Seasonal temperatures from δ18O in recent Spanish tufa stromatolites: Equilibrium redux!

This study focuses on recent debate over the value of stable isotope‐based environmental proxies recorded in riverine tufa stromatolites. A twelve‐year record (1999 to 2012) of river‐bed tufa stromatolites in the River Piedra (north‐east Spain) was recovered in this study, along with a partly overlapping fifteen‐year record (1994 to 2009) of accumulations in a drainage pipe: both deposits formed in water with near identical physico/chemical parameters. Measured water temperature data and near‐constant δ ¹⁸O_water composition allowed selection of an ‘equilibrium’ palaeotemperature equation that best replicated actual temperatures. This study, as in some previous studies, found that just two published formulas for water temperature calculation from equilibrium calcite δ ¹⁸O compositions were appropriate for the River Piedra, where tufa deposition rates are high, with means between 5·6 mm and 10·8 mm in six months. The δ ¹⁸O_calcite in both the river and the pipe deposits essentially records the full actual seasonal water temperature range. Only the coldest times (water temperature <10°C), when calcite precipitation mass decreased to minimum, are likely to be unrepresented, an effect most noticeable in the pipe where depositional masses are smaller and below sample resolution. While kinetic effects on δ ¹⁸O_calcite‐based calculated water temperature cannot be ruled out, the good fit between measured water temperature and δ ¹⁸O_calcite‐calculated water temperature indicates that temperature is the principal control. Textural and deposition rate variability between the river and pipe settings are caused by differences in flow velocity and illumination. In the river, calcification of growing cyanobacterial mat occurred throughout the year, producing composite dense and porous laminae, whereas in the pipe, discontinuous cyanobacterial growth in winter promoted more abiogenic calcification. High‐resolution δ ¹⁸O_calcite data from synchronous pipe and river laminae show that reversals in water temperature occur within laminae, not at lamina boundaries, a pattern consistent with progressive increase in calcite precipitation rate as cyanobacterial growth re‐established in spring.     

高寒地区渠道防治冻害技术措施

依据黑龙江省水利科学研究院近20年来水工建筑物抗冻技术研究的主要成果,简述了高寒地区渠道防治冻害技术的主要内容,包括:抗冻胀设计参数的确定方法、渠道衬砌工程防治冻害技术措施的要点等,可供工程设计人员参考。     

乐清湾海域浮游动物群落分布的季节变化特征及其环境影响因子

2006年10月、2007年1月、4月及7月对乐清湾海域浮游动物群落的种类组成、优势种、生态类群、水平分布的季节性变化特征进行了调查,分析了浮游动物群落分布与环境因子的关系。结果表明,在调查海域共鉴定出浮游动物82种(包括浮游幼体11种),隶属于15大类,其中秋季为46种、夏季为42种、春季为25种和冬季为16种。乐清湾浮游动物可分为近岸低盐类群、暖水性近海类群、暖温带近海类群和暖水性广布类群4个生态类群,其中近岸低盐类群在全年均占优势,其它类群则呈现明显的季节变化。中华哲水蚤Calanus sinicus、真刺唇角水蚤Labidocera euchaeta、针刺拟哲水蚤Paracalanus aculeatus和背针胸刺水蚤Centropages dorsispinatus为调查海域主要优势种。浮游动物生物量年平均值为82.7mg/m3,其大小依序为:夏季(121.1mg/m3)>秋季(119.2mg/m3)>春季(48.5mg/m3)>冬季(42.2mg/m3);丰度年平均值为82.1个/m3,其大小依序为:夏季(193.4个/m3)>秋季(73.7个/m3)>春季(53.4个/m3)>冬季(9.8个/m3)。相同季节浮游动物生物量和丰度的平面分布趋势类似,季节间则存在明显差异。相关性分析结果表明,浮游动物物种数与水温、盐度、叶绿素a质量浓度和浮游植物细胞密度均呈极显著相关;丰度与水温、叶绿素a质量浓度和浮游植物细胞密度呈极显著相关;生物量与水温、叶绿素a质量浓度呈极显著相关。与历史资料相比,近30a来浮游动物数量呈下降趋势,但群落结构和组成没有发生明显改变。     

Technical note on a track-pattern-based model for predicting seasonal tropical cyclone activity over the western North Pacific

Recently, the National Typhoon Center (NTC) at the Korea Meteorological Administration launched a track-pattern-based model that predicts the horizontal distribution of tropical cyclone (TC) track density from June to October. This model is the first approach to target seasonal TC track clusters covering the entire western North Pacific (WNP) basin, and may represent a milestone for seasonal TC forecasting, using a simple statistical method that can be applied at weather operation centers. In this note, we describe the procedure of the track-pattern-based model with brief technical background to provide practical information on the use and operation of the model. The model comprises three major steps. First, long-term data of WNP TC tracks reveal seven climatological track clusters. Second, the TC counts for each cluster are predicted using a hybrid statistical-dynamical method, using the seasonal prediction of large-scale environments. Third, the final forecast map of track density is constructed by merging the spatial probabilities of the seven clusters and applying necessary bias corrections. Although the model is developed to issue the seasonal forecast in mid-May, it can be applied to alternative dates and target seasons following the procedure described in this note. Work continues on establishing an automatic system for this model at the NTC.     

某地铁区间隧道冻结施工冻胀效应随机预测分析

土层冻结引发冻胀,引起地面上升和变形,过量的不均匀沉降或变形可能危及周围地面建筑.南京地铁某区间隧道穿过地层为软一流塑状淤泥质粉质粘土,拟采用人工冻结法作为辅助施工方法穿越该不良地段.为对地面建筑物进行变形控制,需要对冻结法施工冻胀效应进行预测.采用随机介质理论对该工程冻结施工的冻胀效应进行预测,介绍了冻胀效应分析的基本过程,编制了计算分析程序,分析了水平冻胀引起的地面隆起、曲率变形规律.结果表明:水平冻胀引起的地面变形均满足地面变形控制要求.     

全球气候模式中赤道东太平洋海表温度的季节循环：从CMIP5到CMIP6

The sea surface temperature(SST) seasonal cycle in the eastern equatorial Pacific(EEP) plays an important role in the El Ni?o–Southern Oscillation(ENSO) phenomenon. However, the reasonable simulation of SST seasonal cycle in the EEP is still a challenge for climate models. In this paper, we evaluated the performance of 17 CMIP6 climate models in simulating the seasonal cycle in the EEP and compared them with 43 CMIP5 climate models. In general, only CESM2 and SAM0-UNICON are able to successfully capture the annual mean SST characteristics,and the results showed that CMIP6 models have no fundamental improvement in the model annual mean bias.For the seasonal cycle, 14 out of 17 climate models are able to represent the major characteristics of the observed SST annual evolution. In spring, 12 models capture the 1–2 months leading the eastern equatorial Pacific region 1(EP1; 5°S–5°N, 110°–85°W) against the eastern equatorial Pacific region 2(EP2; 5°S–5°N, 140°–110°W). In autumn,only two models, GISS-E2-G and SAM0-UNICON, correctly show that the EP1 and EP2 SSTs vary in phase. For the CMIP6 MME SST simulation in EP1, both the cold bias along the equator in the warm phase and the warm bias in the cold phase lead to a weaker annual SST cycle in the CGCMs, which is similar to the CMIP5 results. However,both the seasonal cold bias and warm bias are considerably decreased for CMIP6, which leads the annual SST cycle to more closely reflect the observation. For the CMIP6 MME SST simulation in EP2, the amplitude is similar to the observed value due to the quasi-constant cold bias throughout the year, although the cold bias is clearly improved after August compared with CMIP5 models. Overall, although SAM0-UNICON successfully captured the seasonal cycle characteristics in the EEP and the improvement from CMIP5 to CMIP6 in simulating EEP SST is clear, the fundamental climate models simulated biases still exist.     

福建霜冻时空分布特征及环流背景分析

利用福建省内68个地面测站1981—2011年1—4月、10—12月逐日观测资料,结合最低地表温度、天气现象、最低气温作为福建霜冻判别指标,探讨福建霜冻气候特征及环流背景形势。研究发现:1)福建年平均霜冻天数、初(终)霜冻日、无霜冻期具有明显地域差异,等值线基本呈东北—西南走向,与台站海拔高度具有良好相关性。区域平均初霜冻日、终霜冻日、无霜冻期总体分别呈推迟、提前、延长的变化趋势。2)全省大范围霜冻天气呈现发生频率低、过程持续时间短、总体逐渐减少的特征。3)霜冻越强,发生越晚,结束越早,且出现天数越少。4)随着形势场特征线略有南压,霜冻逐渐增强,反之减弱。     

Water quality trends at an upland site in wales,UK, 1983–1993

Ten years of detailed upland stream and bulk deposition water quality data from Plynlimon, mid-Wales, are examined for trend. A robust statistical test (the seasonal Kendall test) is applied and data are presented graphically. Smoothing techniques are used to highlight the patterns of change which underlie high data scatter. The graphs show long-term cycles within the data which violate the assumptions of common statistical tests for trend. These cycles relate to fluctuations in the weather patterns at Plynlimon. Even though the seasonal Kendall test is significant for some determinands, the evidence from the graphs suggests that many of these ‘trends’ are unlikely to continue. For solutes in rainfall, there is no convincing long-term trend. There is a possible increase in ammonium concentrations, which may indicate an increasing atmospheric source generated by farming activities, but this will require a longer data series for confirmation. Several trace metal concentrations increased significantly part way through the study period, but later returned to the original levels. The bulk precipitation sea salt input has been uneven over the 10-year sampling period, with the highest inputs occurring during the wetter winters. For solutes in streamwaters, there are clear trends in dissolved organic carbon (DOC), iodine and bromide, which increase over time and may be attributed to an increase in organic decomposition in the catchment. Previous studies in Wales have shown similar behaviour for colour, which is related to DOC, but the corresponding changes for bromide and iodine are new. For most other streamwater determinands, any changes are masked by the effects of year to year variations in the quality and quantity of rainfall. For example, zinc and chromium variations parallel the corresponding rainfall quantity variations. The effect of rainfall quality variation is marked for marine-derived elements such as chloride. For sulphate, streamwater variations are inverted relative to chloride. This suggests that dry deposition may vary with weather conditions: high when the wind direction is from the land and low when weather systems are predominantly frontal and laden with sea salts. Alternatively, high sea salt rainfall may be affecting absorption/solubility reactions in the soils. There are four main conclusions. Firstly, there is no indication of changing acid deposition inputs or changing acidity within the runoff, despite a decline in UK sulphur dioxide emissions. Secondly, streamwater DOC has shown an increase over time, but there is no clear corresponding decrease in pH as might be expected from acidification theory. Thirdly, there are cyclical variations in bulk precipitation inputs and in streamwater quality, which mean that trends cannot be established even with 10 years of data. Long-term cycles are likely to exist in other environmental data and extreme care is required for the interpretation of trend, especially if data sets are short. This aspect strongly supports the continuation of long-term monitoring programmes over several decades. Finally, the graphical application strongly enhances data analysis and should be considered an essential component of trend investigation.     

西港海洋牧场底层海水溶解氧浓度时变特征

利用海底有缆在线观测系统获得的连续实时观测数据,研究了2016年6月2日至10月22日期间威海市西港海洋牧场底层海水溶解氧浓度的时间变化特征,并探讨了其影响机制。结果表明,观测期间底层海水溶解氧浓度整体呈先减小后增大的变化趋势,其变化范围为2.99 mg/L至11.43 mg/L,均值约为6.65 mg/L。进一步分析表明：（1）底层海水饱和溶解氧浓度的变化并不显著,于6月出现过饱和现象;（2）海水温度是底层海水溶解氧浓度日际变化和月变化的主要影响因素;（3）7月至8月中旬,在季节性温跃层抑制垂向混合和水温升高的共同影响下,底层溶解氧浓度总体呈下降趋势;（4）日平均风速与日平均海水溶解氧浓度的相关性并不显著,但大风期间底层海水溶解氧浓度存在先升高后降低的变化特征;（5）底层海水溶解氧浓度的日变化以全日周期为主,可能主要受生物过程、垂向混合扩散和潮流输运等日变化的影响。本研究对于进一步探讨山东半岛海洋牧场区域海水溶解氧的时空分布特征及其影响机制具有重要意义。     

Seasonal Variation in the Phytoplanktonic Community,Seston and Environmental Variables During a 2-Year Period and Oyster Growth at Two Mariculture Sites,Southern Chile

Phytoplankton and its relationships with physical and chemical variables were analysed over a 2-year period in Hueihue and Linao Bays (southern Chile). Samples were collected on a monthly basis from May 1991 to May 1993. The growth rate of a single stock of hatchery-produced oysters (Ostrea chilensis) distributed between these two bays was also monitored monthly. The growth rate of oysters maintained at Linao Bay (site associated with a fish farm) was significantly higher, at every depth, compared with the oysters maintained at Hueihue Bay. Temperature and salinity values and their annual fluctuations were similar at both locations, presenting higher variations at the surface (1 m) due to the influence of air temperature and local precipitation than at depth. However, significant differences in phytoplankton abundance and composition were found between the two locations. The phytoplankton community was characterized by high biomass values during spring and summer, the dominance of diatoms and an inverse relationship between temperature and species diversity. However, phytoplankton cell abundance, biovolume and chlorophyll a concentration were significantly higher at Linao at every depth sampled. Cell abundance ranged between 4.49 × 10⁴ and 7.45 × 10⁶ cells · l^?1 in Hueihue and between 6.48 × 10⁴ and 8.71 × 10⁶ cells ·1^?1 in Linao. The influence of temperature on chlorophyll a concentration was significant except at 8 m at both locations. The instantaneous oyster growth rate was found to be positively correlated with temperature, chlorophyll a concentration and particulate organic matter at both locations. A significant negative relationship between oyster growth and amount of particulate inorganic matter was found; this confirms the important role played by seston composition in oyster growth. The demonstration of variation in oyster growth rate associated with differences in food availability between the two locations provides insight into the ecological role played by fish farms in southern Chile. The results suggest a strong link between food availability and oyster growth.