1,720,965 research outputs found
Northen hemisphere meridional and zonal temperature gradients and their relation to hydrologic extremes at mid-latitude: trends, variability and link to climate modes in observation and simulations
No full textThe jet stream dynamics and the associated mid-latitude storm track are modulated by large scale ocean-land boundary conditions, which depend
on both the evolution of the known interannual and multi-decadal natural variability and on changes in meridional and zonal surface temperature
gradients due to anthropogenic forcing. Here, within the framework of the Lorenz (1984) low-order atmospheric model, the Equator-to-Pole
temperature Gradient (EPG) and the Ocean-Land temperature Contrast (OLC) are considered as drivers of mid-latitudinal circulation.
The historical trends of the seasonal NH Equator-to-Pole temperature Gradient (EPG) and the Ocean-Land temperature Contrast (OLC) are
explored, as well as their probability structure, and their potential relation to anthropogenic warming. The connection between dierent
combinations of EPG and OLC and precipitation patterns at mid-latitudes are shown. Then, these variables and the relations described above are
examined in two CGCM simulations of the 20th century.
The results show that there exist systematic biases in the temporal simulation of the gradients at hand, which is likely propagated to the
simulation of precipitation. However, we show that if a model is able to reasonably capture the observed relationship between the gradients and
precipitation, then it produces large-scale spatial distributions of rainfall that are consistent with observed patterns. Therefore, an eort to address
the biases in simulating EPG and OLC could lead to improved temporal and spatial simulations of precipitation in the models
Extreme precipitation in the south and south-east Mediterranean climate structure and predictability
No full textAs part of a Global Flood project, we assess the conditions that lead to the changing frequency and spatial structure of extreme daily precipitation events in this region for the 6 month winter period from Oct-March. Spatial and temporal trends in the ECA&D data for this region are analyzed in the precipitation frequency and intensity for events exceeding the 99th percentile of daily precipitation. The associated climatic conditions (SST, atmospheric circulation patterns, canonical moisture sources and moisture transport patterns) are analyzed using re-analysis data to establish the concurrent and season ahead conditions associated with the leading space and time patterns. Analogs of these patterns are investigated for GCM integrations for future climate (seasonal forecasts as well as IPCC scenarios) to assess potential predictability and outcomes
21st Projections of precipitation extremes in the Mediterranean from a medium resolution GCM
No full textPrecipitation extremes simulated by a medium resolution GCM ( INMCM3.0) are analyzed for
the Mediterranean region. A structured analysis of low frequency variability in the control
and forced ( corresponding to the IPCC scenarios) model runs is performed. The preliminary
results of the analysis of rainfall patterns under global warming conditions, during the
extended winter ONDJFM season, show an increase of rainfall extremes in both frequency
and intensity in northern Europe and a decrease in the most part of Mediterranean. In the
latter region an increase of dry conditions is also observed. The change in the rainfall patterns
can be explained by a northward shift of the North Atlantic winter storm track. This
shift is related changes in meridional and zonal surface temperature gradients ( Equator-
Pole and Ocean-Land contrast, respectively) due to anthropogenic forcing. Changes in the
inter-annual and multi-decadal natural variability are also noted
GCM projection of precipitation extremes in the mediterranean: changes ansd low frequency characteristic
No full textPrecipitation extremes simulated a medium by resolution GCM ( INMCM3.0) as are analyzed
for the Mediterranean region. A structured analysis of low frequency variability in the
control and forced ( corresponding to the IPCC scenarios) model runs is performed. The
preliminary results of the analysis of rainfall patterns under global warming conditions,
during the extended winter ONDJFM season, show an increase of rainfall extremes in
both frequency and intensity in northern Europe and a decrease in the most part of Mediterranean.
In the latter region an increase of dry conditions is also observed. The change in
the rainfall patterns can be explained by a northward shift of the North Atlantic winter
storm track. This shift is related changes in meridional and zonal surface temperature gradients
( Equator- Pole and Ocean-Land contrast, respectively) due to anthropogenic forcing.
Changes in the inter-annual and multi-decadal natural variability are also noted
Insights from low order model of increasing complexity: probability and temporal structure of climate extreme
No full textThis study provides insight to changes in the probability and temporal
structure of mid-latitude circulation features under possible shift of average
conditions to a more El Ni ̃ no-like or La Ni ̃ na-like state.
I Analysis shows that the response to dierent El Ni ̃no events in mid-latitudes is
highly variable, depending on the corresponding changes to the combination
of Equator-to-Pole Gradient and Ocean-Land Contrast.
I Types of ENSO events and their potential impacts could be classified based on
corresponding fF,Gg and the associated pdf’s of energy (X2 + Y2 + Z2), as well
as the attractor’s properties.
I The general impact of El Ni ̃no conditions is dissipation and organization of the
eddies via enhancement of the jet stream.
I La Ni ̃na conditions cannot be considered as the opposite of El Ni ̃no conditions.
Similar responses in mid-latitudes are possible.
I The question whether ENSO information is transmitted to mid-latitudes via
EPG or OLC changes, or both (ultimately seen as fF,Gg combinations) needs
further investigation.
I Seasonality eects on ENSO impact in mid-latitudes are important.
I Many impacts identified in the present study are qualitatively consistent with
high-order GCM results, thus illustrating the ability of low order models to
represent atmospheric processes in a correct manner.
I Hence, introducing low-frequency modes interactively in a plausible way may
be useful in understanding the behavior and potential outcomes associated
with low frequency forcings in the coupled ocean-atmosphere system
Mid Latitude Extreme Precipitation under future changed climate
No full textPrecipitation patterns under global warming scenario are statistically analyzed for the Mediterranean and North Europe areas. Simulation data from the global coupled atmosphere-ocean model INMCM.3 are used and compared with obervations.
Changes in intensity, frequency, duration and amount of precipitation due to different IPCC scenarios are investigated.
Furthermore we analyze the precipitation patterns for the better understanding of the hydrologic cycle, including a statistical analysis of precipitation extreme events
NATURAL VARIABILITY OF THE ATLANTIC MERIDIONAL OVERTURNING CIRCULATION IN THE INMCM3.0 MODEL
No full textNatural variability of the Atlantic Meridional Overturning Circulation (AMOC) in a 720-year pre-industrial simulation from the coupled climate model INMCM3.0 is analyzed. In the model, AMOC has the strongest spectral maximum at a period of 15 years. On the basis of a 5-year running mean AMOC index it is shown that the transition from negative to positive AMOC phase corresponds with high water density at 35-60N and low density at 15-25N, while during the positive
AMOC phase, density anomalies are weaker. A correspondence between the positive AMOC phase and positive Arctic Oscillation is identified. Positive, negative and delayed feedbacks between AMOC and surface heat and fresh water fluxes, and heat and salinity transport in the ocean are studied. The meridional oceanic fresh water flux is found to be mainly responsible for a positive feedback, while the meridional heat flux is a main factor for a delayed negative feedback for the AMOC variability
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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