bluuebunny/crossref_metadata_2025_split huggingface dataset:
The potential of high‐density observations for numerical weather prediction: A study with simulated observations
Authors: Liu Z.‐Q. , Rabier F. 
Published: August 2007

AbstractThe skill of numerical weather prediction depends to a large extent upon the quantity of globally available observations. Only a fraction of the available observations (especially high‐density observations) is used in current operational assimilation systems. In this paper, the potential of high‐density observations is studied in a practical four‐dimensional variational assimilation context. Two individual meteorological situations are used to examine the impact of different observation densities on the analysis and the forecast. A series of observing‐system simulation experiments are performed. Both direct observations (temperature and surface pressure) and indirect observations (radiance) are simulated, with uncorrelated or correlated errors. In general, it is verified that a small reduction (increase) of the initial error in a sensitive area can produce a considerable improvement (degradation) of the targeted forecast. In particular, the results show that increasing the observation density for the uncorrelated‐error case can generally improve the analysis and the forecast. However, for correlated observation errors and the use of a diagonal observation‐error covariance matrix in the assimilation, an increase in the observation number such that the error correlation between two adjacent observations becomes greater than a threshold value (around 0.2) degrades the analysis and the forecast. Posterior diagnostics of the sub‐optimality of the assimilation scheme for correlated observation errors are analysed. Finally, it is shown that a risk of using high‐density observations and poor vertical resolution is that deficiencies in the background‐error statistics can lead to unrealistic analysis increments at some levels where no observations are present, and so produce a degradation of the analysis at these levels. Copyright © 2003 Royal Meteorological Society
Validity of anelastic and other equation sets as inferred from normal‐mode analysis
Authors: Davies Terry , Staniforth Andrew , Wood Nigel , Thuburn John 
Published: August 2007

AbstractVarious simplifications of the fully compressible inviscid (Euler) equations have been made over the years to filter out rapidly‐propagating acoustic oscillations, resulting in various anelastic, hydrostatic and pseudo‐incompressible equation sets. The principal tool used to develop approximate equation sets, and to assess their validity as a function of flow regime, has been scale analysis which has proven quite subtle to apply. Here it is shown that normal‐mode analysis provides a useful complementary tool for assessing the validity of the abovementioned approximate equation sets for both small‐ and large‐scale flows, and leads to the following conclusions. Whilst of key importance for small‐scale theoretical studies and process modelling, the anelastic equations are not recommended for either operational numerical weather prediction or climate simulation at any scale. The pseudo‐incompressible set appears to be viable for numerical weather prediction, but only at short horizontal scales. For global non‐hydrostatic modelling, only the fully compressible equations are suitable. Advances in numerical techniques in the past decade allow these to be integrated in a computationally efficient manner. © Crown copyright, 2003. Royal Meteorological Society
Simulations of the effects of interannual and decadal variability on the clear‐sky outgoing long‐wave radiation spectrum
Authors: Brindley Helen E. , Allan Richard P. 
Published: August 2007

AbstractUsing atmospheric profiles derived from the Hadley Centre atmosphere climate model version 3 (HadAM3) as input to a radiative transfer code, the sensitivity of the resolved spectrum of clear‐sky outgoing long‐wave radiation to both interannual and longer‐term atmospheric variability has been analysed. A comparison of the simulated spectra with available observations from two satellite‐based instruments indicates a reasonable match, although consistent differences are present. These may be explained by a combination of uncertainties in the atmospheric state, and in the relative calibration of the two instruments. Focusing on the simulations: if HadAM3 is forced by the observed sea surface temperature (SST) record alone, and long‐term alterations in the well‐mixed greenhouse gases are imposed in the radiance simulations, the changes seen within the major absorption bands are robust. Under a second scenario, where the effects of solar variability, volcanic aerosol, ozone changes and increases in the well‐mixed greenhouse gases are also included in the forcing of HadAM3, the long‐term profile changes tend to show an enhanced upper‐tropospheric warming and low/mid‐stratospheric cooling, with increased near‐surface humidities compared to the SST‐only case. However, the tropospheric response of the system, manifested in the spectral change pattern over the atmospheric window and water vapour bands, falls within the range of year‐to‐year variability. Copyright © Royal Meteorological Society, 2003. R. P. Allan's contribution is Crown copyright.
Clear‐sky infrared aerosol radiative forcing at the surface and the top of the atmosphere
Authors: Markowicz Krzysztof M. , Flatau Piotr J. , Vogelmann Andrew M. , Quinn Patricia K. , Welton Ellsworth J. 
Published: August 2007

AbstractWe study the aerosol radiative forcing at infrared (IR) wavelengths using data from the Aerosol Characterization Experiment, ACE‐Asia, cruise of the National Oceanic and Atmospheric Administration research vessel Ronald H. Brown. The analyses apply to the daytime periods of clear‐sky conditions for the area within the immediate vicinity of the ship. An optical model is derived from chemical measurements, lidar profiles, and visible‐extinction measurements, which are used to estimate the IR aerosol optical thickness and the single‐scattering albedo. The IR model results are compared to detailed Fourier transform interferometer‐based IR aerosol forcing estimates, pyrgeometer‐based IR downward fluxes, and to observations of the direct aerosol solar forcing. This combined approach attests to the self‐consistency of the optical model, and allows us to derive quantities such as the IR forcing at the top of the atmosphere (TOA) and the IR optical thickness. The mean IR aerosol optical thickness at 10 µm is 0.08 and the single‐scattering albedo is 0.55. The modelled IR aerosol surface forcing reaches 10 W m−2 during the cruise, which is a significant contribution compared to the total direct aerosol forcing. The surface IR aerosol radiative forcing is between 10 and 25% of the short‐wave aerosol forcing. The IR aerosol forcing at the TOA can be up to 19% of the solar aerosol forcing. We show good agreement between TOA aerosol IR forcing derived from the model and from the CERES (Clouds and the Earth's Radiant Energy System) satellite data. Over the Sea of Japan, the average IR aerosol radiative forcing is 4.6 W m−2 at the surface, and 1.5 W m−2 at the TOA. The IR forcing efficiency at the TOA is a strong function of aerosol temperature (which is coupled to vertical structure) and changes between 10 and 18 W m−2 (per IR optical depth unit), while the surface IR forcing efficiency varies between 37 and 55 W m−2 (per IR optical depth unit). Copyright © 2003 Royal Meteorological Society
Dynamic predictability of intraseasonal variability associated with the Asian summer monsoon
Authors: Waliser D. E. , Stern W. , Schubert S. , Lau K. M. 
Published: August 2007

AbstractThe objective of this study is to estimate the limit of dynamical predictability for the tropical intraseasonal oscillation (ISO) associated with the Asian summer monsoon. Ensembles of ‘twin’ predictability experiments were carried out with the National Aeronautics and Space Administration Goddard Laboratory for the Atmospheres atmospheric general circulation model using specified annual cycle sea surface temperatures. Initial conditions were taken from a 10‐year control simulation during periods of strong ISO activity identified via extended empirical orthogonal function analysis of 30–90 day band‐passed tropical rainfall. From this analysis, 21 cases were chosen for each of four distinct phases of the ISO cycle, making 84 cases in total. Two different sets of small random perturbations were added to these 84 initial states. Simulations were then performed for 90 days from each of these 168 perturbed initial conditions. A measure of potential predictability was constructed based on a ratio of the signal associated with the ISO, in terms of rainfall or 200 hPa velocity potential (VP200), and the mean‐square difference between sets of twin forecasts. This ratio indicates that the limit of predictability for this model's ISO extends out to about 25 days for VP200 and to about 15 days for rainfall. The predictability measure shows modest dependence on the strength of the ISO events, with stronger events having a greater limit of predictability by a few days. It also exhibits a dependence on the phase of the ISO, with greater predictability for the convective phase at short (≲5 days) lead times and for the suppressed phase at longer (≳15 days) lead times. The implications of these results as well as their associated model and analysis caveats are discussed. Copyright © 2003 Royal Meteorological Society
On the time variability of the net ocean‐to‐atmosphere heat flux in midlatitudes, with application to the North Atlantic basin
Authors: Czaja Arnaud 
Published: August 2007

AbstractA new diagnostic to investigate the role of ocean dynamics in midlatitude air–sea interactions is presented and tested against observations. It is based on the analysis of the time variability of the net ocean‐to‐atmosphere heat flux (FS).A hierarchy of air–sea interaction models indicate that, in the absence of ocean dynamics, the power spectrum of FS should be blue at time‐scales longer than a threshold set by the late‐winter ocean mixed‐layer thickness and the sensitivity of FS to sea surface temperature anomalies. Comparison of the predicted FS spectrum with observations over the North Atlantic shows a good agreement over the subpolar gyre where the deep ocean mixed layer combined with strong stochastic forcing allows large fluctuations in FS at decadal and longer time‐scales. Discrepancies, however, arise over the Gulf Stream extension region. Here it is suggested that the observed variability of FS at time‐scales longer than a decade is controlled by geostrophic ocean dynamics rather than local atmospheric forcing.The diagnostic appears to be a useful and simple tool to investigate the role of ocean dynamics in the upper‐ocean heat budget. It is particularly well suited to the analysis of long simulations of coupled ocean–atmosphere models.One implication of the study for ocean‐only numerical simulations is that one cannot specify externally the low‐frequency variability of FS. The latter should only arise as a consequence of ocean dynamics. Copyright © 2003 Royal Meteorological Society
Simulation of wind profiles from a space‐borne Doppler wind lidar
Authors: Marseille G. J. , Stoffelen A. 
Published: August 2007

AbstractThe importance of wind observations for meteorological analysis has been recognized for many years. The current global observing system lacks a uniform distribution of tropospheric wind measurements, especially in the tropics and southern hemisphere, and over the northern‐hemisphere oceans. A Doppler wind lidar (DWL) mounted on a space‐borne platform has the potential to provide a global three‐dimensional coverage of wind data. The European Space Agency has decided to fly in 2007 a DWL on a polar‐orbiting satellite platform as part of the Atmospheric Dynamics Mission, now called Aeolus. The proposed DWL is a non‐scanning single‐perspective instrument, operating in the ultraviolet part of the electromagnetic spectrum, providing profiles of line‐of‐sight (LOS) wind components from detected light backscattered from the illuminated atmospheric volume. The concept has been simulated and was used in observation‐system simulation experiments to assess its potential impact on numerical weather prediction and climate processes. This paper describes the simulation of Aeolus LOS wind‐component profiles and their expected quality in cloud‐free and cloudy conditions. Copyright © 2003 Royal Meteorological Society
Water vapour line and continuum absorption in the thermal infrared—reconciling models and observations
Authors: Taylor Jonathan P. , Newman Stuart M. , Hewison Tim J. , McGrath Andrew 
Published: August 2007

AbstractHigh‐spectral‐resolution thermal infrared radiance observations made with the Airborne Research Interferometer Evaluation System instrument on the Met Office C130 aircraft in tropical and sub‐arctic atmospheres are used to evaluate the water vapour continuum and line absorption. Coincident microwave radiometer measurements at 183 GHz are used to help constrain the water vapour profile. Through careful selection of wavelengths where the water vapour continuum has varying impacts on the observed radiances, analysis shows that the continuum is too strong; this is using the General Line‐by‐line Atmospheric Transmittance and Radiance Model with the CKD2.4 water vapour continuum and High Resolution Transmission Molecular Absorption 2000 spectral database. Zenith observations from low altitude indicate that the continuum requires reducing by between 6% and 15% depending on the frequency, which is in good agreement with recent laboratory data. A modified continuum is presented and used in modelling to compare against upper‐troposphere nadir measurements obtained in tropical and sub‐arctic atmospheres. Copyright © Crown copyright, 2003
The Reverberation Time and Equivalent Sound Absorption Area of Rooms in Dwellings
Authors: Díaz César , Pedrero Antonio 
Published: August 2007

The study gives the results of the measurements of the reverberation time in 11,687 rooms, of which 11,457 are furnished (8,246 bedrooms, 3,211 living rooms), and 230 unfurnished. All the rooms have thick walls and ceilings, and a heavy floor covering. The reverberation times measured are quite similar in bedrooms and living rooms within the same size range, and decrease fairly uniformly as the frequency increases. Moreover, in each frequency band the greater the volume of the room, the greater the reverberation time. The results of this extensive fieldwork allow us to predict accurately the reverberation time in these kinds of spaces as a function of their size and the frequency. These data may be useful for improving the accuracy of calculation models to estimate the reverberation time of enclosed spaces. The equivalent sound absorption area of these rooms was also calculated.
Josephin domain-containing proteins from a variety of species are active de-ubiquitination enzymes
Authors: Tzvetkov Nikolay , Breuer Peter 
Published: August 2007

Abstract
The neurodegenerative disease spinocerebellar ataxia type 3 (SCA3) is caused by the presence of an extended polyglutamine stretch (polyQ) in the unstructured C-terminus of the human ataxin-3 (AT3) protein. The structured N-terminal Josephin domain (JD) of AT3 is conserved within a novel family of potential ubiquitin proteases, the JD-containing proteins, which are sub-divided into two groups termed ataxins and Josephins. These AT3 orthologs are encoded by the genomes of organisms ranging from Plasmodium falciparum to humans, with most species possessing more than one homolog. While Josephins consist of JDs alone, ataxins contain additional functional domains that may influence their enzyme activity. Here, we show that the enzyme activity of human AT3 (hAT3) is not affected by the length of polyQ in its C-terminus, even when it is in the range associated with SCA3. We also show that JDs of all human proteins with homology to AT3 and its homologs from various species possess de-ubiquitination activity. These results establish JD-containing proteins as a novel family of active de-ubiquitination enzymes with wide phylogenic distribution.
Diversity of proteasomal missions: fine tuning of the immune response
Authors: Borissenko Ljudmila , Groll Michael 
Published: August 2007

AbstractThe majority of cellular proteins are degraded by proteasomes within the ubiquitin-proteasome ATP-dependent degradation pathway. Products of proteasomal activity are short peptides that are further hydrolysed by proteases to single amino acids. However, some peptides can escape this degradation, being selected and taken up by major histocompatibility complex (MHC) class I molecules for presentation to the immune system on the cell surface. MHC class I molecules are highly selective and specific in terms of ligand binding. Variability of peptides produced in living cells arises in a variety of ways, ensuring fast and efficient immune responses. Substitution of constitutive proteasomal subunits with immunosubunits leads to conformational changes in the substrate binding channels, resulting in a modified protein cleavage pattern and consequently in the generation of new antigenic peptides. The recently discovered event of proteasomal peptide splicing opens new horizons in the understanding of additional functions that proteasomes apparently possess. Whether peptide splicing is an occasional side product of proteasomal activity still needs to be clarified. Both γ-interferon-induced immunoproteasomes and peptide splicing represent two significant events providing increased diversity of antigenic peptides for flexible and fine-tuned immune response.
Cysteine protease inhibitors reduce brain β-amyloid and β-secretase activity in vivo and are potential Alzheimer's disease therapeutics
Authors: Hook Gregory , Hook Vivian Y.H. , Kindy Mark 
Published: August 2007

Abstract
β-Secretase inhibitors that lower brain β-amyloid peptides (Aβ) are likely to be effective for treating Alzheimer's disease (AD). Irreversible epoxysuccinyl cysteine protease inhibitors are known to reduce brain Aβ and β-secretase activity in the guinea pig model of human Aβ production. In this study, acetyl-l-leucyl-l-valyl-l-lysinal (Ac-LVK-CHO) is also shown to significantly reduce brain Aβ and β-secretase activity and brain Aβ in the same model. Ac-LVK-CHO is structurally distinct from the epoxysuccinyl inhibitors and is a reversible cysteine protease inhibitor. The results suggest that cysteine protease inhibitors generally, and reversible cysteine protease inhibitors specifically, have potential for development as AD therapeutics.
Chloroplast photorelocation movement mediated by phototropin family proteins in green plants
Authors: Suetsugu Noriyuki , Wada Masamitsu 
Published: August 2007

AbstractChloroplasts gather in areas irradiated with weak light to maximize photosynthesis (the accumulation response). They move away from areas irradiated with strong light to minimize damage of the photosynthetic apparatus (the avoidance response). The processes underlying these chloroplast movements can be divided into three parts: photoperception, signal transduction, and chloroplast movement. Photoreceptors for chloroplast movement have been identified recently in various plant species. A blue light receptor phototropin (phot) mediates chloroplast photorelocation movement in the seed plantArabidopsis thaliana, the fernAdiantum capillus-veneris, the mossPhyscomitrella patensand possibly the green algaMougeotia scalaris. A chimeric photoreceptor between phytochrome and phototropin, neochrome (neo), was found in some advanced ferns and in the green algaM. scalaris. While the mechanism of chloroplast movement is not well understood, it is known that actin filaments play an important role in this process. To understand the molecular mechanisms associated with chloroplast movement, several mutants were isolated inA.thaliana(jac1andchup1) and the corresponding genes were cloned. In this review, recent progress in photoreceptor research into chloroplast movement in various plant species and the possible factors functioning in signal transduction or the regulation of actin filaments identified inA. thalianais discussed.
Transport of nuclear-encoded proteins into secondarily evolved plastids
Authors: Hempel Franziska , Bozarth Andrew , Sommer Maik S. , Zauner Stefan , Przyborski Jude M. , Maier Uwe-G. 
Published: August 2007

Abstract
Many algal groups evolved by engulfment and intracellular reduction of a eukaryotic phototroph within a heterotrophic cell. Via this process, so-called secondary plastids evolved, surrounded by three or four membranes. In these organisms most of the genetic material encoding plastid functions is localized in the cell nucleus, with the result that many proteins have to pass three, four, or even five membranes to reach their final destination within the plastid. In this article, we review recent models and findings that help to explain important cellular mechanisms involved in the complex process of protein transport into secondary plastids.
Cross polarisation/magic angle spinning 13C-NMR spectroscopic studies of cellulose structural changes in hardwood dissolving pulp process
Authors: Nocanda Xolani , Larsson Per Tomas , Spark Andrew , Bush Tamara , Olsson Ann , Madikane Mzekelo , Bissessur Ajay , Iversen Tommy 
Published: August 2007

Abstract
Cross polarisation/magic angle spinning 13C NMR spectroscopy has been used to study structural changes in cellulose induced by the dissolving pulp process. The cellulose structure in several dissolving pulps was investigated for commercial and laboratory cooked Eucalyptus 92α and 96α. The average lateral dimension, or average thickness, of the cellulose fibril aggregates is related to the amount of surface area exposed and could be one controlling factor for the chemical reactivity of commercial dissolving pulps during modification reactions. The thickness of the cellulose fibril aggregates governs the amount of surface area present in the fibre wall, and cellulose surface material constitutes the part of the cellulose that is directly accessible to reagents. In all sample series investigated, the raw pulp was found to be less aggregated than the corresponding bleached final pulp. Furthermore, an irreversible increase in fibril aggregate width was observed on free drying for both laboratory cooked and commercial pulps. Upon rewetting with water, the freely dried 96α pulp was found to be more aggregated than the freely dried 92α pulp, although sugar analysis showed very similar carbohydrate compositions. As indicated by the molecular mass distribution, the commercial 92α pulp contained larger amounts of degraded cellulose; this may be a plausible explanation for the different behaviour of the 92α and 96α pulps during free drying.