Comparison of atmospheric forcing in four sub-arctic seas

A comparative analysis was conducted on climate variability in four sub-arctic seas: the Sea of Okhotsk, the Bering Sea shelf, the Labrador Sea, and the Barents Sea. Based on data from the NCEP/NCAR reanalysis, the focus was on air–sea interactions, which influence ice cover, ocean currents, mixing, and stratification on sub-seasonal to decadal time scales. The seasonal cycles of the area-weighted averages of sea-level pressure (SLP), surface air temperature (SAT) and heat fluxes show remarkable similarity among the four sub-arctic seas. With respect to variation in climate, all four seas experience changes of comparable magnitude on interannual to interdecadal time scales, but with different timing. Since 2000 warm SAT anomalies were found during most of the year in three of the four sub-arctic seas, with the exception of the Sea of Okhotsk. A seesaw (out of phase) pattern in winter SAT anomalies between the Labrador and the Barents Sea in the Atlantic sector is observed during the past 50 years before 2000; a similar type of co-variability between the Sea of Okhotsk and the Bering Sea shelf in the Pacific is only evident since 1970s. Recent positive anomalies of net heat flux are more prominent in winter and spring in the Pacific sectors, and in summer in the Atlantic sectors. There is a reduced magnitude in wind mixing in the Sea of Okhotsk since 1980, in the Barents Sea since 2000, and in early spring/late winter in the Bering Sea shelf since 1995. Reduced sea-ice areas are seen over three out of four (except the Sea of Okhotsk) sub-arctic seas in recent decades, particularly after 2000 based on combined in situ and satellite observations (HadISST). This analysis provides context for the pan-regional synthesis of the linkages between climate and marine ecosystems.     

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.     

黄河入海水沙通量变化规律

根据利津站1950-2003年的水、沙实测资料,采用水文学和数理统计学相结合方法,对黄河入海水沙通量进行分析,分别得出了水、沙通量的年代变化、年际变化、季节变化规律以及水、沙通量之间关系.结果表明：黄河入海水、沙通量递减趋势明显,尤其在近20a来这种趋势更加显著;年际、年内沙量变化幅度都大于水量;黄河入海水沙主要集中在汛期,汛期与非汛期的水沙量差异将会持续减小;年输沙量和年径流量、多年平均月输沙量和径流量分别以乘幂、多项式回归,各月多年输沙量和径流量以多项式、指数回归,相关性都很高.     

Seasonal and interannual variability of the air–sea CO2 flux in the Atlantic sector of the Barents Sea

The seasonal and interannual variability of the air–sea CO₂ flux (F) in the Atlantic sector of the Barents Sea have been investigated. Data for seawater fugacity of CO₂ (fCO₂^sw) acquired during five cruises in the region were used to identify and validate an empirical procedure to compute fCO₂^sw from phosphate (PO₄), seawater temperature (T), and salinity (S). This procedure was then applied to time series data of T, S, and PO₄ collected in the Barents Sea Opening during the period 1990–1999, and the resulting fCO₂^sw estimates were combined with data for the atmospheric mole fraction of CO₂, sea level pressure, and wind speed to evaluate F.The results show that the Atlantic sector of the Barents Sea is an annual sink of atmospheric CO₂. The monthly mean uptake increases nearly monotonically from 0.101 mol C m^− 2 in midwinter to 0.656 mol C m^− 2 in midfall before it gradually decreases to the winter value. Interannual variability in the monthly mean flux was evaluated for the winter, summer, and fall seasons and was found to be ± 0.071 mol C m^− 2 month^− 1. The variability is controlled mainly through combined variation of fCO₂^sw and wind speed. The annual mean uptake of atmospheric CO₂ in the region was estimated to 4.27 ± 0.68 mol C m^− 2.     

Niche characterization of dominant estuarine benthic species

Benthic macroinfaunal species in a south Texas estuarine environment were studied over a 2·5 year period to characterize their distributions and ecology. The 13 dominant taxa chosen for investigation exhibited distinct habitat usage differences as judged both by the use of discriminant analysis and the differentiation of behavioral characteristics. Species coexistence in the estuarine bethic community of Corpus Christi Bay was examined with respect to resource partitioning for such parameters as food and space. Utilization of these resources by the dominant taxa differed in both temporal and spatial dimensions, with the spatial dimension consisting of horizontal and vertical attributes. Benthic species were separated according to (1) occurrences in certain sediment types with varying organic content, (2) presence in estuarine regions characterized by different phytoplankton productivity rates, (3) different periods of annual occurrence, and (4) occurrence in different sediment microhabitats characterized by varying sediment depth and relation to depth of oxygenated sediments. Superimposed upon differences in habitat usage of these species were behavioral traits, such as feeding differences, which further discriminated how benthic species obtained resources. Based upon species occurrence in a certain characteristic environment, we speculated on the structural division of the benthic habitat by various taxa often classified as common members of the same species' assemblages in the past. Although other investigators have demonstrated interactions among co-occurring benthic infaunal species, the information presented here illustrated how these species could minimize interactions in order to maintain their populations.     

A modified profile method for determining the vertical fluxes of NO,NO2, ozone,and HNO3 in the atmospheric surface layer

A modified profile method for determining the vertical deposition (or/and exhalation) fluxes of NO, NO₂, ozone, and HNO₃ in the atmospheric surface layer is presented. This method is based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these trace gases. The analysis (aerodynamic profile method) includes a detailed determination of the micrometeorological quantities (such as the friction velocity, the fluxes of sensible and latent heat, the roughness length and the zero plane displacement), and of the height-invariant fluxes of the composed chemically conservative trace gases with group concentrations c ₁=[NO]+[NO₂]+[HNO₃], c ₂=[NO₂]+[O₃]+3/2·[HNO₃], and c ₃=[NO]–[O₃]–1/2·[HNO₃]. The fluxes of the individual species are finally determined by the numerical solution of a system of coupled nonlinear ordinary differential equations for the concentrations of ozone and HNO₃ (decoding method). The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The model requires only the vertical profile data of wind velocity, temperature and humidity and concentrations of NO, NO₂, ozone, and HNO₃.The method has been applied to vertical profile data obtained at Jülich (September 1984) and collected in the BIATEX joint field experiment LOVENOX (Halvergate, U.K., September 1989).     

Upper Cretaceous deposits in the northwest of Saratov oblast,Part 1: Litho- and biostratigraphic analysis of the Vishnevoe section

The work is dedicated to multidisciplinary study of Upper Cretaceous deposits exposed at the day surface in a ravine near the village of Vishnevoe, the Petrovsk district of Saratov oblast. The exposed section includes deposits of the Bannovka, Mozzhevelovyi Ovrag, Mesino-Lapshinovka, Rybushka, Ardym, Lokh formations and of the Borisoglebsk sequence first distinguished in the Volga River basin. Age ranges of the formations studied are confirmed or defined more precisely (the Ardym and Lokh formations) based on fossil faunas of cephalopods, bivalves, radiolarians, planktonic and benthic foraminifers. The middle-upper Coniacian range of the Borisoglebsk sequence is substantiated. Distribution of brachiopods, sponges, radiolarians, ostracodes and calcareous nannoplankton in the section is established. Radiolarian assemblages are used to distinguish biostratigraphic subdivisions corresponding in rank to faunal beds. Based on nannofossil assemblages, zones and subzones of standard zonations after Perch-Nielsen (1985) and Burnett (1998) are established. Stratigraphic ranges of certain radiolarian, ostracode and calcareous nannoplankton taxa are verified.     

The European Water Framework Directive 2000/60/EC in the evaluation of the ecological status of watercourses. Case study: the river Chienti (central Apennines,Italy)

The quality of the river Chienti (eastern‐central Apennines, Italy) has been evaluated according to the Water Framework Directive 2000/60/EC, taking into consideration both biotic (animal and vegetable) and chemical parameters. In studying the biotic component, two indices were used: the E.B.I, Extended Biotic Index (version adapted to the Italian rivers), based on macroinvertebrates, and the EPI‐D, the Eutrophication and/or Pollution Index, based on diatoms. For both macroinvertebrates and diatoms, two samplings were conducted, one in June and the other in October 2003. Instead, according to the Italian Law 152/99 the chemical and bacteriological analyses were conducted monthly for the entire year. The results of biomonitoring and chemical‐bacteriological analyses unanimously demonstrated a good ecological situation for the upper section of the Chienti, though the situation tends to worsen as the river continues its descent and undergoes increased anthropogenic pressure. Data obtained were correlated with Spearman's coefficients and principal component analysis. Both statistical calculations showed clear, direct correlation between the two biotic indices and an inverse correlation between these and the chemical and bacteriological parameters. However, a few differences of judgement that emerged among the various indices highlight the importance of using them simultaneously in order to obtain a more accurate diagnosis of the ecological status of the watercourses.     

Advanced insights into sources of vertical velocity in the ocean

Estimating vertical velocity in the oceanic upper layers is a key issue for understanding ocean dynamics and the transport of biogeochemical elements. This paper aims to identify the physical sources of vertical velocity associated with sub-mesoscale dynamics (fronts, eddies) and mixed-layer depth (MLD) structures, using (a) an ocean adaptation of the generalized Q-vector form of the ω-equation deduced from a primitive equation system which takes into account the turbulent buoyancy and momentum fluxes and (b) an application of this diagnostic method for an ocean simulation of the Programme Océan Multidisciplinaire Méso Echelle (POMME) field experiment in the North-Eastern Atlantic. The approach indicates that w-sources can play a significant role in the ocean dynamics and strongly depend on the dynamical structure (anticyclonic eddy, front, MLD, etc.). Our results stress the important contribution of the ageostrophic forcing, even under quasi-geostrophic conditions. The turbulent w-forcing was split into two components associated with the spatial variability of (a) the buoyancy and momentum (Ekman pumping) surface fluxes and (b) the MLD. Process (b) represents the trapping of the buoyancy and momentum surface energy into the MLD structure and is identified as an atmosphere/oceanic mixed-layer coupling. The momentum-trapping process is 10 to 100 times stronger than the Ekman pumping and is at least 1,000 times stronger than the buoyancy w-sources. When this decomposition is applied to a filamentary mixed-layer structure simulated during the POMME experiment, we find that the associated vertical velocity is created by trapping the surface wind-stress energy into this structure and not by Ekman pumping.     

Latent heat fluxes simulated with a non-hydrostatic weather forecast model using actual surface properties from measurements and remote sensing

In this study the influence of land-surface parameters on latent heat fluxes simulated with the numerical weather prediction model Lokalmodell (LM) of the German Meteorological Service is investigated. The area of interest is the LITFASS area during the LITFASS-2003 campaign. Based on simulations with varying soil and vegetation properties, we confirm that simulated latent heat fluxes strongly depend on soil moisture and leaf area index. Both parameters are difficult to obtain from in situ measurements with sufficient spatial resolution over heterogeneous land surfaces. Therefore, a procedure is proposed to determine area average values of soil moisture from time domain reflectometer measurements performed at a limited number of sites. The area averages cover the 7 × 7 km² grid cells of the LM around Lindenberg (south-east of Berlin). Furthermore, satellite inferred plant parameters from NOAA–AVHRR are used to initialise model runs; the derived vegetation parameters show notable differences with those in the standard input of LM. The latent heat fluxes from the LM are compared with the aggregated eddy-covariance-measurements, and while the operational LM shows a strong overestimation of latent heat fluxes, it is demonstrated that the application of land-surface parameters derived from measurements can significantly reduce the deviation between the simulated and measured latent heat fluxes.