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Author Correction: El Niño-Southern Oscillation complexity
Timmermann, Axel,An, Soon-Il,Kug, Jong-Seong,Jin, Fei-Fei,Cai, Wenju,Capotondi, Antonietta,Cobb, Kim M.,Lengaigne, Matthieu,McPhaden, Michael J.,Stuecker, Malte F.,Stein, Karl,Wittenberg, Andrew T.,Yu Springer Science and Business Media LLC 2019 Nature Vol.567 No.7746
El Niño–Southern Oscillation complexity
Timmermann, Axel,An, Soon-Il,Kug, Jong-Seong,Jin, Fei-Fei,Cai, Wenju,Capotondi, Antonietta,Cobb, Kim,Lengaigne, Matthieu,McPhaden, Michael J.,Stuecker, Malte F.,Stein, Karl,Wittenberg, Andrew T.,Yun, Nature Publishing Group UK 2018 Nature Vol.559 No.7715
<P>El Nino events are characterized by surface warming of the tropical Pacific Ocean and weakening of equatorial trade winds that occur every few years. Such conditions are accompanied by changes in atmospheric and oceanic circulation, affecting global climate, marine and terrestrial ecosystems, fisheries and human activities. The alternation of warm El Nino and cold La Nina conditions, referred to as the El Nino-Southern Oscillation (ENSO), represents the strongest year-to-year fluctuation of the global climate system. Here we provide a synopsis of our current understanding of the spatio-temporal complexity of this important climate mode and its influence on the Earth system.</P>
A Simple Model for Runoff Predictability
Roman Olson,Axel Timmermann,June-Yi Lee,Soon-Il An 한국기상학회 2021 한국기상학회 학술대회 논문집 Vol.2021 No.10
Recent work has identified potential multi-year predictability in soil moisture (Chikamoto et al., 2015). Whether this long-term predictability translates into an extended predictability of runoff still remains an open question. To address this question we develop a physically-based zero-dimensional stochastic runoff model. The model extends previous work of Dolgonosov and Korchagin (2007) by including a runoff-generating soil moisture threshold. We consider several assumptions on the input rainfall noise. We analyze the applicability of analytical solutions for the stationary probability density function (pdf) and for the waiting time for runoff under different assumptions. Out results suggest that knowing soil moisture provides important information on the waiting time for runoff. In addition, we fit the simple model to the daily NCEP1 reanalysis output on a near-global scale, and analyze the fitted model performance. Over many tropical regions, the model reproduces the simulated runoff in NCEP1 reasonably well. More detailed analysis over a single gridpoint illustrates that the model, despite its simplicity, is able to capture some key features of the runoff time series and pdfs of a more complex model. Our model exhibits runoff predictability of up to two months in advance. Our results suggest that there is an optimal predictability “window” in the transition zone between runoff-generating and dry conditions. Our model can serve as a “null hypothesis” model reference against more complex models for runoff predictability.
Tigchelaar, Michelle,Timmermann, Axel,Pollard, David,Friedrich, Tobias,Heinemann, Malte Elsevier 2018 Earth and planetary science letters Vol.495 No.-
<P><B>Abstract</B></P> <P>The Antarctic ice sheet – storing ∼27 million cubic kilometres of ice – has the potential to contribute greatly to future sea level rise; yet its past evolution and sensitivity to long-term climatic drivers remain poorly understood and constrained. In particular, a long-standing debate questions whether Antarctic climate and ice volume respond mostly to changes in global sea level and atmospheric greenhouse gas concentrations or to local insolation changes. So far, long-term Antarctic simulations have used proxy-based parameterizations of climatic drivers, presuming that external forcings are synchronous and spatially uniform. Here for the first time we use a transient, three-dimensional climate simulation over the last eight glacial cycles to drive an Antarctic ice sheet model. We show that the evolution of the Antarctic ice sheet was mostly driven by CO<SUB>2</SUB> and sea level forcing with a period of about 100,000 yr, synchronizing both hemispheres. However, on precessional time scales, local insolation forcing drives additional mass loss during periods of high sea level and CO<SUB>2</SUB>, enhancing the Antarctic interglacial and putting northern and southern ice sheet variability temporarily out of phase. In our simulations, partial collapses of the West Antarctic ice sheet during warm interglacials are only simulated with unrealistically large Southern Ocean subsurface warming exceeding ∼4 °C. Overall, our results further elucidate the complex interplay of global and local forcings in driving Late Quaternary Antarctic ice sheet evolution, and the unique and overlooked role of precession therein.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 800,000-year simulation of Antarctic ice sheet uses forcing from transient climate simulation. </LI> <LI> Northern and southern hemisphere ice sheets are synchronized through global sea level and CO<SUB>2</SUB>. </LI> <LI> Local precessionally-driven insolation changes enhance Antarctic interglacials. </LI> </UL> </P>