Response of the South China Sea summer monsoon onset to air-sea heat fluxes over the Indian Ocean     

陈锦年  左涛  王宏娜 《中国海洋湖沼学报》2012,30(6):974-979

We objectively define the onset date of the South China Sea (SCS) summer monsoon, after having evaluated previous studies and considered various factors. Then, interannual and interdecadal characteristics of the SCS summer monsoon onset are analyzed. In addition, we calculate air-sea heat fluxes over the Indian Ocean using the advanced method of CORARE3.0, based on satellite remote sensing data. The onset variation cycle has remarkable interdecadal variability with cycles of 16 a and 28 a. Correlation analysis between air-sea heat fluxes in the Indian Ocean and the SCS summer monsoon indicates that there is a remarkable lag correlation between them. This result has important implications for prediction of the SCS summer monsoon, and provides a scientific basis for further study of the onset process of this monsoon and its prediction. Based on these results, a linear regression equation is obtained to predict the onset date of the monsoon in 2011 and 2012. The forecast is that the onset date of 2011 will be normal or 1 pentad earlier than the normal year, while the onset date in 2012 will be 1-2 pentads later.  相似文献   

Benthic fluxes of dissolved inorganic carbon in the Tinto–Odiel system (SW of Spain)     

T. Ortega  R. PonceJ. Forja  A. Gómez-Parra 《Continental Shelf Research》2008

The benthic fluxes (diffusive and with chambers) of dissolved inorganic carbon (DIC), dissolved oxygen (DO) and total alkalinity (TA) have been calculated in summertime in the estuary system formed by the mouths of the Tinto and Odiel rivers (SW of Spain). An increase of DIC in interstitial water with depth was found for all stations showing values of up to 28 mM at a depth of 5 cm. The diffusive fluxes of DIC and TA obtained ranging between 1.8–7.8 and 1.5–7.3 mmol m⁻² d⁻¹, respectively. These intervals are in agreement with those found for other coastal systems. Considering the plots of DIC vs. alkalinity (ΔDIC/ΔTA) in the first 30 cm of interstitial water, it was deduced that sulphate reduction and the oxidation of sulphides seem to have special relevance in the sediments of the stations studied. The benthic fluxes of inorganic carbon and DO measured by benthic chambers were variable, presenting elevated values (309–433 mmol DIC m⁻² d⁻¹ and 50–120 mmol DO m⁻² d⁻¹). The most elevated fluxes of DIC were seen at the stations with high anthropogenic influence (close to populated areas and industrial discharges). A great proportion of these fluxes are due to CaCO₃ dissolution processes, which constitute an estimated 49% of total DIC flux. DIC and DO benthic flux quotients were far in excess of unity, indicating the significance processes of anaerobic degradation of organic material at the stations studied.  相似文献   

Characteristics and Drivers of Methane Fluxes from a Rice Paddy Based on the Flux Measurement     

Chaoqing Song  Wei Liu  Haibo Lu  Wenping Yuan 《地球科学进展》2019,34(11):1141-1151

Rice paddies are an important anthropogenic source of methane (CH₄) to the atmosphere, which aggravate the global warming greatly. CH₄ fluxes from a rice paddy in Central China were continuously measured with the eddy covariance method in 2018. The characteristics, dynamics and drivers of the observed CH₄ fluxes from this paddy field were subsequently analyzed. The results indicated that \mathrm{①} a distinct seasonal variation of daily CH₄ fluxes was found over the whole observed period. Daily CH₄ fluxes were the highest in the vegetative period, then decreased gradually, and became the lowest in the fallow period; \mathrm{②} observed CH₄ fluxes had a clear single-peak diurnal pattern during the vegetative and reproductive periods, and reached daily peaks at about 14:00-16:00. However, no obvious diurnal variation in CH₄ fluxes was observed during the fallow period; \mathrm{③} air temperature was the most important drivers that controlled the seasonal variation of CH₄ fluxes from this paddy field, and Vapor Pressure Deficit (VPD) was also found related to the CH₄ emissions; \mathrm{④} the largest daily CH₄ flux was 0.69 μmol/(m²·s), occurred in the late of vegetative period, and the total amount of CH₄ emissions over the whole observed period was about 28 g C/m².  相似文献   

Calibration of an estuarine sediment transport model to sediment fluxes as an intermediate step for simulation of geomorphic evolution     

Neil K. Ganju  David H. Schoellhamer 《Continental Shelf Research》2009

Modeling geomorphic evolution in estuaries is necessary to model the fate of legacy contaminants in the bed sediment and the effect of climate change, watershed alterations, sea level rise, construction projects, and restoration efforts. Coupled hydrodynamic and sediment transport models used for this purpose typically are calibrated to water level, currents, and/or suspended-sediment concentrations. However, small errors in these tidal-timescale models can accumulate to cause major errors in geomorphic evolution, which may not be obvious. Here we present an intermediate step towards simulating decadal-timescale geomorphic change: calibration to estimated sediment fluxes (mass/time) at two cross-sections within an estuary. Accurate representation of sediment fluxes gives confidence in representation of sediment supply to and from the estuary during those periods. Several years of sediment flux data are available for the landward and seaward boundaries of Suisun Bay, California, the landward-most embayment of San Francisco Bay. Sediment flux observations suggest that episodic freshwater flows export sediment from Suisun Bay, while gravitational circulation during the dry season imports sediment from seaward sources. The Regional Oceanic Modeling System (ROMS), a three-dimensional coupled hydrodynamic/sediment transport model, was adapted for Suisun Bay, for the purposes of hindcasting 19th and 20th century bathymetric change, and simulating geomorphic response to sea level rise and climatic variability in the 21st century. The sediment transport parameters were calibrated using the sediment flux data from 1997 (a relatively wet year) and 2004 (a relatively dry year). The remaining years of data (1998, 2002, 2003) were used for validation. The model represents the inter-annual and annual sediment flux variability, while net sediment import/export is accurately modeled for three of the five years. The use of sediment flux data for calibrating an estuarine geomorphic model guarantees that modeled geomorphic evolution will not exceed the actual supply of sediment from the watershed and seaward sources during the calibration period. Decadal trends in sediment supply (and therefore fluxes) can accumulate to alter decadal geomorphic change. Therefore, simulations of future geomorphic evolution are bolstered by this intermediate calibration step.  相似文献   

Modeling the impact of wind and waves on suspended particulate matter fluxes in the East Frisian Wadden Sea (southern North Sea)   总被引：3，自引：1，他引：2  

Karsten A. Lettmann  Jörg-Olaf Wolff  Thomas H. Badewien 《Ocean Dynamics》2009,59(2):239-262

Suspended particulate matter (SPM) fluxes and dynamics are investigated in the East Frisian Wadden Sea using a coupled modeling system based on a hydrodynamical model [the General Estuarine Transport Model (GETM)], a third-generation wave model [Simulating Waves Nearshore (SWAN)], and a SPM module attached to GETM. Sedimentological observations document that, over longer time periods, finer sediment fractions disappear from the Wadden Sea Region. In order to understand this phenomenon, a series of numerical scenarios were formulated to discriminate possible influences such as tidal currents, wind-enhanced currents, and wind-generated surface waves. Starting with a simple tidal forcing, the considered scenarios are designed to increase the realism step by step to include moderate and strong winds and waves and, finally, to encompass the full effects of one of the strongest storm surges affecting the region in the last hundred years (Storm Britta in November 2006). The results presented here indicate that moderate weather conditions with wind speeds up to 7.5 m/s and small waves lead to a net import of SPM into the East Frisian Wadden Sea. Waves play only a negligible role during these conditions. However, for stronger wind conditions with speeds above 13 m/s, wind-generated surface waves have a significant impact on SPM dynamics. Under storm conditions, the numerical results demonstrate that sediments are eroded in front of the barrier islands by enhanced wave action and are transported into the back-barrier basins by the currents. Furthermore, sediment erosion due to waves is significantly enhanced on the tidal flats. Finally, fine sediments are flushed out of the tidal basins due to the combined effect of strong erosion by wind-generated waves and a longer residence time in the water column because of their smaller settling velocities compared to coarser sediments.

Karsten A. LettmannEmail:

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湍流混合输运通量的数学物理描述基础——高确定性闭合的湍流二阶矩和基本特征量控制方程组     

袁业立  庄展鹏  杨光兵 《海洋与湖沼》2017,48(5):895-911

湍流,在海洋动力系统其他类运动的控制方程组中,主要以输运通量剩余项的形式出现,它是最重要的海洋混合运动主体。本文的主要研究目标是,在湍流最新研究成果及其子系统控制方程组基础上,提出高确定性的二阶矩闭合原理,导出闭合的二阶矩和基本特征量控制方程组,建立湍流输运通量的数学物理描述基础。现有的湍流基本特征量方程组,其右端项的闭合办法实际上是非独立的。因此要么在今后的研究中引入独立的闭合办法,要么回归到湍流的现场实验分析研究,给出独立的特征量实验关系,从而有可能得到湍流混合系数的解析估计。  相似文献   

Plankton carbon metabolism and air–water CO2 fluxes at a hypereutrophic tropical estuary          下载免费PDF全文

Mariana Guenther  Moacyr Araújo  Carlos Noriega  Manuel Flores‐Montes  Eliane Gonzalez‐Rodriguez  Sigrid Neumann‐Leitão 《Marine Ecology》2017,38(2)

Multiple biotic and abiotic drivers regulate the balance between CO₂ assimilation and release in surface waters. In the present study, we compared in situ measurements of plankton carbon metabolism (primary production and respiration) to calculated air–water CO₂ fluxes (based on abiotic parameters) during 1 year (2008) in a hypereutrophic tropical estuary (Recife Harbor, NE Brazil – 08°03′S, 34°52′W) to test the hypothesis that high productivity leads to a net CO₂ flux from the atmosphere. The calculated CO₂ fluxes through the air–water interface (FCO₂) were negative throughout the year (FCO₂: –2 to –9 mmol C·m^?2·day^?1), indicating that Recife Harbor is an atmospheric CO₂ sink. Respiration rates of the plankton community ranged from 2 to 45 mmol C·m^?2·hr^?1. Gross primary production ranged from 0.2 to 281 mmol C·m^?2·hr^?1, exceeding respiration during most of the year (net autotrophy), except for the end of the wet season, when the water column was net heterotrophic. The present results highlight the importance of including eutrophic tropical shallow estuaries in global air–water CO₂ flux studies, in order to better understand their role as a sink of atmospheric CO₂.  相似文献   

Experimental study on settling velocity of soil particles in dredged slurry     

Nan Zhang  Wei Zhu  Hongtao He  Yiyan Lv  Shengwei Wang 《Marine Georesources & Geotechnology》2017,35(6):747-757

Studying sedimentation and consolidation of dredged slurry has significant implications to the design of storage yard and subsequent ground improvement. In this study, settling velocity of soil particles in dredged slurry during sedimentation and consolidation processes was investigated using an improved multilayer extraction sampling (MES) method. A series of sedimentation column tests were performed on dredged slurry with three different initial water contents. Distributions of volume of soil particles and density of dredged slurry were first obtained by the MES method, settling velocity of soil particles was then calculated by volume flux function approach. It was found that the density and velocity inflection points can be used to distinguish the settling zone and the consolidation zone. The experimental results reveal that the velocity of soil particles was quite low and monotonically decreased with sedimentation height at low initial water content throughout the whole test period, whereas it was increased at 0–1 hours and almost remained constant at 1–7 hours in the settling zone at high initial water content. The effects of initial water content on sedimentation and consolidation mode of dredged slurry and the settling velocity of soil particles were discussed. The relationship between settling velocity of soil particles and particle diameter was also studied. It is indicated that the measured velocity of soil particles was much lower than that calculated by the Stokes equation, and it was related to 0.4881–0.5906 order of particle diameter at 0–1 hours and 0.1117–0.1825 order of particle diameter at 1–7 hours for the test slurries.  相似文献   

南海北部海区太阳辐射观测分析与计算方法研究   总被引：9，自引：2，他引：7  

王举  姚华栋  蒋国荣  何金海  阎俊岳  郑静  陈奕德 《海洋与湖沼》2005,36(5):385-393

利用2000年与2002年南海海气通量观测资料及同期西沙站资料,研究分析了4-6月份南海北部海区太阳总辐射与云量以及日照时间等因子的对应关系.研究发现,日均太阳辐射与日总日照时间对应关系最好,依次是低云量、总云量.据此首先利用2000年资料建立了除考虑云量外还包括日总日照时间的计算日均太阳辐射的估计公式,并利用2002年观测资料进行独立检验.误差分析结果表明,包括日总日照时间的经验公式远优于单纯考虑云量的计算公式,误差减少了近50%.最后,应用该经验公式对观测期间缺测段资料进行了补插及外推估算,分析了2000年与2002年南海季风爆发前后太阳辐射的一些变化特征,估算结果表明,季风爆发前太阳辐射日均值缓慢增加并始终处于较高值.  相似文献   

Evaluation of monthly turbulent heat fluxes from WHOI analysis and NCEP reanalysis in the tropical Atlantic   总被引：2，自引：1，他引：1  

JIANG Hu  WANG Hui  WU Dexing 《海洋学报(英文版)》2005,24(5):14-26

1 IntroductionThe empirical and simple model studies suggestthe existence of a SST dipole mode in the tropical At-lantic which is antisymmetric about the annual-meanthe intertropical convergence zone (ITCZ) and in-volves air- sea interaction through the wind- SST-evaporation (WES) feedback (Carton, 1996; Chang etal., 1997; Zhao et al., 2003). Chang et al. (2000)found that the dominant near-surface atmospheric re-sponse in the tropical Atlantic sector primarily comesfrom the local SST f…  相似文献