Recent Advances in Understanding Multi-scale Climate Variability of the Asian Monsoon

Studies of the multi-scale climate variability of the Asian monsoon are essential to an advanced understanding of the physical processes of the global climate system.In this paper,the progress achieved in this field is systematically reviewed,with a focus on the past several years.The achievements are summarized into the following topics:(1)the onset of the South China Sea summer monsoon;(2)the East Asian summer monsoon;(3)the East Asian winter monsoon;and(4)the Indian summer monsoon.Specifically,new results are highlighted,including the advanced or delayed local monsoon onset tending to be synchronized over the Arabian Sea,Bay of Bengal,Indochina Peninsula,and South China Sea;the basic features of the record-breaking mei-yu in 2020,which have been extensively investigated with an emphasis on the role of multi-scale processes;the recovery of the East Asian winter monsoon intensity after the early 2000s in the presence of continuing greenhouse gas emissions,which is believed to have been dominated by internal climate variability(mostly the Arctic Oscillation);and the accelerated warming over South Asia,which exceeded the tropical Indian Ocean warming,is considered to be the main driver of the Indian summer monsoon rainfall recovery since 1999.A brief summary is provided in the final section along with some further discussion on future research directions regarding our understanding of the Asian monsoon variability.

Preface to the Special Issue on Changing Arctic Climate and Low/Mid-latitudes Connections

The Arctic climate system has changed rapidly during recent decades with a two-four times faster warming rate than the global average subject to the uncertainties of analysis datasets and approaches.These changes have apparently resulted in broader and sizeable impacts within the Arctic,in the low/mid-latitudes,and globally.The importance of these changes and impacts makes the Arctic stand out within the global climate systems,drawing great attention and interests from the climate research community,the general public,and the government sector.One of the persistent,leading-edge topics in climate stud-ies during recent decades has therefore been to improve understanding of the underlying driving mechanisms,evaluate socioe-conomic and ecological impacts,and enhance the ability of the prediction and projections of Arctic climate changes.

Influence of Soil Moisture in Eastern China on the East Asian Summer Monsoon

The sensitivity of the East Asian summer monsoon to soil moisture anomalies over China was investigated based on ensembles of seasonal simulations （March-September） using the NCEP GCM coupled with the Simplified Simple Biosphere Model （NCEP GCM/SSiB）. After a control experiment with free-running soil moisture, two ensembles were performed in which the soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China （YRNC） was double and half that in the control, with the maximum less than the field capacity. The simulation results showed significant sensitivity of the East Asian summer monsoon to wet soil in YRNC. The wetter soil was associated with increased surface latent heat flux and reduced surface sensible heat flux. In turn, these changes resulted in a wetter and colder local land surface and reduced land-sea temperature gradients, corresponding to a weakened East Asian monsoon circulation in an anomalous anticyclone over southeastern China, and a strengthened East Asian trough southward over Northeast China. Consequently, less precipitation appeared over southeastern China and North China and more rainfall over Northeast China. The weakened monsoon circulation and strengthened East Asian trough was accompanied by the convergence of abnormal northerly and southerly flow over the Yangtze River valley, resulting in more rainfall in this region. In the drier soil experiments, less precipitation appeared over YRNC. The East Asian monsoon circulation seems to show little sensitivity to dry soil anomalies in NCEP GCM/SSiB.

Influence of Intraseasonal Oscillation on the Asymmetric Decays of El Ni?o and La Ni?a

Warm and cold phases of El Nino–Southern Oscillation (ENSO) exhibit a significant asymmetry in their decay speed. To explore the physical mechanism responsible for this asymmetric decay speed, the asymmetric features of anomalous sea surface temperature (SST) and atmospheric circulation over the tropical Western Pacific (WP) in El Nino and La Nina mature-to-decay phases are analyzed. It is found that the interannual standard deviations of outgoing longwave radiation and 850 hPa zonal wind anomalies over the equatorial WP during El Nino (La Nina) mature-to-decay phases are much stronger (weaker) than the intraseasonal standard deviations. It seems that the weakened (enhanced) intraseasonal oscillation during El Nino (La Nina) tends to favor a stronger (weaker) interannual variation of the atmospheric wind, resulting in asymmetric equatorial WP zonal wind anomalies in El Nino and La Nina decay phases. Numerical experiments demonstrate that such asymmetric zonal wind stress anomalies during El Nino and La Nina decay phases can lead to an asymmetric decay speed of SST anomalies in the central-eastern equatorial Pacific through stimulating di erent equatorial Kelvin waves. The largest negative anomaly over the Nino3 region caused by the zonal wind stress anomalies during El Nino can be threefold greater than the positive Nino3 SSTA anomalies during La Nina, indicating that the stronger zonal wind stress anomalies over the equatorial WP play an important role in the faster decay speed during El Nino.

Modulation of the Intensity of Nascent Tibetan Plateau Vortices by Atmospheric Quasi-Biweekly Oscillation

The modulation of the intensity of nascent Tibetan Plateau vortices(ITPV) by atmospheric quasi-biweekly oscillation(QBWO) is investigated based on final operational global analysis data from the National Centers for Environmental Prediction. The spatial and temporal distributions of the ITPV show distinct features of 10–20-day QBWO. The average ITPV is much higher in the positive phases than in the negative phases, and the number of strong TPVs is much larger in the former,with a peak that appears in phase 3. In addition, the maximum centers of the ITPV stretch eastward in the positive phases,indicating periodic variations in the locations where strong TPVs are generated. The large-scale circulations and related thermodynamic fields are discussed to investigate the mechanism by which the 10–20-day QBWO modulates the ITPV. The atmospheric circulations and heating fields of the 10–20-day QBWO have a major impact on the ITPV. In the positive QBWO phases, the anomalous convergence at 500 hPa and divergence at 200 hPa are conducive to ascending motion. In addition, the convergence centers of the water vapor and the atmospheric unstable stratification are found in the positive QBWO phases and move eastward. Correspondingly, condensational latent heat is released and shifts eastward with the heating centers located at 400 hPa, which favors a higher ITPV by depressing the isobaric surface at 500 hPa. All of the dynamic and thermodynamic conditions in the positive QBWO phases are conducive to the generation of stronger TPVs and their eastward expansion.

Impacts of major volcanic eruptions over the past two millennia on both global and Chinese climates:A review

Major volcanic eruptions(MVEs)have attracted increasing attention from the scientific community.Previous studies have explored the climatic impact of MVEs over the past two millennia.However,proxy-based reconstructions and climate model simulations indicate divergent responses of global and China’s regional climates to MVEs.Here,we used multiple data from observations,reconstructions,simulations,and assimilations to summarize the historical facts of MVEs,the characteristics and mechanisms of their climatic impact,and directions for future research.We reviewed volcanic datasets and determined intensive MVE periods;these periods corresponded to the years 530–700,1200‒1460,and 1600‒1840 CE.After tropical MVEs,a substantial cooling effect is observed throughout the globe and China on the interannual-interdecadal time scales but an inconsistent cooling magnitude is detected between reconstructions and simulations.In the first summer after tropical MVEs,a decrease in global and monsoonal precipitation is observed.In reconstructions and simulations,an increased precipitation is seen for the Yangtze River Basin,while large uncertainties in precipitation changes are present for other regions of China.Decadal drought can be induced by frequent eruptions and volcanism superimposed on low solar irradiation and internal variability.MVEs affect climate directly through the radiative effect and indirectly by modulating internal variability,such as the El Niño‒Southern Oscillation(ENSO)and Atlantic Multidecadal Oscillation(AMO).However,changes in the phase,amplitude,and periodicity of ENSO and AMO after MVEs and the associated mechanisms remain controversial,which could account for model-reconstruction disagreements.Moreover,other internal variability,uncertainties in reconstruction methods and aerosol‒climate models,and climate background may also induce model-reconstruction disagreements.Knowledge gaps and directions for future research are also discussed.

保持土壤湿度对减缓气候变化重要性

A troubling feedback loop, where drier soil contributes to hotter climates, has been widely recognized.This study, drawing on climate model simulations, reveals that maintaining current global soil moisture levels could significantly alleviate 32.9% of land warming under low-emission scenarios. This action could also postpone reaching critical warming thresholds of 1.5 °C and 2.0 °C by at least a decade. Crucially,preserving soil moisture at current levels could prevent noticeable climate change impacts across 42%of the Earth's land, a stark deviation from projections suggesting widespread impacts before the 2060s.To combat soil drying, afforestation in mid-to-low latitude regions within the next three decades is proposed as an effective strategy to increase surface water availability. This underscores the substantial potential of nature-based solutions for managing soil moisture, benefiting both climate change mitigation and ecological enhancement.

Resilience Building and Collaborative Governance for Climate Change Adaptation in Response to a New State of More Frequent and Intense Extreme Weather Events

The weather conditions of the summer of 2022 were very unusual,particularly in Eastern Asia,Europe,and North America.The devasting impact of climate change has come to our attention,with much hotter and drier conditions,and with more frequent and intense flooding events.Some extreme events have reached a dangerous level,increasingly threatening human lives.The interconnected risks caused by these extreme disaster events are triggering a chain effect,forcing us to respond to these crises through changes in our living environment,which affect the atmosphere,the biosphere,the economy including the availability of energy,our cities,and our global society.Moreover,we have to confront the abnormal consequences of untypical,rapid changes of extreme events and fast switches between extreme states,such as from severe drought to devastating flooding.Recognizing this new situation,it is crucial to improve the adaptation capacity of our societies in order to reduce the risks associated with climate change,and to develop smarter strategies for climate governance.High-quality development must be science-based,balanced,safe,sustainable,and climate-resilient,supported by the collaborative governance of climate mitigation and adaptation.This article provides some recommendations and suggestions for resilience building and collaborative governance with respect to climate adaptation in response to a new planetary state that is characterized by more frequent and severe extreme weather events.

A Diagnostic Study of the Influence of Early Spring Soil Moisture in Southeastern China on Interannual Variability of the East Asian Subtropical Summer Monsoon Onset

The effect of soil moisture(SM)on the onset of East Asian subtropical summer monsoon(EASSM)is investigated based on multiple sets of reanalysis data in the period of 1981–2010.It is found that the EASSM is characterized by persistent 2-m s^(−1) southerly winds for about 3 months in spring at 850 hPa over the subtropical region of East Asia.Considering this feature of the meridional winds,we define the EASSM onset date,and obtain that the climatological onset date is pentad 17.7,around 26 March.On the interannual timescale,the onset date of EASSM exhibits statistically significant correlation with the SM in southeastern China in the month preceding the onset,with wetter(drier)conditions being associated with later(earlier)onset.The physical process by which the preceding SM affects the EASSM onset is further explored by examining the surface energy balance as well as its impacts.Positive(negative)SM anomalies in southeastern China in the month before onset may induce negative(positive)surface temperature anomalies.The decreased(increased)surface temperature in southeastern China before the EASSM onset weakens(strengthens)the zonal sea–land thermal contrast in the surface and low-level atmosphere in the subtropical East Asia.The zonal sea–land thermal contrast in wetter(drier)years induces anomalous northerly(southerly)winds over southeastern China,which tends to delay(advance)the zonal thermal seasonal transition in spring and is conducive to a later(earlier)onset of EASSM.These results are helpful for understanding and prediction of the variability of EASSM and the EASSM onset.

Theories on Formation of an Anomalous Anticyclone in Western North Pacific during El Nino:A Review

The western Noah Pacific anomalous anticyclone （WNPAC） is an important atmospheric circulation system that conveys El Nifio impact on East Asian climate. In this review paper, various theories on the formation and maintenance of the WNPAC, including warm pool atmosphere-ocean interaction, Indian Ocean capacitor, a combination mode that emphasizes nonlinear interaction between ENSO and annual cycle, moist enthalpy advecfion/Rossby wave modulation, and central Pacific SST forcing, are discussed. It is concluded that local atmosphere-ocean interaction and moist enthalpy advection/Rossby wave modulation mechanisms are essential for the initial development and maintenance of the WNPAC during El Nifio mature winter and subsequent spring. The Indian Ocean capacitor mechanism does not contribute to the earlier development but helps maintain the WNPAC in El Nifio decaying summer. The cold SST anomaly in the western North Pacific, although damped in the summer, also plays a role. An inter- basin atmosphere-ocean interaction across the Indo-Pacific warm pool emerges as a new mechanism in summer. In addition, the central Pacific cold SST anomaly may induce the WNPAC during rapid El Nifio decaying/La Nina developing or La Nifia persisting summer. The near-annual periods predicted by the combination mode theory are hardly detected from observations and thus do not contribute to the formation of the WNPAC. The tropical Atlantic may have a capacitor effect similar to the tropical Indian Ocean.

Changes in East Asian summer monsoon and summer rainfall over eastern China during recent decades

In the East Asian monsoon region over eastern China,east of 100°E,summer rainfall controlled by the East Asian summer monsoon(EASM)is mainly concentrated during June–August.Summer rainfall accounts for more than half of the annual total,or 52%,according to rainfall observations from 160 meteorological stations in China

Relationship between the Circumglobal Teleconnection and Silk Road Pattern over Eurasian continent

During boreal summer, two remarkable upper-level wave trains over Eurasia were documented in literature, i.e., Circumglobal Teleconnection (CGT) and Silk Road Pattern (SRP). They are widely discussed because of their influences throughout the entire midlatitude Eurasia. SRP was defined by 200 hPa meridional winds [1]. Enomoto et al.[2] found that the wave train influenced the climate variation over Japan when they detected the mechanism of Bonin High, and then named it as "Silk Road Pattern". SRP has 3 prominent action centers, which are located in west-central Asia, Mongolia and the Far East, respectively [3].

Boreal Summer Intraseasonal Oscillation in the Asian–Pacific Monsoon Region Simulated in CAMS-CSM

The boreal summer intraseasonal oscillation(BSISO) is simulated by the Climate System Model(CSM) developed at the Chinese Academy of Meteorological Sciences(CAMS), China Meteorological Administration. Firstly, the results indicate that this new model is able to reasonably simulate the annual cycle and seasonal mean of the precipitation, as well as the vertical shear of large-scale zonal wind in the tropics. The model also reproduces the eastward and northward propagating oscillation signals similar to those found in observations. The simulation of BSISO is generally in agreement with the observations in terms of variance center, periodicity, and propagation, with the exception that the magnitude of BSISO anomalous convections are underestimated during both its eastward propagation along the equator and its northward propagation over the Asian–Pacific summer monsoon region. Our preliminary evaluation of the simulated BSISO by CAMS-CSM suggests that this new model has the capability, to a certain extent, to capture the BSISO features, including its propagation zonally along the equator and meridionally over the Asian monsoon region.

Daily CO_(2) Emission Reduction Indicates the Control of Activities to Contain COVID-19 in China

Lockdown measures are essential to containing the spread of coronavirus disease 2019(COVID-19),but they will slow down economic growth by reducing industrial and commercial activities.However,the benefits of activity control from containing the pandemic have not been examined and assessed.Here we use daily carbon dioxide(CO_(2))emission reduction in China estimated from statistical data for energy consumption and satellite data for nitrogen dioxide(NO_(2))measured by the Ozone Monitoring Instrument(OMI)as an indicator for reduced activities consecutive to a lockdown.We perform a correlation analysis to show that a 1%day-1 decrease in the rate of COVID-19 cases is associated with a reduction in daily CO_(2) emissions of 0.22%±0.02%using statistical data for energy consumption relative to emissions without COVID-19,or 0.20%±0.02%using satellite data for atmospheric column NO_(2).We estimate that swift action in China is effective in limiting the number of COVID-19 cases<100,000 with a reduction in CO_(2) emissions of up to 23%by the end of February 2020,whereas a 1-week delay would have required greater containment and a doubling of the emission reduction to meet the same goal.By analyzing the costs of health care and fatalities,we find that the benefits on public health due to reduced activities in China are 10-fold larger than the loss of gross domestic product.Our findings suggest an unprecedentedly high cost of maintaining activities and CO_(2) emissions during the COVID-19 pandemic and stress substantial benefits of containment in public health by taking early actions to reduce activities during the outbreak of COVID-19.

Fourteen Actions and Six Proposals for Science and Technology-Based Disaster Risk Reduction in Asia Second Asian Science and Technology Conference for Disaster Risk Reduction:SciencePolicy Dialogue for Implementation of the Sendai Framework,April 2018

1 Introduction The Sendai Framework for Disaster Risk Reduction 2015–2030 shifts the focus from managing disasters to reducing risks.Such a shift requires a better understanding of risk in all its dimensions of environment,hazards,exposure,and vulnerability;a disaster risk governance that

From concept to action: a united, holistic and One Health approach to respond to the climate change crisis

It is unequivocal that human influence has warmed the planet,which is seriously affecting the planetary health including human health.Adapting climate change should not only be a slogan,but requires a united,holistic action and a paradigm shift from crisis response to an ambitious and integrated approach immediately.Recognizing the urgent needs to tackle the risk connection between climate change and One Health,the four key messages and recommendations that with the intent to guide further research and to promote international cooperation to achieve a more climate-resilient world are provided.

Important role of the ENSO combination mode in the maintenance of the anomalous anticyclone over the western North Pacific in boreal summer

This study demonstrates the main physical mechanism for the maintenance of the western North Pacific(WNP)anomalous anticyclone(WNPAC)during the El Niño decaying summer by analyzing the respective effects of the cold sea surface temperature(SST)anomalies in the WNP,the warm SST anomalies in the Indian Ocean(IO),and the El Niño and Southern Oscillation(ENSO)combination mode.We find that the WNPAC is usually accompanied by significant cold WNP SST anomalies in the El Niño mature winter and following spring,which almost disappear in the decaying summer and cannot explain the maintenance of the WNPAC in summer.The influence of the IO warm SST anomalies on the WNPAC exhibits conspicuous decadal differences.Before the 2000 s,the IO warm SST anomalies played a role in the WNPAC maintenance through the response of the baroclinic atmospheric Kelvin wave;however,this effect cannot be evidently detected after the 2000 s.This decadal difference may be related to changes in the decaying speed of ENSO events.In contrast to El Niño events before the 2000 s,El Niño events after the 2000 s decay more rapidly,and the associated tropical central-eastern Pacific SST features a La Ni?a-like condition in the El Niño decaying summer.Concomitantly,no significant warm SST anomalies appear over the tropical Indian Ocean,exerting a weak influence on the WNPAC.Relative to the cold WNP SSTanomalies and warm IO SST anomalies,the ENSO combination mode,originating from the nonlinear interaction between ENSO and the annual cycle,has a relatively stable relationship with the WNPAC during the El Niño decaying summer,which exhibits a crucial role in the maintenance of the WNPAC.Considering the persistence of the ENSO combination mode,the WNPAC and associated climate variability during the El Niño decaying summer can be skillfully predicted at least one season in advance based on the ENSO combination mode.

Quantitative Causality, Causality-Aided Discovery, and Causal Machine Learning

It has been said,arguably,that causality analysis should pave a promising way to interpretable deep learning and generalization.Incorporation of causality into artificial intelligence algorithms,however,is challenged with its vagueness,nonquantitativeness,computational inefficiency,etc.During the past 18 years,these challenges have been essentially resolved,with the establishment of a rigorous formalism of causality analysis initially motivated from atmospheric predictability.This not only opens a new field in the atmosphere-ocean science,namely,information flow,but also has led to scientific discoveries in other disciplines,such as quantum mechanics,neuroscience,financial economics,etc.,through various applications.This note provides a brief review of the decade-long effort,including a list of major theoretical results,a sketch of the causal deep learning framework,and some representative real-world applications pertaining to this journal,such as those on the anthropogenic cause of global warming,the decadal prediction of El Niño Modoki,the forecasting of an extreme drought in China,among others.