太平洋悬浮体特征及近底雾状层(雾浊层)探讨

2005年在太平洋12个测站分层采集了悬浮体水样及连续的水体温度、盐度、深度等数据.利用水体悬浮体含量在垂向上的分布特征初步分析了大洋雾状层的特点,并讨论了水体中悬浮体颗粒物质的来源,对不同海洋环境中悬浮体分布进行了对比,发现大洋水体中悬浮体含量总体很小,一般不超过0.30 mg/dm3,但在一定水层内悬浮体含量相对较高,形成雾状层.雾状层在大洋内广泛分布,一般以表层雾状层和近底雾状层形式存在.大洋水体中悬浮体颗粒物来源广泛.表层雾状层的形成主要受透光层内生物作用的影响,而底质沉积物的再悬浮是影响底部雾状层形成的重要因素.因受水体物理海洋环境和物质来源的影响,不同区域水体中悬浮体含量不同,雾状层的分布不同.海山顶部受水流及岩石基底影响雾状层分布不明显,海山底部与开辟区洋盆海域雾状层更普遍.开辟区东西区由于物源差异水体中悬浮体含量差别明显,靠近火山喷口的西区水体中悬浮体含量明显高于东区的.

东巽他弧的龙自弧前盆地的新生代演化和地震地层

1 前言 在活动大陆边缘和大洋岛弧内可见到由板块消减作用导致的岛弧—海沟系的弧前区。会聚边缘体系的各种形态是由初始地质背景和在俯冲过程期间构造演化的差异引起的。 增生柱的构造演变主要受俯冲大洋层的厚度、性质、时代、海沟和陆坡沉积物的不同厚度、板块会聚速率和斜交度以及轻浮壳块的碰撞所控制。

Evaluation of CORDEX regional climate models in simulating temperature and precipitation over the Tibetan Plateau

Using a regional climate model（RCM） is generally regarded as a promising approach in researching the climate of the Tibetan Plateau, due to the advantages provided by the high resolutions of these models. Whilst previous studies have focused mostly on individual RCM simulations, here, multiple RCMs from the Coordinated Regional Climate Downscaling Experiment are evaluated in simulating surface air temperature and precipitation changes over the Tibetan Plateau using station and gridded observations. The results show the following：（1） All RCMs consistently show similar spatial patterns, but a mean cold（wet） bias in the temperature（precipitation） climatology compared to station observations. The RCMs fail to reproduce the observed spatial patterns of temperature and precipitation trends, and on average produce greater trends in temperature and smaller trends in precipitation than observed results. The multi-model ensemble overall produces superior trends in both simulated temperature and precipitation relative to individual models. Meanwhile, Reg CM4 presents the most reasonable simulated trends among the five RCMs.（2） Considerable dissimilarities are shown in the simulated quantitative results from the different RCMs, which indicates a large model dependency in the simulation of climate over the Tibetan Plateau. This implies that caution may be needed when an individual RCM is used to estimate the amplitude of climate change over the Tibetan Plateau.（3） The temperature（precipitation） in 2016–35, relative to 1986–2005, is projected by the multi-model ensemble to increase by 1.38 ± 0.09 °C（0.8% ± 4.0%） and 1.77 ± 0.28 °C（7.3% ± 2.5%） under the RCP4.5 and RCP8.5 scenario, respectively. The results of this study advance our understanding of the applicability of RCMs in studies of climate change over the Tibetan Plateau from a multiple-RCM perspective.

Singularly Perturbed Solution of Coupled Model in Atmosphere-ocean for Global Climate

A box model of the interhemispheric thermohaline circulation (THC) in atmosphere-ocean for global cli-mate is considered. By using the multi-scales method, the asymptotic solution of a simplified weakly nonlinear model is discussed. Firstly, by introducing first scale, the zeroth order approximate solution of the model is obtained. Sec-ondly, by using the multi-scales, the first order approximate equation of the model is found. Finally, second order ap-proximate equation is formed to eliminate the secular terms, and a uniformly valid asymptotic expansion of solution is decided. The multi-scales solving method is an analytic method which can be used to analyze operation sequentially. And then we can also study the diversified qualitative and quantitative behaviors for corresponding physical quantities. This paper aims at providing a valid method for solving a box model of the nonlinear equation.

Variations in the Lower Level of the PBL Associated with the Yellow Sea Fog-New Observations by L-Band Radar

The Chinese east coastal areas and marginal seas are foggy regions. The development of effective forecasting methods rests upon a comprehensive knowledge of the fog phenomena. This study provides new observations associated with the sea togs over the northwestern Yellow Sea by means of L-band radar soundings with a high vertical resolution of 30m. The monthly tem- perature lapse rate, the Richardson Nulnbers, and the humidity show obvious seasonal variations in the lower level of the planetary boundary layer （PBL） that are related to the onset, peak and end of the Yellow Sea fog season. The typical pattern of stratification for the sea fog season in the northwestern Yellow Sea is that a stable layer of about 400 m thick caps a 150 m conditionally unstable layer Besides, the differences between togs and stratus clouds in terms of humidity, turbulence and temperature are analyzed, which is of significance for sea fog forecast and detection by satellites. The thickness of the sea fogs varies in different stages of the fog season, and is associated with the temperature inversion. The numerical simulation proves that the seasonal variations obtained by the radar well represent the situations over the Yellow Sea.

The Effect of the East China Sea Kuroshio Front on the Marine Atmospheric Boundary Layer

Various satellite data,JRA-25(Japan reanalysis of 25 years) reanalyzed data and WRF(Weather Research Forecast) model are used to investigate the in situ effect of the ESKF(East China Sea Kuroshio Front) on the MABL(marine atmospheric boundary layer).The intensity of the ESKF is most robust from January to April in its annual cycle.The local strong surface northerly/northeasterly winds are observed right over the ESKF in January and in April and the wind speeds decrease upward in the MABL.The thermal wind effect that is derived from the baroclinic MABL forced by the strong SST gradient contributes to the strong surface winds to a large degree.The convergence zone existing along the warm flank of the ESKF is stronger in April than in January corresponding to the steeper SST(sea surface temperature) gradient.The collocations of the cloud cover maximum and precipitation maximum are basically consistent with the convergence zone of the wind field.The clouds develop higher(lower) in the warm(cold) flank of the ESKF due to the less(more) stable stratification in the MABL.The lowest clouds are observed in April on the cold flank of the ESKF and over the Yellow Sea due to the existence of the pronounced temperature inversion.The numerical experiments with smoothed SST are consistent with the results from the ovservations.

Marine Atmospheric Boundary Layers Associated with Summer Monsoon Onset over the South China Sea in 1998

The variations of the marine atmospheric boundary layer (MABL) associated with the South China Sea Summer Monsoon were examined using the Global Positioning System (GPS) sounding datasets obtained four times daily during May-June 1998 on board Research Vessels Kexue 1 and Shiyan 3. The MABL height is defined as the height at the lowest level where virtual potential temperature increases by 1 K from the surface. The results indicate that the MABL height decreased over the northern South China Sea (SCS) and remained the same over the southern SCS, as sea surface temperature (SST) fell for the northern and rose for the southern SCS after the monsoon onset. Over the northern SCS, a decrease in both the SST and the surface latent-heat flux after the onset resulted in a reduction of the MABL height as well as a decoupling of MABL from clouds. It was found that MABL height reduction corresponded to rainfall occurrence. Over the southern SCS, a probable reason for the constant increase of SST and surface heat flux was the rainfall and internal atmospheric dynamics.

Toward deeper development of Biogeochemical-Argo floats

The Biogeochemical-Argo （BGC-Argo） Program aims at operating a network of profiling floats equipped with sensors of key biogeochemical variables for support- ing research activities that address impacts of climate change on oceanic biogeochemical cycles and ecosystems （Claustre et al. 2010; IOCCG 2011; Johnson et al. 2009）.

Recent Observations and Modeling Study About Sea Fog over the Yellow Sea and East China Sea

This review presents some of the latest achievements in sea fog research,including fog climatology,fog structure in the marine atmospheric boundary layer,and numerical simulations and forecasting of fog.With the development of atmospheric observational techniques and equipments,new facts about sea fog are revealed.The mechanisms involved in the formation,development and dissipation of sea fog are further explored with the help of advanced atmospheric models.

Meridional distribution of 226Ra in the west Pacific and the Southern Ocean surface waters

During the 134 （1996 1997） and the 19th （2002-2003） Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River （Yangtze） estuary （30^.59%, 122^.26＇E） through Taiwan Strait, the South China Sea, and the Eastern Indian Ocean to Prydz Bay, Antarctica （69^.10＇S, 74^.30＇E）, and analyzed them for the 226Ra specific activity. The 226Ra specific activity of the Chanjiang River estuary surface water （3.15 Bq/m3） was found to be the highest among all the surface samples because of the desorption of 226Ra from riverine particles. Between Chanjiang River estuary and 40^.S, 226Ra specific activity was found to be relatively uniform with a mean value of 1.07 Bq/m3 （n= 19, SD=0.14）, similar to that of the open ocean. From 40^.S to 65^.S, 226Ra specific activity increased intensively, then decreased moderately further southwards. Near the Antarctic shore, it increased again, to 2.31 Bq/m3. This distribution was controlled by a combination of deep water upwelling, Southern Ocean fronts, water mixing and the continental 226Ra import. In Prydz Bay and the adjacent sea area, the mean 226Ra activity value was 2.26 Bq/m3 （n=31, SD=0.28）, with a relatively higher value outside of the bay and low 226Ra activity value in the center of the bay. This was consistent with the topography and hydrological setting of the bay. In addition, we extended the study area northward to the Arctic, by combining the published Z26Ra dataset for surface water from the Bering Sea to the Japan Sea. We also discuss the 226Ra distribution of high latitude oceanic surface water and its mechanisms.

The Formation of Wind Curl in the Marine Atmosphere Boundary Layer over the East China Sea Kuroshio in Spring

Various data are used to investigate the characteristics of the surface wind field and rainfall on the East China Sea Kuroshio(ESK) in March and April, 2011. In March, the wind speed maximum shows over the ESK front(ESKF) in the 10 meter wind field, which agrees with the thermal wind effect. A wind curl center is generated on the warm flank of the ESKF. The winds are much weaker in April, so is the wind curl. A rainband exists over the ESKF in both the months. The Weather Research and Forecasting(WRF) model is used for further researches. The winds on the top of the marine atmosphere boundary layer(MABL) indicate that in March, a positive wind curl is generated in the whole MABL over the warm flank of the ESKF. The thermal wind effect forced by the strong SST gradient overlying the background wind leads to strong surface northeasterly winds on the ESKF, and a positive shearing vorticity is created over the warm flank of the ESKF to generate wind curl. In the smoothed sea surface temperature experiment, the presence of the ESKF is responsible for the strong northeast winds in the ESKF, and essential for the distribution of the rainfall centers in March, which confirms the mechanism above. The same simulation is made for April, 2011, and the responses from the MABL become weak. The low background wind speed weakens the effect of the thermal wind, thus no strong Ekman pumping is helpful for precipitation. There is no big difference in rainfall between the control run and the smooth SST run. Decomposition of the wind vector shows that local wind acceleration induced by the thermal wind effect along with the variations in wind direction is responsible for the pronounced wind curl/divergence over the ESKF.

The effect of current and wave on whitecap coverage via relative speed:the Atlantic Ocean case

Whitecapping plays an important role in many air-sea exchange and upper ocean processes.Traditionally,whitecap coverage is parameterized as a function of wind speed only.At present,the relative speed of ocean current to wind is considered to be important in the air-sea exchange parameterization which is the function of wind speed only.In this paper,the effects of ocean surface velocity (current velocity and wave induced velocity) and the wave parameters on whitecap coverage through relative speeds are investigated,by applying a 2-parameter whitecap coverage model to the Atlantic Ocean.It is found that the impacts of both current and wave on whitecap coverage are considerable in the most part of the Atlantic Ocean.It is interesting that the effect of wave is more significant than that of current.

Air-Sea Exchange of Volatile Organic Compounds: A New Model with Microlayer Effects

The authors propose a new "three-layer" conceptual model for the air-sea exchange of organic gases, which includes a dynamic surface microlayer with photochemical and biological processes. A parameterization of this three-layer model is presented, which was used to calculate the air-sea fluxes of acetone over the Pacific Ocean. The air-sea fluxes of acetone calculated by the three-layer model are in the same direction but possess half the magnitude of the fluxes calculated by the traditional two-layer model in the absence of photochemical and biological processes. However, photochemical and biological processes impacting acetone in the microlayer can greatly vary the calculated fluxes in the three-layer model, even reversing their direction under favorable conditions. Our model may help explain the discrepancies between measured and calculated acetone fluxes in previous studies. More measurements are needed to validate our conceptual model and provide constraints on the model parameters.

Structure of summer atmospheric boundary layer in the center of Arctic Ocean and its relation with sea ice extent change

The atmospheric vertical structure and changed characteristics of boundary layer parameters, as well as their relations with sea ice and temperature changes in the center of Arctic Ocean(80°–88°N) are presented by adopting GPS sounding data obtained by the 4th–6th Arctic expeditions of China and NCEP(National Centre for Environmental Prediction) reanalysis data. Obvious differences are observed regarding the tropopause, boundary layer height, temperature inversion, and vertical structure of wind speed and direction in the center Arctic Ocean in the summer of 2012, 2010, and 2014. These differences can be explained by the relations between temperature and changes in sea ice extent in September from 1979 to 2014. In September 2012, the Arctic sea ice extent decreased by 44% an with obvious warming process. In September 2010 and 2014, it decreased by 22.6% and 17% with an obvious cooling process, respectively. A comparison of the two processes shows that sea ice change has a significant influence on the structure of the atmospheric boundary layer. In the recent 30 years, the temperature changes of 1000 and 850 h Pa in the center of the Arctic Ocean have displayed an obvious warming trend and negative correlation with sea ice extent. These changes indicate that the continuous reduction of Arctic sea ice will continue the warming of the troposphere middle layer.

Research progress in artificial upwelling and its potential environmental effects

Artificial upwelling, as a geoengineering tool, has received worldwide attention because it may actualize ocean fertilization in a sustainable way, which could potentially alleviate the pressures on the fish stocks and human-driven climate change in the ocean. We reviewed the current knowledge on the development of an artificial upwelling system and its potential environmental effects. Special attention was given to the research progress on the air-lift concept artificial upwelling by Zhejiang University. The research on artificial upwelling over the past few decades has generated a range of devices that have been successfully applied in the field for months. Based on field experiments and the associated modeling results, part of them reported positive effects on increasing primary production and enhancing CO2 sequestration. However, as a significant disturbance to the environment, especially for large-scale applications, the uncertainties related to the potential effects on ecosystem remain unsolved. Zhejiang University has overcome the technical challenges in designing and fabricating a robust and high efficiency artificial upwelling device which has been examined in two field experiments in Qiandao Lake and one sea trial in the East China Sea. It was investigated that cold and hypoxic deep ocean water(DOW) could be uplifted to the euphotic layer, which could potentially change the nutrient distribution and adjust the N/P ratio. Both simulation and field experiments results confirmed that utilizing self-powered energy to inject compressed air to uplift DOW was a valid and efficient method. Therefore, further field-based research on artificial upwelling, especially for long-term field research is required to test the scientific hypothesis.