bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neural Mechanisms, Temporal Dynamics, and Individual Differences in Interference Control
Authors: Forstmann Birte U. , van den Wildenberg Wery P. M. , Ridderinkhof K. Richard 
Published: March 2008

Abstract
Functional magnetic resonance imaging (fMRI) methods may help in understanding processes of response capture and response inhibition in conflict tasks, such as the Simon task. However, data-driven approaches thus far have not yielded consistent insights into these processes. Here, a theory-driven approach is introduced that capitalizes on individual differences in the processes of central interest. Based on the so-called activation-suppression model, specific behavioral parameters for each individual derived from reaction time (RT) distribution analysis were computed and entered into model-based fMRI analyses. These parameters correspond closely to the processes of inappropriate location-driven response activation (capture) and the subsequent inhibition of this activation as detailed by the model. Data from 24 participants revealed activation in the pre-supplementary motor area, which covaried with the RT distribution measure of response capture. Activation in the right inferior frontal cortex was found to covary with the RT distribution measure of response inhibition. These results, which are consistent against the backdrop of the larger literature on cognitive control, could have been derived neither from the standard data-driven fMRI approach, nor from inspecting overall mean RT alone.
Estimating Topographic Blocking Using a Froude Number When the Static Stability Is Nonuniform
Authors: Reinecke Patrick A. , Durran Dale R. 
Published: March 2008

Abstract
A parameter widely used to predict topographic flow blocking is the nondimensional mountain height or, synonymously, the inverse Froude number. Predictions using this parameter are based on the morphology of flows with uniform upstream static stability and wind speed, which rarely occur in the real world. The appropriateness of applying this theory in the presence of nontrivial background stability is therefore investigated using a numerical model. Two methods were considered to estimate the low-level stability, averaging the Brunt–Väisälä frequency below the crest and using the bulk change in θ between the ground and crest level.
No single best method emerged for estimating the upstream static stability and thereby mapping the simulations with inversions onto the set of solutions with constant stratification. Instead, the best method depended on the application at hand. To predict the onset of flow stagnation, averaging the low-level stability worked best, while to predict low-level flow diversion the bulk estimate of low-level stability was most appropriate. These results are consistent across a range of inversion thicknesses and strengths. In addition, it is shown that variations in static stability above the mountain crest have little impact on flow blocking.
The IMPROVE-1 Storm of 1–2 February 2001. Part IV: Precipitation Enhancement across the Melting Layer
Authors: Woods Christopher P. , Locatelli John D. , Stoelinga Mark T. 
Published: March 2008

Abstract
Previous model simulations indicate that in stratiform precipitation, the precipitation rate can increase by 7% in the melting layer through direct condensation onto melting snow and the resultant cooled rain. In the present study, a model simulation of stratiform precipitation in a wide cold frontal rainband indicates that the precipitation rate can also increase by 5% in the melting layer through accretion, by melting snow and rain, of additional cloud water produced by the latent cooling of the ambient air associated with melting snow. The contribution of the combined processes, and therefore the additional precipitation gained through the latent cooling of melting snow within the melting layer, may contribute as much as 10% to the precipitation rate in stratiform precipitation.
Unimodality of Wave Amplitude in the Northern Hemisphere
Authors: Ambaum Maarten H. P. 
Published: March 2008

Abstract
A novel statistic for local wave amplitude of the 500-hPa geopotential height field is introduced. The statistic uses a Hilbert transform to define a longitudinal wave envelope and dynamical latitude weighting to define the latitudes of interest. Here it is used to detect the existence, or otherwise, of multimodality in its distribution function. The empirical distribution function for the 1960–2000 period is close to a Weibull distribution with shape parameters between 2 and 3. There is substantial interdecadal variability but no apparent local multimodality or bimodality.
The zonally averaged wave amplitude, akin to the more usual wave amplitude index, is close to being normally distributed. This is consistent with the central limit theorem, which applies to the construction of the wave amplitude index. For the period 1960–70 it is found that there is apparent bimodality in this index. However, the different amplitudes are realized at different longitudes, so there is no bimodality at any single longitude.
As a corollary, it is found that many commonly used statistics to detect multimodality in atmospheric fields potentially satisfy the assumptions underlying the central limit theorem and therefore can only show approximately normal distributions. The author concludes that these techniques may therefore be suboptimal to detect any multimodality.
An Enhanced Moisture Convergence–Evaporation Feedback Mechanism for MJO Air–Sea Interaction
Authors: Marshall Andrew G. , Alves Oscar , Hendon Harry H. 
Published: March 2008

Abstract
Simulations using an atmospheric model forced with observed SST climatology and the same atmospheric model coupled to a slab-ocean model are used to investigate the role of air–sea interaction on the dynamics of the MJO. Slab-ocean coupling improved the MJO in Australia’s Bureau of Meteorology atmospheric model over the Indo-Pacific warm pool by reducing its period from 70–100 to 45–70 days, thereby showing better agreement with the 30–80-day observed oscillation.
Air–sea coupling improves the MJO by increasing the moisture flux in the lower troposphere prior to the passage of active convection, which acts to promote convection and precipitation on the eastern flank of the main convective center. This process is triggered by an increase in surface evaporation over positive SST anomalies ahead of the MJO convection, which are driven by the enhanced shortwave radiation in the region of suppressed convection. This in turn generates enhanced convergence into the region, which supports evaporation–wind feedback in the presence of weak background westerly winds. A subsequent increase in low-level moisture convergence acts to further moisten the lower troposphere in advance of large-scale convection in a region of reduced atmospheric pressure. This destabilizing mechanism is referred to as enhanced moisture convergence–evaporation feedback (EMCEF) and is utilized to understand the role of air–sea coupling on the observed MJO. The EMCEF mechanism also reconciles traditionally opposing ideas on the roles of frictional wave–conditional instability of the second kind (CISK) and wind–evaporation feedback. These results support the idea that the MJO is primarily an atmospheric phenomenon, with air–sea interaction improving upon, but not critical for, its existence in the model.
Vertical-Mode Decompositions of 2-Day Waves and the Madden–Julian Oscillation
Authors: Haertel Patrick T. , Kiladis George N. , Denno Andrew , Rickenbach Thomas M. 
Published: March 2008

Abstract
Vertical structures of 2-day waves and the Madden–Julian oscillation (MJO) are projected onto vertical normal modes for a quiescent tropical troposphere. Three modes capture the gross tropospheric structure of 2-day waves, while only two modes are needed to represent most of the baroclinic structure of the MJO. Deep circulations that project onto the first baroclinic mode are associated with deep cumulonimbus and stratiform rainfall. Shallow circulations that project onto higher wavenumber modes are associated with precipitating shallow cumulus and congestus and stratiform rainfall. For both disturbances the horizontal divergence contributed by shallow modes is an important factor in the column-integrated moist enthalpy budget. These modes converge moist static energy for a time prior to when deep circulations export moist static energy. These results highlight the importance of properly representing the effects of shallow cumulus, congestus, and stratiform precipitation in theories of convectively coupled waves and in atmospheric models.
Subsiding Shells around Shallow Cumulus Clouds
Authors: Heus Thijs , Jonker Harm J. J. 
Published: March 2008

Abstract
In this study large-eddy simulations (LES) are used to gain more knowledge on the shell of subsiding air that is frequently observed around cumulus clouds. First, a detailed comparison between observational and numerical results is presented to better validate LES as a tool for studies of microscale phenomena. It is found that horizontal cloud profiles of vertical velocity, humidity, and temperature are in good agreement with observations. They show features similar to the observations, including the presence of the shell of descending air around the cloud. Second, the availability of the complete 3D dataset in LES has been exploited to examine the role of lateral mixing in the exchange of cloud and environmental air. The origin of the subsiding shell is examined by analyzing the individual terms of the vertical momentum equation. Buoyancy is found to be the driving force for this shell, and it is counteracted by the pressure-gradient force. This shows that evaporative cooling at the cloud edge, induced by lateral mixing of cloudy and environmental air, is the responsible mechanism behind the descending shell. For all clouds, and especially the smaller ones, the negative mass flux generated by the subsiding shell is significant. This suggests an important role for lateral mixing throughout the entire cloud layer. The role of the shell in these processes is further explored and described in a conceptual three-layer model of the cloud.
Modeling Supersaturation and Subgrid-Scale Mixing with Two-Moment Bulk Warm Microphysics
Authors: Morrison Hugh , Grabowski Wojciech W. 
Published: March 2008

Abstract
This paper describes further developments of a two-moment warm rain bulk microphysics scheme suitable for addressing the indirect impact of atmospheric aerosols on ice-free clouds in large-eddy simulation (LES) models. The emphasis is on the prediction of supersaturation, activation of cloud droplets, and the representation of microphysical transformations during parameterized turbulent mixing. A comprehensive approach is proposed that is capable of simulating droplet activation at the cloud base, in the cloud interior due to increasing updraft strength, and at the lateral edges due to entrainment. Such an approach requires high spatial resolution to capture maximum supersaturation at cloud base as well as to resolve entraining eddies that lead to additional activation above the cloud base. This approach can be used as a benchmark for developing and testing schemes suitable for lower spatial resolutions.
A novel approach for predicting the supersaturation field is proposed, with an emphasis on its application in an Eulerian framework. This approach produces consistency among the thermodynamic variables and mitigates the problem of spurious cloud-edge supersaturation noted in the past. A new subgrid scheme is also developed to treat microphysical transformations during turbulent entrainment and mixing. This scheme is designed to be as flexible as possible, allowing for the entire range of mixing scenarios from homogeneous to extremely inhomogeneous.
The above developments are applied in 2D simulations of moist convection for an idealized rising thermal, assuming either pristine or polluted aerosol conditions. The mixing scenario has a substantial impact on the cloud microphysical and optical properties. As expected, extremely inhomogeneous mixing results in substantially smaller mean droplet number concentration, larger effective radius, and smaller cloud optical depth compared to the run with homogeneous mixing. The subgrid mixing of cloud condensation nuclei (CCN) and formation of CCN from evaporated droplets during extremely inhomogeneous mixing are relatively less important for this case.
A Moisture-Stratiform Instability for Convectively Coupled Waves
Authors: Kuang Zhiming 
Published: March 2008

Abstract
A simple model of two vertical modes is constructed and analyzed to reveal the basic instability mechanisms of convectively coupled waves. The main novelty of this model is a convective parameterization based on the quasi-equilibrium concept and simplified for a model of two vertical modes. It hypothesizes 1) the approximate invariance of the difference between saturation moist static energy in the lower half of the troposphere and moist static energy in the subcloud layer, regardless of free troposphere humidity, and 2) that variations in the depth of convection are determined by moisture-deficit variations in the midtroposphere. Physical arguments for such a treatment are presented. For realistic model parameters chosen based on cloud system resolving model simulations (CSRMs) of an earlier study, the model produces unstable waves at wavelengths and with structures that compare well with the CSRM simulations and observations.
A moisture–stratiform instability and a direct–stratiform instability are identified as the main instability mechanisms in the model. The former relies on the effect of midtroposphere humidity on the depth of convection. The latter relies on the climatological mean convective heating profile being top heavy, and it is identified to be the same as the stratiform instability mechanism proposed by B. E. Mapes. The moisture–stratiform instability appears to be the main instability mechanism for the convectively coupled wave development in the CSRM simulations. The finite response time of convection has a damping effect on the waves that is stronger at high wavenumbers. The net moistening effect of the second-mode convective heating also damps the waves, but more strongly at low wavenumbers. These effects help to shape the growth rate curve so that the most unstable waves are of a few thousand kilometers in scale.
A Low-Level Circulation in the Tropics
Authors: Folkins Ian , Fueglistaler S. , Lesins G. , Mitovski T. 
Published: March 2008

Abstract
Deep convective tropical systems are strongly convergent in the midtroposphere. Horizontal wind measurements from a variety of rawinsonde arrays in the equatorial Pacific and Caribbean are used to calculate the mean dynamical divergence profiles of large-scale arrays (≥1000 km in diameter) in actively convecting regions. Somewhat surprisingly, the magnitude of the midtropospheric divergence calculated from these arrays is usually small. In principle, the midlevel convergence of deep convective systems could be balanced on larger scales either by a vertical variation in the radiative mass flux of the background clear sky atmosphere, or by a divergence from shallow cumuli. The vertical variation of the clear sky mass flux in the midtroposphere is small, however, so that the offsetting divergence must be supplied by shallow cumuli. On spatial scales of ∼1000 km, the midlevel convergent inflow toward deep convection appears to be internally compensated, or “screened,” by a divergent outflow from surrounding precipitating shallow convection. Deep convective systems do not induce a large-scale inflow of midlevel air toward actively convecting regions from the rest of the tropics, but instead help generate a secondary low-level circulation, in which the net downward mass flux from mesoscale and convective-scale downdrafts is balanced by a net upward mass flux from precipitating shallow cumuli. The existence of this circulation is consistent with observational evidence showing that deep and shallow convection are spatiotemporally coupled on a wide range of both spatial and temporal scales. One of the mechanisms proposed for coupling shallow convection to deep convection is the tendency for deep convection to cool the lower troposphere. The authors use radiosonde temperature profiles and the Tropical Rainfall Measuring Mission (TRMM) 3B42 gridded rainfall product to argue that the distance over which deep convection cools the lower troposphere is approximately 1000 km.
On “A Consistent Theory for Linear Waves of the Shallow-Water Equations on a Rotating Plane in Midlatitudes”
Authors: Poulin Francis J. , Rowe Kristopher 
Published: March 2008

AbstractRecently, Paldor et al. provided a consistent and unified theory for Kelvin, Poincaré (inertial–gravity), and Rossby waves in the rotating shallow-water equations (SWE). Unfortunately, the article has some errors, and the effort is made to correct them in this note. Also, the eigenvalue problem is rewritten in a dimensional form and then nondimensionalized in terms of more traditional nondimensional parameters and compared to the dispersion relations of the old and new theories. The errors in Paldor et al. are only quantitative in nature and do not alter their major results: Rossby waves can have larger phase speeds than what is predicted from the classical theory, and Rossby and Poincaré waves can be trapped near the equatorward boundary.
Improved Forecasts of the Diurnal Cycle in the Tropics Using Multiple Global Models. Part II: Asian Summer Monsoon
Authors: Chakraborty Arindam , Krishnamurti T. N. 
Published: March 2008

Abstract
The diurnal mode of the Asian summer monsoon during active and break periods is studied using four versions of the Florida State University (FSU) global spectral model (GSM). These versions differ in the formulation of cloud parameterization schemes in the model. Observational-based estimates show that there exists a divergent circulation at 200 hPa over the Asian monsoon region in the diurnal time scale that peaks at 1200 local solar time (LST) during break monsoon and at 1800 LST during active monsoon. A circulation in the opposite direction is seen near the surface. This circulation loop is completed by vertical ascending/descending motion over the monsoon domain and its surroundings. This study shows that global models have large phase and amplitude errors for the 200-hPa velocity potential and vertical pressure velocity over the monsoon region and its surroundings. Construction of a multimodel superensemble could reduce these errors substantially out to five days in advance. This was on account of assigning differential weights to the member models based on their past performance. This study also uses a unified cloud parameterization scheme that inherits the idea of a multimodel superensemble for combining member model forecasts. The advantage of this model is that it is an integrated part of the GSM and thus can improve the forecasts of other parameters as well through improved cloud cover. It was seen that this scheme had a larger impact on forecasting the diurnal cycle of cloud cover and precipitation of the Asian summer monsoon compared to circulation. The authors show that the diurnal circulation contributes to about 10% of the rate of change of total kinetic energy of the monsoon. Therefore, forecasting this pronounced diurnal mode has important implications for the energetics of the Asian summer monsoon.
Contrails, Natural Clouds, and Diurnal Temperature Range
Authors: Dietmüller Simone , Ponater Michael , Sausen Robert , Hoinka Klaus-Peter , Pechtl Susanne 
Published: March 2008

Abstract
The direct impact of aircraft condensation trails (contrails) on surface temperature in regions of high aircraft density has been a matter of recent debate in climate research. Based on data analysis for the 3-day aviation grounding period over the United States, following the terrorists’ attack of 11 September 2001, a strong effect of contrails reducing the surface diurnal temperature range (DTR) has been suggested. Simulations with the global climate model ECHAM4 (including a contrail parameterization) and long-term time series of observation-based data are used for an independent cross check with longer data records, which allow statistically more reliable conclusions. The climate model underestimates the overall magnitude of the DTR compared to 40-yr ECMWF Re-Analysis (ERA-40) data and station data, but it captures most features of the DTR global distribution and the correlation between DTR and either cloud amount or cloud forcing. The diurnal cycle of contrail radiative impact is also qualitatively consistent with expectations, both at the surface and at the top of the atmosphere. Nevertheless, there is no DTR response to contrails in a simulation that inhibits a global radiative forcing considerably exceeding the upper limit of contrail radiative impact according to current assessments. Long-term trends of DTR, the level of natural DTR variability, and the specific effect of high clouds on DTR are also analyzed. In both ECHAM4 and ERA-40 data, the correlation of cloud coverage or cloud radiative forcing with the DTR is mainly apparent for low clouds. None of the results herein indicates a significant impact of contrails on reducing the DTR. Hence, it is concluded that the respective hypothesis as derived from the 3-day aviation-free period over the United States lacks the required statistical backing.
Prospects for a New General Classification
Authors: Austin Derek 
Published: March 2008

In traditional classification schemes, the universe of knowledge is brokeii down into self- contained disciplines which are further analysed to the point at which a particular concept is located. This leads to problems of: (a) currency: keeping the scheme in line with new discoveries. (b) hospitality: allowing room for insertion of new subjects (c) cross-classification: a concept may be considered in such a way that it fits as logically into one discipline as another. Machine retrieval is also hampered by the fact that any individual concept is notated differently, depending on where in the scheme it appears. The approach now considered is from an organized universe of concepts, every concept being set down only once in an appropriate vocabulary, where it acquires the notation which identifies it wherever it is used. It has been found that all the concepts present in any compound subject can be handled as though they belong to one of two basic concept types, being either Entities or Attributes. In classing, these concepts are identified, and notation is selected from appropriate schedules. Subjects are then built according to formal rules, the final class number incorporating operators which convey the fundamental relationships between concepts. From this viewpoint, the Rules and Operators of the proposed system can be seen as the grammar of an IR language, and the schedules of Entities and Attributes as its vocabulary.