bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linking synoptic forcing and local mesoscale processes with biological dynamics off Ningaloo Reef
Authors: Rossi Vincent , Feng Ming , Pattiaratchi Charitha , Roughan Moninya , Waite Anya M. 
Published: April 2013

AbstractA hydrographic survey offshore Ningaloo reef, north‐west Australia, in austral autumn 2010 revealed relatively stable subsurface water masses in the region, despite the influence of interannual variability of the Leeuwin Current (LC). The surface water mass seems slightly more variable at seasonal time scale, probably due to various contributions of the geographically distinct source waters of the LC. A subsurface nitrate maximum (~110–230 m), a prominent feature of the Ningaloo area during autumn, was consistently observed within different water masses. Tightly coupled variations of subsurface nitrate and oxygen at small vertical scale suggest it is due to local in situ remineralization of organic matter likely to accumulate along sharp physical interfaces and possibly favored by injections of oxygenated subsurface waters. Offshore, enhanced levels of surface chlorophyll a within the downwelling‐favorable LC are associated with deeper mixed layer depth, eroding the shallow source of nutrients. Close to the continental shelf, these nutrients are observed to be efficiently uplifted within the core of quasi‐persistent topographically trapped submesoscale cyclonic eddies dominated by nonlinear effects. A wind‐driven coastal upwelling event occurred in autumn and was characterized by a relatively deep source (~100–150 m), coinciding with the subsurface maximum of nutrients, thus promoting coastal productivity locally and farther north by alongshore advection within the Ningaloo current.
Seasonal variability and coastal upwelling near Cape Santa Marta (Brazil)
Authors: Campos Paula C. , Möller Osmar O. , Piola Alberto R. , Palma Elbio D. 
Published: April 2013

AbstractThe Santa Marta Grande Cape (CSM) area, a relatively steep and narrow continental shelf off southeast Brazil, is under the influence of the Brazil Current and intense seasonal variations of the wind field that affect the composition of water masses and their circulation. Hydrographic data, satellite‐derived wind stress, and numerical simulations are used to characterize the seasonal and shorter period variability of the oceanographic conditions off CSM, in the area between 27°S and 30°S. The study is focused on the upwelling episodes and the dynamical mechanisms associated with these events. Field data and numerical results indicate significant seasonal changes in the oceanographic structure, the water mass composition, and the dynamical balance. During fall and winter, when southwesterly winds prevail and the frequency of meteorological frontal systems increases, the region is characterized by waters of continental origin, the Plata Plume Water (PPW). During spring and summer, deeper waters reach the surface layer due to the action of northeasterly winds. Coastal upwelling events are revealed by surface temperature minima observed south of CSM. Synoptic data show that these events occur in pulses associated with changes in the wind direction. Analysis of the numerical results shows that this particular location of the upwelling band results from the synergy between shelf‐break upwelling and the regional shelf circulation induced by the northeasterly winds, both of which are modulated by changes in the coastline orientation and shelf width.
On the seasonal freshwater stratification in the proximity of fast‐flowing tidewater outlet glaciers in a sub‐Arctic sill fjord
Authors: Mortensen J. , Bendtsen J. , Motyka R. J. , Lennert K. , Truffer M. , Fahnestock M. , Rysgaard S. 
Published: April 2013

AbstractThe Greenland Ice Sheet releases large amounts of freshwater into the fjords around Greenland and many fjords are in direct contact with the ice sheet through tidewater outlet glaciers. Here we present the first seasonal hydrographic observations from the inner part of a sub‐Arctic fjord, relatively close to and within 4–50 km of a fast‐flowing tidewater outlet glacier. This region is characterized by a dense glacial and sea ice cover. Freshwater from runoff, subglacial freshwater (SgFW) discharge, glacial, and sea ice melt are observed above 50–90 m depth. During summer, SgFW and subsurface glacial melt mixed with ambient water are observed as a layered structure in the temperature profiles below the low‐saline summer surface layer (<7 m). During winter, the upper water column is characterized by stepwise halo‐ and thermoclines formed by mixing between deeper layers and the surface layer influenced by ice melt. The warm (T > 1°C) intermediate water mass is a significant subsurface heat source for ice melt. We analyze the temperature and salinity profiles observed in late summer with a thermodynamic mixing model and determine the total freshwater content in the layer below the summer surface layer to be between 5% and 11%. The total freshwater contribution in this layer from melted glacial ice was estimated to be 1–2%, while the corresponding SgFW was estimated to be 3–10%. The winter measurements in the subsurface halocline layer showed a total freshwater content of about 1% and no significant contribution from SgFW.
Chlorophyll bloom development and the subtropical front in the North Pacific
Authors: Wilson Cara , Villareal Tracy A. , Brzezinski Mark A. , Krause Jeffrey W. , Shcherbina Andrey Y. 
Published: April 2013

AbstractIn late summer, satellite ocean color data consistently show localized chlorophyll blooms in the oligotrophic NE Pacific. Based on historical data and the results from recent cruises, these blooms are associated with elevated diatom abundance. However, the physical dynamics that stimulate the blooms remain unknown. Mechanisms suggested to be driving the blooms include mixing at the subtropical front, breaking of internal waves at the critical latitude, shoaling of the mixed layer depth, eddy interactions, and winter mixing of nutrients. To examine these hypotheses, we use data from four summer cruises (2002, 2007, 2008, and 2009) in this region that sampled near a bloom temporally and/or spatially. Conditions associated with five blooms (two blooms were sampled in 2009) are examined. Each area was sampled at a different stage in bloom development, including prebloom, initiation, full bloom, decline, and postbloom conditions. No one variable is found which can explain unequivocally the development of a chlorophyll bloom at a certain location. We describe a set of conditions that could result in the injection of nutrients into the surface water to stimulate a bloom. This “perfect storm” of conditions requires a subsurface stratification minimum layer that intersects the nutricline and that this minimum is close to the base of the mixed layer. These conditions are not predictable in the sense of an annual climatology; however, they do occur often enough to create a reasonably certain, if spatially variable, summer NE Pacific bloom.
Kuroshio‐induced wake in the lee of Green Island off Taiwan
Authors: Chang Ming‐Huei , Tang Tswen Yung , Ho Chung‐Ru , Chao Shenn‐Yu 
Published: April 2013

AbstractThe wake of Green Island was investigated in the alongshore flowing Kuroshio east of Taiwan, where current speeds range from 1 to 1.5 ms–1. Vertical profiling with shipboard lowered acoustic Doppler current profiler and conductivity‐temperature‐depth profiler revealed sizable anomalies in flow and water characteristics in the lee of Green Island. Two different stages of wake evolution were observed from two shipboard surveys. In the first stage, a recirculation developed leeward of the island, followed by a wavy (wave‐like) tail that resembled a weak vortex street. In the second stage, a cold eddy probably originating from the leeward side of the island showed up 14 km downstream of the island. The wake water was colder, saltier, higher in chlorophyll‐a concentration, and produced isopycnal doming up to 60 m. In the recirculation area, the relative vorticity, either positive or negative, was 10 times of planetary vorticity, and the horizontal divergence or convergence was O (10–4 s–1) on average. Flow divergence and convergence in the wake were expected to form upwelling and downwelling zones, producing a vertical circulation that vertically displaces isotherms. High inverse Richardson number, produced by strong vertical shear of horizontal currents, was associated with intense overturning events in the wake. High vertical shear of horizontal currents drove the mixing. The dissipation rate of turbulent kinetic energy in the overturn regions is O (10–7–10–5) W Kg–1; the corresponding eddy diffusivity is O (10–3–10–1) m2 s–1. The wake water properties are vertically diffused via upwelling and turbulence and can be delivered downstream through eddy shedding or advection. The extent of downstream influence remains to be investigated.
Influence of Amur River discharge on phytoplankton photophysiology in the Sea of Okhotsk during late summer
Authors: Isada Tomonori , Iida Takahiro , Liu Hongbin , Saitoh Sei‐Ichi , Nishioka Jun , Nakatsuka Takeshi , Suzuki Koji 
Published: April 2013

AbstractWe investigated the photosynthetic parameters of phytoplankton in the Sea of Okhotsk during the late summer of 2006 to characterize their spatiotemporal variability and to test the hypothesis that discharge from the Amur River could influence the algal photophysiology. The highest maximum quantum yield of carbon fixation in photosynthesis (Φcmax; 0.098 mol C mol photons‐1) was found near the Amur River mouth, where nitrate was depleted. However, none of the photosynthetic parameters, including primary productivity (PP) at the surface, were correlated with temperature, daily photosynthetically available radiation (PAR), or ambient nutrient concentrations. Variations in Φcmax depended on the variations in not only the mean chlorophyll a specific absorption coefficient of phytoplankton (ā*ph) but also the slope index of the absorption coefficient of phytoplankton (aph slope), an indicator for the ratio of nonphotosynthetic carotenoids to photosynthetic carotenoids. These results indicated that the phytoplankton assemblages acclimated to the ambient light conditions by regulating their cellular pigments. Additionally, ā*ph and euphotic depth (Zeu) were significantly correlated with salinity, suggesting that photoacclimation of the phytoplankton assemblages observed in this study could be induced by discharge of Amur River. Because spatiotemporal variations in PP were concomitant with Φcmax, ā*ph, and the chlorophyll a concentration, PP models based on inherent optical property (IOP) were suitable for estimating PP in the Sea of Okhotsk. This study is the first to investigate the factors controlling phytoplankton photophysiology in the Sea of Okhotsk, one of the highest primary production areas in the world.
Multisegment statistical bias correction of daily GCM precipitation output
Authors: Grillakis Manolis G. , Koutroulis Aristeidis G. , Tsanis Ioannis K. 
Published: April 2013

AbstractAn improved bias correction method for daily general circulation model (GCM) precipitation is presented. The method belongs to the widely used family of quantile mapping correction methods. The method uses different instances of gamma function that are fitted on multiple discrete segments on the precipitation cumulative density function (CDF), instead of the common quantile‐quantile approach that uses one theoretical distribution to fit the entire CDF. This imposes to the method the ability to better transfer the observed precipitation statistics to the raw GCM data. The selection of the segment number is performed by an information criterion to poise between complexity and efficiency of the transfer function. The global precipitation output of Institut Pierre Simon Laplace Coupled Model for the period 1960–2000 is bias corrected using the precipitation observations of WATCH Forcing Data. The 1960–1980 period of observations was used to calibrate the bias correction method, while 1981–2000 was used for validation. The proposed method performs well on the validation period, according to two performance estimators.
Heterogeneous ice nucleation ability of crystalline sodium chloride dihydrate particles
Authors: Wagner Robert , Möhler Ottmar 
Published: April 2013

AbstractThe aerosol and cloud chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) of the Karlsruhe Institute of Technology has been used to quantify the deposition mode ice nucleation ability of airborne crystalline sodium chloride dihydrate (NaCl ∙ 2H2O) particles with median diameters between 0.06 and 1.1 µm. For this purpose, expansion cooling experiments with starting temperatures from 235 to 216 K were conducted. Recently, supermicron‐sized NaCl ∙ 2H2O particles deposited onto a surface have been observed to be ice‐active in the deposition mode at temperatures below 238 K, requiring a median threshold ice saturation ratio of only 1.02 in the range from 238 to 221 K. In AIDA, heterogeneous ice nucleation by NaCl ∙ 2H2O was first detected at a temperature of 227.1 K with a concomitant threshold ice saturation ratio of 1.25. Above that temperature, the crystallized salt particles underwent a deliquescence transition to form aqueous NaCl solution droplets upon increasing relative humidity. At nucleation temperatures below 225 K, the inferred threshold ice saturation ratios varied between 1.15 and 1.20. The number concentration of the nucleated ice crystals was related to the surface area of the seed aerosol particles to deduce the ice nucleation active surface site (INAS) density of the aerosol population as a function of the ice supersaturation. Maximum INAS densities of about 6 ⋅ 1010 m−2 at an ice saturation ratio of 1.20 were found for temperatures below 225 K. These INAS densities are similar to those recently derived for deposition mode ice nucleation on mineral dust particles.
An assessment of the diurnal variation of upper tropospheric humidity in reanalysis data sets
Authors: Chung Eui‐Seok , Soden Brian J. , Sohn B. J. , Schmetz Johannes 
Published: April 2013

AbstractDiurnal variations of upper tropospheric humidity (UTH) in five different reanalysis data sets are compared over convective land and ocean regions and evaluated using multiple satellite observations as a reference. All reanalysis data sets reproduce the day‐night contrast of upper tropospheric humidity and the land‐ocean contrast in the diurnal amplitude. The infrared satellite measurements indicate a slightly later diurnal minimum over land relative to most reanalyses and the microwave satellite measurements, suggesting that cloud masking of the infrared radiances may introduce a small (∼3 h) bias in the phase. One reanalysis exhibits a substantially different diurnal cycle over land which is inconsistent with both infrared and microwave satellite measurements and other reanalysis products. This product also exhibits a different covariance between vertical velocity, cloud water, and humidity than other reanalyses, suggesting that the phase bias is related to deficiencies in the parameterization of moist convective processes.
Trajectory analysis of Saudi Arabian dust storms
Authors: Notaro Michael , Alkolibi Fahad , Fadda Eyad , Bakhrjy Fawzieh 
Published: April 2013

AbstractTemporal and spatial characteristics of Saudi Arabian dust storms, with focus on associated air parcel trajectories, are investigated using station and gridded weather observations and remotely‐sensed aerosol optical depth (AOD). For 13 focal stations, an extensive pool of 84‐h backward trajectories is developed for dust storm days, and the trajectories are grouped into 3–5 representative clusters based on the K‐means technique and Silhouette Coefficients. Saudi Arabian dust storms are most prominent during February–June, with a mid‐winter peak along the southern coast of the Red Sea, spring peak across northern Saudi Arabia around the An Nafud Desert, and early summer peak in eastern Saudi Arabia around the Ad Dahna Desert. Based on backward trajectories, the primary local dust source is the Rub Al Khali Desert and the primary remote sources are the Saharan Desert, for western Saudi Arabia, and Iraqi Deserts, for northern and eastern Saudi Arabia. During February–April, the Mediterranean storm track is active, with passing cyclones and associated cold fronts carrying Saharan dust to Saudi Arabian stations along the northern coast of the Red Sea. Across Saudi Arabia, the highest AOD is achieved during dust storms that originate from the Rub Al Khali and Iraqi Deserts. Most stations are dominated by local dust sources (primarily Rub Al Khali), are characterized by three dominant trajectory paths, and achieve AOD values exceeding 1. In contrast, for stations receiving predominantly remote dust (particularly Saharan), 3–5 trajectory paths emerge and AOD values only reach approximately 0.6 as dust is lost during transport.
Vertical structure of aerosols, temperature, and moisture associated with an intense African dust event observed over the eastern Caribbean
Authors: Jung Eunsil , Albrecht Bruce , Prospero Joseph M. , Jonsson Haflidi H. , Kreidenweis Sonia M. 
Published: April 2013

AbstractAn unusually intense African dust event affected a large area of the western Atlantic and eastern Caribbean in early April 2010. Measurements made east of Barbados from the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter research aircraft are used to characterize particle size distributions; vertical distributions of aerosols, temperature, and moisture; and processes leading to the observed stratification in the boundary layer. The vertical profiles of various aerosol characterizations were similar on both days and show three layers with distinct aerosol and thermodynamic characteristics: the Saharan Air Layer (SAL; ~2.2 km ± 500 m), a subcloud layer (SCL; surface to ~500 m), and an intermediate layer extending between them. The SAL and SCL display well‐mixed aerosol and thermodynamic characteristics; but the most significant horizontal and vertical variations in aerosols and thermodynamics occur in the intermediate layer. The aerosol variability observed in the intermediate layer is likely associated with modification by shallow cumulus convection occurring sometime in the prior history of the air mass as it is advected across the Atlantic. A comparison of the thermodynamic structure observed in the event from its origin over Africa with that when it reached Barbados indicates that the lower part of the SAL was moistened by surface fluxes as the air mass was advected across the Atlantic. Mixing diagrams using aerosol concentrations and water vapor mixing ratios as conserved parameters provide insight into the vertical transports and mixing processes that may explain the observed aerosol and thermodynamic variability in each layer.
Shadow‐band correction for diffuse ultraviolet radiation measurements
Authors: Sánchez G. , Serrano A. , Cancillo M. L. 
Published: April 2013

AbstractAlthough the correction of shadow‐band solar total diffuse measurements has been extensively studied, the case of diffuse ultraviolet measurements has not been properly addressed. This study analyzes the correction factor to be applied to experimental measurements performed adapting a shadow‐band to a UV radiometer at a radiometric station in Badajoz (Spain). Three different models, based on approaches widely used for correcting total diffuse measurements, have been revised and adapted for the ultraviolet spectral range. Results reveal that some aspects of the correction proposed for total diffuse radiation are not suitable for ultraviolet diffuse radiation. The mathematical expressions are consequently modified to match the behavior in the ultraviolet range. Thus, three correction models particularized for ultraviolet diffuse measurements are proposed and validated against experimental data. The two models adapted from the original expressions proposed by Battles et al., and Steven show the best performance, with rRMSE of 2.74% and 2.20% and rMBE of 1.53% and 0.46%, respectively.
An observed negative trend in West Antarctic accumulation rates from 1975 to 2010: Evidence from new observed and simulated records
Authors: Burgener Landon , Rupper Summer , Koenig Lora , Forster Rick , Christensen William F. , Williams Jessica , Koutnik Michelle , Miège Clément , Steig Eric J. , Tingey David , Keeler Durban , Riley Laura 
Published: April 2013

AbstractObservations of snow accumulation rates from five new firn cores show a negative trend that is statistically significant over the past several decades across the central West Antarctic ice sheet (WAIS). A negative temporal trend in accumulation rates is unexpected in light of rising surface temperatures as well as model simulations predicting higher accumulation rates for the region. Both the magnitude of the mean accumulation rates and the range of interannual variability observed in the new records compare favorably to older records collected from a broad area of the WAIS, suggesting that the new data may serve as a regional proxy for recent temporal trends in West Antarctic accumulation rates. The observed negative trend in accumulation is likely the result of a shift in low‐pressure systems over the Amundsen Sea region, dominated by changes in the austral fall season. Regional‐scale climate models and reanalysis data do not capture the negative trend in accumulation rate observed in these firn cores. Nevertheless the models and reanalyses agree well in both accumulation‐rate means and interannual variability, with no single model or dataset standing out as significantly more skilled at capturing the observed magnitude of and trend in accumulation rates in this region of the WAIS.
Improving the seasonal forecast for summertime South China rainfall using statistical downscaling
Authors: Tung Ying Lut , Tam Chi‐Yung , Sohn Soo‐Jin , Chu Jung‐Lien 
Published: April 2013

AbstractThe performance of various seasonal forecast systems in predicting the station‐scale summer rainfall in South China (SC) was assessed and was compared with that based on a statistical downscaling scheme. Hindcast experiments from 11 dynamical models covering the period of 1983–2003 were taken from the Asia‐Pacific Economic Cooperation Climate Center multimodel ensemble. Based on observations, singular value decomposition analysis (SVDA) showed that SC precipitation is strongly related to the broad‐scale sea level pressure (SLP) variation over Southeast Asia, western north Pacific, and part of the Indian Ocean. Analogous covariability was also found between model hindcasts and the observed station precipitation. Based on these results from SVDA, a statistical downscaling scheme for predicting SC station rainfall with model SLP as predictor was constructed. In general, the statistical scheme is superior to the original model prediction in two geographical regions, namely, western SC (near Guangxi) and eastern coastal SC (eastern Guangdong to part of Fujian). Further analysis indicated that dynamical models are able to reproduce the large‐scale circulation patterns associated with the recurrent modes of SC rainfall, but not the local circulation features. This probably leads to erroneous rainfall predictions in some locations. On the other hand, the statistical scheme was able to map the broad‐scale SLP patterns onto the station‐scale rainfall anomalies, thereby correcting some of the model biases. Overall, our results demonstrate how SC summer rainfall predictions can be improved by tapping the source of predictability related to large‐scale circulation signals from dynamical models.