A comparative study of the land-atmosphere energy and water exchanges over the Tibetan Plateau and the Yangtze River Region

正确认识不同区域能量和水分循环特征是研究局地地气相互作用及准确预测区域天气,气候变化的关键.为了研究属于干旱/半干旱气候的青藏高原(TP)和湿润/半湿润气候的长江流域(YRR)之间地表能量和水分交换的异同,本文对比分析了两个区域8个不同地表类型(包括高山荒漠,高山草地,(平原)城市和(平原)草地等)观测站点的地表辐射和能量通量数据.结果显示:(1)TP由于高原大气层稀薄且空气洁净,年平均入射短波辐射为251.3W m^(-2),是YRR的1.7倍.加之高原地表反照率高导致反射辐射(59.6 W m^(-2))是YRR的2.87倍.入射及出射的长波辐射为231.5和338.0 W m^(-2),分别为YRR的0.64和0.83.而两个区域的净辐射差异不大;(2)草地站更多的潜热释放使得地表总加热效率高于城市和高山荒漠,TP和YRR的草地站的年平均潜热分别为35.0和38.8 W m^(-2),而植被稀疏且土壤干燥的高山荒漠地区感热最大,年平均感热为42.1 W m^(-2);其次是城市下垫面,其年平均感热为37.7 W m^(-2).研究结果揭示了不同气候背景下典型下垫面地气相互作用特征,为地气相互作用过程深入分析奠定了基础.

The Effect of Bioturbation Activity of the Ark Clam Scapharca subcrenata on the Fluxes of Nutrient Exchange at the Sediment–Water Interface

Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value.However,there is little information regarding the effects of the bioturbation of S.subcrenata on the fluxes of nutrient exchange in the sediment-water interface(SWI).In this regard,S.subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI.The results showed that the biological activity of S.subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments.The bioturbation of S.subcrenata could allow the nutrients to permeate into the surface sediments at 6-10cm and increase the release rate of nutrients at the SWI.The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region.The culture of S.subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay.Nutrients exchange in the SWI contributes a part of 86%DIN,71%PO43−-P and 18%SiO32−-Si for the aquaculture farm.

Laminar Heat Transfer Modeling and Investigation of Thermal Dispersion in a Flat Plate Heat Exchanger： Estimating Heat Transfer Coefficient, Heat Flux and Nusselt Number

PHEs （plate heat exchangers） are among the most common thermal equipments in diverse industries particularly in oil and gas companies. This wide usage is obviously due to significant benefits of these heat exchangers over other types. In this article, a behavioral analysis of heat transfer in fiat plates of these heat exchangers in laminar flow situation through CFD （computational fluid dynamics） simulation using FLUENT 6.3.26 software is done. The study reveals results graphically based on fluid＇s behavior in co-current and counter current flows and discusses thermal indexes consisting of heat transfer coefficient, Nusslet and total heat flux in both conditions. Eventually, a comparison via the graphical results is presented between the two types of flow directions.

Role of Kuroshio frontal eddy in exchange between shelf water and Kuroshio water in East China Sea

Basic patterns of the reversal of the Kuroshio water toward the shelf, intrusion of the shelf mixed water into the Kuroshio and uplifting of the near-bottom nutrient-rich water into the upper layer by the pumping of the frontal eddy are analyzed on the basis of satellite infrared images and hydrologic, chemical and biological observations. Results show that the Kuroshio frontal eddies play a very important role in the exchange between the shelf water and the Kuroshio water. The estimation of the average volume transports for three frontal eddy events indicates that the shelf mixed water entrained by an eddy into Kuroshio is 0.44×10~6 m3/s and the reversal Kuroshio water onto the shelf region only 0.04×10~6 m3/s. Along the whole shelf edge, the volume transport of the shelf mixed water entrained by the eddies into the Kuroshio is 1.8×10~6 m3/s. The nutrient (NO3-N) flux pumped to the euphotic zone and input to the continental shelf through a column with 1 m wide is 974 μmol/(s·m) when there is frontal eddy and only 79 μmol/(s·m) in the case of no frontal eddy. Yearly nutrient (NO3-N) flux input to the shelf area caused by the frontal eddy is 1.7×10~5 t/a.

Numerical Study of Water and Suspended Matter Exchange Between the Yellow Sea and the East China Sea

POM was used to study the monthly mean circulation in the Yellow Sea and East China Sea. The calculated results showed almost all major characteristics of the circulation system. The calculated circulation system and observational data were used to determine the sediment concentration, volume transport, heat flux and suspended matter flux between the Yellow Sea and the East China Sea. The conclusions obtained were that the volume and heat are transported northward through the 32°N section during each season; that in winter and autumn, total suspended matter is transported southward, and is larger in winter than in autumn. The reason is that the Yellow Sea Coastal Current is strong and always contains more suspend matter in winter and autumn. The seasonal suspended matter exchange between the Yellow Sea and the East China Sea are 0.58×10 7 tons in spring, 2.81×10 7 tons in summer, -2.60×10 7 tons in autumn and -3.40×10 7 tons in winter. Net flux of suspended matter from the Yellow Sea to the East China Sea is 2.61×10 7 tons every year.

Cholangiocyte anion exchange and biliary bicarbonate excretion

Primary canalicular bile undergoes a process of fluidization and alkalinization along the biliary tract that is influenced by several factors including hormones, innervation/neuropeptides, and biliary constituents. The excretion of bicarbonate at both the canaliculi and the bile ducts is an important contributor to the generation of the so-called bile-salt independent flow. Bicarbonate is secreted from hepatocytes and cholangiocytes through parallel mechanisms which involve chloride efflux through activation of Cl- channels, and further bicarbonate secretion via AE2/SLC4A2-mediated Cl-/HCO3- exchange. Glucagon and secretin are two relevant hormones which seem to act very similarly in their target cells （hepatocytes for the former and cholangiocytes for the latter）. These hormones interact with their specific G protein-coupled receptors, causing increases in intracellular levels of cAMP and activation of cAMP-dependent Cl- and HCO3- secretory mechanisms. Both hepatocytes and cholangiocytes appear to have cAMP-responsive intracellular vesicles in which AE2/SLC4A2 colocalizes with cell specific Cl- channels （CFTR in cholangiocytes and not yet determined in hepatocytes） and aquaporins （AQP8 in hepatocytes and AQP1 in cholangiocytes）, cAMP-induced coordinated trafficking of these vesicles to either canalicular or cholangiocyte lumenal membranes and further exocytosis results in increased osmotic forces and passive movement of water with net bicarbonate-rich hydrocholeresis.

Net water vapour exchange over a mixed needle and broad-leaved forest in Changbai Mountain during autumn

Water vapour and CO2 fluxes were measured by the eddy-covariance technique above a mixed needle and broad-leaved forest with affiliated meteorological measurements in Changbai Mountain as part of China's FLUX projects since late August in 2002. Net water vapour exchange and environmental control over the forest were examined from September 1 to October 31 in 2002. To quantify the seasonal dynamics, the transition period was separated into leafed, leaf falling and leafless stages according to the development of leaf area. The results showed that (a) seasonal variation of water vapour exchange was mainly controlled by net radiation (Rn) which could account for 78.5%, 63.4% and 56.6% for leafed, leaf falling and leafless stages, respectively, while other environmental factors' effects varied evidently; (b) magnitude of water vapour flux decreased remarkably during autumn and daily mean of water vapour exchange was 24.2 mg m-2 s-1 (100%), 14.8 mg m-2 s-1 (61.2%) and 10.3 mg m-2 s-1 (42.6%) for leafed, leaf falling and leafless stage, respectively; and (c) the budget of water vapour exchange during autumn was estimated to be 87.1 kg H2O m-2, with a mean of 1427.2 g H2O d-1' varying markedly from 3104.0 to 227.5 g H2O m-2d-1.

A Sensitivity Study of Arctic Ice-Ocean Heat Exchange to the Three-Equation Boundary Condition Parametrization in CICE6

In this study,we perform a stand-alone sensitivity study using the Los Alamos Sea ice model version 6(CICE6)to investigate the model sensitivity to two Ice-Ocean(IO)boundary condition approaches.One is the two-equation approach that treats the freezing temperature as a function of the ocean mixed layer(ML)salinity,using two equations to parametrize the IO heat exchanges.Another approach uses the salinity of the IO interface to define the actual freezing temperature,so an equation describing the salt flux at the IO interface is added to the two-equation approach,forming the so-called three-equation approach.We focus on the impact of the three-equation boundary condition on the IO heat exchange and associated basal melt/growth of the sea ice in the Arctic Ocean.Compared with the two-equation simulation,our three-equation simulation shows a reduced oceanic turbulent heat flux,weakened basal melt,increased ice thickness,and reduced sea surface temperature(SST)in the Arctic.These impacts occur mainly at the ice edge regions and manifest themselves in summer.Furthermore,in August,we observed a downward turbulent heat flux from the ice to the ocean ML in two of our three-equation sensitivity runs with a constant heat transfer coefficient(0.006),which caused heat divergence and congelation at the ice bottom.Additionally,the influence of different combinations of heat/salt transfer coefficients and thermal conductivity in the three-equation approach on the model simulated results is assessed.The results presented in this study can provide insight into sea ice model sensitivity to the three-equation IO boundary condition for coupling the CICE6 to climate models.

Air-Water Carbon Dioxide Exchange in the Littoral Zone of Lake Baikal (Ice-Free Period)

Lake Baikal is one of the most unique natural environments in Siberia, and it affects to a large extent the natural state in this region. Processes of gas exchange in the air-water system have been studied in Lake Baikal since 2002. Measurements have been carried out in the littoral area on the western shore of Southern Baikal (51°51'N, 105°04'E). The method of accumulative chambers was prioritized for measuring carbon dioxide fluxes in the air-water system. Chemical analysis of the water samples collected every three hours at the chamber locations was carried out in the on-land laboratory. We measured pH, content of dissolved oxygen, bicarbonate, nitrate and phosphate. The CO2 content in the water was measured from pH values and the bicarbonate concentration. The total sink of CO2 on the water surface is increasing in the littoral area of Lake Baikal from 20 mg·CO2·m-2·day-1 in June to 110 mg·CO2·m-2·day-1 in August. The decrease in the flux rate usually begins in September from 95 mg·CO2·m-2·day-1 to the zero balance in late October - early November. The maximal rate of mean diurnal CO2 emissions is recorded in December in the pre-ice period (110 mg·CO2·m-2·day-1). Based on the long-term measurements during all seasons, the sink of atmospheric CO2 in the littoral zones of Lake Baikal was estimated to be 3 - 5 g·CO2·m-2.

Energy Analysis of a Counter-Flow Plate Heat Exchanger Working in Stationary Mode and Using Geothermal Energy for Drying

This paper presents an energy analysis of a counter-flow plate heat exchanger operating in stationary mode. The exchanger comprises a rectangular plate of which we vary the heat transfer surface (by fixing its width and varying its length) and analyze the evolution of some parameters as a function of this heat transfer surface. The parameters to be analyzed are the NTU (number of transfer units), the effectiveness, the temperatures of both primary and secondary fluids and the heat flux. The analysis carried out will help understand the behavior of the counter-flow plate heat exchanger operating in stationary mode. Then, the heat transfer surface of the exchanger is determined for the sizing of a counter-flow plate heat exchanger intended to produce hot air for drying. That plate heat exchanger uses water vapor heated by geothermal energy as a primary fluid and atmospheric air as a secondary fluid. The products to be dried are onions with a mass flow of water to be evacuated of 100 kg/h.

Surface-exchange of NOx and NH_3 above a winter wheat field in the Yangtze Delta, China

A four-dynamic-chamber system was constructed to measure NOx and NH3 surface-exchange between a typical wheat field and the atmosphere in the Yangtze Delta, China. The average fluxes of NO, NO2 and NH3 were 79, -5.6 and -5.1 ngN/（m^2·s）, and 91, -1.8 and 23 ngN/（m^2·s）, respectively for the wheat field and the bare soil. The NO flux was positively correlated with soil temperature and the fluxes of NO2 and NH3 were negatively correlated with their ambient concentrations during the investigated period. The compensation point of NO2 between the wheat field and the atmosphere was 11.9 μg/m3. The emissions of NO-N and NH3-N from the urea applied to the wheat field were 2.3% and 0.2%, respectively, which indicated that the main pathway of N loss from the investigated winter wheat field was NO. Application of a mixture of urea and lignin increased the emissions of NO, but also greatly increased the yield of the winter wheat.

Effect of Deformation of Red Cell on Nutritional Transport in Capillary-Tissue Exchange System

A mathematical analysis of a model for nutritional exchange in a capillary-tissue exchange system is presented in this paper. This model consist of a single file flow of red blood cell in capillary when diameter of red blood cell is greater than tube diameter, In this case, the cell must be deformed. Due to concentration gradients, the dissolved nutrient in substrate diffuses into surrounding tissue. Introducing approximations of the lubrication theory, squeezing flow of plasma in between the gap between cell and capillary wall have been solved with the help of approximate mathematical techniques. The computational results for concentration of dissolved nutrients, diffusive flux and normal component of velocity have been presented and discussed through graphs. We have also shown the effect of deformation parameter and permeability on these results.

我国东部山地针阔混交林碳通量特征分析

以浙江省金华市武义县大毛尖山为研究区域,开展复杂山地森林生态系统碳汇能力的观测研究,并利用涡动相关法在2022年6月~2023年5月进行观测,经过数据质量控制和质量评价分析,得到42%的优质CO_(2)通量数据.结果表明,大毛尖山周边以针阔混交林为主,能量闭合度为0.89,能够很好的代表站点通量情况.CO_(2)通量在日尺度上均表现为U型变化,范围为-1.20~0.89mgCO_(2)/(m^(2)·s).四季碳汇能力强弱依次为,夏季、春季、秋季、冬季;各月份净生态系统碳交换量(NEE)均为负值,整体表现为碳汇.CO_(2)通量与气象因子中的空气温度呈负相关,相对湿度和平均风速正相关,夜间因呼吸作用产生的CO_(2)通量与土壤温度正相关.本研究初步解释了大毛尖山森林生态系统的碳汇特征.

青藏高原东南缘不同类型生态系统碳、水交换特征

青藏高原东南缘横断山脉地区是南亚和东亚季风的交汇处,也是大气变化的敏感区和热源区。开展该地区地气相互作用对区域水热过程影响机制及其参数化研究,对于研究青藏高原大气水汽传输的关键过程问题有重大意义。本文介绍了基于涡动观测法开展的青藏高原东南缘地区的地气相互作用观测试验,并总结了洱海湖面、丽江高山草甸及腾冲北海湿地的地气交换特征,以及利用数值模式开展复杂山地局地环流特征的研究工作。目前已初步明确和揭示青藏高原东南缘横断山脉不同类型下垫面的地气交换特征及其影响因素,主要结论如下:青藏高原东南缘高山草甸的碳、水交换过程受降水分布影响显著,“浮毯型”湿地(水面常年覆盖有“浮毯”状苔草草排)的碳、水交换除了受气象因素影响外,也受到下垫面植被和水体比例变化的影响。不同类型生态系统的碳、水交换过程在不同时间尺度的影响因子存在差别。风速始终是湖泊潜热和CO_(2)交换的关键影响因子,而降水在较长时间尺度对湖泊CO_(2)通量也有显著影响。此外,青藏高原东南缘的复杂地形对于生态系统的碳、水交换过程也有显著影响。复杂地形产生的不同类型的局地环流对于生态系统的碳、水交换过程有不同的影响。

季风降雨前后深圳地区地表通量差异分析

为进一步认识夏季西南季风对深圳地区地表通量的影响,采用深圳气象梯度塔的辐射和涡动协方差系统观测资料,研究该地区季风强降水过程中地表通量的变化特征。结果显示:在季风降水期间和降水后,深圳地区近地面太阳辐射明显减弱,同时反照率减小。在降水期间,深圳地区地表感热和潜热通量均明显低于降水前和降水后,而且由碳汇转为碳源。

脱庚烷塔分离效果差的原因分析及改进措施

异构化装置脱庚烷塔主要任务是分离C 8芳烃中的C 6~C 7馏分,为二甲苯装置提供原料。脱庚烷塔分离效果差,造成C 8芳烃损失,其主要原因一是外购混合二甲苯带有溶解氧,引起烯烃在进料换热器壳层升温后发生聚合,生成黏稠产物,导致脱庚烷塔进料温度低;二是高通量管换热器E-707基管表面多孔涂层覆有垢层,导致换热效果下降,换热能力不足。经过流程优化和更换换热器后,脱庚烷塔分离效果提升明显,塔顶C 8芳烃质量分数由10.00%降至1.34%,塔底苯质量分数低于0.01%,甲苯质量分数由1.16%降至0.38%。

河口离子交换过程对流域化学风化通量估算的影响

大陆风化是构造尺度上维持地球系统气候稳定的重要机制,河水主要离子组成分析是约束流域风化类型和速率的主要方法,然而悬浮物与水体间阳离子置换对风化通量评估的重要性并未得到足够重视。本研究使用NH4Cl及Mg(NO_(3))_(2)溶液提取长江入海口悬浮物可交换态组分,探讨离子交换过程对元素循环及流域风化通量评估的影响。结果表明,悬浮物向口门外搬运过程中,可交换态Ca^(2+)含量降低了9.3×10^(-2) meq/g,约占河流端元悬浮物可交换态Ca^(2+)含量的53.8%,Na^(+)、Mg^(2+)、K^(+)含量分别增加了19.6×10^(-2) meq/g(约3266.7%),8.9×10^(-2) meq/g(约89.9%)和1.1×10^(-2)meq/g(约220.0%);离子交换量与颗粒粒径、矿物组成以及有机碳含量(TOC)等参数无明显相关性,主要受控于水体阳离子组成;根据可交换态阳离子含量变化以及长江入海泥沙通量,估算长江悬浮物入海过程中可释放Ca^(2+)通量约为7.9×10^(9)mol/a,吸附的Na^(+)、Mg^(2+)和K^(+)通量分别为26.3×10^(9)mol/a、6.0×10^(9)mol/a和1.4×10^(9) mol/a,相当于长江每年输入这些阳离子通量的2.5%、9.2%、4.4%和2.3%;大河河口离子交换过程是海陆间元素地球化学循环的重要环节,流域内海相沉积岩或沉积物吸附的Na^(+)和K^(+)再释放到河水中会导致硅酸岩风化通量的高估,初步估算现在长江流域的硅酸岩风化通量被高估15%,考虑到近几十年流域内人类活动导致入海泥沙量显著下降,地质历史时期该占比可能显著增大。因此,未来流域风化与河口元素循环研究应充分考虑水体和沉积物阳离子交换和人类活动的可能影响。

中国北方针叶林碳通量动态变化及其影响因素分析

基于北方针叶林典型站点——呼中定位观测站2014~2018年不同时间尺度碳通量观测数据,探究了该生态系统长时间序列碳通量动态变化及其影响因素。结果表明:受总初级生产力(Gross Primary Productivity,GPP)和生态系统呼吸(Ecosystem Respiration,RE)的综合作用影响,北方针叶林生态系统净碳交换量(Net Ecosystem Exchange,NEE)年际变化差异较大,在2.64~17.63 g(C)m^(-2) a^(-1)之间波动;从季节上看,在生长季(6~8月)GPP值大于RE,北方针叶林以净碳吸收为主,在非生长季,NEE与RE相等,北方针叶林为弱碳源;逐日尺度上,NEE呈倒“U”形变化特征,RE和GPP则呈“U”形特征。日尺度NEE主要受净辐射、相对湿度、气温、土壤温度等因素影响,这些环境因素构建的回归方程可以解释45.19%的NEE日变化;月尺度上NEE主要受净辐射、相对湿度、气温3个因素影响,回归方程可以解释78.42%的NEE月变化。

高深宽比粘接式歧管微通道换热器性能研究

半导体和其他微尺度电子技术的迅速发展导致芯片功率密度急剧增加,而功率的增加使电子设备的散热面临严峻挑战,微通道换热器则可以有效解决电子设备的散热问题。文章设计了一种微通道深宽比(aspect ratio,AR)高达10.5且单个歧管微通道换热器尺寸为13.00 mm×12.00 mm×0.88 mm的粘接式歧管微通道换热器,并从热点温度、热阻、系统压降3个方面评估换热器冷却模块的热工性能和水力性能。研究结果表明,当以去离子水为工作介质且水的体积流量为150 mL/min时,换热器在芯片温度为82.1℃、总热阻为0.052 cm^(2)·K/W、压降为260 kPa时,散热高达1200 W/cm^(2)。该研究为使用单相水来冷却高热通量的电力电子设备提供了一种新的思路。