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Paleoclimate data assimilation: Principles and prospects

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Science China Earth sciences 2025年

作者： Haoxun ZHANG Mingsong LI Yongyun HU Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education School of Earth and Space Sciences Peking University State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development Laboratory for Climate and Ocean-Atmosphere Studies Department of Atmospheric and Oceanic Sciences School of PhysicsPeking University Institute of Ocean Research Peking University

Reconstructing climate states during geological periods is a key focus in studying Earth system evolution. Substantial progress has been achieved in reconstructing paleoclimate and paleoenvironment using both Earth system models and paleoclimate proxies. However, current paleoclimate reconstructions face several challenges:the accuracy of Earth system model simulations relies on model parameter settings. Paleoclimate proxy data exhibit significant variability across different periods and regions, and proxy data are often sparse, hindering the accuracy and global relevance of proxy-based *** the pros and cons of these methods, paleoclimate data assimilation can effectively integrate Earth system models and paleoclimate proxy data, enhancing the precision and global relevance of reconstructions. Using approaches such as the ensemble Kalman filter as an example, this paper introduces the principles of paleoclimate data assimilation and reviews recent advancements in reconstructing paleoclimate states using these techniques. Paleoclimate data assimilation offers new insights and advanced techniques for paleoclimate reconstruction, with potential applications extending to the entire Cenozoic, Mesozoic, and even Paleozoic eras. These applications could deepen our understanding of the past climatic backgrounds of extreme climate events such as glacial-interglacial cycles, hyperthermals, and oceanic anoxic events, providing a reference for predicting future climate change.

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Two Modes and Their Seasonal and Interannual Variation of the Baroclinic Waves/Storm Tracks over the Wintertime North Pacific

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Advances in atmospheric sciences 2015年第9期32卷 1244-1254页

作者： JIANG Yuxin TAN Benkui department of atmospheric and oceanic sciences Peking University

In this study,a newly developed method,termed moving empirical orthogonal function analysis（MEOF）,is applied to the study of midlatitude baroclinic waves over the wintertime North Pacific from 1979 to *** is shown that when the daily,high-pass filtered（2–10 days） meridional wind at 250 h Pa is chosen as the variable of the MEOF analysis,typical features of baroclinic waves/storm tracks over the wintertime North Pacific can be well described by this *** is found that the first two leading modes of the MEOF analysis,MEOF1 and MEOF2,assume quite different ***1 takes the form of a single wave train running in the east–west direction along 40°N,while MEOF2 is a double wave train pattern running in the east–west direction along 50°N and 30°N,*** shift composites of various anomalous fields based on MEOF1 and MEOF2 assume typical baroclinic wave ***1 represents a primary storm track pulsing with an intrinsic time scale of two *** shows significant ＂midwinter suppression＂ and apparent interannual *** is stronger after the mid-1990 s than before the mid-1990 ***2 represents a double-branch storm track,also with an intrinsic time scale of approximately two days,running along 50°N and 30°N,*** shows no apparent seasonal variation,but its interannual and decadal variation is quite *** oscillates with larger amplitude and longer periods after the mid-1990 s than before the mid-1990 s,and is heavily modulated by El Ni n°o–Southern Oscillation（ENSO）.

关键词： baroclinic waves Pacific storm tracks MEOF analysis ENSO

New findings on the influence of El Nino events on tropical cyclone formation

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Science China Earth sciences 2024年第3期67卷 892-893页

作者： Liguang WU department of atmospheric and oceanic sciences Institute of Atmospheric SciencesFudan UniversityShanghai 200438China

Tropical cyclones typically form over warm tropical and subtropical ocean surfaces, as their formation and intensification rely primarily on the energy provided by the ocean. Pioneering research by Gray (1968) revealed that the formation of tropical cyclones requires the sea surface temperature (SST) to be no less than 26.5℃. Consequently, SST is commonly recognized as a crucial parameter among the environmental factors influencing tropical cyclone formation(Gray, 1979;Emanuel and Nolan, 2004).

关键词： tropical cyclone ocean

Rivers increasingly warmer:Prediction of changes in the thermal regime of rivers in Poland

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Journal of Geographical sciences 2025年第1期35卷 139-174页

作者： Mariusz PTAK Teerachai AMNUAYLOJAROEN Mariusz SOJKA department of Hydrology and Water Management Adam Mickiewicz University School of Energy and Environment University of Phayao atmospheric Pollution and Climate Research Unit School of Energy and Environment University of Phayao department of Land Improvement Environmental Development and Spatial Management Poznań University of Life Sciences

Emphasis on future environmental changes grows due to climate change, with simulations predicting rising river temperatures globally. For Poland, which has a long history of thermal studies of rivers, such an approach has not been implemented to date. This study used 9 Global Climate Models and tested three machine-learning techniques to predict river temperature changes. Random Forest performed best, with R2=0.88 and lowest error(RMSE:2.25, MAE:1.72). The range of future water temperature changes by the end of the 21st century was based on the Shared Socioeconomic Pathway scenarios SSP2-4.5 and SSP5-8.5. It was determined that by the end of the 21st century, the average temperature will increase by 2.1°C(SSP2-4.5) and 3.7°C(SSP5-8.5). A more detailed analysis, divided by two major basins Vistula and Odra, covered about 90% of Poland's territory. The average temperature increase, according to scenarios SSP2-4.5 and SSP5-8.5 for the Odra basin rivers,is 1.6°C and 3.2°C and for the Vistula basin rivers 2.3°C and 3.8°C, respectively. The Vistula basin's higher warming is due to less groundwater input and continental climate *** findings provide a crucial basis for water management to mitigate warming effects in Poland.

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Co-adsorption of gaseous benzene, toluene, ethylbenzene,m-xylene(BTEX) and SO_2 on recyclable Fe_3O_4 nanoparticles at 0–101% relative humidities

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Journal of Environmental sciences 2015年第5期27卷 164-174页

作者： Connie Z.Ye Parisa A.Ariya department of Chemistry McGill University department of atmospheric and oceanic sciences McGill University

We herein used Fe3O4 nanoparticles（NPs） as an adsorption interface for the concurrent removal of gaseous benzene, toluene, ethylbenzene and m-xylene（BTEX） and sulfur dioxide（SO2）, at different relative humidities（RH）. X-ray diffraction, Brunauer-Emmett-Teller, and transmission electron microscopy were deployed for nanoparticle surface ***-dispersed Fe3O4（Fe2O3·Fe O） NPs synthesized with oleic acid（OA） as surfactant, and uncoated poly-dispersed Fe3O4 NPs demonstrated comparable removal *** experiments of BTEX on NPs were measured using gas chromatography equipped with flame ionization detection, which indicated high removal efficiencies（up to（95 ± 2）%） under dry conditions. The humidity effect and competitive adsorption were investigated using toluene as a model compound. It was observed that the removal efficiencies decreased as a function of the increase in RH, yet, under our experimental conditions, we observed（40 ± 4）% toluene removal at supersaturation for Fe3O4 NPs, and toluene removal of（83 ± 4）% to（59 ± 6）%, for OA-Fe3O4 NPs. In the presence of SO2, the toluene uptake was reduced under dry conditions to（89 ± 2）% and（75 ± 1）% for the uncoated and coated NPs, respectively, depicting competitive adsorption. At RH 〉 100%,competitive adsorption reduced the removal efficiency to（27 ± 1）% for uncoated NPs whereas OA-Fe3O4 NPs exhibited moderate efficiency loss of（55 ± 2）% at *** point to heterogeneous water coverage on the NP surface. The magnetic property of magnetite facilitated the recovery of both types of NPs, without the loss in efficiency when recycled and reused.

关键词： Fe3O4 nanoparticles Co-adsorption Competitive adsorption BTEX removal SO2 removal

Influence of the Arctic on the Predictability of Eurasian Winter Extreme Weather Events

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Advances in atmospheric sciences 2020年第4期37卷 307-317页

作者： Guokun DAI Mu MU department of atmospheric and oceanic sciences and Institute of atmospheric sciences Fudan UniversityShanghai 200438China

The linkage between the Arctic and midlatitudes has received much attention recently due to the rapidly changing *** investigations have been conducted to reveal the relationship between the Arctic and Eurasian extreme events from the perspective of climatological *** a prediction source for extreme events in Eurasia,Arctic conditions are crucial for extreme event ***,it is urgent to explore the Arctic influence on the predictability of Eurasian extreme events due to the large uncertainties in Arctic *** the sensitivity and nonlinearity of the atmospheric circulations in midlatitude to Arctic conditions,it is necessary to investigate the Arctic influences on Eurasian extreme weather events in case studies at weather time *** studies indicate that only perturbations in specific patterns have fast ***,the conditional nonlinear optimal perturbation approach is recommended for exploring the uncertainties in Arctic initial and boundary conditions and their synergistic effect on Eurasian extreme ***,the mechanism for extreme event formation may differ in different ***,more extreme cases should be investigated to reach robust conclusions.

关键词： Arctic uncertainties Eurasian extreme weather events synergistic effect optimization algorithms

Bifurcation of Nonlinear Kelvin Wave-CISK with ConditionalHeating in a Truncated Spectral Model: A PossibleMechanism of 30-60-Day Oscillation at the Equator

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Advances in atmospheric sciences 1999年第2期16卷 279-296页

作者：罗德海 department of atmospheric and oceanic sciences Ocean University of Qingdao Qingdao

In this paper, the nonlinear Kelvin wave equations with 'positive-only' nonlinear (conditional) heating at the equator are reduced to a sixth-order nonlinear ordinary differential equation by using the Galerkin spectral truncated method. The stability analysis indicates that when the heating parameter increases, the supercritical pitchfork and Hopf bifurcations can occur for the prescribed three heating profiles. Numerical calculations are made with the help of the fourth-order Rung-Kutta method. It is found that the convection heating-related Hopf bifurcation can lead to limit cycle and chaotic solutions. In a wide range of heating parameter, the solutions possess 30-60-day periods, and are dominated by wavenumbers one and two, especially by wavenumber-one. In addition, the zonal winds of the low-frequency solutions have a phase reversal between the upper and lower tropospheres. Thus, it appears that the convection heating-related Hopf bifurcation might be a possible mechanism of 30-60-day oscillation in the tropical atmosphere.

关键词： bifurcation wave-CISK 30-60-day oscillation

The Role of Initial Cloud Condensation Nuclei Concentration in Hail Using the WRF NSSL 2-moment Microphysics Scheme

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Advances in atmospheric sciences 2017年第9期34卷 1106-1120页

作者： Xiaofei LI Qinghong ZHANG Huiwen XUE department of atmospheric and oceanic sciences School of PhysicsPeking University

The effects of the initial cloud condensation nuclei （CCN） concentrations （100-3000 mg-1） on hail properties were investigated in an idealized non-severe hail storm experiment using the Weather Research and Forecasting （WRF） model, with the National Severe Storms Laboratory 2-moment microphysics scheme. The initial CCN concentration （CCNC） had obvious non-monotonic effects on the mixing ratio, number concentrations, and radius of hail, both in clouds and at the surface, with a CCNC threshold between 300 and 500 mg-1. An increasing CCNC is conducive （suppressive） to the amount of surface hail precipitation below （above） the CCNC threshold. The non-monotonic effects were due to both the thermodynamics and microphysics. Below the CCNC threshold, the mixing ratios with the increasing CCNC, resulting in more latent heat released of cloud droplets and ice crystals increased dramatically from condensation and frozen between 4 and 8 km and intensified updraft volume. The extent of the riming process, which is the primary process for hail production, increased dramatically. Above the CCNC threshold, the mixing ratio of cloud droplets and ice crystals increased continuously, but the maximum updraft volume was weakened because of reduced frozen latent heating at low level. The smaller ice crystals reduced the formation of hail and smaller clouds, with decreased rain water reducing riming efficiency so that graupel and hail also decreased with increasing CCNC, which is unfavorable for hail growth.

关键词： CCN hail microphysics thermodynamics threshold

Nonlinear Three-Wave Interaction among Barotropic Rossby Waves in a Large-scale Forced Barotropic Flow

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Advances in atmospheric sciences 1999年第3期16卷 451-466页

作者：罗德海 department of atmospheric and oceanic sciences Ocean University of Qingdao Qingdao

In this paper. the coupling equations describing nonlinear three-wave interaction amongRossby waves including the forcing of an external vorticity source are obtained. Under certainconditions, the coupling equations with a constant amplitude forcing, the stability analysis indicates that when the amplitude of the external forcing increases to a certain extent, a pitchforkbifurcation occurs. Also. it is shown fi-o m numerical results that the bifurcation can lead to chaoticbehavior of' strange' attractor. For the obtained three-variable equation, when the amplitude ofmodulated external forcing gradually increases, a Period-doubling bifurcation is found to lead tochaotic behavior. Thus, in a nonlinear three-wave coupling model in the large-scale forcedbarotropic atmospheric flow, chaotic behavior can be observed. This chaotic behavior can explainin part 30-60-day low-flequency oscillations observed in mid-high latitudes.

关键词： Rossby waves Three-wave interaction 30-60-day low frequency oscillation