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Modeled Influence of East Asian Black Carbon on Inter-Decadal Shifts in East China Summer Rainfall 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event. 相似文献
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The strength of the East Asian summer monsoon and associated rainfall has been linked to the western North Pacific subtropical high (WNPSH) and the lower-tropospheric low pressure system over continental East Asia (EA). In contrast to the large number of studies devoted to the WNPSH, little is known about the variability of the East Asian continental low. The present study delineates the East Asian continental low using 850-hPa geopotential height. Since the low is centered over northern EA (NEA), we refer to it as the NEA low (NEAL). We show that the intensity of the NEAL has large interannual variation, with a dominant period of 2–4 years. An enhanced NEAL exhibits a barotropic structure throughout the whole troposphere, which accelerates the summer-mean upper-tropospheric westerly jet and lower-tropospheric monsoon westerly to its south. We carefully identify the anomalous NEAL-induced rainfall anomalies by removal of the tropical heating effects. An enhanced NEAL not only increases rainfall locally in northern Northeast China, but also shifts the East Asian subtropical front northward, causing above-normal rainfall extending eastward from the Huai River valley across central-northern Japan and below-normal rainfall in South China. The northward shift of the East Asian subtropical front is attributed to the following processes without change in the WNPSH: an enhanced NEAL increases meridional pressure gradients and the monsoon westerly along the East Asian subtropical front, which in turn induces a cyclonic shear vorticity anomaly to its northern side. The associated Ekman pumping induces moisture flux convergence that shifts the East Asian subtropical front northward. In addition, the frequent occurrence of synoptic cut-off lows is found to be associated with an enhanced NEAL. Wave activity analysis indicates that the interannual intensity change of the NEAL is significantly associated with the extratropical Polar Eurasian teleconnection, in addition to the forcing of the tropical WNP heating. 相似文献
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Centennial-scale dry-wet variations in East Asia 总被引：7，自引：0，他引：7
This study attempts to combine four independent long-term climatic data and modern observations into one cohesive set; to describe the spatial and temporal patterns of variability of dry and wet periods in East Asia over the past one thousand years; and to examine physical causes of the pattern variations. The data include the 220-year observed precipitation in Seoul, South Korea, the dryness-wetness intensity data in eastern China for the last 530 years, and other two independent chronologies of dryness-wetness grades in the past millennium in eastern China based on instrumental observations and historical documents. Various analysis methods including wavelet transform and rotated empirical orthogonal function were used in revealing climate variations from these datasets. Major results show that the dry and wet anomalies initially appeared in the north part of eastern China and then migrated southward to affect south China. This process is repeated about every 70 years. However, in contrast in the last two decades of the twentieth century a dry situation appeared in north China and a wet climate predominated in the south part of the country. The multidecadal variations of the monsoon circulation in East Asia and the thermal contrast between inland Asia and its surrounding oceans may contribute to the dry-wet phase alternation or the migration of dry-wet anomalies. In regional scale variations, a consistent dry or wet pattern was observed spreading from the lower Yangtze River valley to South Korea. Frequencies of severe dry-wet situations were low in the eighteenth and nineteenth century and they were higher in the twentieth century. The recent increasing trend in frequencies of severe dry-wet chances occurred along with global warming and regional climatic changes in China. 相似文献
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东疆沙尘暴天气的分析 总被引：1，自引：0，他引：1
阿依夏木 《沙漠与绿洲气象(新疆气象)》2004,27(5):4-6
对1961～2001年东疆6个气象站沙尘暴资料的分析表明：东疆沙尘暴高发区在平原地区，主要出现在3～7月，4月份最多。沙尘暴多出现在午后到晚上，傍晚最多，持续时间多在1．5h之内。东疆局地和区域性沙尘暴天气过程，从80年代到90年代减少明显，年平均气温的升高和降水的增多是造成这种变化的主要因素。 相似文献
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气溶胶已是东亚地区最主要的大气污染物之一,其时空分布会受到东亚季风气候的影响。利用2000～2014年MODIS/AOD（Moderate-resolution Imaging Spectroradiometer/Aerosol Optical Depth）和NCEP月平均气象场再分析资料,本研究分析了东亚冬季风长期变化趋势、气溶胶年际变化规律,探讨了东亚冬季风强度变化对气溶胶分布的影响。基于MODIS/AOD,发现近10年东亚地区冬季AOD呈现上升趋势,最大值为2007年的0.44,高值区覆盖四川盆地、华北平原及长江中下游大部分地区。风场特征类冬季风指数分析表明,东亚冬季风存在明显的年际和年代际差异,近年出现逐渐减弱的趋势。强冬季风年,海陆气压差增大、东亚大槽加深增强,东亚地区偏北风异常,风场的增强将引导更多冷空气南下,从而给东亚大部分地区带来明显的降温天气;弱年相反。气象场差异引起气溶胶分布变化,强年较强的偏北风将气溶胶向南方输送,东亚地区AOD出现“北低南高”的空间分布;弱年偏北风较弱,导致气溶胶集中在华北平原一带,AOD出现“北高南低”的空间分布。 相似文献
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秋季区域海冰面积异常与冬季大气环流及东亚区域气候的关系 总被引：7，自引：0，他引：7
利用北极海冰面积资料和NCEP／NCAR再分析逐月高度场、风场资料以及中国160站气温资料，探讨秋季区域海冰异常与冬季大气环流及区域气候的关系，结果表明，秋季东西伯利亚海海冰的年际变化与北半球冬季大气环流及东亚冬季风有着密切的关系，秋季该海区海冰偏多（偏少），相应冬季东亚冬季风偏强（偏弱）；进一步分析发现秋季该海区海冰面积偏大（偏小），相应冬季中国大部地区气温明显偏低（偏高）。 相似文献
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东亚季风区夏季陆地生态系统碳循环对东亚夏季风的响应 总被引：3，自引：1，他引：2
东亚地区陆地生态系统的时空变率表现出明显的对季风气候的响应特征。使用EOF（经验正交分解）方法分析了AVIM2动态植被陆面模式离线模拟试验模拟的1953～2004年东亚季风区夏季陆地生态系统总初级生产力（GPP）、生态系统净初级生产力（NPP）、净生态系统初级生产力（NEP）、植被呼吸以及土壤呼吸的时空分布特点,探讨了东亚夏季风对陆地生态系统碳循环影响机制。研究发现,在强季风年,江淮地区高温少雨的特点限制了光合作用,造成GPP偏低;而华南地区在强季风年气候温暖湿润,利于植被生长,GPP偏高。季风对于植被呼吸和土壤呼吸影响不明显,使得GPP和植被呼吸之差NPP的变化及NPP和土壤呼吸之差NEP的变化与GPP的变化保持一致。在强季风年江淮流域地区干热的气候条件使得NPP和NEP降低;但是在华南地区温度升高的同时降水增多使得在NPP偏高的基础上NEP也偏高。 相似文献
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Close relationship between the East Asian westerly jet and Russian far East surface air temperature in summer 下载免费PDF全文
下载免费PDF全文 本文研究了夏季东亚副热带高空西风急流的年际变化与俄罗斯远东地面温度的关系并揭示了二者的相互作用机制。结果表明:副热带西风急流北侧环流与俄罗斯远东地区地面温度关系密切,二者存在着正反馈机制。一方面,急流北侧西风减弱(增强)可以通过关联的反气旋(气旋)式环流引起下沉(上升)运动,使得俄罗斯远东地区地面增温(降温)。另一方面,俄罗斯远东地区地面温度也能作为热源(热汇)在高层激发出反气旋式(气旋式)环流,导致急流北侧西风减弱(增强),进而影响急流的南北移动。这些结果揭示了俄罗斯远东地区地表状况的重要性,有助于进一步认识和提高东亚夏季气候的季度预测水平。 相似文献
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分析了7月东亚高空西风急流北跳和急流中心西移时我国雨带的变化特征,发现急流北跳与长江中下游梅雨结束有很好的对应关系;急流中心西移则与长江中下游梅雨结束无对应关系,但急流中心西移相对于急流北跳发生的早晚对雨带北移过程有重要影响:在急流中心西移晚于急流北跳发生年份,雨带北移依次为长江中下游地区—淮河流域—黄淮地区逐渐北推,其他年份雨带则从长江流域直接北跳至黄淮地区。进一步分析表明:(1)急流北跳和急流中心西移引起中纬度大气环流发生显著变化,从而引起西太平洋水汽输送发生显著变化,孟加拉湾水汽输送无变化。(2)急流北跳和急流中心西移时大气环流调整不同,导致来自西太平洋的水汽输送变化不同,进而对雨带北移产生不同的影响。急流中心西移相对于急流北跳发生时间早晚不同,大气环流调整过程和水汽输送调整过程也不同,使得雨带北推进程不同。 相似文献
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In this paper,the synoptic-climatology of Meiyu in East Asia is discussed.It is proposed that the location of the rain band of Meiyu is stable from the viewpoint of climatology,even though the active(wet)and break(dry)Meiyu are influenced by synoptic systems.The duration and the onset and retreat dates of Meiyu exhibit tremendous interannual variabilities,and thus,they are almost unpredictable in seasonal climate prediction.The Meiyu has been used as a synoptic concept and applied to the operational forecast for many decades by meteorological agencies in East Asian countries.As a result,the prediction of the onset and retreat dates of Meiyu has become an important operational work for meteorological services.This has also misled the public’s and scientists’attention.The northward propagation of the East Asian summer monsoon(EASM)surge associated with the intraseasonal oscillation is closely related to the active and break Meiyu.The activities and propagation of the EASM surge modulate the active/break Meiyu that cause concentrative severe precipitation processes and floods or droughts;hence,the authors suggest changing the current forecasting methodology of Meiyu.It is more meaningful from the scientific as well as application viewpoints to establish the monitoring and forecasting of the EASM surge to replace the current operational forecast of Meiyu after the seasonal progress enters the climatological Meiyu period in a year. 相似文献
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东亚季风近几十年来的主要变化特征 总被引：14，自引：4，他引：10
本文简要综述了关于东亚夏季风和冬季风近几十年来的主要变化特征的若干研究结果,特别是关于其年代际变化方面.夏季风及夏季气候的主要变化特征有:1970年代末之后东亚夏季风的年代际时间尺度的减弱以及相应的我国夏季降水江淮流域增多而华北减少、1992年之后我国华南夏季降水增多、1999年之后我国长江中下游夏季降水减少而淮河流域夏季降水增多、东亚夏季风和ENSO之间的年际变化相关性存在不稳定性.而关于东亚冬季风与冬季气候的主要变化特征有:1980年代中期之后东亚冬季风及其年际变率减弱、1970年代中期之后冬季风和ENSO的年际变化相关性较弱、近年来的北极秋季海冰减少对北半球冬季积雪增多有显著贡献、东北冬季积雪在1980年代中期以后增多.与上述变化有关的极端气候和物候都发生了多方面的变化. 相似文献
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In this study, the authors simulate the East Asian climate changes in the mid-Pliocene (～3.3 to 3.0 Ma BP) with the Community Atmosphere Model version 3.1 (CAM3.1) and compare the simulated East Asian monsoon with paleoclimate data. The simulations show an obvious warming pattern in East Asia in the mid-Pliocene compared with the pre-industrial climate, with surface air temperature increasing by 0.5 4.0°C. In the warm mid-Pliocene simulation, the East Asian Summer Monsoon (EASM) becomes stronger, while the East Asian Winter Monsoon (EAWM) is similar relative to the pre-industrial climate. Compared with the paleoclimate data, our simulations depict the intensified EASM well but cannot reproduce the weakened EAWM. This model-data discrepancy may be attributed to the uncertainty in the reconstructed mid-Pliocene sea surface temperature. 相似文献
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