.e. around 8 events per decade). Examination of the climatological eddy heat flux shows a misrepresentation of the seasonal cycle in Low-Top, with a peak in late-winter that explains the timing of SSW increase. This peak of the eddy heat flux can be traced to the wave injection over Central Siberia in the lower stratosphere, which appears to be dominated by small-scale waves (wavenumbers 3–4). It follows that simulating realistic eddy heat flux seasonality is fundamental to obtain a realistic SSW seasonal cycle.
