Precipitation In Eastern China Research Articles

Interdecadal variability of winter and spring Eurasian snow depth and its impact on Eastern China precipitation

AbstractEmpirical orthogonal function (EOF) and correlation analyses were employed to investigate the winter and spring snow depth in Eurasia and its relationship with Eastern China precipitation based on the observed and reanalyzed data from 1980 to 2016. The results show that the winter and spring snow cover in Eurasia not only highlights a decreasing trend due to global warming (the first EOF mode, its variance accounted for 24.4% and 22.6% of the total variance) but also exhibits notable interdecadal variation (the second EOF mode, its variance accounted for 10.2% and 11.5% of the total variance). The second EOF mode of winter snow depth in Eurasia is characterized by a west-east dipole pattern. It was observed that the spatial correlation pattern between the EOF2 of Eurasian snow depth and summer precipitation in China closely resembles the meridional quadrupole structure of the third EOF mode of summer precipitation in China. This pattern is characterized by excessive rainfall in Northeast China and the lower-middle reaches of the Yangtze River, and less rainfall over the Yellow River basin and southern China. The EOF mode of spring snow depth not only reflects the declining trend but also regulates precipitation in Eastern China. The possible mechanisms by which snow depth causes changes in soil moisture and subsequently affects atmospheric circulation are then explored from the perspective of the hydrological effects of snow cover. Decreased (Increased) snow depth in Eurasia during the winter and spring directly leads to diminished (increased) soil moisture while increasing (decreasing) net radiation and sensible heat flux at the surface. The meridional distribution of surface temperature also exhibits a dipole pattern, leading to enhanced subtropical westerly jet in the upper troposphere. The Eurasian snow cover anomalies pattern triggered an anomalous mid-latitude Eurasian wave train, which strengthened significantly in the Western Siberian Plain. It then splits into two branches, one continuing to propagate eastward at high latitudes and the other shifting towards East Asia, thereby impacting precipitation in Eastern China. This work indicates that the second EOF mode of Eurasian snow cover can impact the precipitation variability in Eastern China during the same period and in summer on an interdecadal scale.

Impacts of different El Niño events in the decaying summer on the oceanic source of summer rainfall for eastern China: A perspective from stable isotope

ABSTRACT Extreme precipitation in eastern China (EC) is closely related to the diversity of the decaying phases of El Niño (warm-pool El Niño, i.e., WP El Niño and cold-tongue El Niño, i.e., CT El Niño), but little attention is paid to how the El Niño event variability influences precipitation sources for EC from an isotopic perspective. Stable isotopes are ideal physical tracers that can distinguish different sources of precipitation and quantify their relative contributions to precipitation. Accordingly, this study investigates spatiotemporal variations of water vapor flux and oceanic fraction to precipitation during different ENSO events by an isotopic mixing model. The results show that spatiotemporal patterns of moisture divergence for the decaying phase of WP El Niño are different from that of CT El Niño. The oceanic fraction anomalies present similar spatiotemporal trends with advection fraction anomalies. The spatiotemporal variations of precipitation source anomalies for different El Niño events are closely related to atmospheric circulations, i.e., the intensity and location of the western Pacific subtropical high (WPSH). These findings provide isotopic insights into the precipitation sources by El Niño events in EC. Future studies may further focus on the mechanisms producing extreme precipitation between the two kinds of El Niño.

Midsummer precipitation prediction over eastern China by the dynamic downscaling method

AbstractThis study assesses the midsummer precipitation prediction over eastern China by the dynamic downscaling method. Based on the Climate Forecast System version 2 of the National Centers for Environmental Prediction and the Weather Research and Forecasting Model, the prediction performance of global and regional models on the July precipitation over eastern China is further analyzed by hindcast experiments from 1982 to 2010 and prediction experiments from 2011 to 2021. The results suggest that the regional model forced by the global model can noticeably improve the prediction skill for precipitation in eastern China, especially in the region from the South of North China to the Yangtze River Basin, referred as the northern China in this paper. In addition, we perform a diagnostic analysis of the reason for the improvement of the model prediction skill. The results indicate that the high resolution of the regional model and the refinement of physical process parameterizations contribute to improving the simulation ability for the East Asian atmospheric circulation pattern, heat flux, especially for the meridional teleconnection pattern in East Asia and the sensible heat flux in the northern China, thus further improving precipitation prediction.

How the enhanced East Asian summer monsoon regulates total gross primary production in eastern China

Recognizing the relationship between gross primary production (GPP) and precipitation in eastern China, the East Asian Summer Monsoon (EASM) plays a crucial role in shaping GPP. Despite confirmation of the strong link between EASM and GPP, there remains a notable research gap in understanding the specific impact of the EASM on GPP in different regions of eastern China. Here we used simulations from Trends in Net Land–Atmosphere Carbon Exchanges (TRENDY) models from 1951 to 2010 and divided eastern China into five subregions for the study. We also used the New East Asian Summer Monsoon Index (NEWI) as a quantitative metric to distinguish between periods of strong and weak EASM. Building on this, this study aims to investigate the response of GPP in different subregions of eastern China. Regionally, under strengthened EASM years (1954, 1957, 1965, 1969, 1977, 1980, 1983, 1987, 1993 and 1998), East China experienced the most pronounced increase in GPP at 12 ± 21 (mean ± 1 sigma) gC m−2 mon−1 compared to the weak EASM years (1958, 1961, 1972, 1973,1978, 1981, 1985, 1994, 1997 and 2004). In contrast, Southwest China showed a decline in GPP at −4 ± 10 gC m−2 mon−1. Moreover, GPP also increased in Northeast and North China when EASM strengthened, while South China showed a decline in GPP. This indicated that GPP changed with monsoon intensity. According to the mechanism analysis, during strong EASM, there was intense moisture convergence through alterations in the atmospheric circulation field over East China and abundant precipitation, which further contributed to the increase in GPP. Downward solar radiation in Southwest China decreased with EASM enhancement, which suppressed GPP and hindered vegetation growth. Overall, the results highlight the importance of accurately predicting the impact of different EASM intensities of regional carbon fluxes.

Towards Improved Satellite Data Utilization in China: Insights from an Integrated Evaluation of GSMaP-GNRT6 in Rainfall Patterns

To improve the utilization of satellite-based data and promote their development, this analysis comprehensively evaluates the performance of GSMaP Near-real-time Gauge-adjusted Rainfall Product version 6 (GSMaP_GNRT6) data in depicting precipitation over China from 2001 to 2020 by comparing four precipitation indices—accumulated precipitation, number of rainy days and rainstorm days, and precipitation maxima—with daily precipitation data from 2419 stations across China on monthly and annual time scales. The results show that the GSMaP-GNRT6 data effectively capture the overall spatial pattern of the four precipitation indices, but biases in the spatial distribution of the number of rainy days from July to September and the precipitation maxima during the wintertime are evident. A general underestimation of GSMaP-GNRT6 data is observed in the average for China. The annual precipitation amount, the number of rainy days and rainstorm days, and the precipitation maxima based on the GSMaP-GNRT6 data are 17.6%, 35.5%, 31.6% and 11.8% below the station observations, respectively. The GSMaP-GNRT6 data better depict the precipitation in eastern China, with the errors almost halved. And obvious overestimation of the number of rainstorm days and precipitation maxima occurs in western China, reaching up to 60%. Regarding the accumulated precipitation, the number of rainstorm days and the precipitation maxima, the GSMaP-GNRT6 data show an almost consistent interannual variation and increasing trends that are consistent with the station observations. However, the magnitude of the increasing trend based on the GSMaP-GNRT6 data is larger, especially at the beginning of the 21st century. Conversely, a considerable discrepancy in the annual variation and an almost opposite trend can be observed in the number of rainy days between the GSMaP-GNRT6 data and the station observations.

Modulation of the intraseasonal variability in early summer precipitation in eastern China by the Quasi-Biennial Oscillation and the Madden–Julian Oscillation

Abstract. Using the reanalysis and multiple observations, the possible impact of the Madden–Julian Oscillation (MJO) on early summer (June–July) rainfall in eastern China and its modulation by the Quasi-Biennial Oscillation (QBO) are examined. The composite results show that the suppressed (enhanced) convection anomalies for MJO phases 8–1 (4–5) are more concentrated over the maritime continent and the western Pacific during easterly QBO (EQBO). As a consequence, more significant wet (dry) anomalies develop in South (eastern) China during MJO phases 8–1 (4–5) configured with easterly (westerly) QBO. The enhancement and expansion of the anomalous tropical convection band do not necessarily correspond to enhancement of the extratropical circulation response to MJO phases 8–1 (4–5) configured with westerly (easterly) QBO. The anomalous high (low) over the maritime continent and western Pacific associated with MJO phases 8–1 (4–5) is intensified (deepened) during easterly (westerly) QBO, leading to large southwesterly (northeasterly) anomalies in South China and the coasts, carrying abundant (sparse) moisture. Two anomalous meridional circulation cells are observed for MJO phases 8–1 in the East Asia sector, with downwelling anomalies around 5–20∘ N, upwelling anomalies around 20–30∘ N, and another downwelling branch northward of 30∘ N, which are enhanced during easterly QBO. The anomalous meridional circulation cells are reversed for MJO phases 4–5, which are stronger during westerly QBO with the anomalous downwelling and dry anomalies covering eastern China. The combined impact of MJO phases 8–1 and easterly QBO on the early summer rainfall is noticeable in 1996, 2016, and 2020. The enormous rainfall amount appeared along the Yangtze River in 1996, 2016, and 2020 due to the extended period of MJO phases 8–1 under the background of the easterly QBO.

Sea–air coupling leads to a decrease in precipitation in East Asia under present day conditions that is partially alleviated in future simulations

The offshore region of East Asia has a crucial role in recycling precipitation, especially in the current context of a warming climate. This is because the atmospheric feedback from the sea offshore East Asia directly impacts and modifies precipitation patterns by influencing the seasonal cycles of the surface energy and water budgets. We used a regional climate model incorporating sea–air coupling to investigate and better understand these climate feedback mechanisms in East Asia. We identified a reduction in precipitation caused by sea-air coupling over East Asia during the time period 1991 − 2014 under present day conditions. Specifically, we observed an average decrease in precipitation of about 0.1 ± 0.40 mm day−1 during June–July–August. This decrease in precipitation can be attributed to a combination of factors, including the effects of upward solar radiation, the asymmetry of the thermal contrast between the land and the sea, decreased evaporation in the southeastern ocean and the weakened transport of water vapor from the sea to the land. Our research suggests that the decrease triggered by sea–air coupling will be partially alleviated under future conditions, although not completely reversed, in terms of its impact on precipitation in eastern China. Although some relief is anticipated, the overall influence of sea–air coupling on patterns of precipitation in East Asia will persist, especially south of the Yellow River in eastern China.

Long-term coupled variability of temperature and precipitation in eastern China and the underlying mechanisms

Long-term coupled variability of temperature and precipitation in eastern China and the underlying mechanisms

Combined Impacts of the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation on Summer Precipitation in Eastern China During the Medieval Climate Anomaly and Little Ice Age

AbstractWe investigate the joint effects of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) on eastern China summer precipitation (ECSP) during two typical periods in the last millennium [i.e., the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA)] using simulations from five selected climate models. The multimodel mean indicates that the ECSP anomalies under the four combined AMO and PDO phases differ between the MCA and the LIA. During the MCA, the meridional wave train induced by the PDO‐related convective heating over the northwestern Pacific is dominant and the zonal wave train related to the AMO is secondary. Independent of the AMO phase, deficient precipitation appears over South China in both PDO+ phases and vice versa. Meanwhile, most areas north of the Yangtze River valley feature positive anomalies in the PDO+/AMO+ phase but deficits in the PDO+/AMO− phase. In comparison, the Huanghe‐Huaihe River valley and southern Northeast China receive excessive and deficient precipitation in the PDO−/AMO+ and PDO−/AMO− phases, respectively. During the LIA, the zonal wave train induced by the AMO locates more southeastward than that during the MCA and has an overwhelming impact on the ECSP. Specifically, regardless of the PDO phase, excessive ECSP exists over Northeast China and South China in both AMO+ phases and vice versa. Moreover, precipitation between the two regions is excessive when the PDO is in phase with the AMO but deficient when they are out of phase.

Modelling the effect of aerosol and greenhouse gas forcing on the South Asian and East Asian monsoons with an intermediate-complexity climate model

Abstract. The South Asian and East Asian summer monsoons are globally significant meteorological features, creating a strongly seasonal pattern of precipitation, with the majority of the annual precipitation falling between June and September. The stability the monsoons is of extreme importance for a vast range of ecosystems and for the livelihoods of a large share of the world's population. Simulations are performed with an intermediate-complexity climate model in order to assess the future response of the South Asian and East Asian monsoons to changing concentrations of aerosols and greenhouse gases. The radiative forcing associated with absorbing aerosol loading consists of a mid-tropospheric warming and a compensating surface cooling, which is applied to India, Southeast Asia, and eastern China both concurrently and independently. The primary effect of increased absorbing aerosol loading is a decrease in summer precipitation in the vicinity of the applied forcing, although the regional responses vary significantly. The decrease in precipitation is not ascribable to a decrease in the precipitable water and instead derives from a reduction in the precipitation efficiency due to changes in the stratification of the atmosphere. When the absorbing aerosol loading is added in all regions simultaneously, precipitation in eastern China is most strongly affected, with a quite distinct transition to a low precipitation regime as the radiative forcing increases beyond 60 W m−2. The response is less abrupt as we move westward, with precipitation in southern India being least affected. By applying the absorbing aerosol loading to each region individually, we are able to explain the mechanism behind the lower sensitivity observed in India and attribute it to remote absorbing aerosol forcing applied over eastern China. Additionally, we note that the effect on precipitation is approximately linear with the forcing. The impact of doubling carbon dioxide levels is to increase precipitation over the region while simultaneously weakening the circulation. When the carbon dioxide and absorbing aerosol forcings are applied at the same time, the carbon dioxide forcing partially offsets the surface cooling and reduction in precipitation associated with the absorbing aerosol response. Assessing the relative contributions of greenhouse gases and aerosols is important for future climate scenarios, as changes in the concentrations of these species has the potential to impact monsoonal precipitation.

Typhoon-related changes in moisture pathways and sources for precipitation in Eastern China during the three major rainy seasons

Typhoons (TYs) and their interactions with large-scale ambient flow might exert an important control on moisture transport and precipitation. In this study, we used a Lagrangian model, the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT), to quantify changes in moisture pathways and sources associated with TY activity in relation to precipitation in eastern China during the three major rainy seasons. We compared TY-active and TY-inactive periods, i.e., the periods with and without TYs (maximum sustained surface wind speeds of up to 32.7 m/s), over the western North Pacific (WNP) to investigate TY-associated changes for the period 1979–2020. During the pre-summer rainy season in South China, anomalous moisture exhibited a north–south dipole pattern, with moisture contributions from the region extending from the South China Sea to the adjacent tropical WNP showing a 17.0% decrease during TY-active compared with TY-inactive periods (34.7% versus 41.8%, respectively), and contributions from the region extending from southwestern China to the northwestern North Pacific showing a 18.9% increase (17.0% versus 14.3%, respectively) and those from the Bay of Bengal showing a 16.6% increase (17.6% versus 15.1%, respectively). The moisture anomaly during the Meiyu rainy season in the Yangtze–Huaihe River Basin had an east–west dipole structure, with the moisture contribution from the Bay of Bengal reduced by 21.8% as compared with TY-inactive periods, and that from the WNP increased by 62.3%. During the rainy season of North China, the moisture contribution from the Indian Ocean decreased by 7.2%, while that from the WNP increased by 8.7% and from Northeast China increased by 10.0%. In addition, during TY-active periods, moisture contributions with local origins showed a slight increase.

Evaluation and correction of sub-seasonal dynamic model forecast of precipitation in eastern China

Evaluation and correction of sub-seasonal dynamic model forecast of precipitation in eastern China

Lagged Linkage between the Kara–Barents Sea Ice and Early Summer Rainfall in Eastern China in Chinese CMIP6 Models

The lagged relationship between Kara–Barents sea ice and summer precipitation in eastern China is evaluated for Chinese models participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6). A previous study revealed a dipole rainfall structure in eastern China related to winter Arctic sea ice variability. Almost all Chinese CMIP6 models reproduce the variability and climatology of the sea ice in most of the Arctic well except the transition regions with evident biases. Further, all Chinese CMIP6 models successfully simulate the decreasing trend for the Kara–Barents sea ice. The dipole centers located in the Yangtze–Huai River Valley (YHRV) and South China (SC) related to Kara–Barents sea ice variability are simulated with different degrees of success. The anomalous dipole rainfall structure related to the winter Kara–Barents sea ice variability can roughly be reproduced by two models, while other models reproduce a shifted rainfall anomaly pattern or with the sign reversed. The possible delayed influence of sea ice forcing on early summer precipitation in China is established via three possible processes: the long memory of ice, the long-lasting stratospheric anomalies triggered by winter sea ice forcing, and the downward impact of the stratosphere as the mediator. Most Chinese models can simulate the negative Northern Hemisphere Annular Mode (NAM) phase in early winter but fail to reproduce the reversal of the stratospheric anomalies to a positive NAM pattern in spring and early summer. Most models underestimate the downward impact from the stratosphere to the troposphere. This implies that the stratospheric pathway is essential to mediate the winter sea ice forcing and rainfall in early summer over China for CMIP6 models.

Stage-dependent influence of PDO on interdecadal summer precipitation anomalies in eastern China

Pacific decadal oscillation (PDO) has been regarded as one of the most important interdecadal factors to the interdecadal summer precipitation in eastern China, which, however, cannot keep a consistent pattern during the same positive or negative PDO phase. Because sea surface temperature (SST) anomalies vary along with PDO evolvement, the PDO impacts are investigated in terms of developing and decaying stages of its positive and negative phases, respectively. It is found that the SST cooling in mid-latitude North Pacific and SST warming in off-equator central-eastern Pacific are generally intensified from the developing stage to the decaying stage for positive PDO phase, and vice versa. Particularly, during the decaying stage of positive (negative) PDO phase, the enhanced SST warming (cooling) in northeastern tropical Pacific triggers a stronger (weaker) large-scale Walker circulation and suppresses (enhances) the convective activities in western tropical Pacific, which favors a meridional wave train like East Asia–Pacific (EAP) teleconnection over East Asia. Meanwhile, the westward extended SST cooling (warming) in mid-latitude North Pacific together with the SST warming (cooling) to its south significantly increases (decreases) the meridional SST gradient and low-level atmospheric baroclinicity, conductive to the strengthened (weakened) and southward (northward) shifted East Asian subtropical westerly jet as well as an equivalent barotropic “cold trough” in western North Pacific. Because of such tropical and extratropical dynamical processes, a meridional tripole pattern of precipitation anomalies occurs in eastern China which dominates the PDO impact in the same phase and distinctly different from the dipole pattern during the developing stage.

Change in mean and extreme precipitation in eastern China since 1901

Extreme precipitation in the monsoon region of China can cause a variety of weather and climate disasters, and its long-term change has a significant impact on human life and social production. However, due to the lack of high-resolution precipitation data for the early 20th century, the variation characteristics and causes or mechanisms of extreme precipitation change in eastern China in the last 100 yr or more are still unclear. Based on the ‘daily precipitation dataset of 60 city stations in mainland China from 1901 to 2020’ developed by the National Meteorological Information Center, China Meteorological Administration, the main characteristics of extreme precipitation changes at 38 stations in eastern China during a recent 120 yr period (1901-2020) are analyzed in this paper. The results show that: (1) From 1901 to 2020, there was no significant trend in precipitation amount and precipitation days in the region, but a quasi-period of about 15 to 20 yr or longer existed during the period. (2) The average daily precipitation intensity and most of the extreme precipitation indices first decreased and then increased over the whole time period. In the period 1901-1950, which has rarely been studied in the past, most of the extreme precipitation indices, including intense rainfall, rainstorms, and the maximum precipitation within 1 day, 3 consecutive days, and 5 consecutive days, showed a significant decreasing trend. Since 1951, however, various indices have tended to increase. (3) From 1901 to 2020, the precipitation and extreme precipitation indices to the north of 35° N generally decreased, while they consistently increased in the south. The spatial pattern of extreme precipitation changes for the first half of 20th century was also quite different from that of the last 70 yr. Overall, the mean and extreme precipitation change trends in eastern China were not consistent in different sub-periods during the past century.

Decade-to-decade variations in summer precipitation patterns in eastern China since the 1960s: roles of water vapor transport and sea surface temperature

Based on the observational precipitation data and multiple reanalysis datasets, this study analyzes the decade-to-decade spatiotemporal evolution of anomalous summer precipitation in eastern China (SPEC) for 1961-2019 and explores the roles of water vapor transport and global sea surface temperatures (SSTs). Results show that SPEC patterns in the last 60 yr were mainly classified into 3 categories: dipole (the 1960s and 1970s), tripole (the 1990s) and quadrupole (the 1980s and 2000s), with marked decade-to-decade variations. In the 2010s, the precipitation pattern exhibited a more complex nature. Obvious differences can be detected in the water vapor channels (WVCs) associated with the 3 SPEC patterns. Specifically, the dipole pattern of the SPEC was mainly related to the Pacific Ocean WVC (POW) and the westerly WVC (WW). The tripole pattern was mainly associated with the Tibetan Plateau Southern Side WVC (TPW), the South China Sea WVC, the POW and the WW. The quadrupole pattern was quite clearly correlated with the Indian Ocean WVC, the Bay of Bengal WVC, the TPW, the POW and the WW. Furthermore, the dipole SPEC pattern was correlated with the Pacific decadal oscillation (PDO), the Indian Ocean basin mode (IOBM) and the Atlantic multi-decadal oscillation. The tripole and quadrupole patterns were related to the IOBM and PDO, respectively. The PDO has a marked influence on the interdecadal shifting of the SPEC pattern in the late 1970s, favoring the formation of the quadrupole SPEC pattern. However, the decadal shifting of the SPEC pattern in the early 1990s is mainly influenced by the IOBM, which favored the formation of the tripole precipitation pattern.

Precipitation in eastern China over the past millennium varied with large-scale climate patterns

Modern precipitation variability over East China is known to be characterized by meridional tripole and dipole structures, linked to atmosphere and ocean dynamics. As the instrumental data may be influenced by anthropogenic global warming, it is unclear whether the physical mechanism underlying the tripole and dipole pattern have remained constant since the pre-industrial period. Here we investigate spatiotemporal precipitation variability over the past 1150 years using three high-resolution stalagmite δ18O records from southern, central and northern China. Principal component analysis results suggest that the first principal component, reflecting large-scale Asian monsoon strength, is closely linked to solar variability. The second and third principal components, which reflect rainfall, reveal tripole and dipole patterns that persist over the last millennium and are driven by the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). We find that interactions between the monsoon, PDO, and AMO influence spatiotemporal rainfall patterns in East China.

Evaluating the effects of topographical factors on the precipitation simulated by kilometer-scale versus quarter-degree dynamical downscaling models in eastern China

Topography as well as its attributes are fundamental factors during precipitation generation. Various models with different complexity have been established to interpret the topography–precipitation relationship. In this study, the topography–precipitation relationships simulated by two dynamical downscaling models (DDMs) at the kilometer-scale and traditional quarter-degree resolution in eastern China are evaluated by utilizing multi-scale geographically weighted regression with station precipitation observations as reference. The precipitation simulated by the kilometer-scale DDM had a higher agreement with observations than the quarter-degree simulation. For the effects of topography on precipitation, observations revealed a dominant role played by the topographical relief in the precipitation distribution at most stations in the study region. The kilometer-scale DDM generally reflected this dominant role of topographical relief. However, the quarter-degree DDM showed an excessive dependency of the precipitation distribution on the topographical elevation. This research highlights the key role of underground sub-grid variations on the precipitation in eastern China, which implies a potential way forward for precipitation simulation improvements.摘要与传统的1/4度 (≈25-30 km) 动力降尺度模拟相比, 公里尺度模拟的降水空间分布与观测结果更为接近. 为了研究这一差异原因, 本研究以华东地区为例, 探究了地形因子在观测和模拟的降水中的作用. 为了更好地体现地形因子对降水分布非均匀性的影响, 以及不同地形因子作用的尺度差异, 本研究采用多尺度地理加权回归模型, 对五个主要地形因子与公里尺度和1/4度分辨率模拟的降水的关系进行了评估. 基于观测数据的研究结果显示地形起伏度, 地形高程和离海岸线距离对华东地区降水分布的非均匀性都有重要影响, 其中地形起伏度在研究区大部分站点降水分布中起主导作用; 公里尺度模拟结果基本反映了地形起伏度的主导作用; 而1 / 4度模拟结果表现出降水对地形高程的过度依赖. 本研究揭示了公里尺度地形分布对中国东部降水的非均匀分布的关键作用, 研究结果可以为改进降水模拟提供新的思路.

Impact of Mountains in Southern China on the Eocene Climates of East Asia

AbstractInconsistencies in the Eocene climates of East Asia have been revealed in both geological studies and simulations. Several earlier reconstructions showed an arid zonal band in mid‐latitude China, but others showed a humid climate in the same region. Moreover, previous Eocene modeling studies have demonstrated that climate models can simulate both scenarios in China. Therefore, it is essential to investigate the cause of this model spread. We conducted a series of experiments using Norwegian Earth System Model 1‐F and examined the impact of mountains in Southern China on the simulated Eocene climate. These mountains, including the Gangdese and Southeast Mountains, are located along the main path of water vapor transport to East Asia. Our results reveal that the Southeast Mountains play the dominant role in controlling the simulated precipitation in Eastern China during the Eocene. When the heights of the Southeast Mountains exceed ∼2,000 m, an arid zonal band appears in mid‐latitude China, whereas humid climates appear in Eastern China when the elevation of the Southeast Mountains is relatively low.

Possible Lagged Impact of the Arctic Sea Ice in Barents–Kara Seas on June Precipitation in Eastern China

Based on the Hadley Centre sea ice concentration, the ERA5 reanalysis, and three precipitation datasets, the possible lagged impact of the Barents–Kara sea ice on June rainfall across China is investigated. Using the singular value decomposition, it is revealed that the state of sea ice concentration in Barents–Kara Seas from November to December is closely related to regional precipitation in June, which is most evident across the Yangtze–Huai Rivers Valley and South China. Possible pathways from preceding Arctic sea ice concentration to June precipitation are examined and discussed. First, the sea ice concentration usually has a long memory, which exerts a long-lasting and lagged impact, although the sea ice anomaly amplitude gradually weakens from early winter to early summer. Second, an increase in Barents–Kara sea ice usually corresponds to a stronger stratospheric polar vortex in midwinter by suppressing extratropical wave activities, which is projected to the positive phase of northern annular mode (NAM). Strong vortex gradually recovers to its normal state and even weakens in spring, which corresponds to the negative NAM response from spring to early summer. Third, the stratospheric anomalies associated with the Barents–Kara sea ice variations propagate downward. Due to the out-of-phase relationship between the lower and upper stratospheric circulation anomalies after midwinter, westerly anomalies in midwinter are followed by easterly anomalies in later months in the circumpolar region, consistent with the positive NAM response in midwinter, negative NAM response in spring, and a wave train-like response in early summer to Barents–Kara sea ice increase (and vice versa). The observed lagged impact of Barents–Kara sea ice on China rainfall in June is limitedly simulated in the ten CMIP6 models used in this study.