scholarly journals Progress in ENSO prediction and predictability study

2018 ◽  
Vol 5 (6) ◽  
pp. 826-839 ◽  
Author(s):  
Youmin Tang ◽  
Rong-Hua Zhang ◽  
Ting Liu ◽  
Wansuo Duan ◽  
Dejian Yang ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Global Climate ◽  
Theoretical Studies ◽  
Error Growth ◽  
Coupled Models ◽  
Optimal Error ◽  
Enso Prediction ◽  
The Past ◽  
Societal Impacts ◽  
Climate Mode

AbstractENSO is the strongest interannual signal in the global climate system with worldwide climatic, ecological and societal impacts. Over the past decades, the research about ENSO prediction and predictability has attracted broad attention. With the development of coupled models, the improvement in initialization schemes and the progress in theoretical studies, ENSO has become the most predictable climate mode at the time scales from months to seasons. This paper reviews in detail the progress in ENSO predictions and predictability studies achieved in recent years. An emphasis is placed on two fundamental issues: the improvement in practical prediction skills and progress in the theoretical study of the intrinsic predictability limit. The former includes progress in the couple models, data assimilations, ensemble predictions and so on, and the latter focuses on efforts in the study of the optimal error growth and in the estimate of the intrinsic predictability limit.

scholarly journals Global climatology and trends in convective environments from ERA5 and rawinsonde data

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mateusz Taszarek ◽  
John T. Allen ◽  
Mattia Marchio ◽  
Harold E. Brooks
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Convective Available Potential Energy ◽  
Global Climate Models ◽  
Convective Precipitation ◽  
The Past ◽  
The Tropics ◽  
Rawinsonde Data

AbstractGlobally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

Modulation of the relationship between summer temperatures in the Qinghai–Tibetan Plateau and Arctic over the past millennium by external forcings

2021 ◽  
pp. 1-9
Author(s):  
Feng Shi ◽  
Anmin Duan ◽  
Qiuzhen Yin ◽  
John T Bruun ◽  
Cunde Xiao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Global Climate ◽  
Volcanic Eruptions ◽  
Warm Period ◽  
Temperature Correlation ◽  
The Past ◽  
External Forcings ◽  
Centennial Variation ◽  
Summer Temperatures ◽  
Past Millennium

Abstract The Qinghai–Tibetan Plateau and Arctic both have an important influence on global climate, but the correlation between climate variations in these two regions remains unclear. Here we reconstructed and compared the summer temperature anomalies over the past 1,120 yr (900–2019 CE) in the Qinghai–Tibetan Plateau and Arctic. The temperature correlation during the past millennium in these two regions has a distinct centennial variation caused by volcanic eruptions. Furthermore, the abrupt weak-to-strong transition in the temperature correlation during the sixteenth century could be analogous to this type of transition during the Modern Warm Period. The former was forced by volcanic eruptions, while the latter was controlled by changes in greenhouse gases. This implies that anthropogenic, as opposed to natural, forcing has acted to amplify the teleconnection between the Qinghai–Tibetan Plateau and Arctic during the Modern Warm Period.

scholarly journals Ensemble models on palaeoclimate to predict India's groundwater challenge

2013 ◽  
Vol 2 (3) ◽  
Author(s):  
Partha Sarathi Datta
Keyword(s):  
Climate Change ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Humid Climate ◽  
Ensemble Models ◽  
North West ◽  
The Past ◽  
The North ◽  
14C Age

In many parts of the world, freshwater crisis is largely due to increasing water consumption and pollution by rapidly growing population and aspirations for economic development, but, ascribed usually to the climate. However, limited understanding and knowledge gaps in the factors controlling climate and uncertainties in the climate models are unable to assess the probable impacts on water availability in tropical regions. In this context, review of ensemble models on δ18O and δD in rainfall and groundwater, 3H- and 14C- ages of groundwater and 14C- age of lakes sediments helped to reconstruct palaeoclimate and long-term recharge in the North-west India; and predict future groundwater challenge. The annual mean temperature trend indicates both warming/cooling in different parts of India in the past and during 1901–2010. Neither the GCMs (Global Climate Models) nor the observational record indicates any significant change/increase in temperature and rainfall over the last century, and climate change during the last 1200 yrs BP. In much of the North-West region, deep groundwater renewal occurred from past humid climate, and shallow groundwater renewal from limited modern recharge over the past decades. To make water management to be more responsive to climate change, the gaps in the science of climate change need to be bridged.

ON "PLASTIC" WAVES IN SOLIDS

1959 ◽  
Vol 37 (9) ◽  
pp. 1017-1035 ◽  
Author(s):  
John M. Bowsher
Keyword(s):  
Theoretical Study ◽  
Short Review ◽  
Future Research ◽  
Past Work ◽  
The Past ◽  
Engineering Significance ◽  
The Subject

The study of the propagation of "plastic" waves in solids has reached a stage where it is necessary to consider which direction future research should take. In the past 90 or so years many experiments, mostly designed to elucidate certain points of engineering significance, and a few attempts at a theoretical study have cast some light on the subject and revealed it as one of formidable difficulty.Nearly all the experiments have of necessity relied on rather dubious theories for their interpretation, and part of the present paper will be devoted to a description of an apparatus which gives results capable of being interpreted with a very minimum of theory. The remainder of the paper is devoted to a short review of past work with particular emphasis on basic phenomena and to a brief discussion on the most pressing problems still remaining. The experiments described in the present paper bring to light a factor in the propagation of "plastic" waves that seems to have been overlooked in previous work.

scholarly journals An Analysis of the Temporal Evolution of ENSO Prediction Skill in the Context of the Equatorial Pacific Ocean Observing System

2015 ◽  
Vol 143 (8) ◽  
pp. 3204-3213 ◽  
Author(s):  
Arun Kumar ◽  
Mingyue Chen ◽  
Yan Xue ◽  
David Behringer
Keyword(s):  
Pacific Ocean ◽  
Time Evolution ◽  
Tropical Pacific ◽  
Sea Surface ◽  
Prediction Skill ◽  
Steady Increase ◽  
Coupled Models ◽  
Enso Prediction ◽  
Subsurface Ocean ◽  
Ocean Observations

Abstract Subsurface ocean observations in the equatorial tropical Pacific Ocean dramatically increased after the 1990s because of the completion of the TAO moored array and a steady increase in Argo floats. In this analysis the question explored is whether a steady increase in ocean observations can be discerned in improvements in skill of predicting sea surface temperature (SST) variability associated with El Niño–Southern Oscillation (ENSO)? The analysis is based on the time evolution of skill of sea surface temperatures in the equatorial tropical Pacific since 1982 based on a seasonal prediction system. It is found that for forecasts up to a 6-month lead time, a clear fingerprint of increases in subsurface ocean observations is not readily apparent in the time evolution of prediction skill that is dominated much more by the signal-to-noise consideration of SSTs to be predicted. Finding no clear relationship between an increase in ocean observations and prediction skill of SSTs, various possibilities for why it may be so are discussed. This discussion is to motivate further exploration on the question of the tropical Pacific observing system, its influence on the skill of ENSO prediction, and the capabilities of the current generation of coupled models and ocean data assimilation systems to take advantage of ocean observations.

Gradient-Free Optimization in Thermoacoustics: Application to A Low-Order Model

2021 ◽  
Author(s):  
Johann Moritz Reumschüssel ◽  
Jakob G. R. von Saldern ◽  
Yiqing Li ◽  
Christian Oliver Paschereit ◽  
Alessandro Orchini
Keyword(s):  
Optimization Algorithms ◽  
Optimization Methods ◽  
Theoretical Studies ◽  
Order Model ◽  
Output Data ◽  
Fuel Injectors ◽  
Solution Strategies ◽  
The Past ◽  
Downhill Simplex ◽  
Low Order

Abstract Machine learning and automatized routines for parameter optimization have experienced a surge in development in the past years, mostly caused by the increasing availability of computing capacity. Gradient-free optimization can avoid cumbersome theoretical studies as input parameters are purely adapted based on output data. As no knowledge about the objective function is provided to the algorithms, this approach might reveal unconventional solutions to complex problems that were out of scope of classical solution strategies. In this study, the potential of these optimization methods on thermoacoustic problems is examined. The optimization algorithms are applied to a generic low-order thermoacoustic can-combustor model with several fuel injectors at different locations. We use three optimization algorithms — the well established Downhill Simplex Method, the recently proposed Explorative Gradient Method, and an evolutionary algorithm — to find optimal fuel distributions across the fuel lines while maintaining the amount of consumed fuel constant. The objective is to have minimal pulsation amplitudes. We compare the results and efficiency of the gradient-free algorithms. Additionally, we employ model-based linear stability analysis to calculate the growth rates of the dominant thermoacoustic modes. This allows us to highlight general and thermoacoustic-specific features of the optimization methods and results. The findings of this study show the potential of gradient-free optimization methods on combustor design for tackling thermoacoustic problems, and motivate further research in this direction.

scholarly journals Changes in the strength and width of the Hadley Circulation since 1871

2012 ◽  
Vol 8 (4) ◽  
pp. 1169-1175 ◽  
Author(s):  
J. Liu ◽  
M. Song ◽  
Y. Hu ◽  
X. Ren
Keyword(s):  
20Th Century ◽  
Global Climate ◽  
Hadley Circulation ◽  
Recent Change ◽  
Early 20Th Century ◽  
Greenhouse Warming ◽  
Long Period ◽  
The Past ◽  
Period Oscillation

Abstract. Recent studies demonstrate that the Hadley Circulation has intensified and expanded for the past three decades, which has important implications for subtropical societies and may lead to profound changes in global climate. However, the robustness of this intensification and expansion that should be considered when interpreting long-term changes of the Hadley Circulation is still a matter of debate. It also remains largely unknown how the Hadley Circulation has evolved over longer periods. Here, we present long-term variability of the Hadley Circulation using the 20th Century Reanalysis. It shows a slight strengthening and widening of the Hadley Circulation since the late 1970s, which is not inconsistent with recent assessments. However, over centennial timescales (1871–2008), the Hadley Circulation shows a tendency towards a more intense and narrower state. More importantly, the width of the Hadley Circulation might have not yet completed a life-cycle since 1871. The strength and width of the Hadley Circulation during the late 19th to early 20th century show strong natural variability, exceeding variability that coincides with global warming in recent decades. These findings raise the question of whether the recent change in the Hadley Circulation is primarily attributed to greenhouse warming or to a long-period oscillation of the Hadley Circulation – substantially longer than that observed in previous studies.

Late-Holocene Formation of Lake Michigan Beach Ridges Correlated with a 70-yr Oscillation in Global Climate

1996 ◽  
Vol 45 (3) ◽  
pp. 321-326 ◽  
Author(s):  
Paul A. Delcourt ◽  
William H. Petty ◽  
Hazel R. Delcourt
Keyword(s):  
Late Holocene ◽  
Lake Michigan ◽  
Global Climate ◽  
Temperature Oscillation ◽  
Beach Ridges ◽  
Climate Fluctuations ◽  
The Past ◽  
Fundamental Part ◽  
Atmosphere System ◽  
Centennial Time Scale

AbstractA radiocarbon-dated series of 75 beach ridges, formed at regular intervals averaging 72 yr over the past 5400 yr, provides further support for the existence of a 70-yr oscillation in Northern Hemisphere climate, postulated recently from instrument data representing less than two cycles of this climate oscillation. Results from this study lend support to the interpretation that internal variations in the ocean–atmosphere system are an important factor in climate fluctuations on a decadal–centennial time scale. A temperature oscillation with a period of about 70 yr has been a previously unrecognized but fundamental part of the global climate system since at least the middle Holocene.

scholarly journals Geomagnetism, volcanoes, global climate change, and predictability. A progress report

1994 ◽  
Vol 37 (5 Sup.) ◽  
Author(s):  
G. P. Gregori
Keyword(s):  
State Of The Art ◽  
Global Climate ◽  
Data Series ◽  
Theoretical Studies ◽  
Data Handling ◽  
Future Perspectives ◽  
Proxy Data ◽  
Interstellar Clouds ◽  
The Earth ◽  
Glacier Melting

A model is investigated, by which the encounters of the solar system with dense interstellar clouds ought to trigger either geomagnetic field reversals or excursions, that produce extra electric currents within the Earth dynamo, that cause extra Joule's heating, that supplies volcanoes and endogenous processes. Volcanoes increase the Earth degassing into the atmosphere, hence the concentration of the minor atmospheric constituents, including the greenhouse gases, hence they affect climate temperature, glacier melting, sea level and global change. This investigation implies both theoretical studies and observational data handling on different time scales, including present day phenomena, instrumental data series, historical records, proxy data, and geological and palaeontological evidences. The state of the art is briefly outlined, mentioning some already completed achievements, investigations in progress, and future perspectives.

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