European drought during the last two millennia from reconstructions and model simulations

2020 ◽  
Author(s):  
Fidel González-Rouco ◽  
María Angeles López-Cayuela ◽  
Jorge Navarro ◽  
Elena García-Bustamante ◽  
Nuria García-Cantero ◽  
...  
Keyword(s):  
Temporal Variability ◽  
Low Frequency ◽  
Internal Variability ◽  
Mediterranean Area ◽  
Spatial And Temporal Variability ◽  
Low Frequency Variability ◽  
Community Earth System Model ◽  
Complete Set ◽  
Definition Of ◽  
The Last Two Millennia

<p>The spatial and temporal variability of droughts in the Euro-Mediterranean area during the last two millennia has been analyzed by comparing the Old World Drought Atlas (OWDA) dentrochronological based reconstruction and 13 simulations including a complete set of natural and anthropogenic forcings from the Community Earth System Model- Last Millennium Ensemble (CESM-LME). The OWDA represents scPDSI estimates, whereas for the CESM-LME soil moisture is used. A clustering into regions of objectively different behavior is achieved through rotation of principal components and the resulting regionalizations of the OWDA and the CESM-LME are compared.</p><p>The resulting regions from the reconstructions and model are overall consistent. Some regions are coincident in both and in some cases model regions are a combination of the reconstructed ones. The resulting classification is also robust across the model ensemble, although It is found that the definition of some hydroclimatic regions shows some sensitivity to internal variability.</p><p>The temporal variability of drought within each region is analyzed. Differences are found in the level of low frequency variability among regions with implications for the probability of having long intense droughts in different areas. Megadroughts have been found to exist both in the reconstructions and in the simulations and their occurrence suggest rather internal variability dependances rather than responses to external forcing.</p>

scholarly journals Global oscillatory modes in high-end climate modeling and reanalyses

2021 ◽  
Author(s):  
Yizhak Feliks ◽  
Justin Small ◽  
Michael Ghil
Keyword(s):  
Sea Level ◽  
Climate Modeling ◽  
Singular Spectrum Analysis ◽  
Low Frequency ◽  
Sea Level Pressure ◽  
The North ◽  
The Pacific ◽  
Low Frequency Variability ◽  
Community Earth System Model ◽  
Spatio Temporal

AbstractInterannual oscillatory modes, atmospheric and oceanic, are present in several large regions of the globe. We examine here low-frequency variability (LFV) over the entire globe in the Community Earth System Model (CESM) and in the NCEP-NCAR and ECMWF ERA5 reanalyses. Multichannel singular spectrum analysis (MSSA) is applied to these three datasets. In the fully coupled CESM1.1 model, with its resolution of $$0.1 \times 0.1$$ 0.1 × 0.1 degrees in the ocean and $$0.25 \times 0.25$$ 0.25 × 0.25 degrees in the atmosphere, the fields analyzed are surface temperatures, sea level pressures and the 200-hPa geopotential. The simulation is 100-year long and the last 66 yr are used in the analysis. The two statistically significant periodicities in this IPCC-class model are 11 and 3.4 year. In the NCEP-NCAR reanalysis, the fields of sea level pressure and of 200-hPa geopotential are analyzed at the available resolution of $$2.5 \times 2.5$$ 2.5 × 2.5 degrees over the 68-years interval 1949–2016. Oscillations with periods of 12 and 3.6 years are found to be statistically significant in this dataset. In the ECMWF ERA5 reanalysis, the 200-hPa geopotential field was analyzed at its resolution of $$0.25 \times 0.25$$ 0.25 × 0.25 degrees over the 71-years interval 1950–2020. Oscillations with periods of 10 and 3.6 years are found to be statistically significant in this third dataset. The spatio-temporal patterns of the oscillations in the three datasets are quite similar. The spatial pattern of these global oscillations over the North Pacific and North Atlantic resemble the Pacific Decadal Oscillation and the LFV found in the Gulf Stream region and Labrador Sea, respectively. We speculate that such regional oscillations are synchronized over the globe, thus yielding the global oscillatory modes found herein, and discuss the potential role of the 11-year solar-irradiance cycle in this synchronization. The robustness of the two global modes, with their 10–12 and 3.4–3.6 years periodicities, also suggests potential contributions to predictability at 1–3 years horizons.

scholarly journals Timescape: A Simple Spatiotemporal Interpolation Tool

2021 ◽  
Author(s):  
Marco Ciolfi ◽  
Francesca Chiocchini ◽  
Rocco Pace ◽  
Giuseppe Russo ◽  
Marco Lauteri
Keyword(s):  
Temporal Variability ◽  
Spatial Interpolation ◽  
Spatial Modelling ◽  
Spatial Distance ◽  
Spatial And Temporal Variability ◽  
Ecological Research ◽  
Spatiotemporal Interpolation ◽  
Novel Approach ◽  
Interpolation Technique ◽  
Definition Of

We developed a novel approach in the field of spatiotemporal modelling, based on the spatialisation of time: the Timescape algorithm. It is especially aimed at sparsely distributed datasets in ecological research, whose spatial and temporal variability is strongly entangled. The algorithm is based on the definition of a spatiotemporal distance that incorporates a causality constraint and that is capable of accommodating the seasonal behaviour of the modelled variable as well. The actual modelling is conducted exploiting any established spatial interpolation technique, substituting the ordinary spatial distance with our Timescape distance, thus sorting, from the same input set of observations, those causally related to each estimated value at a given site and time. The notion of causality is expressed topologically and it has to be tuned for each particular case. The Timescape algorithm originates from the field of stable isotopes spatial modelling (isoscapes), but in principle it can be used to model any real scalar random field distribution.

scholarly journals Assessment of Seasonal and Annual Rainfall Trends and Variability in Sharjah City, UAE

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Tarek Merabtene ◽  
Mohsin Siddique ◽  
Abdallah Shanableh
Keyword(s):  
Climate Change ◽  
Temporal Variability ◽  
Low Frequency ◽  
Annual Rainfall ◽  
Spatial And Temporal Variability ◽  
Rainfall Trend ◽  
Significant Drop ◽  
Statistical Measures ◽  
Rainfall Trends ◽  
The Impact

Although a few studies on rainfall spatial and temporal variability in the UAE have been carried out, evidence of the impact of climate change on rainfall trends has not been reported. This study aims at assessing the significance of long-term rainfall trends and temporal variability at Sharjah City, UAE. Annual rainfall and seasonal rainfall extending over a period of 81 years (1934–2014) recorded at Sharjah International Airport have been analyzed. To this end, several parametric and nonparametric statistical measures have been applied following systematic data quality assessment. The analyses revealed that the annual rainfall trend decreased from −3 mm to −9.4 mm per decade over the study periods. The decreasing annual rainfall trend is mainly driven by the significant drop in winter rainfall, particularly during the period from 1977 to 2014. The results also indicate that high probability extreme events have shifted toward low frequency (12.7 years) with significant variations in monthly rainfall patterns and periodicity. The findings of the present study suggest reevaluating the derivation of design rainfall for infrastructure of Sharjah City and urge developing an integrated framework for its water resources planning and risk under climate change impacts scenarios.

scholarly journals Low-Frequency North Atlantic Climate Variability in the Community Earth System Model Large Ensemble

2018 ◽  
Vol 31 (2) ◽  
pp. 787-813 ◽  
Author(s):  
Who M. Kim ◽  
Stephen Yeager ◽  
Ping Chang ◽  
Gokhan Danabasoglu
Keyword(s):  
Boundary Conditions ◽  
Time Scales ◽  
North Atlantic ◽  
Low Frequency ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Large Ensemble ◽  
Low Frequency Variability ◽  
Community Earth System Model

There is observational and modeling evidence that low-frequency variability in the North Atlantic has significant implications for the global climate, particularly for the climate of the Northern Hemisphere. This study explores the representation of low-frequency variability in the Atlantic region in historical large ensemble and preindustrial control simulations performed with the Community Earth System Model (CESM). Compared to available observational estimates, it is found that the simulated variability in Atlantic meridional overturning circulation (AMOC), North Atlantic sea surface temperature (NASST), and Sahel rainfall is underestimated on multidecadal time scales but comparable on interannual to decadal time scales. The weak multidecadal North Atlantic variability appears to be closely related to weaker-than-observed multidecadal variations in the simulated North Atlantic Oscillation (NAO), as the AMOC and consequent NASST variability is impacted, to a great degree, by the NAO. Possible reasons for this weak multidecadal NAO variability are explored with reference to solutions from two atmosphere-only simulations with different lower boundary conditions and vertical resolution. Both simulations consistently reveal weaker-than-observed multidecadal NAO variability despite more realistic boundary conditions and better resolved dynamics than coupled simulations. The authors thus conjecture that the weak multidecadal NAO variability in CESM is likely due to deficiencies in air–sea coupling, resulting from shortcomings in the atmospheric model or coupling details.

Response of Corn Grain Yield to Spatial and Temporal Variability in Emergence

Crop Science ◽  
2004 ◽  
Vol 44 (3) ◽  
pp. 847 ◽  
Author(s):  
Weidong Liu ◽  
Matthijs Tollenaar ◽  
Greg Stewart ◽  
William Deen
Keyword(s):  
Grain Yield ◽  
Temporal Variability ◽  
Spatial And Temporal Variability ◽  
Corn Grain ◽  
Corn Grain Yield
Sign in / Sign up

Export Citation Format

Share Document