关于南海暖水季节和年际变化的研究

阐述了研究南海暖水的意义,综述了关于南海暖水的现状,提出了关于南海暖水季节和年际变化方面应该研究的问题。     

南海Sverdrup环流的季节变化特征

利用气候平均的风应力资料,计算了平底南海内区海盆尺度的Sverdrup输送,得到南海海盆尺度Sverdrup环流的季节变化基本特征.将这些基本特征与历史观测资料相比,证实了在冬、夏、秋季风生环流在南海表层环流中的重要地位.明确指出风的非均匀性是南海海盆尺度环流呈现多中心的重要原因之一,秋、冬季南海北部18°N纬带处的西向强流可仅由局地风生成,南海南部环流比北部环流具有更明显的季节变化,春季风场有利于在海盆的中部发生环流的季节转换,秋季气旋式环流的向北输送最大.     

洪泽湖地区杨树人工林碳水通量昼夜和季节变化特征

【目的】通过对洪泽湖地区杨树人工林生态系统碳水通量的昼夜变化和季节变化特征进行分析,为评估该杨树人工林生态系统的固碳能力提供必要的基础数据,揭示杨树人工林生态系统碳循环及对外部气象环境因子的响应,同时为增强森林生态系统固碳能力提供依据。【方法】以洪泽湖地区杨树人工林生态系统为研究对象,利用涡度相关技术和微气象观测系统进行长期且连续的通量以及气象环境观测。选取2017年5月至2018年4月期间的原始观测数据,对异常数据进行剔除和插补处理,同时,利用EddyPro软件中的Express Mode模块对通量数据进行二次坐标旋转、频率损失订正以及WPL密度效应修正,最终转化为30 min数据。分析杨树人工林生态系统与大气间的二氧化碳(CO₂)、甲烷(CH₄)和潜热(latent heat, LE)通量的季节动态变化和昼夜变化特征及其与外部气象环境因子的相互关系。【结果】洪泽湖地区杨树人工林生态系统碳通量均有显著的昼夜和季节变化,净生态系统碳交换(net ecosystem exchange, NEE)白天为较强的碳汇,夜晚为较弱的碳源,整年表现为固碳作用,年通量为-506.9 g/(m²·a)。其日变化在生长季和非生长季均呈“U”形曲线,生长季的碳吸收明显大于非生长季;在生长季白天,NEE与光合有效辐射(photosynthetically active radiation, PAR)呈显著的对数关系;而在非生长季,NEE与夜间土壤温度(soil temperature,T_s)呈显著的指数关系。洪泽湖地区杨树人工林生态系统LE的昼夜和季节变化显著,在生长季和非生长季均呈“单峰型”曲线,且在生长季大于非生长季,LE与饱和水汽压差(vapor pressure deficit, VPD)在生长季和非生长季均呈显著的线性正相关关系。洪泽湖地区杨树人工林生态系统CH₄通量在生长季和非生长季均无显著的昼夜变化,在生长季为较弱的CH₄吸收,非生长季为中性至微弱的CH₄排放,全年可能表现为较微弱的CH₄汇。【结论】洪泽湖地区杨树人工林生态系统整体具有较高的固碳能力,CO₂和LE通量具有显著的昼夜变化和季节变化规律,而CH₄通量季节和昼夜变化并不显著,生态系统碳水通量受环境因子的影响较显著,可以为今后提升杨树人工林的固碳能力提供参考。因此,营造杨树人工林将是短期内吸收大气中的CO₂和CH₄并缓解气候变化的有效途径。     

厦门港小型浮游生物对可溶性活性磷吸收和再生通量的季节变化

用３２ＰＯ４３－同位素稀释法测定了厦门港小型浮游生物（＜２００μｍ）对可溶性活性磷（ＳＲＰ的吸收和再生通量；并同时测定了现场的Ｃｈｌａ、初级生产力和各种形态磷．厦门港ＳＲＰ吸收和再生通量有明显的季节变化，夏季最大、冬季最小，且ＳＲＰ通量与生源要素呈现协变性；表层（０．５ｍ）ＳＲＰ通量与Ｃｈｌａ成较好的正相关，ＳＲＰ通量的变化与浮游植物的消长密切相关．全年平均表层ＳＲＰ再生能满足初级生产磷吸收的４３．３％；底层（１６ｍ）再生与吸收比远大于１，ＳＲＰ的再生对初级生产的调控具有重要作用．表层全年平均ＳＲＰ的周转时间为８８．７５ｈ，７月ＳＲＰ最低，但其周转时间也最短仅为３．７ｈ，以最大程度地利用磷维持较高的初级生产力．较低的碳、磷同化原子比及较短的ＳＲＰ周转时间表明厦门港磷同化速率较高．     

南海表层水温的季节内振荡

采用谱估计和相关分析等方法分析了１９８５年夏半年的水文气象资料，证实南海表层水温存在季节内振荡，这种振在深水区与浅海区有着明显的差异。分析表明：南海水温季节内振荡与南海纬向风分量ｕ的振荡密切相关。     

南海地区对流活动的时空变化特征

利用美国NCEP1958-1998年高斯网格月平均再分析资料,分析了南海地区(0°-20°N,100°-125°E)对流活动(OLR)的时空变化,结果表明:南海地区对流活动具有明显的季节转换特征,南海地区对流活动主要呈一致性的分布形势,且具有多时间尺度的变化特征,不同时间尺度的振动,其周期显著性和强度存在明显的年际差异。     

南海热带气旋路径与海气通量的特征分析

海气间潜热和感热的交换对热带气旋的发展和维持起着十分重要的作用。本文利用MEKKHALA、LEO、TED、VONGFONG、ZEKE和WILLIE等南海热带气旋个例,对南海地区热带气旋期间,气旋移动路径与海气之间潜热通量的关联特征进行了初步的分析。结果表明：气旋有向其路径前方海气潜热强输送中心靠拢的趋势,而且移动方向与输送中心位置分布间存在对称性,表现为：当气旋位于两个输送中心之间时,移动方向与两个中心的轴线约平行;而且气旋前进方向常与身后输送中心最近处的切线垂直。     

内蒙古温带半干旱羊草原温室气体N2O和CH4通量变化特征

利用透光密闭箱对内蒙古半干旱典型草原羊草草地土壤－植被系统温室气体N2O和CH4通量进行了较长期的原位观测研究,研究结果表明,内蒙古温带关干旱典型草原作为大气N2O的源和CH4的汇而起作用,N2O与CH4的通量强度分别是：0．6－22.6ugm^-2h^-1和－5－－217ugm^-2h^-1,N2O和CH4的通量具有明显的日变化和委节变化特征,并且主要的环境因子（温度,水分）对其有重要影响,N2O通量的季节变化特征表现为：夏季最高,由春,秋至冬逐次降低,CH4通量的季节变化特征表现为：由春至冬依次减弱。     

南海表面海温异常对南海季风影响的数值模拟

采用P-σ混合坐标系区域气候模式模拟了4－7月南海季风的爆发、演变过程，并进行了3组敏感性数值试验，研究南海表面海温异常对南海季风的影响，得到以下结论：（1）南海4月份海温异常对南海季风的爆发日期影响不大，但对季风爆发后的强度有所影响，异常增温造成南海季风增强，异常降温则南海季风减弱。（2）南海季风爆发和强度的变化与南海本身的海温变化情况有密切的关系，尤其是5月份南海海温异常。5月份南海异常增温可以使南海季风提前爆发，季风增强，南海海温异常降低时，南海季风爆发的时间推迟，季风减弱。（3）南海海温持续异常可以影响南海及中国大陆的高低空环流变化，海温持续异常增温可以使南海季风提前爆发，显地加强南海季风，并有利于南海季风向北推进，但当海温在6月份进一步持续增温时，则有利于季风维持在较南地区，阻碍季风向北发展；当海温持续异常降低时，南海季风推迟爆发，且明显减弱。     

Benthic foraminiferal fauna turnover at 2.1 Ma in the northern South China Sea

Quantitative analysis of benthic foraminifera from ODP Site 1146 in the northern South China Sea (SCS) shows that abundance of Bulimina alazanensis, sometimes up to about 90%, decreased gradually since 3.2 Ma, especially at 2.1 Ma. Abundance of other benthic foraminiferal species, Globobulimina sub-globosa and Cibicidoides wuellerstorfi, increased after 2.1 Ma. Comparison with changes in oxygen and carbon isotopes of planktonic and benthic foraminifera shows that high abundance values of B. alazanensis corresponded with lower values of oxygen isotope, but for carbon isotope, high values of the species were consistent with heavier carbon isotope of benthic foraminifera and lighter carbon isotope of planktonic foraminifera, respectively, and vice versa. Considering factors such as uplift of Bashi Strait, expansion of the North Hemisphere Glaciation, strengthening of East Asian winter mon-soon and variations in oxygen and carbon isotope of foraminifera, changes of B. alazanensis in ODP Site 1146 suggest that the source of deep water masses of the northern South China Sea changed from the warm Pacific deep water with high oxygen content to Pacific Intermediate water with low oxygen content at 2.1 Ma. In addition, the strengthened East Asian winter monsoon resulted in increased pri-mary productivity, high nutrient and suboxic bottom water. Variations in species of B. alazanensis seemed to be unable to tolerate environmental stress induced by deep water masses and productivity changes.     

近10年南海海表风场季节特征统计

基于Fortran程序和Grads(Grid Analysis and Display System)软件,利用QN(QuikSCAT/NCEP)混合风场,统计了近10年(1999年8月~2009年7月)期间南海海表风场特征,主要统计了风速风向的季节特征,期望研究结果可以为航海、防灾减灾等提供参考。结果表明:(1)春季,风速的大值区位于南海北部,约3.5~5.0 m/s,台湾海峡能达到5.5 m/s;除泰国湾和北部湾以外的大部分海域以东北风为主,北部湾以偏东风为主,泰国湾以偏南风为主。(2)夏季,受西南季风影响,大部分海域以西南风为主;风速的大值区位于中南半岛附近海域,该海域为传统的南海大风区,约5~7 m/s。(3)秋季,为季风过渡季节,风向稍显凌乱,南海中北部已转东北风,而南部部分海域的西南风尚未完全消退,泰国湾在该季节则以西北风为主;风速的相对大值区位于南海北部和台湾周边海域,约6~9 m/s,台湾海峡基本都在9 m/s左右。(4)冬季,受冷空气影响显著,整个南海均以强势的东北风为主;风速大值区呈东北-西南走向,大部分海域的风速在8 m/s以上,台湾海峡能达到11 m/s左右。     

Satellite-derived surface water pCO2 and air-sea CO2 fluxes in the northern South China Sea in summer

An empirical approach is presented for the estimation of the partial pressure of carbon dioxide (pCO2) and air-sea CO2 fluxes in the northern South China Sea in summer using satellite-derived sea surface temperatures (SSTs), chlorophyll-a (Chl a) concentrations, and wind fields. Two algorithms were tested. The first used an SST-dependent equation, and the other involved the introduction of Chl a. Regression equations were developed for summer based on in situ data obtained in July, 2004. Using the monthly average SST and Chl a fields derived from the advanced very high resolution radiometer (AVHRR) and the SeaWiFS (sea-viewing wide field of view sen-sor), respectively, the monthly pCO2 fields were computed. The derived pCO2 was compared with the shipboard pCO2 observations con-ducted in July, 2000. This resulted in a root-mean-square error of 4.6 μatm, suggesting that the satellite-derived pCO2 was in general agreement with the in situ observations. The air-sea CO2 flux was further computed with the aid of the monthly mean QuikSCAT wind speed. We contend that more shipboard data are necessary for refining the empirical algorithms and reducing the uncertainty in the results.     

Upper pycnocline turbulence in the northern South China Sea

The first regional mapping of the averaged turbulent kinetic energy dissipation rate <εp> in the upper pycnocline of the northern South China Sea is presented and discussed.At φ=20°N and to the north of this latitude,<εp> appears to be more than two times larger than that to the south of 20°N.It is suggested that this asymmetry is associated with the predominant northwestward propagation and dissipation of the internal waves originated in the Luzon Strait area.An approximately linear relationship between <εp> and the available potential energy of the waves P IW,suggests a characteristic time of the P IW dissipation of about 6 h.     

南海中部表层沉积物中脂肪酸的组成、分布及来源

对5个采自南海中部地区的表层海洋近代沉积物样品的脂肪酸的组成进行了测试．测试结果表明,南海中部近代沉积物中脂肪酸由正构饱和脂肪酸、一元不饱和脂肪酸、多元不饱和脂肪酸及带支链的异构、反异构脂肪酸组成．较高含量的C12：C20短链脂肪酸和较丰富的一元不饱和脂肪酸以及其它细菌标志脂肪酸的出现表明,细菌等海洋微生物是脂肪酸的主要贡献者,海洋浮游生物对南海近代沉积物脂肪酸的贡献仅占次要位置．     

Long-range correlations in remotely sensed chlorophyll in the South China Sea

A 8-year time series of 8-day Seaviewing Wide Field-of-view Sensor （SeaWiFS） data, which spans from Oct 1997 to Oct 2005, was used to study the temporal correlations and scaling behaviour of ocean chlorophyll fluctuations in the South China Sea （SCS） by means of detrended fluctuation analysis （DFA）. Long-range correlations in chlorophyll fluctuations were detected in almost all the SCS. The scaling exponents vary over a wide range from 0.5 to 1.14, with an average value of 0.79. High values are found in the upwelling regions, such as the northwest of Luzon and the north of Sunda Shelf. Low values occur in the southwest of Luzon, the east of Hainan Island and a majority of the southern SCS. This spatial pattern is considerably different from that of the scaling exponents of the sea surface temperature （SST） time series. It is also demonstrated that SST exhibits more persistence than chlorophyll in almost all the SCS.     

Crustal activities recorded in coral reefs in the northwestern South China Sea

Coral reefs in the northwest of South China Sea have recorded the information from not only the environmental variation but also the crustal activities there during their development. The main crustal activities correlated with the coral reef development include fault, seismic, and volcano activities, etc. The high-resolution spark seismic profiles in the northwestern South China Sea show that the fault activities in the coral reef region have been clearly recorded, and appear as neonatal faults incising reefs. Earthquakes in the coral reef region are rather intense, especially the two occurring on December, 31, 1994, and January, 10, 1995, around the southwest of Leizhou Peninsula, with the magnitude of 6.1 and 6.2, respectively. They have great influence on the growth of the local coral reefs. Quaternary volcanos are active in the northwestern South China Sea, especially around the southwest of Leizhou Peninsula, and they have obvious control of the coral reef development. Some submarine volcanoes form the substrates of coral reef, while a few emerge above the sea surface and form coral islands.     

南海夏季风活动激发的大气遥相关型

北半球夏季,南海地区是全球大气热状况变化最为激烈的区域之一,而南海夏季风则是该地区最为活跃的天气事件,它的演变必将导致其它地区大气环流的响应．通过相关计算、合成分析等手段,揭示与南海夏季风活动相关联的北半球大气遥相关型的存在．该波列状的遥相关型与东亚地区相连,经北太平洋延伸至北美西岸．最高的相关位于西太平洋副热带高压区域,因而它可能对我国旱涝天气产生重要影响．