The SOLAS air-sea gas exchange experiment (SAGE) 2004

The SOLAS air-sea gas exchange experiment (SAGE) was a multiple-objective study investigating gas-transfer processes and the influence of iron fertilisation on biologically driven gas exchange in high-nitrate low-silicic acid low-chlorophyll (HNLSiLC) Sub-Antarctic waters characteristic of the expansive subpolar zone of the southern oceans. This paper provides a general introduction and summary of the main experimental findings. The release site was selected from a pre-voyage desktop study of environmental parameters to be in the south-west Bounty Trough (46.5°S 172.5°E) to the south-east of New Zealand and the experiment was conducted between mid-March and mid-April 2004. In common with other mesoscale iron addition experiments (FeAX’s), SAGE was designed as a Lagrangian study, quantifying key biological and physical drivers influencing the air-sea gas exchange processes of CO₂, DMS and other biogenic gases associated with an iron-induced phytoplankton bloom. A dual tracer SF₆/³He release enabled quantification of both the lateral evolution of a labelled volume (patch) of ocean and the air-sea tracer exchange at tenths of kilometer scale, in conjunction with the iron fertilisation. Estimates from the dual-tracer experiment found a quadratic dependency of the gas exchange coefficient on windspeed that is widely applicable and describe air-sea gas exchange in strong wind regimes. Within the patch, local and micrometeorological gas exchange process studies (100 m scale) and physical variables such as near-surface turbulence, temperature microstructure at the interface, wave properties and windspeed were quantified to further assist the development of gas exchange models for high-wind environments.There was a significant increase in the photosynthetic competence (F_v/F_m) of resident phytoplankton within the first day following iron addition, but in contrast to other FeAX’s, rates of net primary production and column-integrated chlorophyll a concentrations had only doubled relative to the unfertilised surrounding waters by the end of the experiment. After 15 days and four iron additions totalling 1.1 ton Fe²⁺, this was a very modest response compared to other mesoscale iron enrichment experiments. An investigation of the factors limiting bloom development considered co-limitation by light and other nutrients, the phytoplankton seed-stock and grazing regulation. Whilst incident light levels and the initial Si:N ratio were the lowest recorded in all FeAXs to date, there was only a small seed-stock of diatoms (less than 1% of biomass) and the main response to iron addition was by the picophytoplankton. A high rate of dilution of the fertilised patch relative to phytoplankton growth rate, the greater than expected depth of the surface mixed layer and microzooplankton grazing were all considered as factors that prevented significant biomass accumulation. In line with the limited response, the enhanced biological draw-down of pCO₂ was small and masked by a general increase in pCO₂ due to mixing with higher pCO₂ waters. The DMS precursor DMSP was kept in check through grazing activity and in contrast to most FeAX’s dissolved dimethylsulfide (DMS) concentration declined through the experiment. SAGE is an important low-end member in the range of responses to iron addition in FeAX’s. In the context of iron fertilisation as a geoengineering tool for atmospheric CO₂ removal, SAGE has clearly demonstrated that a significant proportion of the low iron ocean may not produce a phytoplankton bloom in response to iron addition.     

Sterile neutrino fits to dark matter mass profiles in the Milky Way and in galaxy clusters

In recent papers it was claimed that SN 1987A data supports the existence of 4.0 eV and 21.4 eV active neutrino mass eigenstates, and it was suggested that such large active neutrino masses could be made consistent with existing constraints including neutrino oscillation data and upper limits on the neutrino flavor state masses. The requirement was that there exist a pair of sterile neutrino mass states nearly degenerate with the active ones, plus a third active-sterile doublet that is tachyonic (m ²<0). Here, independent evidence is presented for the existence of sterile neutrinos with the previously claimed masses based on fits to the dark matter distributions in the Milky Way galaxy and four clusters of galaxies. The fits are in excellent agreement with observations within the uncertainties of the masses. In addition, sterile neutrinos having the suggested masses address the “cusp” problem and the missing satellites problem, as well as that of the “top down” scenario of structure formation—previously a chief drawback of HDM particles. Nevertheless, due to the highly controversial nature of the claim, and the need for two free parameters in the dark matter fits, additional confirming evidence will be required before it can be considered proven.     

Spaxel analysis: probing the physics of star formation in ultraluminous infrared galaxies

This paper presents a detailed spectral pixel (spaxel) analysis of the ten Luminous Infrared Galaxies (LIRGs) previously observed with the Wide Field Spectrograph (WiFeS), an integral field spectrograph mounted on the ANU 2.3 m telescope, and for which an abundance gradient analysis has already been presented by Rich et al. (Astrophys. J., 753:5, 2012). Here we use the strong emission line analysis techniques developed by Dopita et al. (Astrophys. J. Suppl. Ser., accepted, 2013) to measure the ionisation parameter and the oxygen abundance in each spaxel. In addition, we use the observed Hα flux to determine the surface rate of star formation ( $\mathrm {M}_{\odot }{\rm yr}^{-1}$ kpc^?2) and use the [S II] λλ6717/6731 ratio to estimate the local pressure in the ionised plasma. We discuss the correlations discovered between these physical quantities, and use them to infer aspects of the physics of star formation in these extreme star forming environments. In particular, we find a correlation between the star formation rate and the inferred ionisation parameter. We examine the possible reasons for this correlation, and determine that the most likely explanation is that the more active star forming regions have a different distribution of molecular gas which favour higher ionisation parameters in the ionised plasma.     

Revisiting the Climatology of Atmospheric Blocking in the Northern Hemisphere

In addition to the occurrence of atmospheric blocking,the climatology of the characteristics of blocking events,including duration,intensity,and extension,in four seasons over the Northern Hemisphere was analyzed for the period 1950-2009.The seasonality and spatial variations of these characteristics were studied according to their longitudinal distributions.In general,there were sharp discrepancies in the blocking characteristics between winter and summer,and these differences were more prominent over the Atlantic and Pacific Oceans.The blocking not only occurred more frequently but also underwent stronger amplification in winter;likewise,the blocking occurred less frequently and underwent weaker amplification in summer.There are very strong interrelationships among different blocking characteristics,suggesting that they are supported by similar physical factors.In addition,the relationship between blocking over different regions and East Asian circulation was examined.Ural-Siberia is a major blocking formation region in all seasons that may exert a downstream impact on East Asia.The impact is generally weak in summer,which is due to its lower intensity and smaller duration.However,the extratropical circulation over East Asia in summer can be disturbed persistently by the frequent occurrence of blocking over the Asian continent or the Western Pacific.In particular,the blocking frequency over the Western Pacific significantly increased during the study period.This climatological information provides a background for studying the impact of blocking on East Asian circulation under both present and future climate conditions.     

Spatial modeling of the highest daily maximum temperature in Korea via max-stable processes

This paper examines the annual highest daily maximum temperature （DMT） in Korea by using data from 56 weather stations and employing spatial extreme modeling. Our approach is based on max-stable processes （MSP） with Schlather＇s characterization. We divide the country into four regions for a better model fit and identify the best model for each region. We show that regional MSP modeling is more suitable than MSP modeling for the entire region and the pointwise generalized extreme value distribution approach. The advantage of spatial extreme modeling is that more precise and robust return levels and some indices of the highest temperatures can be obtained for observation stations and for locations with no observed data, and so help to determine the effects and assessment of vulnerability as well as to downscale extreme events.     

Irreversible sorption of benzene in sandy aquifer materials

Hydrocarbon compounds in aquifers are generally known to show a retardation effect due to sorption onto the surfaces of solid particles. In this study, we investigated the effect of sorption on the transport of benzene in sandy aquifer materials by conducting batch and column tests for both sandy aquifer materials and sandy materials to which had been added 0·5% powdered activated carbon. The batch test was conducted by equilibrating dry materials with benzene solutions of various initial concentrations, and by analysing the concentrations of benzene in the initial and equilibrated solutions using high‐performance liquid chromatography (HPLC). The column test was performed to monitor the concentrations of effluent versus time, known as a breakthrough curve (BTC). We injected KCl and benzene solutions as tracers into the inlet boundary as two different types of square pulse and step, and monitored the effluent concentrations at the exit boundary under a steady‐state condition using an electrical conductivity meter and HPLC. Simulation of benzene transport was performed using the convective–dispersive equation model with the distribution coefficients obtained from the batch test and the transport parameters of the conservative solute KCl from the column test. The observed BTCs of KCl and benzene for pulse injection showed that the arrival times of the peaks of both tracers coincided well, but the relative peak concentration of benzene was much lower than that of KCl. Comparison of the simulated and observed BTCs showed a great discrepancy for all cases of injection mode and material texture, indicating the absence of retardation effect. These results reveal that the predominant process affecting the benzene transport in the sandy aquifer materials is an irreversible sorption rather than retardation. This tentative conclusion was verified by simulation of benzene transport using an irreversible sorption parameter that led to a good agreement between the simulated and observed BTCs. Copyright © 2002 John Wiley & Sons, Ltd.     

Direct flows from the Ulleung Basin into the Yamato Basin in the East/Japan Sea

Using the trajectories of ARGO floats, we report direct flows from the Ulleung Basin into the Yamato Basin through a gap between the Oki Spur and the Yamato Rise over the southern part of the East/Japan Sea. The gap is subdivided into two narrow (northern and southern) passages by a seamount located in the middle. The flows, therefore, are narrow and this explains why this flow was not reported earlier. More than half of the 25 ARGO floats, which operated around the gap, drifted through the gap or area near it. The strength of the throughflow estimated using the trajectories of the floats at parking depth is comparable to the mean deep flow found over the southwestern part of the East/Japan Sea. A high resolution regional ocean model whose overall circulation pattern over the Ulleung Basin is consistent with those from previous studies shows that the flow through the gap is supplied mainly by eastward flows crossing the mouth of the basin, and secondarily by the cyclonic circulation following the outer perimeter of the basin. Thus the throughflow is an important component of the deep circulation over the southern East/Japan Sea, and the narrow gap, where the flow is well confined, would be a good place to study the deep circulation.     

Accessing High Pressure States Relevant to Core Conditions in the Giant Planets

We have designed an experimental technique to use on the National Ignition Facility (NIF) laser to achieve very high pressure (P _max > 10 Mbar = 1000 GPa), dense states of matter at moderate temperatures (T < 0.5 eV = 6000 K), relevant to the core conditions of the giant planets. A discussion of the conditions in the interiors of the giant planets is given, and an experimental design that can approach those conditions is described.     

A research on the estimation of coefficient roughness in open channel applying entropy concept

Manning’s roughness coefficient is one of the most important parameters in establishing the plan, design, operation, and maintenance of the water resource projects for hydraulic engineers, and since the worth of this value has a significant effect on the analysis of the water level and flow rate distribution, it is very important to carry out the calculation of flood stage, design of the stream/river structure, and safety assessment of the stream. Due to the importance of these factors, the calculation of objective and quantitative roughness coefficient has long drawn attention from researchers at home and abroad. Many studies have been conducted to estimate the roughness coefficient based on the actual measurements for various types of streams, such as gravel and sand streams, and many others have produced experience equation for various levels of materials and relative depth. Despite many of these efforts, the roughness coefficient uses constant values when applied to the actual model or real design. This application is a major source of error in simulating flood and unsteady flow. To solve these problems, good results were obtained by attempting to calculate the roughness coefficient applied with the entropy concept in open-channel flow. In particular, the proposed roughness coefficient based on the measurements taken from laboratories under conditions showed very similar to the actual stream flow which was found to be about the same as the value from the unsteady flow. Accordingly, the newly developed roughness coefficient equation, which is the result of this study, is a very practical one formula that can be applied to the flood flow of real natural streams. It can also be used as an alternative to make up for the disadvantages of the Manning’s roughness coefficient.