Ocean acidification: Separating evidence from judgment – A reply to Dupont et al.

Recently ocean acidification as a major threat for marine species has moved from a consensus statement into a much discussed and even challenged conception. A simple meta-analysis of Hendriks et al. (2010) showed that based on results of pooled experimental evidence, marine biota may turn out to be more resistant than hitherto believed. Dupont et al. (in press) indicate the importance of evaluating the most vulnerable stages in the life cycle of organisms instead of only adult stages. Here we evaluate additional material, composed of experimental evidence of the effect of ocean acidification on marine organisms during adult, larval, and juvenile stages, and show that the observed effects are within the range predicted by Hendriks et al. (2010). Species-specific differences and a wide variance in the reaction of organisms might obscure patterns of differences between life stages. Future research should be aimed to clarify underlying mechanisms to define the effect ocean acidification will have on marine biodiversity. Conveying scientific evidence along with an open acknowledgment of uncertainties to help separate evidence from judgment should not harm the need to act to mitigate ocean acidification and should pave the road for robust progress in our understanding of how ocean acidification impacts biota of the ocean.     

What meta-analysis can tell us about vulnerability of marine biodiversity to ocean acidification?

Ocean acidification has been proposed as a major threat for marine biodiversity. Hendriks et al. [Hendriks, I.E., Duarte, C.M., Alvarez, M., 2010. Vulnerability of marine biodiversity to ocean acidification: a meta-analysis. Estuarine, Coastal and Shelf Science, doi:10.1016/j.ecss.2009.11.022.] proposed an alternative view and suggested, based on a meta-analysis, that marine biota may be far more resistant to ocean acidification than hitherto believed. However, such a meta-analytical approach can mask more subtle features, for example differing sensitivities during the life-cycle of an organism. Using a similar metric on an echinoderm database, we show that key bottlenecks present in the life-cycle (e.g. larvae being more vulnerable than adults) and responsible for driving the whole species response may be hidden in a global meta-analysis. Our data illustrate that any ecological meta-analysis should be hypothesis driven, taking into account the complexity of biological systems, including all life-cycle stages and key biological processes. Available data allow us to conclude that near-future ocean acidification can/will have dramatic negative impact on some marine species, including echinoderms, with likely consequences at the ecosystem level.     

高空急流区飞机颠簸的一种形成机制的探讨

作者应用动力学分析方法，结合观测飞机颠簸的事实，对高空急流区飞机颠簸的一种形成机理进行了理论探讨。结果表明，高空急流区温度平流分布的不均匀性，会在急流附近等温线密集区边缘激发出空气垂直运动和湍流，引起飞机颠簸。     

台风“麦莎”移动过程中水汽输送特征

利用NCEP1°×1°的再分析资料,用大尺度水汽通量流函数和速度势以及水汽收支对台风“麦莎”在移动过程中水汽输送流函数和速度势进行了分析。结果表明：台风“麦沙”在北上过程中,主要有2支水汽通道,一支是从太平洋开始向西经赤道到达印度洋,在索马里转向,经过孟家加拉湾呈西南气流向西北方向输送;另一支来自副高南侧偏东气流。计算分析还表明,用无辐散风流场来定台风中心要比用总的流场更精确。     

澳大利亚冷空气活动对西北太平洋热带辐合带强度的影响

利用1959～2004年纬向风的NCEP/NCAR候平均再分析资料分析和中国科学院大气物理研究所研制的9层大气环流模式(IAP9L-AGCM)数值试验,考察了南半球越赤道气流和澳大利亚冷空气活动对西北太平洋ITCZ和台风的影响。研究发现:100°E～165°E向北越赤道气流与ITCZ的强度增强具有明显的关系;10～15 d前130°E～140°E与150°E～160°E越赤道气流的加强对145°E～170°E位置上ITCZ强度的增加具有指示意义。越赤道气流强度对同期110°E～140°E经度ITCZ位置的变化也有影响。数值试验表明:南半球澳大利亚冷空气的活动是造成越赤道气流加强的重要原因,澳大利亚地区受较强冷空气影响时易造成100°E～160°E经度带越赤道气流的加强,特别是140°E～165°E的越赤道气流有利于ITCZ强度增加,导致西北太平洋热带气旋的发生和加强。     

城市化进程中平原河网地区河流结构特征及其分类方法探讨

平原河网地区河流结构发育受到自然条件和城市化的双重影响。依据遥感解译数据,围绕城市化水平、河流形态、河流结构和河流调蓄功能四个维度,就建成区面积比例、河流长宽分布、河系分维、河流调蓄能力等具体指标,分析了城市化水平和土地利用特征不同区域的河流空间形态、结构特征和功能状态,探讨了城市化进程中平原河网地区河流结构的可能演化轨迹,尝试建立了城市化影响下平原河网地区河流结构分类方法,提出了城市河流综合整治过程中应充分重视保护自然河流结构,注重发挥河流综合功能等观点。     

基于集中度与集中期的径流年内分配研究

借鉴年降水量年内分配的向量法,描述径流年内分配的径流集中度和集中期,尝试提出一种计算河川径流年内分配不均匀性的定量新方法。实例研究表明,用月径流量计算的集中度比径流年内不均匀系数有更高的分辨能力和敏感性,用月径流量计算的集中期对应的月份与月径流最大值出现的实际月份完全一致,径流集中度、集中期能够充分定量地表征径流在年内分配的非均匀性。     

上海中心城区河流水系百年变化及影响因素分析

分析上海中心城区河流水系1860~2003年变化情况,研究表明:①140余年来中心城区有历史记载河流消失至少310条段,总长超520 km,水面积减少约10.46 km²,水面率下降3.61%。中心城区所在水利片河流水系结构破坏,水系分枝比受河道消亡影响明显降低,水系分维数异常;②中心城区河流水系阶段性集中消亡,消亡驱动力因消亡时期而异;③初步估算,140余年来中心城区河道槽蓄容量减少超过2 029×10⁴m3、单位面积可调蓄容量减少5.06×10⁴m³/km²。河道槽蓄容量较百年前减少超过80%,城市河网调蓄能力明显削弱,且1950~1990年市政雨水泵站累积增加数目与同期区域内河道累积消失数量、长度和槽蓄容量间均呈显著正相关性。     

Manganese in runoff from upland catchments: temporal patterns and controls on mobilization / Teneur en manganèse de l'écoulement en bassins versants d'altitude: variations temporelles et contrôles de la mobilisation

Abstract

Knowledge of the hydrochemical dynamics of the trace metal manganese (Mn) in upland catchments is required for water quality management. Stream water Mn and other solutes and flow were monitored in two upland catchments in northern England with different soils: one dominated by peat (HS7), the other by mineral soils (HS4). Maximum Mn concentrations occurred at different times in the two catchments: in summer baseflow at HS4 and during late summer storm events at HS7. A two-component chemical mixing model was used to identify the hydrological processes controlling Mn concentrations in stream water. This approach was more successful for HS4 than HS7, probably because of different processes of Mn release in the two catchments and also difficulties in selecting conservative solutes. Factor analysis of the stream water chemistry data set for each catchment was more useful in identifying the controls on Mn release into runoff. The factors indicate that the main source of Mn at HS4 is the hydrological pathway supplying summer baseflow, whereas at HS7 Mn is released during the rewetting of dried peat soils. Manganese concentrations in stream water in upland catchments appear to depend on soil type and antecedent moisture conditions. This has implications for the design of sampling strategies in upland catchments and also for managing the quality of water supplies from such areas.     

Pulse generation models for daily intermittent streamflows / Modèles de génération d’impulsions pour des débits journaliers intermittents

Abstract

Abstract Generating pulses and then converting them into flow are two main steps of daily streamflow generation. Three pulse generation models have been proposed on the basis of Markov chains for the purpose of generating daily intermittent streamflow time series in this study. The first one is based on two two-state Markov chains, whereas the second uses a three-state Markov chain. The third model uses harmonic analysis and fits Fourier series to the three-state Markov chain. Results for a daily intermittent streamflow data series show a good performance of the proposed models.