Pressure level of maximum radiative heating enhancement in response to increasing CO_(2) over the global monsoon area

Based on the 1%CO_(2) experiment of CMIP6,in response to increasing CO_(2),the summer-mean radiative heating(RH)over the global monsoon area(MA)generally features an increasing response in the mid-troposphere and a decreasing response in the lower and upper troposphere.The pressure level of the maximum RH increase over the Asian MA is the highest and largest in range(500–775 hPa);the maximum increases over the North African,South American,and Australian MA are at 550–600 hPa;throughout the North American MA,the maximum heating increase is at 600 hPa;and the levels of the maximum over South Africa are 600 and 775 hPa.For most of the global MA,the maximum enhancement of RH is at 500,550,and 600 hPa.It is mainly led by the increase in cloud water at and above the maximum level and the decrease in cloud water below,which leads to similar changes in total cloud mass.Because of the longwave heating(cooling)effect at the cloud base(top),the RH enhancements peak at those levels.For the northeast part of the Asian MA and southeast part of the South African MA,RH enhancement peaks at 700 and 775 hPa,mainly attributable to the cloud water reduction below.The reduction leads to similar changes in total cloud.Due to the longwave cooling effect at the cloud top,the reduction contributes to the RH enhancement at the corresponding maximum levels.

Mid-Holocene Ocean Feedback on Global Monsoon Area and Precipitation

Mid-Holocene ocean feedback on global monsoon area, global monsoon precipitation(GMP), and GMP intensity(GMPI) was investigated by a set of numerical experiments performed with the Community Climate System Model version 4. Results showed that ocean feedback induced an increase in land monsoon area for northern Africa but a decrease for Asia and North and South America, and led to an increase in ocean monsoon area for the western Indian Ocean and southeastern Pacific but a decrease for the eastern Indian Ocean, tropical western Pacific, and tropical West Atlantic between the mid-Holocene and pre-industrial period. Dynamic oceaninduced changes in GMP and GMPI were 10.9×109 m3 d-1and-0.11 mm d-1 between the two periods, respectively.Ocean feedback induced consistent change between the Northern and Southern Hemisphere land or ocean but opposite change between land and ocean in the Northern or Southern Hemisphere monsoon areas for monsoon precipitation. The mid-Holocene summer changes in meridional temperature gradient and land-sea thermal contrast were the underlying mechanisms.

Temporal-Spatial Variances of Holocene Precipitation at the Marginal Area of the East Asian Monsoon Influences from Pollen Evidence

The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.

ROLE IN MOISTURE TRANSPORTATION OF SEASONAL MEAN AND INTRASEASONAL OSCILLATIONS IN ASIAN SUMMER MONSOON AREA——LONG-TERM AVERAGE CHARACTERISTICS

By use of the May—September 1980—1986 ECMWF daily data of u,v,r and T at 850 hPa,a comparative analysis is performed of basic features of moisture transportation at seasonal mean,quasi-40-day,-biweekly,and-weekly oscillations,indicating that the seasonal mean transfer plays a decisive role in the moisture flux over the Asian monsoon region,displaying the integer of the monsoon systems there in character;that the transport related to these tropical intraseasonal oscillations are of equal importance in the monsoon period except the difference in their behaviors,i.e.,the transfer shows considerable relative independence in the South-and East-Asian systems;and that the transport at all these intraseasonal oscillations is found to be feeble at equatorial latitudes with little or no influence on each other for both hemispheres.

Abnormality of the monsoon wind in the sea area along the southeasterncoast of China and the response of the northern areaof the South China Sea during the ENSO events

-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indicate that the monsoon wind is stronger in the summer and weaker in the winter than the normal by 1-1. 5 m/s during the events, and this anomaly will cause a decrease of the sea level by 7-11 cm . Changes of the wind field, therefore, is mainly responsible for a large negative anomalies of the sea level and SST there during the ENSO events.

Environmental record from the mud area on the inner continental shelf of the East China Sea since the mid-Holocene

Paleoclimate record was revealed in Core MZ01 covering the mid-Holocene in age,located in the mud area of the inner continental shelf of the East China Sea. The ancient environment featured low-energy shallow sea shelf deposition formed mainly by coastal currents. The results show that temporal variation in geochemistry corresponds with the climate changes inferred from historical record. Relatively low MgO/Al 2 O 3,CaO/K 2 O and high Al 2 O 3 /Na 2 O,K 2 O/Na 2 O,MnO/CaO values reflected a warm and humid climate in general,and vice versa. Therefore,these chemical indices could be applied to identify the variation of palaeoclimate in eastern China. The authors reconstructed the history of mid-Holocene climatic variation of the inner continental shelf of the East China Sea. From 8 300 a BP to 4 200 a BP,the climate was moderately warm and humid. From 4 200 a BP to 2 000 a BP,the climate turned cool and dry,and the regional climate frequently fluctuated in alternation of cool-dry periods（3 700 a BP,2 850 a BP and 2 400 a BP） and warm-wet periods（3 250 a BP and 2 650 a BP） . After 2 000 a BP,the climate of the study area gradually turned warm again,while the Little Ice Age,a cold event centered at around 250 a BP was indicated by those geochemical indices as mentioned above.

南海南沙海区沉积有机质分布特征及其指示意义

对现在过程的研究可为了解过去沉积环境演变信息提供重要线索。对南海南沙广阔海域23个现代表层沉积物样品总有机碳(TOC)、总氮(TN)含量及同位素组成(δ13CTOC和δ15N)进行测试分析,以期通过沉积有机质的现代组成分布特征为反演其历史时空分布变化规律及其驱动机制提供参考。南沙海区表层沉积物TOC/TN(5.5~7.9,平均为6.5±0.6)和δ13CTOC(–21.9‰~–18.7‰,平均为–21.0‰±0.7‰)揭示了沉积有机质主要来自海源贡献;δ13CTOC与TOC和TOC/TN的相关性分析表明了TOC未受明显的早期成岩作用影响,因此表层沉积物TOC可用于反映现代上层海水生产力状况。南沙海区表层沉积物TOC(0.32%~0.97%,平均为0.67%±0.17%)呈现明显的西-东向分布差异,高值主要位于西部前缘地带,低值主要分布在东部海域。表层沉积物TOC的地理分布特征表明了西南夏季风对南沙海域表层海水生产力的主要调控作用—由夏季风产生的越南上升流和湄公河陆源输入带来的高通量营养盐促进了西部前缘海域浮游植物的勃发,而随着站位距离的增加其施肥效应越来越弱。表层沉积物TOC和TN的强相关性(R2=0.95)以及δ15N的空间分布特征暗示了南沙海域沉积物δ15N未受陆源河流影响,记录了上层海水δ15N信号,从而指示了相关的氮循环过程。

近46年来中国东部季风区夏季气温变化特征分析

利用中国东部季风区375个测站夏季平均气温资料,分析季风区夏季气温的变化特征。结果表明:(1)近46 a东部季风区夏季气温年平均呈缓慢上升趋势,但淮河流域出现下降趋势;(2)夏季气温稳定性随纬度增加而减小;(3)季风区夏季气温年均增温率0.104℃/10 a,全区平均状况看,1970年代中期后开始表现明显上升趋势;(4)季风区夏季气温变化首先表现为全区一致的变化型,然后为南北反相变化型;(5)根据REOF分析将季风区夏季气温异常分6个气候空间类型,东北、华北、江南及华南均呈现上升增温趋势,西南地区增温缓慢,淮河流域则呈现与全球变暖不一致的降温趋势。

青藏高原的热力和动力作用对亚洲季风区环流的影响

利用NCEP/NCAR再分析资料,研究了青藏高原热状况的季节变化、动力和热力作用对周围环流,特别是对亚洲热带季风环流的影响。高原对西风带的机械作用在冬季最强,春季次之。冬季的机械作用形成以高原为主,南侧气旋性、北侧反气旋性的"偶极子"偏差环流,它比传统认识的爬坡、绕流的影响范围大得多,遍及东亚的高、低纬度。随着西风带的北移和高原总加热在4月由负变正,南侧气旋性偏差环流增强并逐渐北移,6月形成气旋盘踞整个高原的夏季型。在高原南侧,高原冬季偶极型、夏季加热的作用导致孟加拉湾地区常年存在印缅槽,使得印度半岛的感热加热始终强于中南半岛,而中南半岛上空的潜热加热大于印度半岛。印缅槽的演变存在明显的半年周期,证明2月初和8月初的较强低压槽分别对应冬季高原最强的动力强迫和夏季高原最强的热力强迫。对低纬经向风场的分析还表明,季风爆发前高原的热力作用尤为重要,是导致江南春雨的形成,亚洲季风最早在孟加拉湾东部爆发,最后在印度半岛爆发的原因。

我国东部季风区冬季气温的气候变暖特征

利用我国东部季风区375个测站1961—2006年平均地面气温资料,采用线性趋势分析、EOF,REOF,Mann-Kendall、小波分析等方法,分析了季风区冬季气温异常变化规律。结果表明:我国东部季风区冬季气温增温明显,近46年增温率为0.39℃/10a,增温率从南向北增大,黄河南部气温的稳定性高于北部,增温不显著的区域主要在季风区的南部,川东和云南局部有显著的下降趋势。根据REOF分析将该区冬季气温异常细分为南、中、北部区3个分区,各区气温异常变化存在准5年和22年周期,从20世纪70年代初期开始气温转为上升,普遍在1986—1987年发生了突变,在21世纪初气温开始回落。异常偏暖年大部分出现在1990年以后。

猪野泽记录的季风边缘区全新世中期气候环境演化历史

通过季风边缘区石羊河古终端湖猪野泽QTL剖面年代学及沉积物粒度、碳酸盐、有机碳、碳氮比和有机质稳定同位素等多项气候代用指标的综合分析,建立了季风边缘区9～3cal.kaB.P.的古气候演化序列。结果表明,9cal.kaB.P.到7.8cal.kaB.P.期间,流域的水分条件和温度逐渐上升,植被状况好转,此时气候逐渐转暖湿;而在7.8～7.5cal.kaB.P.出现了显著的百年尺度的干旱事件,沉积物主要以砂质沉积为主,此时湖泊生产力显著下降;全新世期间最为暖湿的气候适宜期出现在7.5～5.0cal.kaB.P.;约5.0cal.kaB.P.以来,该区域出现了较为明显的干旱化趋势。另外,对猪野泽地区的白碱湖的湖泊地貌学和年代学研究表明该区域在7.5～5.0cal.kaB.P.出现了3次高湖面,并且湖岸堤时序变化指示了全新世后半期湖泊逐渐退缩的过程进而指示该区域出现了显著的干旱化趋势。

环境因子对长江口滨岸沉积物反硝化速率影响

利用多年在长江河口滨岸湿地开展相关研究工作获得的反硝化速率和各类环境参数数据,对数据进行归纳整理,采用相关性分析和主成分分析,将沉积物反硝化作用和环境因素间的相关性进行量化,并筛选出影响长江口沉积物反硝化作用的两大重要因素。研究表明沉积物反硝化速率和温度(T)、沉积物有机碳(SOC)、总氮(STN)呈现Pearson正相关关系(p70.01,p70.05,和p70.05),与水中盐度(S)、溶解氧(DO)及沉积物C/N呈明显负相关关系(p70.05,p70.05,和p70.01)。尽管沉积物中的N_2O自然产生速率和环境参数间没有表现出相关性,但沉积物的反硝化速率和N_2O的自然产生速率却和C/N呈明显负相关(p70.01)。主成分分析结果表明温度和盐度是影响长江口潮滩沉积物反硝化速率的两大主导因素,同时也是亚热带季风河口的主要环境参数。

亚澳中低纬度区域暴雨天气系统研究

以跨越南北半球的亚澳季风区内的暴雨等灾害天气系统为主要讨论内容,分析了影响这一地区的环流和天气系统的主要特征以及它们之间的异同,这对深入了解该区域内季风的影响和降水系统的机理提供了帮助。同时,对于预报的改进也是有益的。

中国东部季风区春季气候的变暖特征

利用中国东部375个测站1961—2006年地面气温资料,采用线性趋势分析、EOF、REOF、Mann-Kendall、小波分析等方法,分析了季风区春季的气候变暖特征。结果表明:季风区春季增温显著,近46 a增温率为0.25℃/(10 a)。从1989年开始增温,1996年有一次显著突变。以38°N为界,气温变化的稳定性是南部高于北部。增温率从南向北增大,增温不显著的区域主要在长江以南;根据EOF分析,该区春季气温异常可分为全区一致型、江南江北相反型、中原型3种常见分布模态。根据REOF又进一步将该区春季气温异常细分为中部、南部、北部3个区。全区性的前10个偏暖年,全部出现在1990年代以后。气温异常变化存在准4年和22年的周期,气温的转折北部比中、南部早,但北部从1990年代末期开始转为下降;北部区和中部区分别在1981、1997年发生了突变,南部突变不明显;蒙古高压是影响春季气温的主要大气活动中心,高压强度从1980年代后期以来有明显减弱趋势,造成入侵东部的偏北冷空气减弱,是春季气候变暖的可能机理。

中国东部季风区末次冰期以来古气候模拟

通过对我国东部季风区现代表土样品孢粉组合与气候因子之间的回归分析，分别建立了孢粉组合与一月、七月气温和年降水量的转换函数，进而建立了本区末次冰期以来的孢粉－气候数据库，模拟了末次冰期盛冰期、消冰期、全新世前北方期－北方期、大西洋期、亚北方期等五个古气候期的冬季和夏季温度场、降水场。结果表明：１）本区气候变率与全球气候变率明显不同。其中，末次冰期盛冰期的降温幅度低于欧洲大陆，而全新世高温期的升温幅度则比欧洲大；２）无论末次冰期还是全新世各气候期，气温和降水量的纬度地带性规律仍然存在，表现在气温的南高北低和降水量的南多北少；３）各气候转型期，本区气候湿热组合特征也与现代一致，表现为雨热同期。

利用封闭湖泊流域进行古降水量重建的历史、现状及未来

回顾了利用封闭湖泊流域进行古降水量重建的简单历史,重点论述了其理论与方法的特点及发展源流;在此基础上,结合作者近几年在青藏高原开展的这方面的研究工作,对季风区进行此项研究的可能方法、理论依据及其初步应用进行了分析,重点阐述了其存在的缺点与不足及未来的改进方式。

青藏高原的热力和机械强迫作用以及亚洲季风的爆发 Ⅱ.爆发时间

本研究的第Ｉ部分用资料分析证明，由于青藏高原的热力强迫和动力强迫，１９８９年亚洲季风首先在孟加拉湾（ＢＯＢ）东岸爆发，接着才有南海（ＳＣＳ）季风爆发和印度季风爆发。在亚洲季风爆发的这三个阶段中，每阶段都伴有高原上空气柱的急速升温。本文是第Ｉ部分的继续。它指出：高原上空气柱的每一次急速升温都与中高纬度源于地中海上空的、频率为２～３周的低频（ＴＴＯ）暖脊东传到高原上空相联系。季风爆发的每一阶段都伴有从南半球向北传播的、频率为３０～６０天的低频（ＭＪＯ）散度扰动和从热带西太平洋向西传播的、频率为２～３周的低频（ＴＴＯ）散度扰动。当这些低频扰动的暖位相和上升位相在所定义的“东亚季风区”（ＥＡＭＡ）锁相时，亚洲季风阶段性爆发出现。

RCP4.5情景下中国季风区及降水变化预估

本文使用国际耦合模式比较计划第五阶段（CMIP5）中共46个全球气候模式的数值试验结果，通过对中国区域的年、夏季和冬季降水气候态的模拟能力评估，择优选取了18个气候模式用来预估RCP4.5情景下21世纪中国季风区范围、季风降水及其强度变化。结果表明，相对于1986～2004年参考时段，RCP4.5情景下多数模式和所有模式集合平均在不同时段内均模拟出中国季风区面积、季风降水及其强度的增加趋势，最明显的时段出现在2081～2099年。其中，季风区面积扩张是导致季风降水增加的主要因素。在机制上，热力与动力条件变化均有利于季风降水强度的增加以及更多的水汽进入中国东部，从而引起季风区范围的扩大。

1961～2009年中国季风区范围和季风降水变化

东亚季风对中国气候和环境有重要影响,以往研究多关注于季风环流和人为给定区域内夏季降水的变化,对于季风区域变化本身及其相伴的季风降水鲜有涉及.本文使用四套降水观测资料,其中包括基于2416个台站最新资料所得到的中国区域高分辨率降水格点数据,集中分析了1961～2009年中国季风区范围、季风区西北边界、季风降水及其强度变化.结果表明,季风区约占中国陆地面积的60％,研究时段内总体上在缩少;季风降水无趋势性变化而是表现为一定的年际和年代际变率;中国季风降水强度平均为4.46 mm d-1.季风区西北部的东、西边界间区域属于典型的干湿交错带,季风区西北边界在40°N以南整体上表现为-0.026°/a的西进趋势,而在其北部则表现为0.041°/a的东退,这主要是源于区域尺度热力对比、大气环流和水汽通量的变化所致.

河北坝上地区湖泊沉积物记录的中全新世干旱气候

根据位于典型草原带的河北坝上地区白诺尔及毗邻的内蒙古乌兰诺尔湖泊沉积物的K、Na、Ca、Mg等化学元素组成、总有机碳（TOC）与氧同位素（δ^18O）的分析，以（K＋Na＋ca＋MS）／（Fe＋Mn）值指示干旱度，δ^18O值指示夏季风的强弱，TOC值指示湖区植被状况，探讨了该地区^14C测年9．8～5．3kaB．P．以来的气候变化与环境变迁。结果表明：两个剖面所记录的气候变化趋势相近，^14C测年7．0～5．7kaB．P．为偏于期。反映夏季风强弱的氧同位素指标与干旱程度的变化没有明显的对应关系，说明夏季风引起的降水量变化不是气候干湿变化的主要影响因子，温度升高导致的蒸发加强可能对气候干旱化的影响更加明显。