大高加索山南部大气降水氧同位素的气候意义

大高加索山脉位于黑海和里海之间,是欧洲与亚洲的分界线,该区域气候受到北大西洋涛动 (North Atlantic Oscillation, NAO)的强烈影响。为了对该区域的大气降水δ18O (δ18OP) 与NAO的关系有更加深入的认识,本文利用大高加索山以南6个全球降水同位素监测网(Global Network of Isotope in Precipitation, GNIP)站点的δ18OP数据,分析该区域δ18OP 的季节变化规律,以及δ18OP与温度和降水量等气象要素及大气环流之间的关系。得到以下主要认识:① 在月时间尺度上,δ18OP与月平均温度之间有着显著的正相关关系(p<0.01),表明该区域δ18OP主要受当地温度控制,表现出“温度效应”。② 北大西洋涛动通过改变西风的强度和位置从而影响δ18OP 的变化:当NAO呈现负相位时,此时西风输送较弱,使得来自地中海的富含18O的水汽能够达到大高加索山以南,该地区δ18OP偏正。而当NAO正相位时,西风急流输送较强,从北大西洋穿越黑海带来更多的δ18OP 偏轻的降水。因此,NAO所导致的水汽输送路径的变化可能是影响大高加索山以南地区δ18OP的重要因素,这一研究结果为利用该地区地质记录中的δ18O记录来重建过去的NAO变化提供了前提。      

Temporal Change Characteristics of Climatic and Its Relationships with Atmospheric Circulation Patterns in Qinghai Lake Basin

Based on monthly meteorological data from 11 stations(1959-2015)in Qinghai Basin(QHB) and its surrounding area, we analyzed monthly average temperature(Tmean), average maximum(TXam), minimum temperature(TNam) and precipitation variation characteristics as well as the influence of atmospheric oscillation on these parameters using Mann-Kendall trend analysis, mutation analysis, continuous Morlet wavelet transform, Pearson correlation analysis and R/S analysis method. In addition, the future trend of climate change in the regional scale was also discussed. We found that the temperature and precipitation increment were obvious in the region, especially the Tmean in autumn, winter, TXam and TNam in summer and winter precipitation showing significant increase. Temperature and precipitation experienced abrupt changes around 1986 and 2002, respectively. The period of oscillation of each temperature indices was similar featuring 2~3 years,8~10 years short- cycle and 30~32 years middle- cycle, while that for the precipitation featured 3~4 years,6~7 years short- cycle and 30~32 years middle- cycle. The East Asian Summer Monsoon Index(EASMI) anomaly is an important factor for the anomaly of autumn temperature and summer precipitation in QHB, while the Indian Summer Monsoon Index(ISMI) mainly affects the spring temperature and precipitation in the research area. The effects of Arctic Oscillation Index (AO) were relatively strong on temperature variation, especially in autumn and winter, and AO had significant effect on the precipitation in spring, summer and winter, too. The North Atlantic Oscillation Index (NAO) and ENSO have weak influence on the study area, NAO mainly affects summer and winter precipitation, while ENSO mainly affects autumn precipitation. The Hurst index of Tmean and annual precipitation in QHB are higher than 0.5, indicating that the temperature and precipitation in the study area will continue to be the positive trend in the future period.     

Link of ocean deep water thermohaline anomalies with atmospheric state anomalies in the Northern Atlantic

Anomalies of thermohaline characteristics of the ocean deep waters formed in the subpolar North Atlantic are shown to be controlled by the natural oscillations of the atmospheric state in the region, i.e., the North Atlantic Oscillation (NAO). A general mechanism behind the NAO effect on the deep water temperature and salinity on a decadal time scale is proposed. The main factors determining the close link of the deep water thermohaline anomalies and the NAO are the zonal extension of the subpolar gyre and the wintertime deep convection intensity in the Labrador Sea.     

Global surface temperature in relation to northeast monsoon rainfall over Tamil Nadu

The local and teleconnective association between Northeast Monsoon Rainfall (NEMR) over Tamil Nadu and global Surface Temperature Anomalies (STA) is examined using the monthly gridded STA data for the period 1901–2004. Various geographical regions which have significant teleconnective signals associated with NEMR are identified. During excess (deficient) NEMR years, it is observed that the meridional gradient in surface air temperature anomalies between Europe and north Africa, in the month of September is directed from the subtropics (higher latitudes) to higher latitudes (subtropics). It is also observed that North Atlantic Oscillation (NAO) during September influences the surface air temperature distribution over north Africa and Europe. Also, the NAO index in January shows significant inverse relationship with NEMR since recent times. The central and eastern equatorial Pacific oceanic regions have significant and consistent positive correlation with NEMR while the western equatorial region has significant negative correlation with NEMR. A zonal temperature anomaly gradient index (ZTAGI) defined between eastern equatorial Pacific and western equatorial Pacific shows stable significant inverse relationship with NEMR     

青藏高原初春积雪的多尺度变化与北大西洋海温的关系

青藏高原冬、春季积雪变化影响东亚甚至全球春、夏季的环流及气候异常。利用中国西部环境与生态科学数据中心提供的中国雪深长时间序列数据集,美国大气海洋局提供的全球逐月扩展重建海表温度,以及欧洲中期天气预报中心提供的逐月再分析数据,对青藏高原初春（3、4月）积雪的多尺度变化与北大西洋海表温度的关系进行了研究。结果表明,初春青藏高原雪深异常与初春北大西洋关键区海温异常有显著的负相关关系。当初春关键区海温正（负）异常时,初春高原中部偏北腹地地区、东南部地区积雪深度减少（增加）;初春北大西洋关键区海温异常通过激发下游青藏高原上空大气波列以及波作用通量异常来影响高原局地区域的温度和垂直运动,从而影响降雪的产生和积雪的累积。该结果为青藏高原初春积雪的多尺度变化及其影响提供了依据。     

巴伦支-喀拉海海温和青藏高原冬季地表气温的年代际联系

基于1961—2017年中国气象局地表气温数据、JRA-55大气再分析数据以及美国国家海洋和大气管理局延伸重建的海温资料,研究了青藏高原冬季地表气温的年代际变化特征及其与海温的可能联系。结果表明：巴伦支-喀拉海冬季海温年代际变化可以激发出向东传播的Rossby波,在西伯利亚对流层高层产生异常的气旋或反气旋性环流,通过影响副极地以及副热带西风急流强度,在青藏高原的南侧产生异常的反气旋或气旋性环流,从而使得青藏高原上空的垂直运动发生变化,导致青藏高原冬季地表气温异常。     

Rare Earth Elements in Egyptian Phosphorites

Egyptian phosphorites from Abu Tartur(Western Desert),El Mahamide mine(Nile Valley) and Rabah mne(Eastern Desert)show variable degrees of relative REE enrichment.Black plateau phosphorites of Abu Tartur are substantially enriched in REE as compared to the Red Sea and Nile Valley phosphorites.P-rich organic matter from the Abu Tartur and Rabah mines recorded negative Ce and positive Eu anomalies.Positive Eu anomaly reveals an anoxic event prior to the phase of Late Cretaceous phosphate formation.Ce is a redox indicator.Mixing of sea water and upwelling during the Late Cretaceous was responsible for the recording of positive Eu and negative Ce anomalies in the Egyptian phosphorites.     

1880年以来的全球升温趋势探究

由于导致全球温度异常的因素的多样性,使得至21世纪末全球温度是否将持续上升存在较大的不确定性.文章基于新兴的非数值算法的遗传算法,对1880～2009年全球温度异常数据,做了驱动因子挖掘,将全球温度异常分解为人类活动的碳排放造成的温度波动和全球气候系统自然振动的温度波动两部分.研究发现,当前全球气候系统存在持续变暖的趋...     

Meteorological fields variability over the Indian seas in pre and summer monsoon months during extreme monsoon seasons

In this study, the possible linkage between summer monsoon rainfall over India and surface meteorological fields (basic fields and heat budget components) over monsoon region (30‡E-120‡E, 30‡S30‡N) during the pre-monsoon month of May and summer monsoon season (June to September) are examined. For this purpose, monthly surface meteorological fields anomaly are analyzed for 42 years (1958-1999) using reanalysis data of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research). The statistical significance of the anomaly (difference) between the surplus and deficient monsoon years in the surface meteorological fields are also examined by Student’s t-test at 95% confidence level. Significant negative anomalies of mean sea level pressure are observed over India, Arabian Sea and Arabian Peninsular in the pre-monsoon month of May and monsoon season. Significant positive anomalies in the zonal and meridional wind (at 2 m) in the month of May are observed in the west Arabian Sea off Somali coast and for monsoon season it is in the central Arabian Sea that extends up to Somalia. Significant positive anomalies of the surface temperature and air temperature (at 2 m) in the month of May are observed over north India and adjoining Pakistan and Afghanistan region. During monsoon season this region is replaced by significant negative anomalies. In the month of May, significant positive anomalies of cloud amount are observed over Somali coast, north Bay of Bengal and adjoining West Bengal and Bangladesh. During monsoon season, cloud amount shows positive anomalies over NW India and north Arabian Sea. There is overall reduction in the incoming shortwave radiation flux during surplus monsoon years. A higher magnitude of latent heat flux is also found in surplus monsoon years for the month of May as well as the monsoon season. The significant positive anomaly of latent heat flux in May, observed over southwest Arabian Sea, may be considered as an advance indicator of the possible behavior of the subsequent monsoon season. The distribution of net heat flux is predominantly negative over eastern Arabian Sea, Bay of Bengal and Indian Ocean. Anomaly between the two extreme monsoon years in post 1980 (i.e., 1988 and 1987) shows that shortwave flux, latent heat flux and net heat flux indicate reversal in sign, particularly in south Indian Ocean. Variations of the heat budget components over four smaller sectors of Indian seas, namely Arabian Sea, Bay of Bengal and west Indian Ocean and east Indian Ocean show that a small sector of Arabian Sea is most dominant during May and other sectors showing reversal in sign of latent heat flux during monsoon season.     

Air-sea interaction over the tropical Indian Ocean during several contrasting monsoon seasons

Monthly mean anomaly fields of various parameters like sea surface temperature, air temperature, wind stress, effective radiation at the surface, heat gain over the ocean and the total heat loss between a good and bad monsoon composite and the evaporation rates over the Arabian Sea and southern hemisphere have been studied over the tropical Indian Ocean. The mean rates of evaporation on a seasonal scale over the Arabian Sea during a good and bad monsoon composites were equal (about 2·48 × 10¹⁰ tons/day). The evaporation rates over the southern hemisphere were greater during all the months. The mean evaporation rates over the southern hemisphere on a seasonal scale for the good and bad monsoon composites were 4·4 × 10¹⁰ and 4·6 × 10¹⁰ tons/day respectively. The maximum evaporation rates over the southern hemisphere were observed in August. The anomalies of wind stress, effective radiation at the surface and the heat gain over the ocean also exhibit large variations in August, as compared to other monsoon months.     

Inter-decadal Variability in Phytoplankton Community in the Middle Adriatic (Kaštela Bay) in Relation to the North Atlantic Oscillation

Evaluation of a 45-year data set of primary production (PP), a 30-year data set of phytoplankton biomass, and a 51-year data set of species composition shows an increase of phytoplankton biomass and abundance in the period from the mid-1980s to the mid-1990s. Phytoplankton biomass showed bimodal seasonal cycles, with winter and spring maxima, which did not change over the past 30 years. Diatoms were the most abundant functional group and they prevailed during the colder part of the year while the dinoflagellate contribution to the phytoplankton community increased in the warmer period from May to August. Diatoms showed a significant negative correlation with sea surface temperature (SST), while dinoflagellates were positively correlated with SST. An increase of phytoplankton abundance, particularly dinoflagellate, in the period from the mid-1980s to the mid-1990s coincided with years characterized by a high North Atlantic Oscillation (NAO) index. Primary production and chlorophyll a concentration in the spring period were negatively correlated with the NAO winter (DJFM) index, probably caused by increased precipitation associated with a low or negative NAO index. PP in winter during the mixing period was positively related to the NAO winter index associated with higher temperatures and dry conditions which brought more clear days and increased input of solar radiation.     

Tropospheric biennial oscillation and south Asian summer monsoon rainfall in a coupled model

In this study Tropospheric Biennial Oscillation (TBO) and south Asian summer monsoon rainfall are examined in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. High correlation between the observations and model TBO index suggests that the model is able to capture most of the TBO years. Spatial patterns of rainfall anomalies associated with positive TBO over the south Asian region are better represented in the model as in the observations. However, the model predicted rainfall anomaly patterns associated with negative TBO years are improper and magnitudes are underestimated compared to the observations. It is noted that positive (negative) TBO is associated with La Niña (El Niño) like Sea surface temperature (SST) anomalies in the model. This leads to the fact that model TBO is El Niño-Southern Oscillation (ENSO) driven, while in the observations Indian Ocean Dipole (IOD) also plays a role in the negative TBO phase. Detailed analysis suggests that the negative TBO rainfall anomaly pattern in the model is highly influenced by improper teleconnections allied to IOD. Unlike in the observations, rainfall anomalies over the south Asian region are anti-correlated with IOD index in CFSv2. Further, summer monsoon rainfall over south Asian region is highly correlated with IOD western pole than eastern pole in CFSv2 in contrast to the observations. Altogether, the present study highlights the importance of improving Indian Ocean SST teleconnections to south Asian summer rainfall in the model by enhancing the predictability of TBO. This in turn would improve monsoon rainfall prediction skill of the model.     

近400年澜沧江源区年平均流量周期特征及其对厄尔尼诺的响应

本文基于重建的1595~2006年澜沧江源区年平均流量(澜沧江流量)和NOAA古气候资料,应用MTM-SVD方法对澜沧江流量周期变化规律及其对厄尔尼诺的响应进行了分析。结果表明,近400年澜沧江流量与厄尔尼诺有显著负相关,在年代际的13.5年和年际的5年周期上存在显著协同变化,并且分别对当年春末和上年秋初的大气环流有很好的响应。在13.5年和5年典型循环过程中,二者都表现出反位相的对应关系,当厄尔尼诺指数偏低(高)时,澜沧江流量偏多(少)。但是进一步分析海温异常空间分布,发现在13.5年周期中,澜沧江流量主要受中部型厄尔尼诺事件影响,而在5年周期循环中,澜沧江流量则主要受东部型厄尔尼诺事件调控。在13.5年典型周期循环中,中部型厄尔尼诺会引起双圈沃克环流异常,同时激发PJ(太平洋-日本涛动)遥相关波列,并影响澜沧江源区气温和降水,从而导致澜沧江流量异常;在5年周期循环中,东部型厄尔尼诺会引起单圈沃克环流异常,同时激发EU(欧亚)遥相关波列,进而影响澜沧江流量变化。     

Magmatism of the Weddell Sea rift system in Antarctica: Implications for the age and mechanism of rifting and early stage Gondwana breakup

Thick (∼800 m) basaltic successions from the eastern Antarctic Peninsula have been dated in the interval 180–177 Ma and preserve a transition from a continental margin arc to a back-arc extensional setting. Amygdaloidal basalts from the Black Coast region of the eastern margin of the Antarctic Peninsula represent a rare onshore example of magmatism associated with back-arc extension that defines the early phase of Weddell Sea rifting and magmatism, and Gondwana breakup. The early phase of extension in the Weddell Sea rift system has previously been interpreted to be related to back-arc basin development with associated magnetic anomalies attributed to mafic-intermediate magmatism, but with no clearly defined evidence of back-arc magmatism. The analysis provided here identifies the first geochemical evidence of a transition from arc-like basalts to the development of depleted back-arc basin basalts in the interval 180–177 Ma. The exposed Black Coast basaltic successions are interpreted to form a minor component of magmatism that is also defined by onshore sub-ice magnetic anomalies, as well as the extensive magnetic anomalies of the southern Weddell Sea. Back-arc magmatism is also preserved on the Falkland Plateau where intrusions postdating 180 Ma are associated with early phase rifting in the Weddell Sea rift system. Back-arc extension was probably short-lived and had ceased by the time the northern Weddell Sea magmatism was emplaced (<175 Ma) and certainly by 171 Ma, when an episode of silicic magmatism was widespread along the eastern Antarctic Peninsula. Previous attempts to correlate mafic magmatism from the eastern Antarctic Peninsula to the Ferrar large igneous province, or, as part of a bimodal association with the Chon Aike silicic province are both dismissed based on age and geochemical criteria.     

珠江流域降水干湿时空特征及气候因子影响研究

利用模糊C-均值聚类算法、皮尔逊相关和滑动相关分析等方法,对珠江流域做了气候一致性分析,在此基础上,研究了珠江流域不同分区年降水和干湿季降水变化的时空特征,分析了区域干湿变化与厄尔尼诺-南方涛动(ENSO)、北大西洋涛动(NAO)、印度洋偶极子(IOD)和太平洋10年涛动(PDO)等主要气候因子的遥相关关系,探讨了珠江流域干湿变化的气候成因。在此基础上,进一步研究上述气候指标对不同时间尺度干湿变化影响的平稳性与差异性。除此之外,还研究了气候指标的冷暖期对基于6个月SPI值的珠江流域干湿状态的影响。研究表明:(1)IOD、NAO和ENSO分别是导致珠江流域年降水、湿季降水和干季降水发生变化的主要影响因素,且对当年及下一年降水的影响是相反的。(2)珠江流域不同时间尺度的降水与对其有显著影响的气候指标(年降水与IOD,湿季降水与NAO,干季降水与ENSO),两者之间不同时期的滑动相关往往具有较强的相关性和前后相关一致性。(3)各气候指标对珠江流域不同时间尺度降水的影响在空间分布上不太均匀。(4)不同位相下气候指标对珠江流域干湿状态的影响存在较大差异。总体而言,当处于各气候指标暖期时珠江流域出现湿润期的概率较冷期时更大且在空间分布上更均匀。     

青海冬季区域持续性低温事件变化及成因分析

利用1961 - 2017年青海省43站逐日最低气温观测资料, 依据区域持续性低温事件判识标准, 提取历史上61次典型事件, 对影响该类事件的环流演变和前兆信号进行分析。结果表明： 事件发展中北半球极涡经历分裂 - 收缩增强的变化过程, 中高纬自西向东逐渐发展为“正 - 负 - 正”异常波列状分布; 事件发生当日, 大西洋地区、 乌拉尔山及西伯利亚地区高度场异常偏高, 东亚大槽偏深, 利于自极地南下的冷空气在西欧上空堆积并沿纬向西风急流路径向东传播影响东亚地区。进一步分析表明, 当出现该类事件时, 中高纬地区存在三个关键影响区, 其中乌拉尔山关键区高度场正异常同此类事件的联系最紧密。     

青藏高原东北缘瑞利面波成像：射线理论与程函方程结果的比较

青藏高原东北缘是青藏高原隆升的前缘地带,其构造变形特征一直是研究的热点。前人在该区域进行过面波成像研究,但不同结果存在较明显的差异,可能与不同成像方法的分辨率有关,此次研究分别使用基于射线的方法和基于程函方程的方法进行了瑞利波相速度成像。笔者对比了20 s、30 s和60 s的成像结果,两种方法的结果表现出相似的速度特征。总体的速度特征与研究区域的主要构造单元分布相吻合,青藏高原东北缘表现出低速异常,鄂尔多斯块体表现出高速异常。在银川河套地堑,基于程函方程的成像在20 s和30 s得到更明显的低速异常,低速异常体的分布与地堑的轮廓吻合更好,说明基于程函方程的方法对数据利用更充分。     

Did postglacial catastrophic flooding trigger massive changes in the Black Sea gas hydrate reservoir?

After the Last Glacial Maximum, the semi-land-locked Black Sea basin was flooded by warm water from the Mediterranean Sea. This major sea level rise and change of physical water properties had a large impact on the gas hydrate reservoir in the sediments below. Modelling of the regional response of the gas hydrate stability zone (GHSZ) to the Black Sea flooding 7100 years ago shows that a strong effect of near-bottom temperature increase pushes the gas hydrate reservoir to a large shrinking of 15–62% that may release up to 1.1–4.6 Gt of methane. This catastrophic scenario is, however, delayed because of the transient nature of the heat wave propagation. The large-scale reduction of the GHSZ is only to take place within the next thousand years. At present, widespread hydrate dissociation is only expected to occur where there is a minimum water depth for hydrate stability.     

Structural relationship between the Sea of Marmara Basin and the North Anatolian Fault Zone

The North Anatolian Fault (NAF) zone is 1500 km long, extending almost up to the Greek mainland in the west. It is a seismically active right-lateral strike-slip fault that accommodates the relative motion between the Turkish block and Black Sea plate. The Sea of Marmara lies along the western part of the NAF and shows evidence of subsidence. In this area pure strike-slip motion of the fault zone changes into extensional strike-slip movement that is responsible for the creation of the Sea of Marmara and the North Aegean basins. The northern half of the Sea of Marmara is interpreted as a large pull-apart basin. This basin is subdivided into three smaller basins separated by strike-slip fault segments of uplifted blocks NE-SW. Basinal areas are covered by horizontally layered sedimentary sequences. Uplifted blocks have undergone compressional stress. All the blocks are subsiding and are undergoing vertical motions and rotations relative to one another. The uplifted blocks exhibit positive Bouguer gravity anomalies. According to gravity interpretation, there is relative crustal thinning under the Sea of Marmara. The northern side of the Sea of Marmara is marked by a distinctive deep-rooted magnetic anomaly, which is dissected and shifted southward by strike-slip faulting. The southern shelf areas of the Sea of Marmara are dominated by short-wavelength magnetic anomalies of shallow origin.     

Geostatistical method to delineate anomalies of multi-scale spatial variation in hydrogeological changes due to the ChiChi earthquake in the ChouShui River alluvial fan in Taiwan

This study uses Ordinary Kriging (OK), Sequential Gaussian Simulation (SGS) and Simulated Annealing Simulation (SAS) to relocate the completely heterotopic dataset from the locations of the Standardized Satellite Oriented Control Point System (SSOCPS) stations to the Groundwater Monitoring Networks (GMNS) stations and factorial kriging to analyze and map relationships among seven variables, including the hydraulic conductivities of three aquifers, the vertical displacements of the ground and groundwater level changes in the wells of three aquifers, and also to delineate the anomalies of multi-scale spatial variation of hydrogeological properties associated with the ChiChi earthquake, measuring 7.3 on the Richter scale, in the ChouShui River alluvial fan in Taiwan. In this study, the anomalies of spatial variation of hydrogeological properties associated with the earthquake are illustrated at micro, local and regional scales of 9, 12 and 36 km, respectively. In the study area, regionalization components associated with variation at local and regional scales are obtained and mapped by factorial kriging. Factorial Kriging Analysis (FKA) also demonstrated that the main effects of the ChiChi earthquake on the spatial variations of groundwater hydrological changes include porous media compression at micro scale, hydrogeological heterogeneousness of the sediments within the aquifer at local scale and the cyclic loading of deviatoric stress at regional scale. Finally, maps of spatial variations of regional components fully depicted all of the anomalies of spatial variation of hydrogeological changes due to the ChiChi earthquake and can be used to identify, confirm and monitor the hydrogeological properties in this study area.