2016年夏季北冰洋浮冰站近地层辐射和湍流通量观测

2016年8月7－14日中国第七次北极科学考察期间,在83°N附近设立的长期浮冰站开展了辐射和湍流通量观测研究。结果表明,观测期间反照率变化范围为0.64~0.92,平均反照率为0.78;基于现场观测数据评估了PW79、HIRHAM、ARCSYM和CCSM3 4种不同复杂度的反照率参数化方案在天气尺度的表现,最为复杂的CCSM3结果优于其他参数化方案,但不能体现降雪条件下的反照率快速增长。浮冰区冰雪面平均净辐射为18.10 W/m2,平均感热通量为1.73 W/m2,平均潜热通量为5.55 W/m2,海冰表面消融率为（0.30±0.22） cm/d,表明此时北冰洋浮冰正处于快速消融期。冰面的平均动量通量为0.098（kg·m/s）/（m2·s）,动量通量与风速有很好的对应关系,相关系数达0.80。     

北冰洋浮冰区湍流通量观测试验及参数化研究

利用2008年8月21～29日我国第3次北极考察期间在北冰洋海区(84°27′N,143°37′W～85°13′N,147°20′W)冰站观测的湍流资料及相关资料,对海冰近地层湍流通量及其特征参数进行了研究.结果表明:观测期间浮冰近地层始终存在逆温和逆湿层.这与我们以前(1999年在75°N和2003年在78°N)的观...     

渤海沿岸固定冰粗糙特征的实测研究

The surface roughness characteristics(e.g., height and slope) of sea ice are critical for determining the parameters of an electromagnetic scattering, a surface emission and a surface drag coefficients. It is also important in identifying various ice types, retrieval ice thickness, surface temperature and drag coefficients from remote sensing data. The point clouds(a set of points which are usually defined by X, Y, and Z coordinates that represents the external surface of an object on earth) of land fast ice in five in situ sites in the eastern coast Bohai Sea were measured using a laser scanner-Trimble GX during 2011–2012 winter season. Two hundred and fifty profiles selected from the point clouds of different samples have been used to calculate the height root mean square, height skewness, height kurtosis, slope root mean square, slope skewness and slope kurtosis of them. The root mean square of the height, the root mean square of the slope and the correlation length are about 0.090, 0.075 and 11.74 m, respectively. The heights of 150 profiles in three sites manifest the Gaussian distribution and the slopes of total 250 profiles distributed exponentially. In addition, the fractal dimension and power spectral density profiles were calculated. The results show that the fractal dimension of land fast ice in the Bohai Sea is about 1.132. The power spectral densities of 250 profiles can be expressed through an exponential autocorrelation function.     

Seasonal and interannual variability of the planktic foraminiferal flux in the vicinity of the Azores Current

Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002–2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic.     

Seasonal variations of the ocean surface circulation in the vicinity of Palau

The surface circulation in the western equatorial Pacific Ocean is investigated with the aim of describing intra-annual variations near Palau (134°30′ E, 7°30′ N). In situ data and model output from the Ocean Surface Currents Analysis—Real-time, TRIangle Trans-Ocean buoy Network, Naval Research Laboratory Layered Ocean Model and the Joint Archive for Shipboard ADCP are examined and compared. Known major currents and eddies of the western equatorial Pacific are observed and discussed, and previously undocumented features are identified and named (Palau Eddy, Caroline Eddy, Micronesian Eddy). The circulation at Palau follows a seasonal variation aligned with that of the Asian monsoon (December–April; July–October) and is driven by the major circulation features. From December to April, currents around Palau are generally directed northward with speeds of approximately 20 cm/s, influenced by the North Equatorial Counter-Current and the Mindanao Eddy. The current direction turns slightly clockwise through this boreal winter period, due to the northern migration of the Mindanao Eddy. During April–May, the current west of Palau is reduced to 15 cm/s as the Mindanao Eddy weakens. East of Palau, a cyclonic eddy (Palau Eddy) forms producing southward flow of around 25 cm/s. The flow during the period July to September is disordered with no influence from major circulation features. The current is generally northward west of Palau and southward to the east, each with speeds on the order of 5 cm/s. During October, as the Palau Eddy reforms, the southward current to the east of Palau increases to 15 cm/s. During November, the circulation transitions to the north-directed winter regime.     

一种新型海-气湍流通量参数化方案的模式测试

将一种新型湍流通量参数化方案代入到大气环流模式CAM3中,对比分析了模式改进前后模拟的风应力、感热通量、潜热通量和降水的全球分布,以及风应力、潜热通量和降水的纬向平均。结果表明:改进后模式的模拟结果更接近ERS、ERA40湍流通量数据和CMAP综合降水数据,其中对西风带上洋面风应力、亚洲季风区的潜热通量和降水改进明显。由于该新型湍流通量参数化方案直接由整体理查逊数、空气动力学粗糙度和热力学粗糙度参数化稳定度参数,避免了通过循环迭代计算Obukhov长度,计算效率得到提高。     

不同海况下六种湍流通量参数化方案的对比分析

利用前人给出的表面波浪动力试验中的部分观测资料,通过六种不同的湍流通量参数化方案,分别计算了不同海面波浪状况所对应的摩擦速度。结果表明:海面状况对计算结果有显著影响,六种参数化方案计算的摩擦速度相对涡动相关法(EC)直接测量值的偏差纯风浪海面状况下,较交叉涌浪或反向涌浪海面状况时小得多。并且在纯风浪海面状况下,当近海层大气处于不稳定层结时,Dyer74方案计算的摩擦速度相对EC直接测量值的归一化误差最小,仅为8.47%,能够较好的估计近海层摩擦速度。在稳定层结条件下,当整体Richardson数小于0.1时,除Businger71方案外,其它五种方案的计算误差接近且较小。     

Observations of turbulent mixing and vertical diffusive salt flux in the Changjiang Diluted Water

Based on micro structure measurements from a repeated sampling station southwest of the Jeju Island during summer,we studied the hydrography,pycnocline turbulence,and vertical salt flux in the Changjiang Diluted Water(CD W).The water column was well stratified with the CDW occupied the surface～20 m.Most of the large turbulent kinetic energy dissipation rate(ε) were found in the bottom boundary layer.Interestingly,intermittent strong turbulence(ε>10^-6 W/kg) occurred in the pycnoclin...     

Some peculiarities of the sea surface temperature in the vicinity of western boundary currents

The sea surface temperature Laplacian and related parameters have been applied to identify the basic elements of water circulation and wave and vortical features. Sources of quasistationary meander generation and areas, where cyclonic and anticyclonic vorticities dominate are determined.Translated by Vladimir A. Puchkin.     

Seasonal variability of turbulent heat fluxes in the tropical Atlantic Ocean based on WHOI flux product

The mean seasonal variability of turbulent heat fluxes in the tropical Atlantic Ocean is examined using the Woods Hole Oceanographic Institution(WHOI) flux product.The most turbulent heat fluxes occur during winter seasons in the two hemispheres,whose centers are located at 10°~20°N and 5°～15°S respectively.In climatological ITCZ,the turbulent heat fluxes are the greatest from June to August,and in equatorial cold tongue the turbulent heat fluxes are the greatest from March to May.Seasonal variability of sensible heat flux is smaller than that of latent heat flux and mainly is dominated by the variations of air-sea temperature difference.In the region with larger climatological mean wind speed(air-sea humidity difference),the variations of air-sea humidity difference(wind speed) dominate the variability of latent heat flux.The characteristics of turbulent heat flux yielded from theory analysis and WHOI dataset is consistent in physics which turns out that WHOI's flux data are pretty reliable in the tropical Atlantic Ocean.     

Simulation of turbulent flow over periodic bottom surface

A mathematical model is developed for the simulation of 2D turbulent flow over a periodic surface. An asymptotic solution is found which allows the estimation of the velocity field and tangential stress at a preset periodic form of a surface and rough peak heights. The solution allows the detection of the flow separation points and maximal tangential stress on the surface. The solution found for the near-bottom tangential stress is compared with experimental data on pressure regions of bottom waves and shows their good agreement.     

Lithology and mineralogy of surface sediments in the vicinity of the Kafireas Strait (Aegean Sea)

The surface sediments of the Kafireas Strait and Petalion Gulf, the area between the islands of Evvoia, Andros, Gyaros and Kea in the Aegean Sea, were examined for grain size, mineralogical composition and geotechnical properties. Contents of sand, silt, clay and carbonates as well as porosity, absolute and relative water contents, grain density and bulk mineralogy were determined in samples collected at 35 localities during two oceanographic cruises in April 1986 and July 1991. In addition, current measurements were carried out at three localities in the periods May-June 1988 and July 1991. Muddy sand and sand (52-96% sand) cover the continental shelf, whereas sandy mud (3-49% sand) predominates in deeper areas. Absolute water content varied between 22 and 42%, whereas the values for relative water content were 28-73%. Porosity showed a moderate range of values (36-62%), whereas grain density varied between 2.52 and 2.77 g/cm³. Carbonate content showed a wide range of values (30-72%). Mica and kaolinite are the dominant minerals (average contents 32 and 16.6%, respectively), and quartz, plagioclase, calcite and aragonite showed lower contents of 12.9, 9.8, 13.5 and 9.6%, respectively. Higher mica, kaolinite, chlorite and plagioclase contents closer to Evvoia Island may be related to local mica-amphibolitic-chloritic schists and cipollin outcrops, whereas higher percentages of mica, calcite and aragonite probably relate to the mica schists and marbles of Andros Island. Strong currents were recorded near the seabed in the vicinity of the Kafireas Strait (24 and 38 cm/s maximum velocity on the continental shelf off Evvoia and Andros islands, respectively). The regional geomorphology and bathymetry, the texture and mineralogical composition of terrigenous material, and the particular meteorological and hydrodynamic conditions in the area are the main factors which control the texture, mineralogy and distribution of seabed sediments in the vicinity of the Kafireas Strait.     

Fine structure of the turbulent atmospheric boundary layer over the water surface

In this paper, the results of a laboratory experiment on investigating the wind-velocity field over a water surface using the PIV method are described. The use of a rapid CCD-camera made it possible to perform a detailed study of the eddy structure of airflow. We have measured the velocity fields over a flat plate by wind waves and waves induced by a wave generator. The model of a turbulent boundary layer over a rough surface was directly verified. It has been shown that the wind-velocity profiles over waves obtained by averaging the instantaneous fields over the ensemble of samples and horizontal coordinate are satisfactorily consistent with the profiles calculated within the frameworks of the model of wind flow over rough water surface.     

Correlation between the low-frequency variability of surface temperature and the heat flux through the surface in the North Atlantic

Using the data of UWM/COADS (University of Wisconsin-Milwaukee/Comprehensive Ocean—Atmosphere Data Set), we have performed cluster and spectral analyses of the average monthly anomalies of temperature and heat balance of the surface of the Atlantic Ocean in three frequency ranges (intraannual, interannual, and decadal). It is shown that these anomalies are closely related on intraannual scales, where the anomalies of the surface temperature of the ocean can be regarded as a result of the direct local generation by heat balance anomalies. The generation mechanism is explained within the known Hasselman model [1, 2]. On interannual scales, this mechanism is not valid, and nonlocal effects related to heat advection become important. On decadal scales, the local generation of anomalies of the surface temperature of the ocean is insignificant, local correlation between fluctuations of heat balance and the surface temperature of the ocean is completely broken, and the spatial structure of anomalies of the surface temperature of the ocean is governed by the global system of currents, which redistributes heat flux from the ocean to the atmosphere. Violations of the local correlation between anomalies of heat balance and the surface temperature of the ocean are observed on intraannual scales in regions with powerful jet currents and in the equatorial region. In some parts of the World's ocean with weak advection, the correlation between heat balance and the surface temperature of the ocean persists up to a decadal period. Translated by Peter V. Malyshey and Dmitry V. Malyshey     

Mesoscale decrease of surface phosphate and associated phytoplankton dynamics in the vicinity of the subtropical South Pacific islands

Surface distributions of nutrients and phytoplankton were investigated in the vicinity of the subtropical South Pacific islands by using a continuous underway system with a highly sensitive nutrient analysis. A total of 17 transects, whose lengths ranged between 42 and 271 km, were sampled for continuous nutrient measurements. The study area was characterized by an overall depletion of nitrate+nitrite (<15 nM), but phosphate varied from 7 to 192 nM. The transects were grouped into 4 patterns according to distribution of phosphate concentrations. In 7 transects, a mesoscale decrease in phosphate occurred, coinciding with an elevation of in vivo chlorophyll fluorescence, which was accompanied by an increase in phytoplankton abundance as revealed by microscopy, flow cytometry, and accessory pigments. This mirror–image relationship between the phosphate concentration and phytoplankton abundance was most apparent on both a 99-km transect east of Tonga, where the phosphate concentration ranged from 17 to 125 nM, and on a 98-km transect west of Fiji, where the phosphate concentration ranged from 23 to 136 nM. Both these transects contained distinct blooms of Trichodesmium in areas with the lowest concentrations of phosphate. In other 2 transects, fluctuations in phosphate concentrations showed no distinct relationship with chlorophyll fluorescence. Other patterns that emerged included consistently high concentrations, ranging from 109 to 192 nM, in 5 transects and consistently low phosphate concentrations, ranging from 7 to 50 nM, in 3 transects. Abundance of Trichodesmium, Prochlorococcus, Synechococcus, and all accessory pigments examined tended to be higher in the low phosphate transects than in the high phosphate ones. In particular, Trichodesmium occurred in low phosphate water (<25 nM). There was no significant relationship between phosphate concentrations and nanoplanktonic unicellular cyanobacteria. Our observations suggest that surface phosphate decreases are associated with phytoplankton utilization of phosphate, and that nitrogen supply from Trichodesmium may contributes to this utilization.     

Optical properties and surface energy flux of spring fast ice in the Arctic

Over the past decades, sea ice in the polar regions has been significantly affecting local and even hemispheric climate through a positive ice albedo feedback mechanism. The role of fast ice, as opposed to drift ice, has not been well-studied due to its relatively small coverage over the earth. In this paper, the optical properties and surface energy balance of land fast ice in spring are studied using in situ observations in Barrow, Alaska. The results show that the albedo of the fast ice varied between 0.57 and 0.85 while the transmittance increased from 1.3×10?3 to 4.1×10?3 during the observation period. Snowfall and air temperature affected the albedo and absorbance of sea ice, but the transmittance had no obvious relationship with precipitation or snow cover. Net solar shortwave radiation contributes to the surface energy balance with a positive 99.2% of the incident flux, with sensible heat flux for the remaining 0.8%. Meanwhile, the ice surface loses energy through the net longwave radiation by 18.7% of the total emission, while the latent heat flux accounts for only 0.1%. Heat conduction is also an important factor in the overall energy budget of sea ice, contributing 81.2% of the energy loss. Results of the radiative transfer model reveal that the spectral transmittance of the fast ice is determined by the thickness of snow and sea ice as well as the amount of inclusions. As major inclusions, the ice biota and particulates have a significant influence on the magnitude and distribution of the spectral transmittance. Based on the radiative transfer model, concentrations of chlorophyll and particulate in the fast ice are estimated at 5.51 mg/m2 and 95.79 g/m2, which are typical values in the spring in Barrow.     

On the distribution of isothermal layers in the vicinity of the shoal,Kokushô-sone

Data from XBT observations in the vicinity of the shoal, Kokushô-sone (30°00′N, 128°30′E) which is located in the current zone of the Kuroshio in the East China Sea, are analysed to show the distribution of isothermal layers. Isothermal layers are found in abundance in and near a cold water region along the slope of the shoal where the existence of upwelling is suggested. It is found that there is a good spatial correlation between the distribution of isothermal layers and that of cold waters along the slope, and that the distribution of isothermal layers is a helpful indicator for elucidating the nature of oceanic structures in the vicinity of the shoal.     

现代黄河三角洲地区地面沉降的机理分析

利用前人在现代黄河三角洲地区进行的大量的野外调查和研究结果,对黄河三角洲地面沉降与第四系沉积体系、构造之间的对应关系进行了研究。研究结果表明现代黄河三角洲地区地面沉降除了因人类活动导致地面缓慢沉降外,新构造运动、第四系沉积相的分布也与三角洲沉降存在很好的相关性。研究区沉降区域的分布与主要断裂带相对应,软土的分布基本上控制了主沉降区的边界。研究结果可为以后三角洲的开发利用和管理以及其他三角洲地面沉降或地质灾害的监测提供必要的基础资料。     

Evaluation of the accuracy of downward radiative flux observations at the sea surface

Observations of downward radiative flux at the sea surface generally contain uncertainty due to limited numbers of observations and limitations of auxiliary equipment. The lack of shading from direct solar radiation and ventilation systems causes bias or random errors. To evaluate the error of radiation measurements at buoys, downward shortwave and longwave radiative fluxes are compared with International Satellite Cloud Climatology Project (ISCCP), Japanese 55-year Reanalysis (JRA55), and Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved model calculations of 3-h and daytime averages. Cloud masking is evaluated by a combination of MTSAT-1R and in situ observations. Coincident observations from a land-surface station located near the buoy observatories are compared with satellite and reanalysis products. The bias at buoys, compared with retrievals, approximately over- and under-estimate for longwave and shortwave fluxes, respectively. The bias at buoys is larger and smaller than the land by 23–34 W m^?2 for longwave and 13–51 W m^?2 for shortwave radiation using 3-h averages under clear-sky conditions. The differences in bias decrease when using daytime averages for longwave, but the difference for shortwave increases with daytime averages. To evaluate the effect of environmental factors on buoy observations, we compared rainfall, wind speed, and solar zenith angle with the biases. We found that rainfall and wind speed affect buoy pyrgeometers such that they overestimate the longwave flux. The cosine of solar zenith angle does not cause overestimation for longwave flux, and the effect of dome heating is small. The strong wind causes underestimation of the shortwave radiative flux due to tilting. The effect of wind is reduced when daily averages are used.