scholarly journals Model Simulation and Projection of European Heat Waves in Present-Day and Future Climates

2014 ◽  
Vol 27 (10) ◽  
pp. 3713-3730 ◽  
Author(s):  
Ngar-Cheung Lau ◽  
Mary Jo Nath
Keyword(s):  
General Circulation ◽  
Western Europe ◽  
Heat Waves ◽  
Model Simulation ◽  
Wave Train ◽  
Mean Shift ◽  
Circulation Model ◽  
Climate Scenario ◽  
First Century ◽  
Twenty First Century

Abstract The synoptic behavior of present-day heat waves (HW) over Europe is studied using the GFDL high-resolution atmospheric model (HiRAM) with 50-km grid spacing. Three regions of enhanced and coherent temperature variability are identified over western Russia, eastern Europe, and western Europe. The simulated HW characteristics are compared with those derived from Climate Forecast System Reanalysis products. Composite charts for outstanding HW episodes resemble well-known recurrent circulation types. The HW region is overlain by a prominent upper-level anticyclone, which blocks the passage of synoptic-scale transients. The altered eddy vorticity transports in turn reinforce the anticyclone. The anticyclone is part of a planetary-scale wave train. The successive downstream development of this wave train is indicative of Rossby wave dispersion. Additional runs of HiRAM are conducted for the “time slices” of 2026–35 and 2086–95 in the climate scenario corresponding to representative concentration pathway 4.5 (RCP4.5). By the end of the twenty-first century, the average duration and frequency of HW in the three European sites are projected to increase by a factor of 1.4–2.0 and 2.2–4.5, respectively, from the present-day values. These changes can be reproduced by adding the mean shift between the present and future climatological temperatures to the daily fluctuations in the present-day simulation. The output from a continuous integration of a coupled general circulation model through the 1901–2100 period indicates a monotonic increase in severity, duration, and HW days during the twenty-first century.

The Atmospheric Response to Projected Terrestrial Snow Changes in the Late Twenty-First Century

2010 ◽  
Vol 23 (23) ◽  
pp. 6430-6437 ◽  
Author(s):  
Michael A. Alexander ◽  
Robert Tomas ◽  
Clara Deser ◽  
David M. Lawrence
Keyword(s):  
Twentieth Century ◽  
Sea Ice ◽  
Greenhouse Gas ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Arctic Sea Ice ◽  
First Century ◽  
Model Experiments ◽  
Twenty First Century

Abstract Two atmospheric general circulation model experiments are conducted with specified terrestrial snow conditions representative of 1980–99 and 2080–99. The snow states are obtained from twentieth-century and twenty-first-century coupled climate model integrations under increasing greenhouse gas concentrations. Sea surface temperatures, sea ice, and greenhouse gas concentrations are set to 1980–99 values in both atmospheric model experiments to isolate the effect of the snow changes. The reduction in snow cover in the twenty-first century relative to the twentieth century increases the solar radiation absorbed by the surface, and it enhances the upward longwave radiation and latent and sensible fluxes that warm the overlying atmosphere. The maximum twenty-first-century minus twentieth-century surface air temperature (SAT) differences are relatively small (<3°C) compared with those due to Arctic sea ice changes (∼10°C). However, they are continental in scale and are largest in fall and spring, when they make a significant contribution to the overall warming over Eurasia and North America in the twenty-first century. The circulation response to the snow changes, while of modest amplitude, involves multiple components, including a local low-level trough, remote Rossby wave trains, an annular pattern that is strongest in the stratosphere, and a hemispheric increase in geopotential height.

scholarly journals A Model Study of Heat Waves over North America: Meteorological Aspects and Projections for the Twenty-First Century

2012 ◽  
Vol 25 (14) ◽  
pp. 4761-4784 ◽  
Author(s):  
Ngar-Cheung Lau ◽  
Mary Jo Nath
Keyword(s):  
Twentieth Century ◽  
North America ◽  
Heat Wave ◽  
General Circulation ◽  
Heat Waves ◽  
General Circulation Models ◽  
Reanalysis Data ◽  
First Century ◽  
Twenty First Century ◽  
The Impact

Abstract The characteristics of summertime heat waves in North America are examined using reanalysis data and simulations by two general circulation models with horizontal resolution of 50 and 200 km. Several “key regions” with spatially coherent and high amplitude fluctuations in daily surface air temperature are identified. The typical synoptic features accompanying warm episodes in these regions are described. The averaged intensity, duration, and frequency of occurrence of the heat waves in various key regions, as simulated in the two models for twentieth-century climate, are in general agreement with the results based on reanalysis data. The impact of climate change on the heat wave characteristics in various key regions is assessed by contrasting model runs based on a scenario for the twenty-first century with those for the twentieth century. Both models indicate considerable increases in the duration and frequency of heat wave episodes, and in number of heat wave days per year, during the twenty-first century. The duration and frequency statistics of the heat waves in the mid-twenty-first century, as generated by the model with 50-km resolution, can be reproduced by adding the projected warming trend to the daily temperature data for the late twentieth century, and then recomputing these statistics. The detailed evolution of the averaged intensity, duration, and frequency of the heat waves through individual decades of the twentieth and twenty-first centuries, as simulated and projected by the model with 200-km resolution, indicates that the upward trend in these heat wave measures should become apparent in the early decades of the twenty-first century.

scholarly journals Impact of Climate Drift on Twenty-First-Century Projection in a Coupled Atmospheric–Ocean General Circulation Model

2013 ◽  
Vol 70 (10) ◽  
pp. 3321-3327 ◽  
Author(s):  
Mao-Chang Liang ◽  
Li-Ching Lin ◽  
Ka-Kit Tung ◽  
Yuk L. Yung ◽  
Shan Sun
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
General Circulation Models ◽  
Forced Response ◽  
First Century ◽  
Intergovernmental Panel ◽  
Climate Drift ◽  
Ocean General Circulation ◽  
Twenty First Century ◽  
The Impact

Abstract Reducing climate drift in coupled atmosphere–ocean general circulation models (AOGCMs) usually requires 1000–2000 years of spinup, which has not been practical for every modeling group to do. For the purpose of evaluating the impact of climate drift, the authors have performed a multimillennium-long control run of the Goddard Institute for Space Studies model (GISS-EH) AOGCM and produced different twentieth-century historical simulations and subsequent twenty-first-century projections by branching off the control run at various stages of equilibration. The control run for this model is considered at quasi equilibration after a 1200-yr spinup from a cold start. The simulations that branched off different points after 1200 years are robust, in the sense that their ensemble means all produce the same future projection of warming, both in the global mean and in spatial detail. These robust projections differ from the one that was originally submitted to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), which branched off a not-yet-equilibrated control run. The authors test various common postprocessing schemes in removing climate drift caused by a not-yet-equilibrated ocean initial state and find them to be ineffective, judging by the fact that they differ from each other and from the robust results that branched off an equilibrated control. The authors' results suggest that robust twenty-first-century projections of the forced response can be achieved by running climate simulations from an equilibrated ocean state, because memory of the different initial ocean state is lost in about 40 years if the forced run is started from a quasi-equilibrated state.

Are Changes in Global Precipitation Constrained by the Tropospheric Energy Budget?

2009 ◽  
Vol 22 (3) ◽  
pp. 499-517 ◽  
Author(s):  
F. Hugo Lambert ◽  
Myles R. Allen
Keyword(s):  
Greenhouse Gas ◽  
Black Carbon ◽  
Energy Budget ◽  
General Circulation ◽  
Circulation Model ◽  
First Century ◽  
Aerosol Forcing ◽  
Twenty First Century ◽  
Precipitation Changes ◽  
Global Precipitation

Abstract A tropospheric energy budget argument is used to analyze twentieth-century precipitation changes. It is found that global and ocean-mean general circulation model (GCM) precipitation changes can be understood as being due to the competing direct and surface-temperature-dependent effects of external climate forcings. In agreement with previous work, precipitation is found to respond more strongly to anthropogenic and volcanic sulfate aerosol and solar forcing than to greenhouse gas and black carbon aerosol forcing per unit temperature. This is due to the significant direct effects of greenhouse gas and black carbon forcing. Given that the relative importance of different forcings may change in the twenty-first century, the ratio of global precipitation change to global temperature change may be quite different. Differences in GCM twentieth- and twenty-first-century values are tractable via the energy budget framework in some, but not all, models. Changes in land-mean precipitation, on the other hand, cannot be understood at all with the method used here, even if land–ocean heat transfer is considered. In conclusion, the tropospheric energy budget is a useful concept for understanding the precipitation response to different forcings but it does not fully explain precipitation changes even in the global mean.

Conclusion: Sincerity Dreams

2017 ◽  
Author(s):  
Ellen Rutten
Keyword(s):  
United States ◽  
Popular Culture ◽  
Western Europe ◽  
The United States ◽  
First Century ◽  
Contemporary Culture ◽  
Cultural Paradigms ◽  
Twenty First Century ◽  
Inclusive Analysis

This conclusion reflects on today's dreams of renewing or revitalizing sincerity and rejects the notion that they are outdated or do not deserve any of our attention. It cites the work of several scholars to show that sincerity is anything but obsolete in twenty-first-century popular culture. Indeed, today's strivings to renew sincerity have not been neglected by scholars such as R. Jay Magill Jr., Epstein, and Yurchak. The rhetoric on new sincerity has been addressed in thoughtful analyses of contemporary culture that have helped the author in crafting a comprehensive and geographically inclusive analysis of present-day sincerity rhetoric. In post-Communist Russia, debates on a shift to late or post-postmodern cultural paradigms are thriving with at least as much fervor as—and possibly more than—in Western Europe or the United States. This conclusion discusses the newly gained insights which the author's sincerity study offers.

scholarly journals A Multivariate Empirical Orthogonal Function Method to Construct Nitrate Maps in the Southern Ocean

2018 ◽  
Vol 35 (7) ◽  
pp. 1505-1519 ◽  
Author(s):  
Yu-Chiao Liang ◽  
Matthew R. Mazloff ◽  
Isabella Rosso ◽  
Shih-Wei Fang ◽  
Jin-Yi Yu
Keyword(s):  
Southern Ocean ◽  
General Circulation ◽  
Model Simulation ◽  
Potential Temperature ◽  
Circulation Model ◽  
Empirical Orthogonal Functions ◽  
Cluster Method ◽  
Sampling Strategies ◽  
Data Sampling ◽  
Mean Square Errors

AbstractThe ability to construct nitrate maps in the Southern Ocean (SO) from sparse observations is important for marine biogeochemistry research, as it offers a geographical estimate of biological productivity. The goal of this study is to infer the skill of constructed SO nitrate maps using varying data sampling strategies. The mapping method uses multivariate empirical orthogonal functions (MEOFs) constructed from nitrate, salinity, and potential temperature (N-S-T) fields from a biogeochemical general circulation model simulation Synthetic N-S-T datasets are created by sampling modeled N-S-T fields in specific regions, determined either by random selection or by selecting regions over a certain threshold of nitrate temporal variances. The first 500 MEOF modes, determined by their capability to reconstruct the original N-S-T fields, are projected onto these synthetic N-S-T data to construct time-varying nitrate maps. Normalized root-mean-square errors (NRMSEs) are calculated between the constructed nitrate maps and the original modeled fields for different sampling strategies. The sampling strategy according to nitrate variances is shown to yield maps with lower NRMSEs than mapping adopting random sampling. A k-means cluster method that considers the N-S-T combined variances to identify key regions to insert data is most effective in reducing the mapping errors. These findings are further quantified by a series of mapping error analyses that also address the significance of data sampling density. The results provide a sampling framework to prioritize the deployment of biogeochemical Argo floats for constructing nitrate maps.

scholarly journals Coherent Lagrangian swirls among submesoscale motions

2018 ◽  
Vol 116 (37) ◽  
pp. 18251-18256 ◽  
Author(s):  
F. J. Beron-Vera ◽  
A. Hadjighasem ◽  
Q. Xia ◽  
M. J. Olascoaga ◽  
G. Haller
Keyword(s):  
Nonlinear Dynamics ◽  
General Circulation ◽  
Satellite Altimetry ◽  
Model Simulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Surface Flow ◽  
Flow Data ◽  
Ocean General Circulation ◽  
Coherence Detection

The emergence of coherent Lagrangian swirls (CLSs) among submesoscale motions in the ocean is illustrated. This is done by applying recent nonlinear dynamics tools for Lagrangian coherence detection on a surface flow realization produced by a data-assimilative submesoscale-permitting ocean general circulation model simulation of the Gulf of Mexico. Both mesoscale and submesoscale CLSs are extracted. These extractions prove the relevance of coherent Lagrangian eddies detected in satellite-altimetry–based geostrophic flow data for the arguably more realistic ageostrophic multiscale flow.

scholarly journals Controls on the water vapor isotopic composition near the surface of tropical oceans and role of boundary layer mixing processes

2019 ◽  
Author(s):  
Camille Risi ◽  
Joseph Galewsky ◽  
Gilles Reverdin ◽  
Florent Brient
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
General Circulation ◽  
Model Simulation ◽  
Circulation Model ◽  
Sea Surface ◽  
Trade Wind ◽  
Mixing Processes ◽  
Tropical Oceans ◽  
Air Mixing

Abstract. Understanding what controls the water vapor isotopic composition of the sub-cloud layer (SCL) over tropical oceans (δD0) is a first step towards understanding the water vapor isotopic composition everywhere in the troposphere. We propose an analytical model to predict δD0 as a function of sea surface conditions, humidity and temperature profiles, and the altitude from which the free tropospheric air originates (zorig). To do so, we extend previous studies by (1) prescribing the shape of δD0 vertical profiles, and (2) linking δD0 to zorig. The model relies on the hypotheses that δD0 profiles are steeper than mixing lines and no clouds are precipitating. We show that δD0 does not depend on the intensity of entrainment, dampening hope that δD0 measurements could help constrain this long-searched quantity. Based on an isotope-enabled general circulation model simulation, we show that δD0 variations are mainly controlled by mid-tropospheric depletion and rain evaporation in ascending regions, and by sea surface temperature and zorig in subsiding regions. When the air mixing into the SCL is lower in altitude, it is moister, and thus it depletes more efficiently the SCL. In turn, could δD0 measurements help estimate zorig and thus discriminate between different mixing processes? Estimates that are accurate enough to be useful would be difficult to achieve in practice, requiring measuring daily δD profiles, and measuring δD0 with an accuracy of 0.1 ‰ and 0.4 ‰ in trade-wind cumulus and strato-cumulus clouds respectively.

scholarly journals Twenty-first century-end climate scenario of Jammu and Kashmir Himalaya, India, using ensemble climate models

2020 ◽  
Vol 162 (3) ◽  
pp. 1473-1491 ◽  
Author(s):  
Shakil Ahmad Romshoo ◽  
Jasia Bashir ◽  
Irfan Rashid
Keyword(s):  
Climate Models ◽  
Climate Scenario ◽  
First Century ◽  
Kashmir Himalaya ◽  
Jammu And Kashmir ◽  
Twenty First Century

scholarly journals Meridionally Extending Anomalous Wave Train over Asia During Breaks in the Indian Summer Monsoon

2019 ◽  
Vol 3 (3) ◽  
pp. 353-366 ◽  
Author(s):  
Uppara Umakanth ◽  
Ramesh K. Vellore ◽  
R. Krishnan ◽  
Ayantika Dey Choudhury ◽  
Jagat S. H. Bisht ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
General Circulation ◽  
Wave Train ◽  
Eastern China ◽  
Circulation Model ◽  
Cyclonic Circulation ◽  
The Arctic ◽  
Indian Landmass ◽  
Central Eastern

Abstract Anomalous interactions between the Indian summer monsoon (ISM) circulation and subtropical westerlies are known to trigger breaks in the ISM on subseasonal time-scales, characterised by a pattern of suppressed rainfall over central-north India, and enhanced rainfall over the foothills of the central–eastern Himalayas (CEH). An intriguing feature during ISM breaks is the formation of a mid-tropospheric cyclonic circulation anomaly extending over the subtropical and mid-latitude areas of the Asian continent. This study investigates the mechanism of the aforesaid Asian continental mid-tropospheric cyclonic circulation (ACMCC) anomaly using observations and simplified model experiments. The results of our study indicate that the ACMCC during ISM breaks is part of a larger meridional wave train comprising of alternating anticyclonic and cyclonic anomalies that extend poleward from the monsoon region to the Arctic. A lead–lag analysis of mid-tropospheric circulation anomalies suggests that the meridional wave-train generation is linked to latent heating (LH) anomalies over the CEH foothills, Indo-China, and the Indian landmass during ISM breaks. By conducting sensitivity experiments using a simplified global atmospheric general circulation model forced with satellite-derived three-dimensional LH, it is demonstrated that the combined effects of the enhanced LH over the CEH foothills and Indo-China and decreased LH over the Indian landmass during ISM breaks are pivotal for generating the poleward extending meridional wave train and the ACMCC anomaly. At the same time, the spatial extent of the mid-latitude cyclonic anomaly over Far-East Asia is also influenced by the anomalous LH over central–eastern China. While the present findings provide interesting insights into the role of LH anomalies during ISM breaks on the poleward extending meridional wave train, the ACMCC anomaly is found to have important ramifications on the daily rainfall extremes over the Indo-China region. It is revealed from the present analysis that the frequency of extreme rainfall occurrences over Indo-China shows a twofold increase during ISM break periods as compared to active ISM conditions.

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