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Evolution of East Asian monsoonal precipitation across the Last Interglacial (LIG) remains controversial, owing to the discrepancies between various proxies and their low temporal resolution. Through a transient high-resolution global climate simulation covering the interval of 130–120 ka, we illustrate a long-term increasing (decreasing) trend in summer precipitation over south China (northeast Asia) during the LIG (i.e. 130–120 ka). The out-of-phase precipitation evolution across latitudes were coherently regulated by the weakened monsoonal circulation, southward moved western North Pacific high, and southward displaced East Asian westerly jet from the early to late LIG. These atmospheric circulation variations were in turn determined by sea surface temperature anomalies over the Pacific and the propagation of extratropical Rossby waves originating from North Africa. Our results may provide important insights for reconciling discrepancies between precipitation proxies during the LIG and for precipitation behavior in a warmer-than-present world. [ABSTRACT FROM AUTHOR]

Glacier growth affects the local climate, and in turn, can either promote or prohibit its own growth. Such feedback has not been considered in modeling the glaciers of the Tibetan Plateau and its surroundings (TPS) during the Last Glacial Maximum (LGM; ∼28–23 ka). We find that the volume/area of the glaciers simulated by a coupled glacier‐climate model is 20%/10% less than that by a standalone glacier model forced with fixed climate fields; glaciers advance toward their western rims and yet decrease in the interior of TPS. Such changes in spatial patterns improve model‐data comparison. Moreover, the expansion of glaciers warms the winter surface temperature of the eastern TPS and decreases precipitation almost everywhere. These effects are primarily due to the added surface elevation, which blocks the water vapor brought by westerlies and south‐westerlies, reducing precipitation and increasing surface temperatures to the east and northeast of the newly grown glaciers. Plain Language Summary: Depending on their area and volume, glaciers could impact regional atmospheric circulations, temperatures, precipitation, surface properties, etc. Changes in these climate variables would in turn feedback on the glacier growth and retreat. The glacial area over the Tibetan Plateau and its surroundings (TPS) should be much broader during the Last Glacial Maximum (LGM) than today, but glacier‐climate feedback was largely ignored in previous numerical studies. We show that the feedback significantly alters the simulated glacier area and distribution in LGM glaciers, and helps improve model‐data comparison. When glaciers grow, the surface elevation increases, which intercepts water vapor. Hence, more glaciers will grow along the western rim of TPS and less over the interior when the glacier‐climate feedback is considered. In the meantime, the winter surface temperature of the eastern Tibetan Plateau increases by more than 2 K and the precipitation over most of TPS decreases. Key Points: Coupled modeling of the Last Glacial Maximum glaciers and climate over the Tibetan Plateau and its surroundings is necessaryThe elevated glaciers blocked water vapor transport, reduced precipitation over most of TPS, and increased winter temperature in eastern TPSThe coupled glacial modeling decreases glacial area, and with changes in spatial distribution better matches the reconstructions [ABSTRACT FROM AUTHOR]

85Kr is a major radioactive byproduct released during nuclear fuel reprocessing and an important atmospheric indicator for nuclear safety and environmental monitoring. In this work, we report on online monitoring of atmospheric 85Kr activities with time resolution of 1.5 hours. An automated Kr purification system and an atom trap based 85Kr measurement system work synchronously in the experiment. The Kr purification system features temperature-controlled cryogenic distillation and gas chromatography, which allows direct sampling of ambient air and continuous operation. The separated Kr is fed into an atom trap capable of measuring the abundance of 85Kr with micro-L size Kr samples. The sample consumption is 3 L STP of air per measurement with a 1.5 hour processing time. Compared to the conventional monitoring method based on proportional counting, both the measurement time and sample size (10 m3 and 1 week) are reduced by several orders of magnitude. The 85Kr analysis technology demonstrated in this work allows analysis of atmospheric 85Kr activities with hourly resolution, enabling applications such as online monitoring of nuclear fuel reprocessing plants and tracing of atmospheric circulation patterns. [ABSTRACT FROM AUTHOR]

Deciphering the Meiyu behavior during the Last Interglacial (∼127 ka; LIG) may deepen our understanding of drought and flooding events over East Asia in a warmer‐than‐present world induced by Earth's orbit. Based on dynamical downscaling simulations, we suggested a 15‐ and 30‐day earlier onset and retreat of the Meiyu during the LIG relative to preindustrial, respectively, leading to a shortened Meiyu season. Meantime, extreme precipitation in the Meiyu season became stronger and occurred more frequently. Intensified monsoonal circulation, poleward‐located western North Pacific subtropical high, and poleward shift of East Asian westerly jet during the LIG provided favorable moisture conditions for earlier onset and retreat of the Meiyu. The variations of atmospheric circulations were further regulated by the joint effect of the three oceans and diabatic heating over Tibetan Plateau. Our results highlight an important role of Earth's orbit in the Meiyu and imply more flooding events in a warmer world. Plain Language Summary: The record‐breaking Meiyu in 2020 reemphasizes the importance of investigating the evolution of the rainy season in East Asia. This study reveals the response of the Meiyu to changes in the Earth's orbit during the Last Interglacial (LIG, 130–115 ka)—the warmest interglacial of the past 800 ka and a warmer world comparable to the low emission scenarios at the end of the 21st century. The Meiyu season occurred and ended earlier compared with the present day, and the duration was shortened. Additionally, more frequent and intense extreme precipitation events occurred in the Meiyu season during the LIG. The enhanced East Asian summer monsoonal flow, strengthened western North Pacific subtropical high, and poleward shift of the East Asian westerly jet in June provided favorable conditions for the earlier occurrence and termination of the Meiyu during the LIG. Moreover, changes in the sea surface temperature over the three oceans can jointly influence the Meiyu via triggering Kelvin waves, Rossby waves, and teleconnections by atmospheric circulations, with the contribution from the diabatic heating over the Tibetan Plateau. The results of this study help us better understand the evolution of the rainy season over East Asia in a warmer world. Key Points: Earlier onset and shortened duration of Meiyu season during the Last Interglacial (LIG)Stronger and more frequent extreme precipitation events occurred in Meiyu season during the LIGIntensified monsoonal circulation, poleward‐located subtropical high and westerly jets led to changes in Meiyu during the LIG [ABSTRACT FROM AUTHOR]

Greenland surface mass balance (SMB) is undergoing dramatic change due to the amplified Arctic warming, with more frequent record‐breaking melt events. To comprehensively understand the behaviour of the Greenland ice sheet, we develop a suite of indices to examine the spatiotemporal variations of extreme events in SMB over Greenland during 1958–2019 based on the RACMO2.3p2 model outputs. We illustrate that the climatological distributions of extreme ablation‐dominated events (i.e., extremes with SMB < 0) share large similarity with the mean SMB in terms of intensity and frequency, showing a coastal‐to‐inland decreasing pattern. This pattern holds for the intensity of the extreme accumulation‐dominated events (i.e., extremes with SMB > 0), but not for the frequency which increases from the coastal to inland Greenland. Regarding the temporal evolution, the intensity and frequency of extreme ablation‐dominated events show a decreasing trend over Greenland during 1958–1978, whereas the trend increases afterwards, especially during the last two decades (2001–2019). However, these trends fluctuate regionally across the GrIS both in terms of magnitude and sign, with the most pronounced variations occurring in southwest Greenland. In contrast, extreme accumulation‐dominated events show, on average, a long‐term increasing trend from 1958 to 2019 in terms of intensity and frequency. However, obvious spatial fluctuations exist across the GrIS during 1958–2019, especially between the southwest and northeast Greenland where an opposite trend is observed. Additionally, the variations of SMB extremes in boreal summer are linked with the changes in regional temperature and precipitation and the associated atmospheric circulations, and the dominating factor varies with different extreme indices and time intervals. Our results may advance our understanding on SMB variability over Greenland and contribute to the design of future Greenland observational networks. [ABSTRACT FROM AUTHOR]

How the remote influences of El Niño-Southern Oscillation (ENSO) may vary in a warmer future remains a hot topic but still elusive. Based on the outputs from the Paleoclimate Modeling Intercomparison Project Phase 4, here we investigated the variations of ENSO teleconnections in boreal winter during the Last Interglacial (LIG), which shares large similarities with the projected climatic features in the 21st century. Our results suggested that the ENSO-temperature teleconnections on average weakened by ∼13.4% during the LIG relative to the preindustrial, whereas the response of precipitation amplified by ∼5.0%. However, there are large regional discrepancies in the variations of ENSO teleconnections in terms of the sign and amplitude. For example, we observed significant ENSO-temperature relationship changes at the high latitudes during the LIG, with a depressed linkage over northern North America but enhanced linkage over the high latitudes of Eurasia. The most profound change in ENSO-precipitation teleconnection occurred over the tropics during the LIG, characterized by a weaker response over the equatorial Pacific Ocean whereas a stronger response over the Maritime Continent and adjacent oceans. Regarding atmospheric circulations, we found that the ENSO-driven Walker Circulations over the Pacific and the Indian Ocean shifted westward during the LIG, whereas the descending branch of the ENSO-driven Atlantic Walker Circulation shifted eastward. Our results provide a model-based scenario for the variations of ENSO teleconnections during the LIG, but the underlying mechanisms deserve further investigation in the future. • ENSO-temperature teleconnections on average weakened during the Last Interglacial. • ENSO-precipitation teleconnections on average enhanced during the Last Interglacial. • There are large regional discrepancies in the variations of ENSO teleconnections. • ENSO-driven Pacific Walker Circulation moved westward during the Last Interglacial. [ABSTRACT FROM AUTHOR]

Understanding the role of the Pacific Decadal Oscillation (PDO) during the Last Interglacial (LIG, ∼127 ka) may advance our knowledge on decadal climate variability in a warmer world. In this study, we investigate the PDO–precipitation relationship over eastern China during the LIG based on the NorESM2-LM, which shows the best performance in capturing the observed PDO pattern and the PDO–precipitation relationship among 12 models from the Paleoclimate Modelling Intercomparison Project Phase 4. Composite analysis shows that summer precipitation during the LIG is generally increased over eastern China in the positive PDO phases relative to the negative phases, which is different from the "drier-wetter-drier" triple pattern in the present day. The discrepant precipitation patterns between the LIG and preindustrial are caused by different responses of composite atmospheric circulations. Moreover, moisture budget analysis indicates that variations of vertical velocity over eastern China largely explain the PDO-linked precipitation patterns during both LIG and preindustrial, although the main causes for vertical motion changes are different across regions and periods based on the quasi-geostrophic ω equation. Additionally, these discrepancies in composite atmospheric circulations are largely linked to differences in PDO patterns and mean climate states between the LIG and preindustrial. Our results suggest a varying relationship between the PDO and precipitation over eastern China in a warmer-than-present world induced by Earth's orbit, which have important implications for PDO reconstructions during the LIG via the PDO-precipitation relationship reported here and shed light on decadal variability of precipitation as well as the associated decadal predictions in a future warmer world. • Divergent response of eastern China precipitation to PDO during the LIG. • Discrepant composite atmospheric circulations cause varied precipitation patterns. • PDO pattern/mean climate state regulate varied precipitation during the LIG jointly. [ABSTRACT FROM AUTHOR]

Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variations based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM-precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase III and Community Earth System Model to investigate the stability of the EASM-precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) was enhanced in the Medieval Climate Anomaly (MCA; ~950-1250 AD), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ~1500-1800 AD), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM-precipitation relationship is only stable on a centennial and longer timescale and is unstable on a shorter timescale. The nonstationary short-timescale EASM- precipitation relationship broadly exhibits a multi-decadal periodicity, which may be attributed to the internal variability of the climate system and has no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies. [ABSTRACT FROM AUTHOR]

The midlatitude westerlies are one of the major components of the global atmospheric circulation. They play an important role in midlatitude weather and climate, and are particularly significant in interpreting aeolian sediments. In this study, we analyzed the behavior and the possible mechanism involved in the change of the westerlies, mainly in terms of the jet stream position, in the mid-Pliocene warm period (3.3 to 3.0 million years ago) using simulations of 15 climate models from the Pliocene Model Intercomparison Project (PlioMIP). Compared to the reference period, the mid-Pliocene midlatitude westerlies generally shifted poleward (approximately 3.6° of latitude in the Northern Hemisphere and 1.9° of latitude in the Southern Hemisphere at 850 hPa level) with a dipole pattern. The dipole pattern of the tropospheric zonal wind anomalies was closely related to the change of the tropospheric meridional temperature gradient as a result of thermal structure adjustment. The poleward shift of the midlatitude westerly jet corresponded to the poleward shift of the mean meridional circulation. The sea surface temperatures and sea ice may have affected the simulated temperature structure and zonal winds, causing the spread of the westerly anomalies in the mid-Pliocene between the atmosphere-only and coupled atmosphere-ocean general circulation model simulations. [ABSTRACT FROM AUTHOR]

Based on the daily sunspot number (SN) data (1954–2011) from the Purple Mountain Observatory, the extreme value theory (EVT) is employed for the research of the long-term solar activity. It is the first time that the EVT is applied on the Chinese SN. Two methods are used for the research of the extreme events with EVT. One method is the block maxima (BM) approach, which picks the maximum SN value of each block. Another one is the peaks-over-threshold (POT) approach. After a declustering process, a threshold value (here it is 300) is set to pick the extreme values. The negative shape parameters are obtained by the two methods, respectively, indicating that there is an upper bound for the extreme SN value. Only one value of the N -year return level (RL) is estimated: N = 19 years. For N = 19 years, the RL values of SN obtained by two methods are similar with each other. The RL values are found to be 420 for the POT method and the BM method. Here, the trend of 25th solar cycle is predicted to be stronger, indicating that the length of meridional forms of atmospheric circulation will be increased. [ABSTRACT FROM AUTHOR]