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Hydroxy fatty acids (FAs) in fresh snow from Sapporo, one of the heaviest snowfall regions in the world, have been studied to ascertain the airborne bacterial endotoxin concentrations and their biomass. The presence of β-hydroxy FAs (C9-C28), constituents of Gram-negative bacteria (GNB), suggests long-range transport of soil microbes. Likewise, the occurrence of α- and ω-hydroxy FAs (C9-C30 and C9-C28, respectively) in snow reveals their contribution from epicuticular waxes and soil microorganisms. Estimated endotoxin and GNB mass can aid in assessing their possible impacts on the diversity and functioning of aquatic and terrestrial ecosystems, as well as lethal effects on pedestrians through dispersal of microbes. Air mass back trajectories together with hydroxy FAs unveil their sources from Siberia, Russian Far East and North China by the Asian monsoon. This study highlights the role of fresh snow that reduces the human health risk of GNB and endotoxin by scavenging from the air. [ABSTRACT FROM AUTHOR]

The Western Ghats (WG) is one of the important biodiversity hotspots and rainfall intense regions in south Asia. In this paper, the long-term trend analysis is carried out during southwest monsoon rainfall over different latitudinal regions of the WG. Further, the gridded daily rainfall data (0.25 × 0.25 spatial grid resolution) is classified into six intensity bins: dry, low, moderate, heavy, very heavy, and extreme, from 1951 to 2015. A detailed trend and variability analysis of rainfall and its frequency in different intensity bins along with their relative contribution were carried out. The results of different rainfall intensity bins depict that the moderate and low intensity bins contribute a maximum share in seasonal rainfall with 45% and 20%, respectively, from the 30% and 50% rainy days in all the regions. Heavy and very heavy intensity bins together contribute about 30% of the seasonal rainfall from about 9% rainy days. Extreme intensity bin recorded an alarming share of 6% with only 1% rainy day occurrences. In general, the relative contribution shows an ascending pattern of moderate, low, very heavy, heavy, extreme, and dry intensity bins. A decreasing trend in rainfall was observed in heavy and very heavy intensity bins, while other intensity bins illustrated mixed trends in different study regions. Extreme rainfall events marked a major shift upward in the WG region during the study period. Overall, our result portrays a negative trend in rainfall during the southwest monsoon season over all the study regions during the study period. [ABSTRACT FROM AUTHOR]

Space-based measurements, such as the Greenhouse gases Observing SATellite (GOSAT) and the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor satellite, provide global observations of the column-averaged CH4 concentration (XCH4). Due to the irregular observations and data gaps in the retrievals, studies on the spatial and temporal variations of regional atmospheric CH4 concentrations are limited. In this paper, we mapped XCH4 data over monsoon Asia using GOSAT and TROPOMI observations from April 2009 to December 2021 and analyzed the spatial and temporal pattern of atmospheric CH4 variations and emissions. The results show that atmospheric CH4 concentrations over monsoon Asia have long-term increases with an annual growth rate of roughly 8.4 ppb. The spatial and temporal trends of XCH4 data are significantly correlated with anthropogenic CH4 emissions from the bottom-up emission inventory of EDGAR. The spatial pattern of gridded XCH4 temporal variations in China presents a basically consistent distribution with the Heihe–Tengchong Line, which is mainly related to the difference in anthropogenic emissions in the eastern and western areas. Using the mapping of XCH4 data from 2019 to 2021, this study further revealed the response of atmospheric CH4 concentrations to anthropogenic emissions in different urban agglomerations. For the urban agglomerations, the triangle of Central China (TCC), the Chengdu–Chongqing City Group (CCG), and the Yangtze River Delta (YRD) show higher CH4 concentrations and emissions than the Beijing–Tianjin–Hebei region and nearby areas (BTH). The results reveal the spatial and temporal distribution of CH4 concentrations and quantify the differences between urban agglomerations, which will support further studies on the drivers of methane emissions. [ABSTRACT FROM AUTHOR]

Co-movement (synchronicity) in food-inflation rates among emerging and developing countries in Asia is partly due to common rainfall shocks – a result which the paper terms the 'monsoon effect'. Economies with higher trade integration and co-movement in nominal effective exchange rates also experience greater food-inflation co-movement. In the context of the growing literature on the globalization of inflation, these results suggest that common weather patterns are partly responsible for any role played by a so-called 'global factor' among inflation rates in emerging and developing economies, in Asia at least. [ABSTRACT FROM AUTHOR]

A few well-annotated datasets for land-cover semantic segmentation have recently been introduced to advance the field of earth observation technologies. However, these datasets overlook the significant diversity among geographic areas with different climates, which can greatly impact and diversify land cover. Consequently, this leads to a domain gap in remote sensing images and severe performance degradation of the segmentation models. To enhance land-cover semantic segmentation with improved generalization ability, we conducted the first investigation into the impact of climate on this task. In this paper, we present a unique large-scale Climate-Aware Satellite Images Dataset (CASID) specifically designed for domain adaptive land-cover semantic segmentation. It consists of 980 satellite images with a size of 5000 × 5000 pixels, collected from 30 different regions around Asia, covering over 24,500 square kilometers. These images are gathered from four distinct climate zones, namely temperate monsoon, subtropical monsoon, tropical monsoon, and tropical rainforest. It includes four sub-datasets/domains, each representing one of the aforementioned climate zones. This characteristic makes CASID the first climate-aware land-cover semantic segmentation dataset with multiple domains. Additionally, we provide a comprehensive analysis of the samples from the four climate zones, emphasizing differences in global image features, image texture, category distribution, spectral value, and object shape. These analyses offer valuable insights for subsequent research in this field. Moreover, we conduct extensive experiments to evaluate the latest semantic segmentation and unsupervised domain adaptation methods on the CASID dataset. These results serve as a robust baseline for future research endeavors. Our dataset will be made publicly available soon at the following link: https://github.com/Linwei-Chen/CASID. [ABSTRACT FROM AUTHOR]

The variability and dynamics of the Asian monsoon (AM, hereafter indicates both of the summer and winter monsoons.) at orbital and millennial timescales has attracted wide interest. Chinese loess deposits, covering an area of ~500 × 103 km2 and with a thickness of several tens to more than three hundred meters, is an ideal continental archive to reconstruct AM variations during the Quaternary epoch. Over the past thirty years, since the earliest paper published in an international journal that linked the Asian monsoon and Chinese loess deposits, many studies have been undertaken focusing on this research topic. These results have greatly deepened our understanding of the variations of the AM climate and their driving mechanisms during the past ~2.6 Myr. In this paper, we emphasize recent progress on the AM variability and dynamics revealed by Chinese loess records; in particular, we discuss the reliability and precision of the timescale and the monsoon proxy indicators for the loess-paleosol sequences, which are two fundamental aspects for understanding AM behavior. We analyze what we know and discuss what we do not know about the AM. We refine the timescale for the typical loess-paleosol sequence in the central Chinese Loess Plateau (CLP), which can be used as a new timescale to study palaeoclimate and palaeoenvironmental changes in the monsoonal Asia. We conclude that low-latitude insolation changes induced by precession, and global ice volume, temperature at high-latitudes, as well as sea-level changes forced variations of the AM at orbital time scales. High-latitude cooling events and low-latitude hydroclimate process at millennial time scales, such as climate changes associated with Heinrich events and Dansgaard-Oeschger cycles in Northern Atlantic and Greenland, have also modulated AM variability. We suggest that high-latitude forcing of AM variations occurs through ocean and atmospheric circulation linkages, although the roles of atmospheric CO 2 , ocean and vegetation feedbacks need further investigation. In future study, high-resolution independent dating, novel proxy indices and transient numerical simulations are still basic tools to understand the loess deposition and AM variations that require considerably more work. Issues such as reliable spatial comparison and regional linkages of records (dependent on precise and accurate numerical chronologies), and quantitative reconstruction of the AM variations, should be given priority in the study the past climate change in Asia, and low-latitude hydroclimate process. [ABSTRACT FROM AUTHOR]

The vast majority of current structural design codes and standards do not separately consider the wind and turbulence profiles for different storm types. Based on the 356-m-high Shenzhen Meteorological Gradient Tower, which is the tallest of its kind in Asia, this paper investigates the characteristics and vertical profiles of mean wind and turbulence for different types of strong wind events, including typhoons, monsoons, and thunderstorms, from a comparative perspective. Commonalities and differences among the vertical profiles of mean wind speed, turbulence intensity, and turbulence integral length scale for these storm events are comprehensively investigated. It is observed that the wind and turbulence profiles in typhoons and monsoons can be reasonably described by design codes and standards, while those in thunderstorms substantially deviate from typhoons and monsoons as well as code stipulations. The outcome of this study is expected to facilitate the different forms of wind and turbulence profiles for typhoons, monsoons, and thunderstorms to be taken into consideration in design codes and standards and improve the wind-resistant design of high-rise structures in regions that are prone to these storm events. [ABSTRACT FROM AUTHOR]

Monsoon onset over the South China Sea occurs in April–May, marking the start of the wet season over East Asia. Skillful prediction of onset timing remains an open challenge. Recently, theoretical studies using idealized models have revealed feedbacks at work during the seasonal transitions of the Hadley cells and have shown that these are relevant to monsoon onset over Asia. Here, I hypothesize that monsoon onset occurs earlier in years when the atmosphere over the South China Sea is already in a state where these feedbacks are more easily triggered. I find that local anomalies in lower‐level moist static energy in the preceding January–March are well correlated with South China Sea Monsoon onset timing. This relationship remains relatively consistent on decadal timescales, while correlations with other teleconnections vary, and is used to develop a simple forecast model for onset timing that shows skill competitive with that of more complex models. Plain Language Summary: Arable land in China is estimated to feed 20% of the world's population on 7% of the world's farmlands, with much of this region watered by rainfall from the East Asian Summer Monsoon. Forecasting the arrival of the monsoon, which occurs first over the South China Sea in April–May, is therefore helpful for agricultural planning. However, producing a reliable forecast remains an open challenge. Recently, simple climate models, for example, models including seasons but with no land, have been used along with observations to investigate the most basic processes controlling climatological monsoon onset over Asia. In this paper, I suggest that year‐to‐year variations in monsoon onset timing are controlled by the same processes and, based on these, I suggest climate variables that may help in predicting when the monsoon will begin. By using this approach, I find that the "Moist Static Energy" (a quantity that combines temperature and humidity) over the South China Sea in January–March is strongly correlated with monsoon onset timing. This insight can be used to predict future onset timing competitively compared with more complex forecast models. Key Points: Recent theoretical studies have revealed feedbacks at work during monsoon onsetIf the spring atmosphere is in a state where these feedbacks are easily triggered, onset is earlierThis insight is used to produce a simple forecast of South China Sea Monsoon onset timing [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mila Zinkova begins this issue weather of Weather with the second in a fascinating series of papers investigating the 'mirage theory' of the Titanic disaster with an examination of the haze reported by lookouts in 'Titanic's mirage, part 2: Did a mysterious mirage‐associated haze camouflage the iceberg?' on p. 151. On 24 April 2017 there was a significant remobilisation of ash deposits in southern Iceland left over from the huge eruptions of Eyjafjallajökull in 2010 and Grímsvötn in 2011. Krista Hammond and Frances Beckett investigate the specific meteorological conditions that led up to the event on p. 167 in 'Forecasting resuspended ash clouds in Iceland at the London VAAC'. The Sumatra squall is a common and yet highly disruptive weather system that affects part of the south‐east Asia region. On p. 176, Man Yau Chan, Jeff Chun‐Fung Lo and Thomas Orton examine the structure of one event in detail with a view to understanding the dynamics in order to improve forecasting of these features in 'The structure of tropical Sumatra squalls'. Staying in the tropics, on p. 181 in 'Monsoon tropical cyclones: Part 3', David Membery looks into the meteorology and impact of five destructive tropical cyclones that have affected the Arabian sea and considers the long‐term trends in their occurrence. The application of satellite technology has been a rapidly expanding field in recent years. In our final paper this month on p. 186, C. Purna Chand, M. V. Rao, K. V. S. R. Prasad and K. H. Rao bring us some important research on the use satellite sensing to estimate low‐level circulations in 'Validation of global sea‐level pressure fields calculated from Oceansat‐2 scatterometer wind data using the UWPBL model'. [ABSTRACT FROM AUTHOR]

The tropical easterly jet (TEJ) is a prominent atmospheric circulation feature observed during the Asian summer monsoon. It is generally assumed that sensible heating over the Tibetan Plateau directly influences the location of the TEJ. However, other studies have suggested the importance of latent heating in determining the jet location. In this paper, the relative importance of latent heating on the maintenance of the TEJ is explored through simulations with a general circulation model. The simulation of the TEJ by the Community Atmosphere Model, version 3.1 is discussed in detail. These simulations showed that the location of the TEJ is well correlated with the location of the precipitation. Significant zonal shifts in the location of the precipitation resulted in similar shifts in the zonal location of the TEJ. These zonal shifts had minimal effect on the large-scale structure of the jet. Further, provided that precipitation patterns were relatively unchanged, orography did not directly impact the location of the TEJ. These changes were robust even with changes in the cumulus parameterization. This suggests the potential important role of latent heating in determining the location and structure of the TEJ. These results were used to explain the significant differences in the zonal location of the TEJ in the years 1988 and 2002. To understand the contribution of the latitudinal location of latent heating on the strength of the TEJ, aqua-planet simulations were carried out. It has been shown that for similar amounts of net latent heating, the jet is stronger when heating is in the higher tropical latitudes. This may partly explain the reason for the jet to be very strong during the JJA monsoon season. [ABSTRACT FROM AUTHOR]

East Asian summer monsoon precipitation is projected to increase under greenhouse warming with strong intraseasonal variation. Using a 35-member CESM Large Ensemble and 30 CMIP6 models, this study reveals that in July and August, maximum rainfall changes in East Asia take place in the midlatitudes, influencing regions encompassing North and Northeast China, the Korean Peninsula, and Japan. The intensified precipitation is attributed to the combined effect of the thermodynamic and dynamic components. The former stems from the enriched low-level moisture, which peaks in continental East Asia in July and August, under global warming. The dynamic effect is due to the enhanced upward motion, associated with the enhanced southerlies throughout the troposphere over midlatitude East Asia. The southerlies also act to intensify the low-level monsoonal circulation, strengthening moisture transport from the tropical ocean to the midlatitudes. In addition to the mean-state changes, the precipitation interannual variability in this region also intensifies, partly due to the enhanced low-level moisture and partly associated with enhanced large-scale circulation anomalies, such as the northwestern Pacific anticyclone. The enhanced background precipitation, along with the intensified interannual variability, may lead to more rainy summers in a warmer climate, with instances where historically extreme precipitation events become more frequent, posing challenges for water resource management and agriculture in the region. [ABSTRACT FROM AUTHOR]

Afro-Asian summer monsoon precipitation (AfroASMP) is the life blood of billions of people living in many developing countries covering West Africa and Asia. Its complex variabilities are always accompanied by natural disasters like floods, landslides and droughts. Reliable AfroASMP prediction several months in advance is valuable for not only decision-makers but also regional socioeconomic sustainability. To address the current predicament of the AfroASMP seasonal prediction, this study provides an effective machine-learning model (Y-model). Y-model uses the monsoon related big climate data for searching the potential predictors, encompassing atmospheric internal factors and external forcings. Only the predictors associated with significant anomalies in summer horizonal winds at 850 hPa over the monsoon domain are retained. These selected predictors are then reorganized into a large ensemble based upon different thresholds of four fundamental principles. These principles include the focused sample sizes, the relationships between predictors and predictand, the independence among predictors, and the extremities of predictors in the forecast year. Real-time predictions can be generated based on the ensemble mean of skillful members during an independent hindcast period. Y-model skillfully predicts four monsoon precipitation indices of AfroASMP during 2011–2022 at lead 4–12 months, correlation skills range from 0.58 to 0.90 and root mean square error skills are reduced by 11–53% compared to CFS v2 model at lead 1 month. This study offers an effective method for preprocessing predictors in seasonal climate prediction. [ABSTRACT FROM AUTHOR]

Reliable attribution of Asian summer monsoon variations to aerosol forcing is critical to reducing uncertainties in future projections of regional water availability, which is of utmost importance for risk management and adaptation planning in this densely populated region. Yet, simulating the monsoon remains a challenge for climate models that suffer from long-standing biases, undermining their reliability in attributing anthropogenically forced changes. We analyze a suite of climate model experiments to identify a link between model biases and monsoon responses to Asian aerosols and associated physical mechanisms, including the role of large-scale circulation changes. The aerosol impact on monsoon precipitation and circulation is strongly influenced by a model's ability to simulate the spatio-temporal variability in the climatological monsoon winds, clouds, and precipitation across Asia, which modulates the magnitude and efficacy of aerosol–cloud–precipitation interactions, an important component of the total aerosol response. There is a strong interplay between South Asia and East Asia monsoon precipitation biases and their relative predominance in driving the overall monsoon response. We found a striking contrast between the early- and late-summer aerosol-driven changes ascribable to opposite signs and seasonal evolution of the biases in the two regions. A realistic simulation of the evolution of the large-scale atmospheric circulation is crucial to realize the full extent of the aerosol impact over Asia. These findings provide important implications for better understanding and constraining the diversity and inconsistencies of model responses to aerosol changes over Asia in historical simulations and future projections. [ABSTRACT FROM AUTHOR]

A growing body of research has underscored the radiative impact of mineral dust in influencing Indian summer monsoon rainfall variability. However, the various aerosol‐cloud‐precipitation interaction mechanisms remain poorly understood. Here we analyze multisatellite observations to examine dust‐induced modification in ice clouds and precipitation susceptibility. We show contrasting dust‐induced changes in ice cloud regimes wherein despite a 25% reduction in ice particle radius in thin ice clouds, we find ~40% increase in ice particle radius and ice water path in thick ice clouds resulting in the cloud deepening and subsequently strengthened precipitation susceptibility, under strong updraft regimes. The observed dust‐ice cloud‐precipitation interactions are supported by a strong correlation between the interannual monsoon rainfall variability and dust frequency. This microphysical‐dynamical coupling appears to provide negative feedback to aerosol‐cloud interactions, which acts to buffer enhanced aerosol wet scavenging. Our results underscore the importance of incorporating meteorological regime‐dependent dust‐ice cloud‐precipitation interactions in climate simulations. Plain Language Summary: The Indian summer monsoon is the central source of freshwater availability to the densely populated regions of southern Asia. The monsoon circulation and rainfall variability are widely known to be governed by large‐scale atmosphere‐land‐ocean dynamics, meteorological processes, and air‐sea interactions. In the past two decades, the role of atmospheric aerosols has emerged as a source of modulating monsoon rainfall, as suggested by a host of climate modeling studies. In this paper, we have investigated a new aspect of aerosols in possibly influencing monsoon clouds and rainfall by specifically examining interaction between mineral dust aerosols and ice clouds, as part of the monsoon system. Using state‐of‐the‐art information derived for aerosols and clouds from multisensor and disparate satellite observations spanning 11 years, we find characteristic signature of dust aerosol‐induced modification of thick ice clouds (so‐called cloud invigoration effect) toward strengthened susceptibility of monsoon precipitation. Overall, our results shed new light on the potential role of dust and ice cloud interactions in modulating the Indian summer monsoon. Key Points: Elevated dust‐induced microphysical‐dynamical coupling in thick ice clouds amplifies ice cloud formation under favorable meteorologyStrengthened summer monsoon precipitation susceptibility is linked to dust‐induced changes in ice clouds under strong updraft regimesMicrophysical‐dynamical coupling provides negative feedback to aerosol‐cloud interaction and buffers the enhanced aerosol wet scavenging [ABSTRACT FROM AUTHOR]

Large-scale climate models (LCM) have been used to understand climate change and its effects, but there remains a concern about their inability fully to reflect local contexts and about a high degree of their uncertainty. Through a case study that involved residents of a coastal community in Central Vietnam, this paper presents how local people perceive climate change and characterize climate impacts on their life. Findings of the study show that local people perceive a variety of important manifestations of climate change, especially temperature, rainfall, sea level rise and monsoons, although they have limited ideas about future climate change. In addition, local people unpack the complexity of climate impacts through interactions among climatic events, livelihoods and the five capitals (physical, natural, financial, human and social resources). Findings of the research suggest that it will be necessary to move away from viewing coastal villages in Vietnam as homogenous units with shared climate experiences, and to combine both local experience and scientific evidence based on LCMs to promote the synergies and address the limitations of the two sources of information for climate interventions at the local level. [ABSTRACT FROM AUTHOR]

This paper presents an experiment on lampenflora removal in show caves located in a tropical monsoon climate in southeast Asia. Lampenflora thrive in wet conditions on surfaces directly illuminated by white light. They colonize different levels in show caves, from the cave ceiling, with a biota characterized of mainly cyanobacteria (Oscillatoria, Spirulina), algae (Chlorella, Oedoclarium), and mosses (Cyathodium, Thuidium), to near the cave floor, with a more complex biota including higher plants like ferns (Asplenium) and flowering plants (Centella). Mature lampenflora mats also harbor non-phototrophic fungi and bacteria. With the use of environmental scanning electron microscopy, speleothem surfaces were found severely damaged by lampenflora and their associates. In this study, we used H2O2 as an environmentally friendly chemical to exterminate lampenflora. The applied solution should be at least 15% H2O2 to efficiently destroy microbiota such as green algae, diatoms, and bacteria. For a complex community including mosses, fungi, and vascular plants, repeated spraying of chemical and, if possible, water jet washing at carefully selected places are required to recover the aesthetic characteristics of speleothems. Only a combination of such cleaning practices, and then some modification of the illumination regime, can minimize lampenflora development in show caves. [ABSTRACT FROM AUTHOR]

• Lake evolution of Sumxi Co has been reconstructed from lacustrine carbonate isotopes. • Hydrological conditions were mainly dominated by regional precipitation on the northwestern QTP. • Millennial hydroclimate events were responding to globally cooling events and solar irradiance. Climatic and hydrological changes on the Qinghai-Tibetan Plateau (QTP) are controlled by the Asian summer monsoon and the mid-latitude westerlies, which directly affect a large population in Asia. However, the millennial temporal and spatial patterns of Holocene hydroclimate variations on the QTP remain unclear due to the lack of high-quality paleoclimatic records. This paper examines high-resolution stable oxygen and carbon isotopes of authigenic carbonate (δ18O carb and δ13C carb) covering the past 5,000 years taken from Sumxi Co, a hydrologically closed lake lies outside the direct influence of the large ice caps on the northwestern QTP. The hydrological environment of Sumxi Co inferred from the covariance between δ18O carb and δ13C carb values was unstable during the middle to late Holocene, with abrupt increases in lake-levels during the 5.0–4.0 cal ka BP, 3.2–3.1 cal ka BP, 1.8–1.3 cal ka BP, and 0.7 cal ka BP to present. Past millennial hydrological fluctuations coincide temporally with the occurrences of glacier advances on the northwestern QTP, implying increased regional moisture and precipitation during cold periods in the region. The 'cold and wet' hydroclimatic pattern is comparable in other records to the arid areas of central Asia dominated by westerlies before the current anthropogenic warming. The four millennial-scale humid events are synchronous with reduced solar irradiance within dating errors, supporting the hypotheses that the regional pattern of hydroclimatic evolution in arid central Asia responds dominantly and directly to changes in solar activity. This external forcing may be amplified by North Atlantic cooling events and southward shifts of the intertropical convergence, which have further modulated the position of mid-latitude westerlies and the strength of the Indian summer monsoon. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper analyzes the relationship between the 1000-850-hPa layer perturbation potential energy (LPPE) as the difference in local potential energy between the actual state and the reference state and the East Asian summer monsoon (EASM) using reanalysis and observational datasets. The EASM is closely related to the first-order moment term of LPPE (LPPE1) from the preceding March to the boreal summer over three key regions: the eastern Indian Ocean, the subtropical central Pacific, and midlatitude East Asia. The LPPE1 pattern (−, +, +), with negative values over the eastern Indian Ocean, positive values over the subtropical central Pacific, and positive values over East Asia, corresponds to negative LPPE1 anomalies over the south of the EASM region but positive LPPE1 anomalies over the north of the EASM region, which lead to an anomalous downward branch over the southern region but an upward branch over the northern region. The anomalous vertical motion affects the local meridional circulation over East Asia that leads to a southwesterly wind anomaly over East Asia (south of 30°N) at 850 hPa and anomalous downward motion over 100°-120°E (along 25°-35°N), resulting in a stronger EASM, more kinetic energy over the EASM region, and less boreal summer rainfall in the middle and lower reaches of the Yangtze River valley (24°-36°N, 90°-125°E). These LPPE1 anomalies in the eastern Indian Ocean and subtropical central Pacific appear to be connected to changes in local sea surface temperature through the release of latent heat. [ABSTRACT FROM AUTHOR]

Stable isotope paleoaltimetry has provided unprecedented insights into the topographic histories of many of the world's highest mountain ranges. However, on the Tibetan Plateau (TP), stable isotopes from paleosols generally yield much higher paleoaltitudes than those based on fossils. It is therefore essential when attempting to interpret accurately this region's paleoaltitudes that the empirical calibrations of local stable isotopes and the relations between them are established. Additionally, it is vital that careful estimations be made when estimate how different isotopes sourced from different areas may have been influenced by different controls. We present here 29 hydrogen isotopic values for leaf wax-derived n-alkanes (i.e., D values, and abundance-weighted average δD values of C and C) in surface soils, as well as the δD values of soil water ( δD) samples (totaling 22) from Mount Longmen (LM), on the eastern TP (altitude ~0.8-4.0 km above sea level (asl), a region climatically affected by the East Asian Monsoon (EAM). We compared our results with published data from Mount Gongga (GG). In addition, 47 river water samples, 55 spring water samples, and the daily and monthly summer precipitation records (from May to October, 2015) from two precipitation observation stations were collected along the GG transect for δD analysis. LM soil D values showed regional differences and responded strongly to altitude, varying from-160‰ to-219‰, with an altitudinal lapse rate (ALR) of-18‰ km ( R =0.83; p<0.0001; n=29). These D values appeared more enriched than those from the GG transect by ~40‰. We found that both the climate and moisture sources led to the differences observed in soil D values between the LM and GG transects. We found that, as a general rule, ε , ε and ε values (i.e., the isotopic fractionation of D corresponding to δD, δD and δD) increased with increasing altitude along both the LM and GG transects (up to 34‰and 50‰, respectively). Basing its research on a comparative study of D, δD, δD( δD) and δD, this paper discusses the effects of moisture recycling, glacier-fed meltwater, relative humidity ( RH), evapotranspiration ( ET), vegetation cover, latitude, topography and/or other factors on ε values. Clearly, if ε values at higher altitudes are calculated using smaller ε values from lower altitudes, the calculated paleowater δD values are going to be more depleted than the actual δD values, and any paleoaltitude would therefore be overestimated. [ABSTRACT FROM AUTHOR]

This paper investigates the processes and mechanisms by which the East Asian winter monsoon (EAWM) affects the Madden-Julian oscillation (MJO) over the equatorial western Pacific in boreal winter (November-April). The results show that both the EAWM and MJO over the equatorial western Pacific have prominent interannual and interdecadal variabilities, and they are closely related, especially on the interannual timescales. The EAWM influences MJO via the feedback effect of convective heating, because the strong northerlies of EAWM can enhance the ascending motion and lead the convection to be strengthened over the equatorial western Pacific by reinforcing the convergence in the lower troposphere. Daily composite analysis in the phase 4 of MJO (i.e., strong MJO convection over the Maritime Continent and equatorial western Pacific) shows that the kinetic energy, outgoing longwave radiation (OLR), moisture flux, vertical velocity, zonal wind, moist static energy, and atmospheric stability differ greatly between strong and weak EAWM processes over the western Pacific. The strong EAWM causes the intensity of MJO to increase, and the eastward propagation of MJO to become more persistent. MJO activities over the equatorial western Pacific have different modes. Furthermore, these modes have differing relationships with the EAWM, and other factors can also affect the activities of MJO; consequently, the relationship between the MJO and EAWM shows both interannual and interdecadal variabilities. [ABSTRACT FROM AUTHOR]

The evolution of global temperature during Holocene is crucial for understanding the mechanisms of climate change and future climate trends. However, there is a discrepancy between the temperature trends reconstructed from proxy and model, which is attributed to the seasonal biases and the appearance of the Holocene thermal maximum was dominated by the temperature of the warm season. In this paper, fossil charcoal assemblages from the southern Chinese Loess Plateau were analysed to provide quantitative mean annual temperatures (MAT) and four-season temperature records during 6.55–3.45 cal ka BP. The results indicate that both the seasonal temperatures and MAT during the middle Holocene reached warm peaks between 5.55 and 5.35 cal ka BP. The similar trend between the winter temperature (WIT) and MAT denotes the highest contribution of WIT changes to the MAT in the study area since the mid-Holocene. • Flowering functional group was used to reconstruct spring-autumn temperature. • Nonhardy plants were used to reconstruct winter temperature. • Winter temperature contributed the most to the annual temperature since mid-Holocene. • Middle-Holocene temperature was not showing a long-term warming trend. [ABSTRACT FROM AUTHOR]

We describe the use of regional relaxation ("nudging") experiments carried out in initialised hindcasts to shed light on the contribution from particular regions to the errors developing in the Asian Summer Monsoon. Results so far confirm previous hypotheses that errors in the Maritime Continent region contribute substantially to the East Asia Summer Monsoon (EASM) circulation errors through their effects on the Western North Pacific Subtropical High. Locally forced errors over the Indian region also contribute to the EASM errors. Errors arising over the Maritime Continent region also affect the circulation and sea surface temperatures in the Equatorial Indian Ocean region, contributing to a persistent error pattern resembling a positive Indian Ocean Dipole phase. This is associated with circulation errors over India and the strengthening and extension of the westerly jet across southeast Asia and the South China Sea into the Western Pacific, thereby affecting the ASM circulation and rainfall patterns as a whole. However, errors developing rapidly in the deeper equatorial Indian Ocean, apparently independently of the atmosphere errors, are also contributing to this bias pattern. Preliminary analysis of nudging increments over the Maritime Continent region suggests that these errors may at least partly be related to deficiencies in the convection and boundary layer parametrisations. [ABSTRACT FROM AUTHOR]

Reconstruction and observational studies imply a potential linkage of moisture and precipitation change in arid central Asia and monsoonal East Asia, in which the evolution of moisture and precipitation in central Asia is out of phase with that in northern China but in phase with that in southern China. In order to ascertain whether there is a robust linkage between the changes in climate in Asian arid regions and monsoon regions and to elucidate the underlying dynamic mechanisms, we analyzed the Last Millennium Reanalysis dataset and outputs from the Community Earth System Model Last Millennium Ensemble (CESM-LME). The results indicate a significant decadal linkage between precipitation changes in central Asia's arid region and the Asian monsoon region during the last millennium, which is primarily driven by the Interdecadal Pacific Oscillation (IPO). In spring, the positive IPO could enhance westerlies over the Mediterranean Sea and to its east, which could transport more water vapor and cause increased precipitation over central Asia. In summer, the positive IPO is accompanied by a weakened Asian monsoon and southward Asian subtropical westerly jet, which can lead to increased (decreased) summer precipitation over southern China (over northern China and South Asia). The IPO plays a dominant role in connecting the decadal variations in precipitation between arid central Asia and monsoonal Asia by modulating the precipitation of their respective major rainy seasons. Model results suggest that this decadal linkage stems entirely from the internal variability present in the CESM-LME control and all single-forcing simulations. Changes in external forcing factors do not alter this inherent linkage caused by the IPO. Moreover, based on analyses of the aridity index and soil moisture content, this relationship of precipitation variation also causes a similar decadal linkage of moisture changes in central Asia and monsoonal Asia. The differences in the multi-centennial-scale moisture and precipitation variations in the Asian arid region and the monsoon region between the Medieval Climate Anomaly and Little Ice Age are also likely caused by IPO-like sea surface temperature anomalies. [ABSTRACT FROM AUTHOR]

Reliable prediction of the South Asian monsoon rainfall and its variability is crucial for various hydrological applications and early warning systems. The National Centers for Environmental Prediction-Global Forecast System (NCEP-GFS) is one of the popular global deterministic numerical weather prediction models, which is recently upgraded from T574 to T1534. In this paper, medium range monsoon precipitation forecasts from both the T1534 and T574 models are critically evaluated over the South Asia for the peak monsoon months (July and August) of 2015. Although both the versions of GFS model show similar large-scale monsoon rainfall patterns, the dry bias over the northwest India and equatorial Indian Ocean is noticeably improved in day-1 through day-5 forecasts in the new high-resolution T1534 model. The error decomposition analysis shows similar error characteristics in the monsoon rainfall prediction from both the versions of GFS model, in general. However, forecast improvement factor shows 10-30 % improvement in precipitation forecast from the latest T1534 model over most parts of the South Asia. These preliminary analyses suggest that a suitable bias-correction to the GFS model precipitation forecasts will be useful for any specific application. [ABSTRACT FROM AUTHOR]

Seasonal prediction of the East Asian summer monsoon (EASM) strength is probably one of the most challenging and crucial issues for climate prediction over East Asia. In this paper, a statistical method called partial-least square (PLS) regression is utilized to uncover principal sea surface temperature (SST) modes in the winter preceding the EASM. Results show that the SST pattern of the first PLS mode is associated with the turnabout of warming (or cooling) phase of a mega-El Niño/Southern Oscillation (mega-ENSO) (a leading mode of interannual-to-interdecadal variations of global SST), whereas that of the second PLS mode leads the warming/cooling mega-ENSO by about 1 year, signaling precursory conditions for mega-ENSO. These indicate that mega-ENSO may provide a critical predictability source for the EASM strength. Based on a 40-year training period (1958-1997), a PLS prediction model is constructed using the two leading PLS modes and 3-month-lead hindcasts are performed for the validation period of 1998-2013. A promising skill is obtained, which is comparable to the ensemble mean of versions 3 and 4 of the Canadian Community Atmosphere Model (CanCM3/4) hindcasts from the newly developed North American Multi-model Ensemble Prediction System regarding the interannual variations of the EASM strength. How to improve dynamical model simulation of the EASM is also examined through comparing the CanCM3/4 hindcast (1982-2010) with the 106-year historical run (1900-2005) by the Second Generation Canadian Earth System Model (CanESM2). CanCM3/4 exhibits a high skill in the EASM hindcast period 1982-2010 during which it also has a better performance in capturing the relationship between the EASM and mega-ENSO. By contrast, the simulation skill of CanESM2 is quite low and it is unable to reproduce the linkage between the EASM and mega-ENSO. All these results emphasize importance of mega-ENSO in seasonal prediction and dynamical model simulation of the EASM. [ABSTRACT FROM AUTHOR]

This paper evaluates the performance of 29 state-of-art CMIP5-coupled atmosphere-ocean general circulation models (AOGCM) in their representation of regional characteristics of monsoon simulation over South Asia. The AOGCMs, despite their relatively coarse resolution, have shown some reasonable skill in simulating the mean monsoon and precipitation variability over the South Asian monsoon region. However, considerable biases do exist with reference to the observed precipitation and also inter-model differences. The monsoon rainfall and surface flux bias with respect to the observations from the historical run for the period nominally from 1850 to 2005 are discussed in detail. Our results show that the coupled model simulations over South Asia exhibit large uncertainties from one model to the other. The analysis clearly brings out the presence of large systematic biases in coupled simulation of boreal summer precipitation, evaporation, and sea surface temperature (SST) in the Indian Ocean, often exceeding 50 % of the climatological values. Many of the biases are common to many models. Overall, the coupled models need further improvement in realistically portraying boreal summer monsoon over the South Asian monsoon region. [ABSTRACT FROM AUTHOR]

This paper provides another look at the response of the Asian summer monsoon (ASM) to insolation forcing and oceanic feedback during the Holocene, using a fully coupled general circulation ocean–atmosphere model forced by Earth’s orbital variations. The model results revealed a recurrent circumglobal teleconnection (CGT) pattern in the summertime (June–July–August) mid-latitude circulation of the Northern Hemisphere during the Holocene. The CGT index showed a decreasing trend before ~5 ka BP and a slight increasing trend afterwards, affected by the combined effects of summer insolation, Indian summer monsoon (ISM), North Atlantic and Indian Ocean–western Pacific Ocean sea surface temperature (SST). The CGT showed a close relationship with ASM precipitation and surface air temperature during the Holocene and, therefore, could act as a bridge linking the ASM to insolation, high-latitude forcing (North Atlantic SST), and low-latitude forcing (tropical Ocean SST). We emphasize that the mid-latitude atmospheric circulation has been a key factor for the evolution of the ASM during the Holocene. In addition, the CGT provides a viable explanation for the out-of-phase relationship in the moisture evolution but an in-phase relationship in the speleothem δ18O between arid central Asia and the ISM region during the Holocene. [ABSTRACT FROM AUTHOR]

Scientific issues relevant to interactions between aerosols and the Asian monsoon climate were discussed and evaluated at the 33rd 'Forum of Science and Technology Frontiers' sponsored by the Department of Earth Sciences at the Chinese Academy of Sciences. Major results are summarized in this paper. The East Asian monsoon directly affects aerosol transport and provides a favorable background circulation for the occurrence and development of persistent fog-haze weather. Spatial features of aerosol transport and distribution are also influenced by the East Asian monsoon on seasonal, inter-annual, and decadal scales. High moisture levels in monsoon regions also affect aerosol optical and radiative properties. Observation analyses indicate that cloud physical properties and precipitation are significantly affected by aerosols in China with aerosols likely suppressing local light and moderate rainfall, and intensifying heavy rainfall in southeast coastal regions. However, the detailed mechanisms behind this pattern still need further exploration. The decadal variation in the East Asian monsoon strongly affects aerosol concentrations and their spatial patterns. The weakening monsoon circulation in recent decades has likely helped to increase regional aerosol concentrations. The substantial increase in Chinese air pollutants has likely decreased the temperature difference between land and sea, which favors intensification of the weakening monsoon circulation. Constructive suggestions regarding future studies on aerosols and monsoons were proposed in this forum and key uncertain issues were also discussed. [ABSTRACT FROM AUTHOR]

The East Asian winter monsoon (EAWM) exhibits significant variability on intraseasonal, interannual, and interdecadal time scales and the variability can be extended to Holocene centennial and millennial scales. Previous Holocene EAWM proxy data records, which were mostly located in Central, Eastern and Southern China, did not show a consistent Holocene EAWM history. Therefore, it is difficult to provide insights into mechanisms of the long-term winter monsoon variability on the basis of the records. Eolian sediments at the southern edge of the Gobi Desert, Western China, are sensitive to the EAWM changes and less affected by the East Asian summer monsoon due to an obstruction of the Qinghai-Tibet Plateau. This paper presents a comparison between a well-dated Holocene EAWM record and coupled climate model simulations, so as to explore physical processes and influencing factors of the Holocene EAWM. Sediment samples from two Holocene eolian sedimentary sections [Huangyanghe (a) and Huangyanghe (b)] were acquired at the southern edge of the Gobi Desert. Chronologies were established based on twenty bulk organic matter AMS C ages and five pollen concentrates AMS C ages. Proxy data, including grain-size, total organic carbon, magnetic susceptibility and carbonate content were obtained from the two eolian sections. The grain-size standard deviation model was applied to determine components sensitive to variability of the Holocene EAWM. After a comparison of environmentally-sensitive grain-size components and proxy data, the 20-200 μm component at the Huangyanghe (a) and the 20-159 μm component at the Huangyanghe (b) section were selected as indicators of the Holocene EAWM, which show a strong early Holocene winter monsoon and a decline of the winter monsoon since the mid-Holocene. We also present equilibrium and transient simulations of the climate evolution for the Holocene using a state-of-art coupled climate model: the Community Climate System Model version 3 (CCSM3). Indices for the Holocene EAWM were calculated and are consistent with the reconstructed Holocene EAWM intensity. The simulations indicate that orbital forcing effects on the land-sea temperature and sea level pressure contrast can account for the observed EAWM trends. Other forcings that were present in the early Holocene, including the remnant Laurentide ice sheet and meltwater forcing in the North Atlantic, were not responsible for the Holocene trends. [ABSTRACT FROM AUTHOR]

The mid-Pliocene warm period was the most recent geological period in Earth's history that featured long-term warming. Both geological evidence and model results indicate that East Asian summer winds (EASWs) strengthened in monsoonal China, and that East Asian winter winds (EAWWs) weakened in northern monsoonal China during this period, as compared to the pre-industrial period. However, the corresponding mechanisms are still unclear. In this paper, the results of a set of numerical simulations are reported to analyze the effects of changed boundary conditions on the mid-Pliocene East Asian monsoon climate, based on PRISM3 (Pliocene Research Interpretation and Synoptic Mapping) palaeoenvironmental reconstruction. The model results showed that the combined changes of sea surface temperatures, atmospheric CO concentration, and ice sheet extent were necessary to generate an overall warm climate on a large scale, and that these factors exerted the greatest effects on the strengthening of EASWs in monsoonal China. The orographic change produced significant local warming and had the greatest effect on the weakening of EAWWs in northern monsoonal China in the mid-Pliocene. Thus, these two factors both had important but different effects on the monsoon change. In comparison, the effects of vegetational change on the strengthened EASWs and weakened EAWWs were relatively weak. The changed monsoon winds can be explained by a reorganization of the meridional temperature gradient and zonal thermal contrast. Moreover, the effect of orbital parameters cannot be ignored. Results showed that changes in orbital parameters could have markedly affected the EASWs and EAWWs, and caused significant short-term oscillations in the mid-Pliocene monsoon climate in East Asia. [ABSTRACT FROM AUTHOR]

Steep slope, heavy rainfall and forested cover have unique soil erosion and sediment transport in South Korea. Sediment transport pattern in the monsoon region (from June to September) is complex and sediment transport modeling in these areas is often difficult as sediment load in the river varies largely from year to year. This paper describes a GIS-based soil erosion model and then developed a sediment transport model to estimate sediment yield (SY) at different basin scales. The model for estimating suspended sediment is based on Revised Universal Soil Loss Equation and suspended delivery ratio (SDR) models. For applying SDR model, basin-specific parameter was validated on the basis of field data, which ranged from 0.6 to 1.2 based on observed SY. In the study region, the high flow rates lasted for 4 months (from July to September) and over 90 % of total SY discharged during that time. At that time, it was found that annual bed loads in this area are 56-84 % of total sediment loads. [ABSTRACT FROM AUTHOR]

China's Loess Plateau is located at the edge of the Asian summer monsoon in a transition zone of climate and ecology. In the Loess Plateau, climate and environments change along with space, which has an obvious impact on the spatial distribution of surface energy fluxes. Because of scarce land-surface observation sites and short observation time in this area, previous studies have failed to fully understand the land-surface energy balance characteristics over the entire the Loess Plateau and their effect mechanisms. In this paper, we first test the simulation ability of the Community Land Model (CLM) model by comparing its simulated data with observed data. Based on the simulation data for the Loess Plateau over the past thirty years, we then analyze the spatial distribution of surface energy fluxes and compare the pattern differences between the area averages for the driest year and wettest year. Furthermore, we analyze the relationship between the spatial distribution of the components of the surface energy balance with longitude, latitude, altitude, precipitation and temperature. The main results are as follows: the spatial distribution of surface energy fluxes are significantly different, with the surface net radiation and sensible heat flux increasing from south to north and latent heat flux and soil heat flux decreasing from southeast to northwest. The sensible heat flux at the driest point is nearly twice as high as that at the wettest point, whereas the latent heat flux and soil heat flux at the driest point are half as much as that at the wettest point. The impact of variations of annual precipitation on the components of the surface energy balance is also obvious, and the maximum magnitude of the changes to the sensible heat flux and latent heat flux is nearly 30%. To a certain extent, geographical factors (including longitude, latitude, and altitude) and climate factors (including temperature and precipitation) affect the surface energy fluxes. However, the surface net radiation is more closely related to latitude and altitude, sensible heat flux is more closely related to the monsoon rainfall and latitude, and latent heat flux and soil heat flux are more closely related to the monsoon rainfall. [ABSTRACT FROM AUTHOR]

Interannual variability of the Indian summer monsoon rainfall (ISMR) is explained through the total column water vapor in the atmosphere, primarily controlled by the incoming zonal moisture flux over the Arabian Sea ( F W ) and outgoing flux over the Bay of Bengal ( F E ). In this study, we discern the underlying mechanisms driving F W and F E leading to ISMR droughts in the observations and seasonal hindcasts by the Climate Forecast System version 2 (CFSv2) model. In observations, a reduction in F W is essential for droughts to occur. In addition, an increase in F E results in a severe drought. On the contrary, droughts in CFSv2 primarily occur due to an enhancement in F E , seldom accompanied by a decrease in F W . This hypersensitivity of the CFSv2 ISMR to F E is further explained using Matsuno–Gill response to moist convection. During El Nino droughts, precipitation decreases over the equatorial western Pacific and eastern Indian Oceans. The resulting anomalous diabatic cooling increases local surface pressure ( SP ), intensifying meridional SP gradient, and thus, F E . The reduction in F W , however, is associated with a cooling of the central north Pacific Ocean in tandem with El Nino. During non-El Nino droughts, frequent occurrences of cold sea surface temperature over the western north Pacific Ocean are noticed. This cooling decreases SP over east Asia, resulting in an increase in F E . To summarize, droughts in CFSv2 are controlled by the pan-Pacific climate, significantly increasing F E but weakly decreasing F W . But in observations, a strong decrease in F W and a moderate increase in F E together lead to droughts. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon (EASM) is a unique regional monsoon in the extratropics involving not only tropical but midlatitude processes. Most of the previous studies identified the role of condensational heating which is largely relevant to the tropical moisture transport in determining the dynamical structure of EASM. However, how midlatitude synoptic eddy activities can affect the EASM structure has not been well recognized. With dynamical diagnoses, this study revisits the EASM structure by emphasizing the roles of feedbacks of condensational heating versus synoptic eddy activities. As EASM is characterized by a grand low-level low with strong humid southerly flows extending from the tropics to the northeastern Asia, its vertical structure is found to have a dramatic meridional difference bounded at around 35.5°N. In the southern domain, EASM features a meridional overturning cell and a baroclinic structure with an upper-level high versus a lower-level low in geopotential height, which are primarily controlled by substantial condensational heating due to abundant monsoon precipitation. However, in the northern domain, EASM exhibits an equivalent barotropic structure with an upper-level low versus a lower-level low. Such a unique structure results from a combined effect of feedbacks of condensational heating and synoptic eddy activities, in which the upper-level low is dominated by the synoptic eddy dynamical feedback while the lower-level low is induced by the both feedbacks. The role of the midlatitude synoptic eddy activities in shaping the EASM structure proposed in this study provides a new perspective for understanding the formation and variation of EASM. [ABSTRACT FROM AUTHOR]

Whether the South Asian summer monsoon (SASM) is controlled by local or remote insolation at the orbital band remains uncertain. Here, we perform a transient simulation forced by Earth's orbital parameters between 400 and 350 ka BP, a period characterized by significant contrast between local and remote insolation, to identify the SASM's response to insolation forcing. Simulation results suggest that the primary driver of orbital‐scale SASM variability is the Northern Hemisphere high‐latitude June insolation, as opposed to local insolation. High June insolation in the Southern Hemisphere might reduce the SASM intensity. Remote insolation influences the SASM by altering the latitudinal thermal gradient and, consequently, the meridional position of the South Asian high (SAH). The SAH is associated with intense convection and hence drives the meridional shift of the intertropical convergence zone and the SASM rain belt. Thus, orbital‐scale SASM variability is strongly related to remote insolation forcing. Plain Language Summary: Because the monsoon is directly related to the movement of the subsolar point, insolation changes are important in regulating the South Asian summer monsoon (SASM) intensity at an orbital timescale. However, it remains unclear whether the SASM is driven by local insolation that directly strikes southern Asia, or remote insolation in the high‐latitude Northern Hemisphere or the Southern Hemisphere at the precession band. We find a time window between 400 and 350 ka BP (ka = thousand years, BP = before present) when local and remote insolations differ significantly, allowing us to determine which insolation dominates the SASM at orbital timescales. We use an Earth system model with orbital forcing to run a transient simulation between 400 and 350 ka BP. Simulations suggest that the SASM is primarily influenced by Northern Hemisphere high‐latitude summer insolation rather than local insolation. Additionally, Southern Hemisphere insolation has a negative impact on orbital‐scale SASM variability. Remote insolation influences the SASM by inducing an anomalous meridional thermal gradient, which moves the South Asian high and thus the Intertropical Convergence Zone. Our findings are significant for future SASM projections because the obvious difference between remote and local insolation will reappear in the next 50 ka. Key Points: Local insolation is not the direct driver for orbital‐scale variability of the South Asian summer monsoon (SASM)The meridional shift of the South Asian high (SAH) affects orbital‐scale SASM variabilityRemote insolation influences the meridional shift in the SAH through altering the latitudinal thermal contrast [ABSTRACT FROM AUTHOR]

The article offers information on the sixth World Meteorological Organization (WMO) International Workshop on Monsoons held in Singapore on November 13-17, 2017 under the World Weather Research Programme. Topics discussed include land-atmosphere-ocean interactions in the South Asian monsoon, weakening of the East Asian winter monsoon, and the continuing rise of global temperature.

Water isotopes‐climate correlations are used to reconstruct paleoclimate from various natural archives. Intra‐seasonal oscillation is one of the major atmospheric patterns that modulate the ratio of precipitation isotope in low latitudes, yet their spatial and temporal distribution patterns are unclear. Here we presented a detailed analysis of how the intra‐seasonal oscillations (MJO, Madden‐Julian Oscillation, and BSISO, Boreal Summer Intra‐seasonal Oscillation) modulate precipitation δ18O and vapor δ18O over the Asian monsoon region and the equatorial region. This analysis found consistent intra‐seasonal variations between the ISO and rain δ18O. We interpret it as the ISO regulating the active and inactive convective systems on the regional scale, leading to the intra‐seasonal oscillations in precipitation δ18O, with amplitudes from 4‰ up to 15‰. The MJO (BSISO) leads to eastward (northeastward) propagation of δ18O intra‐seasonal oscillations in the Asian equatorial (monsoon) region, coinciding with the spatial patterns of OLR oscillations, reflecting the response of precipitation/vapor δ18O to the oscillation of large‐scale convective activity or accumulated depletion of regional precipitation. We proved that the amplitudes of intra‐seasonal variation of precipitation δ18O are comparable to seasonal variations, and both of them are the main patterns for precipitation δ18O in study regions. Our results are conducive to the accurate interpretation of δ18O in climate proxies such as precipitation, ice cores, tree cellulose, cave stalagmites, et al. on the intra‐seasonal scale in this region. Plain Language Summary: Periodicity is a phenomenon in which similar characteristics or states of things reappear steadily and continuously. The Tropical Intra‐seasonal Oscillation (Andersen et al., 2004, https://doi.org/10.1038/nature02805) is the reappearance of a large‐scale envelope of more abundant convective rain systems moving eastward in the tropical regions with a typical oscillatory period of 30–60 days. The ratios of H218O and HDO vary during the cycle of continuous circulation of water in the atmosphere, and therefore are widely used as proxies for climate records. We used the measured data of precipitation or vapor isotopes to reveal that the propagation of ISO can be recorded by the ratio of H218O covering Asian tropical and monsoon regions. Furthermore, the increased (decreased) ISO intensity leads to the increased (decreased) amplitude of convection intensity, which results in the increased (decreased) amplitude of the H218O ratio in precipitation or vapor. Key Points: The intra‐seasonal oscillations are one of the main patterns of precipitation δ18O covering the Asian monsoon and equatorial regionsThe stronger δ18O intra‐seasonal oscillation corresponds to the season with active convective activities, more rainfall, and low‐level δ18OThe stronger regional convective intensity leads to the cumulative effect in the depletion of rain δ18O during the convective phases of ISO [ABSTRACT FROM AUTHOR]

The relationship between the East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM) across time scales has been an interesting topic for decades. In this study, we quantitatively investigate the EASM–EAWM relationship at the obliquity time scales using a set of accelerated transient simulations. By comparing different indices defined with different variables, we find that the EASM and EAWM intensities are positively correlated under obliquity forcing. High obliquity leads to warmer summertime and cooler wintertime surface temperatures, with a stronger response observed over land than over the oceans. The warmer summertime and cooler wintertime temperature responses are accompanied by a strengthened Asian low in summer and Siberian high in winter, with enhanced southerlies in summer and northerlies in winter, indicating an enhanced EASM and EAWM. Modulated by ice sheet forcing, however, the evolution of the simulated EAWM shifts toward the ice sheet maximum, such that the circulation-based EASM–EAWM relationship in the realistically forced simulation exhibits a phase shift of approximately 11 kyr, closer to the phase between the composite δ18O and loess grain size in observations. Our results may have implications for better understanding the distinct changes in the proxy-based EASM–EAWM relationship before and after the rapid growth of global ice volume at around 3 Ma. Significance Statement: Studying the relationship between the EASM and EAWM can help us understand the characteristics and mechanisms of the regional climate in response to external forcings at different time scales. By investigating the EASM–EAWM relationship over the past 300 000 years, we find that, forced by obliquity variations, the EASM and EAWM are positively correlated at the obliquity time scales. The ice sheet forcing, meanwhile, also influences the circulation over East Asia and modulates the evolutionary phases between the EASM and EAWM. Our results highlight the importance of the combined impacts of orbital parameters and ice sheets on past climate changes over Asia. [ABSTRACT FROM AUTHOR]

A comprehensive and integrative view of East Asian monsoon evolution during the Holocene is still under debate, and additional high-resolution proxy records from climatically sensitive locations are requisite to solve this complex issue. In this paper, we present three well-dated mud/peat cores from a paleo-pingo depression in the Sanjiang Plain, a climatically sensitive region to monsoon variation, to reveal the paleoenvironmental history of the wetland and discuss the regional impacts from monsoon evolution. A paleolake developed in the study area before 5.5 ka BP, and a peatland initiated thereafter consequent upon the gradual shrinking of the paleolake. This transition lasted until 4.5 ka BP, when the paleolake changed entirely to a wetland. Considering the prevalent monsoon climate in the Sanjiang Plain, we suggest that the lake-to-wetland transition from 5.5 to 4.5 ka BP indicates a rapid decline of the East Asian summer monsoon in addition to autogenic basin infilling processes. Such a remarkable monsoon weakening event has been documented across northern China, and we associate this with ocean–atmosphere interactions throughout low-latitude regions. [ABSTRACT FROM AUTHOR]

Rainfall in the Asia summer monsoon (ASM) domain has a complex spatial pattern with the temporal variability at different timescales and their long‐term change has not been fully characterized. An updated 320 multiple proxies network is used to reconstruct the May–October precipitation during the past millennium for eight regions in the ASM domain. The spatial consistency of summer monsoon precipitation variability and the possible links to the internal climate oscillations are investigated. The results show that the regional precipitations over the last millennium in the ASM regions are dominated by the interannual cycle of 2–2.5a and 3.5‐5a, the decadal cycle of ~11a and 15–25a and the multidecadal cycle of ~30a and 40–80a. Coherent dry decades in different regions appear in 1100–1250, 1600–1650 and 1960–2000, while the wet decades appear in 970–990, 1330–1350, 1380–1430, 1550–1580, 1700–1780 and 1810–1910. On interannual scale, the relationships between precipitation for each region and El Niño–Southern Oscillation (ENSO) in both developing and decaying stages are unstable over the entire millennium, but they have opposite‐sign correlations most of the time, which implies that the summer precipitation anomaly for a region tends to reverse in the next summer when a strong ENSO event occurs in the winter. For the long‐term change from multidecadal to centennial scales, the longest dry period of the 12th to 13th centuries in eastern Asia coincides with the period with the lowest ENSO variability due to the in phase change of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation, which could result in the neutral interbasin east–west cell in Tropics and low frequency of ENSO events. [ABSTRACT FROM AUTHOR]

In the East Asian monsoon region, eolian deposits widely distributed in the middle-lower reaches of the Yantgze River are among the best materials available for studies on Quaternary climate change in the subtropical zone of Southern China. Typical eolian deposits in this region include upper Xiashu Loess (XL) and underlying Vermiculated Red Soil (VRS) layers. In this paper, chronological and paleoclimatic studies are conducted on an eolian deposit sequence near Jiujiang (JJ) city in northern Jiangxi province. A magnetostratigraphic study, combined with optically stimulated luminescence (OSL) dating, is conducted on the JJ section and provides further evidence that eolian deposits in the middle-lower reaches of the Yangtze River have been formed since the late Early Pleistocene, and that the boundary age between the XL and VRS layers is about 300-400 kaBP. In grain-size records of the JJ section, the median grain-size and content of the >30 μm size fraction increase sharply after 300-400 kaBP, representing an East Asian winter monsoon intensification event. Further pollen analysis reveals differing pollen assemblages before and after 300-400 kaBP: there is an evident increase in plants adapted to grow in a warm humid environment after 300-400 kaBP, implying an increase in precipitation caused by intensification of the East Asian summer monsoon. Global ice volume and uplift of the Tibet Plateau (TP) are regarded as crucial factors influencing variations of the East Asian monsoon on a long-term scale. The deep-sea δ18O record, which reflects variations in global ice volume, shows no obvious change after 300-400 kaBP. Moreover, the influence of global ice volume changes on the East Asian summer and winter monsoons is inverse; the global ice volume increase (decrease) implies a strengthened (weakened) winter monsoon and weakened (strengthened) summer monsoon. We therefore interpret the coupled intensifications of the East Asian summer and winter monsoons at about 300-400 kaBP to the uplift of the TP in the Middle Pleistocene. This climate event is also documented in eolian deposits from the southern margin of the Chinese Loess Plateau (CLP) and from the desert-loess transitional belt. However, it is not recorded in the loess-paleosol sequences from the central part of the CLP, thereby indicating differing climate responses to TP uplift in different regions, which requires further study. [ABSTRACT FROM AUTHOR]

Using abundant rainfall gauge measurements and Global Precipitation Mission (GPM) data, spatial patterns of rainfall diurnal cycles and their seasonality over high mountain Asia (HMA) were examined. Spatial distributions of rainfall diurnal cycles over the HMA have a prominent seasonality regulated by circulations at different spatiotemporal scales, within which large regional contrasts are embedded. Rainfall diurnal variability is relatively weak in the premonsoon season, with larger amplitude over the western HMA, the southeastern HMA, as well as southern periphery regions, characterized by a dominant late afternoon to morning rainfall preference. The pattern of rainfall spatial distributions is closely related to the midlatitude westerlies. Both the mean rainfall and amplitudes of diurnal cycles become more pronounced with the advance of monsoon season but weaken during postmonsoon. The widespread late afternoon to night pattern over HMA migrating with seasonal atmospheric circulation is consistent with the lifetime of convective systems, which become active from the afternoon due to radiative heating and decay during the night. Stationary terrain-dependent night-to-morning rainfall patterns are visible in those east–west-orientated valleys over HMA and the Qaidam basin throughout the seasons. This salient geographical dependence is associated with local circulation produced by the strong differential thermal conditions over mountains and valleys, which can lift the warm moist air at the mouth of the valley and trigger nocturnal convection. Significance Statement: The main purpose of this study is to explore how spatial patterns of rainfall diurnal cycles over high mountain Asia vary with the seasons. Our results show that the widespread late afternoon to night rainfall over high mountain Asia migrating with seasonal atmospheric circulation is consistent with the lifetime of convective systems. Stationary terrain-dependent night-to-morning rainfall patterns are visible in those east–west-orientated valleys over high mountain Asia and the Qaidam basin throughout the seasons. These results highlight the importance of large-scale atmospheric circulation and local circulation on precipitation, which is critical for water resources over high mountain Asia. [ABSTRACT FROM AUTHOR]

Long-term multi-decadal scale variability of South Asian Summer Monsoon (SASM) is known to be associated with the Atlantic Multidecadal Oscillation (AMO) with positive phase associated with above-normal rainfall and vice-versa over SASM region. Analysis of the 120-year historical record suggests that the relationship between the AMO and the SASM has weakened in recent decades. Two possible reasons emerge from the analyses of observational datasets and model experiments. Enhanced Indian Ocean warming and weakened North Atlantic Subtropical High (NASH) are the prime factors weakening AMO-SASM association in the recent decades. Indian Ocean warming co-occurred during the recent AMO warm phase weakens the meridional temperature gradient, weakening the regional Hadley cell, large-scale monsoon circulation and precipitation. The suppressed convection triggers a Rossby wave which manifests as a cyclonic circulation over west central Asia weakening the Tibetan anticyclone. In addition, weakening of NASH weakens the Circum-Global Teleconnection (CGT) connecting AMO to the SASM, leading to weakening of AMO-SASM association. Projected warming of the Indian Ocean and Atlantic demands better understanding of the AMO-SASM teleconnection and their projected changes for assessing future changes in SASM in a warming world. [ABSTRACT FROM AUTHOR]

Global warming has increased the spatio-temporal variations of Extreme Precipitation (EP), causing floods, in turn leading to losses of life and economic damage across the globe. It is found that EP variability strongly correlates with large-scale climate teleconnection resulting from ocean–atmosphere oscillations. In this study, the Non-Stationary Generalized Extreme Value (NSGEV) framework is used to model EP for high resolution daily gridded (0.5° latitude × 0.5° longitude) APHRODITE dataset over Monsoon Asian Region (MAR) using climate indices as covariates. The proposed framework has three major components (i) Selection of non-uniform time-lag climate indices as covariates, (ii) Regionalization of NSGEV model parameters, and (iii) Estimation of zone-wise EP changes. According to Akaike Information Criterion (AICc), results reveal that the NSGEV model is prevalent in 92% of the grid locations across MAR compared to Stationary(S) GEV models. The Gaussian Mixture Model (GMM) clustering algorithm has identified six zones for MAR. It is observed that the derived zonal parameters of NSGEV model is able to mimic the EP characteristics. Further, zone-wise estimation of EP changes for selected return periods shows that the relative percentage change in intensity ranges between 4 and 11% across the six zones. The change in EP is significantly higher in the monsoonal windward and coastal regions when compared to the other parts of MAR. Overall, the intensities of the EP across MAR are increasing, and return periods are decreasing, which can majorly impact on planning, design and operations of the water infrastructure in the region. [ABSTRACT FROM AUTHOR]

Northern Hemisphere planetary waves exhibit an abrupt change in early summer and a significant impact on East Asian summer monsoon rainfall. Although great achievements have been made toward understanding the characteristics and maintenance of planetary waves during winter and summer, the transition of planetary waves during the abrupt-change period is less well understood. This study aims to assess the relative contribution of harmonic waves to the planetary wave transition and mechanism from the perspective of full nonlinear responses to the mountains of Asia (above 500 m) during May and June, with a primary focus on the largest positive geopotential height anomaly over northeastern Asia. The largest positive geopotential height anomaly over northeastern Asia is primarily contributed by wavelengths of around 7000 km, which corresponds to zonal wavenumber 3. The mid–high latitudes planetary waves mainly consist of wavelengths of around 10,000 km (zonal wavenumber 2, roughly) and 7000 km, which are in-phase (out-of-phase) with each other over the Western (Eastern) Hemisphere. Wavelengths of around 10,000 km weaken and displace eastward, while those of 7000 km magnify and hence contribute to the largest positive geopotential height anomaly over northeastern Asia. The full nonlinear response to the forcing by the mountains of Asia provides a considerable contribution to the largest geopotential height anomaly over northeastern Asia. Such a positive contribution comes mainly from the full nonlinear response to sensible heating associated with the mountains over Asia, which is partially offset by the full nonlinear response to dynamical forcing of the Asian mountains. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, interannual variations of convective and stratiform precipitations in summer East Asian monsoon ( SEAM) dominion are analysed using 16-year (1998-2013) Tropical Rainfall Measuring Mission ( TRMM) precipitation radar ( PR) rain products ( 2A25 and 3A25). It is found that the climatological mean patterns of convective and stratiform rain rates ( RRs) are generally similar to each other, but the area fraction ( AF) of stratiform precipitation can always reach about 80% and dominates in summer East Asia. Nonetheless, convective precipitation produces similar rainfall quantity with stratiform rainfall. For the RR, AF and contribution fraction ( CF), their interannual standard deviation and coefficient of variation ( CV) spatial patterns are similar between summer convective and stratiform precipitations in East Asia, because of the fact that they are all maybe influenced by SEAM. Differently, only the intensity of interannual variability (i.e. CV) for convective precipitation AF is much greater than that for stratiform precipitation, while CV for both convective and stratiform precipitations RR/ CF are similar in most areas. Moreover, the interannual variability of SEAM is more highly correlated with that of RR for convective precipitation than that for stratiform precipitation in most land regions. While the opposite conclusion is found in ocean regions. Generally, the SEAM intensity in the lower troposphere mainly controls interannual variability of the atmospheric stability and both stratiform and convective precipitations RR. Then, atmospheric stability variation further modulates the AF and CF variations of both stratiform and convective precipitations on the interannual scale. This work mainly provides possible evidence of linkage between large-scale circulation and convective and stratiform precipitations on the interannual scale. It suggests that the possible dominant mechanism should be explored using more observations and together with model simulations in the future work. [ABSTRACT FROM AUTHOR]

This paper discusses the Anisotropy of Magnetic Susceptibility (AMS) records during late Neogene to early Quaternary from the Lantian loess section near the southern margin of the Chinese Loess Plateau. The AMS results for this site are shown to reflect variations in the direction of the paleomonsoon. The Lantian loess sediments are largely aeolian in origin, but also include a thin layer that exhibits secondary aqueous depositional features. The major ellipsoid axis AMS orientations in the loess samples indicate a pervasive Northwest–Southeast directional component since the late Neogene. Since that time, the W–E component gradually overtakes the N–S component, which may explain the trend toward increased aridity during that time. Finally, a local heavy rainfall event seemingly occurred in the Lantian region about 2.6 Ma, which may have been responsible for the aqueous redeposition of sediments observed in L 33 layer in this study. [ABSTRACT FROM AUTHOR]