海岸沙坝近底悬移质通量实验研究

为了研究海岸沙坝的产生和演化机理,对不规则波和波群作用下沙坝上方的近底悬移质通量进行了实验研究。分析了短波、长波和平均水流对悬移质通量的影响。结果表明:各种波况下平均水流和长波的作用始终使泥沙向离岸方向输移,而短波的作用使泥沙向岸方向运动;平均水流引起的泥沙输移始终占主要成分,长波的次之。不规则波情况下平均水流的影响较规则波的情况相对较弱,三种成分对泥沙输运的贡献属于同一量级。波群情况下长波的影响随着波浪群性的增强而加大,短波的不明显,而平均水流的影响则随着波浪群性的增强而减弱。     

中国东部夏季降水年际变化与同期东海潜热通量的关系

利用1985~2008年OAflux3、NCEP＼NCAR再分析资料与中国大陆东部108个站点的降水资料,应用回归和合成方法,分析了中国东部夏季降水的年际变化与同期东海及邻近海域潜热通量变异的关系。结果表明:东海及邻近海域(以下称东海)夏季潜热通量年际变化显著的区域位于东海区域,为与同期中国东部降水密切相关的关键区域。当东海的潜热通量偏高(低)时,中国东部长江以南地区上空盛行偏东北(西南)风异常,这将不(有)利于水汽由南向北的输送,从而可能使到达长江中下游流域及以北地区的水汽偏少(多);并且,长江中、下游流域为下沉(上升)气流和低层水汽辐散(辐合)正异常,对应降水偏少(偏多);华南地区为上升(下沉)气流和低层水汽辐合(辐散)正异常,对应降水偏多(偏少)。分析结果还表明,东海的潜热通量可通过影响东亚大气环流而成为引起中国东部夏季汛期降水年际异常的重要原因之一。     

First record of Biecheleria cincta (Dinophyceae) from Chinese coasts, with morphological and molecular characterization of the strains

The presence of Biecheleria cincta (=Woloszynskia cincta) in the Chinese coasts is reported for the first time. In scanning electron microscope, three to five series of vesicles and an elongated apical vesicle (EAV) were visible in the epicone, and both the hypocone and the cingulum had three series of vesicles each. Thin sections revealed that B. cincta possesses stalked pyrenoids and an unusual eyespot consisting of a stack of cisternae with brick-like materials (type E), thus supporting its transfer from Woloszynskia to Biecheleria. Spiny cysts formed spontaneously in culture, with an encystment rate of around 20%. Both large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer region (ITS) sequences in 12 strains from the Chinese coasts were determined. Phylogenetic analyses based on LSU rDNA and ITS sequences using Bayesian inference and maximum likelihood revealed two distinct ribotypes (referred to as ribotype A and B) in B. cincta. ITS region pairwise distances within B. cincta ranged from 0.024 to 0.072, suggesting the existence of a complex of cryptic species.     

Remote forcing of Indian Ocean warming on Northwest Pacific during E1 Nino decaying years： a FOAM model approach

This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere coupled Model 1.5 were used to investigate the triggering conditions under which the remote influence is formed between the positive sea surface temperature （SST） anomaly in the North Indian Ocean and the Anomalous Northwest Pacific anticyclone （ANWPA）. Our research show that it is only when there is a contributory background wind field over the Indian Ocean, i,e., when the Indian Summer Monsoon （ISM） reaches its peak, that the warmer SST anomaly in the North Indian Ocean incites significant easterly wind anomalies in the lower atmosphere of the Indo-West tropical Pacific. This then produces the remote influence on the ANWPA. Therefore, the SST anomaly in the North Indian Ocean might interfere with the prediction of the East Asia Summer Monsoon in the year of decaying E1 Nifio. Both the sustaining effect of local negative SST anomalies in the NWP, and the remote effect of positive SST anomalies in the North Indian Ocean on the ANWPA, should be considered in further research.     

绿洲和戈壁近地面层热量和物质输送特征对比

利用甘肃金塔绿洲和戈壁10 m涡旋相关法的观测资料对比研究温度、湿度和二氧化碳浓度(CO₂)的平流和湍流通量特征.结果表明,在典型绿洲-戈壁复杂下垫面上,热量和物质的平流通量比湍流通量的值大1到2个量级;在绿洲和戈壁,受平流输送影响和下垫面强迫,不同性质标量湍流的水平和垂直通量分布具有不同的特征.     

Effects of soil compaction,rain exposure and their interaction on soil carbon dioxide emission

Soils release more carbon, primarily as carbon dioxide (CO₂), per annum than current global anthropogenic emissions. Soils emit CO₂ through mineralization and decomposition of organic matter and respiration of roots and soil organisms. Given this, the evaluation of the effects of abiotic factors on microbial activity is of major importance when considering the mitigation of greenhouse gases emissions. Previous studies demonstrate that soil CO₂ emission is significantly affected by temperature and soil water content. A limited number of studies have illustrated the importance of bulk density and soil surface characteristics as a result of exposure to rain on CO₂ emission, however, none examine their relative importance. Therefore, this study investigated the effects of soil compaction and exposure of the soil surface to rainfall and their interaction on CO₂ release. We conducted a factorial laboratory experiment with three soil types after sieving (clay, silt and sand soil), three different bulk densities (1·1 g cm^–3, 1·3 g cm^–3, 1·5 g cm^–3) and three different exposures to rainfall (no rain, 30 minutes and 90 minutes of rainfall). The results demonstrated CO₂ release varied significantly with bulk density, exposure to rain and time. The relationship between rain exposure and CO₂ is positive: CO₂ emission was 53% and 42% greater for the 90 minutes and 30 minutes rainfall exposure, respectively, compared to those not exposed to rain. Bulk density exhibited a negative relationship with CO₂ emission: soil compacted to a bulk density of 1·1 g cm^–3 emitted 32% more CO₂ than soil compacted to 1·5 g cm^–3. Furthermore we found that the magnitude of CO₂ effluxes depended on the interaction of these two abiotic factors. Given these results, understanding the influence of soil compaction and raindrop impact on CO₂ emission could lead to modified soil management practices which promote carbon sequestration. Copyright © 2012 John Wiley & Sons, Ltd.     

Diagnosis of river basins as CO2 sources or sinks subject to sediment movement

Sediment movement during erosion, transport and deposition greatly affects the ecosystem of river basins. However, there is presently no consensus as to whether particular river basins act as carbon dioxide (CO₂) sources or sinks related to these processes. This paper introduces a rule‐of‐thumb coordinate system based on sediment delivery ratio (SDR) and soil humin content (SHC) in order to evaluate the net effect of soil erosion, sediment transport and deposition on CO₂ flux in river basins. The SDR–SHC system delineates CO₂ source and sink areas, and further divides the sink into strong and weak areas according to the world‐average line. The Yellow River Basin, most severely suffering soil erosion in the world, only appears to be a weak erosion‐induced CO₂ sink in this system. The average annual CO₂ sequestration is ~0·235 Mt from 1960 to 2008, a relatively small value considering its 3·1% contribution to the World's sediment discharge. The temporal analysis shows that the Yellow River Basin was once a source in the 1960s, but changed its role to become a weak sink in the past 40 years due to both anthropogenic and climatic influences. The spatial analysis identifies the middle sub‐basin as the main source region, and the lower as the main sink. For comparison, sediment‐movement‐related CO₂ fluxes of eight other major basins in four continents are examined. It is found that the six basins considered in the Northern Hemisphere appear to be sinks, while the other two in the Southern Hemisphere act as sources. Copyright © 2012 John Wiley & Sons, Ltd.     

山地冰川流动模型探讨

近30 a来冰川动力学模型有了快速发展, 在南极、 格林兰冰盖预测中取得一系列重要成果, 对山地冰川的研究也初见端倪. 从冰川流动的力学过程出发, 利用本构方程、 理想冰川假设、 浅冰层近似(Shallow ice approximation)假设完整地推导了理想冰川流动的物理过程, 揭示了冰川流动的机理, 建立了气候变化和冰川自身重力引起的理想冰川物质和能量再分配的温度耦合三维流动模型. 结合山地冰川的冰床形态, 将理想冰川与实际冰川相结合, 使理想冰川流动模型更好地近似山地冰川的流动.     

Air-sea carbon-dioxide flux estimated by eddy covariance method from a buoy observation

Precise measurements of the CO2 gas transfer across the air-sea interface provide a better understanding of the global carbon cycle.The air-sea CO2 fluxes are obtained by the eddy covariance method and the bulk method from a buoy observation in the northern Huanghai sea.The effects of buoy motion on flux calculated by the eddy covariance method are demonstrated.The research shows that a motion correction can improve the correlation coefficient between the CO2 fluxes estimated from two different levels.Without the CO2-H2 O cross-correlation correction which is termed as PKT correction,the air-sea CO2 fluxes estimated by eddy covariance method using the motion corrected data are nearly an order of magnitude larger than those estimated by the bulk method.After the CO2-H2 O cross-correlation correction,some eddy covariance CO2 fluxes indeed become closer to the bulk CO2 flux,whereas some are overcorrected which are in response to small water vapor flux.     

海洋表层温度对台风"蔷薇"路径和强度预测精度的影响

基于中尺度大气模式WRF(Weather Research and Forecasting Model),首先对2007年3次船舶辐射通量观测进行模拟,以检验WRF对长波和短波辐射通量的模拟能力,结果表明使用中国近海海洋环境数值预报系统环流模式POM(Princeton Ocean Model)模拟的高时空分辨率的海洋表层温度能够显著改进短波辐射通量的模拟,而对长波辐射通量模拟的改进不明显。然后,将业务化运行的中国近海海洋环境数值预报系统后报的逐时海洋表面温度(SST)作为WRF底边界条件,对2008年15号强台风"蔷薇"(Jangmi)过程进行了数值后报试验。结果表明,与使用NCEP/NCAR的SST试验后报的台风中心位置偏差相比,使用高时空分辨率的SST能够较为显著地改善"蔷薇"的路径模拟,台风中心位置模拟偏差减少11%,尤其在台风减弱阶段,台风中心位置模拟偏差减少37%。台风强度在台风发展的不同阶段对下垫面SST的变化敏感性不同。台风路径附近的海表面温度下降会导致海洋向大气输送的热量减少从而减弱台风强度。