bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adjustment to Injections of Mass, Momentum, and Heat in a Compressible Atmosphere
Authors: Chagnon Jeffrey M. , Bannon Peter R. 
Published: September 2005

Abstract
This study compares the response to injections of mass, heat, and momentum during hydrostatic and geostrophic adjustment in a compressible atmosphere. The sensitivity of the adjustment to these different injection types is examined at varying spatial and temporal scales through analysis of the transient evolution of the fields as well as the partitioning of total energy between acoustic waves, buoyancy waves, Lamb waves, and the steady state.
The effect of a cumulus cloud on its larger-scale environment may be represented as a vertical mass source/sink and a localized warming. To examine how the response to such injections may differ, injections of mass and heat that generate identical potential vorticity (PV) distributions and, hence, identical steady states, are compared. When the duration of the injection is very short (e.g., a minute or less), the injection of mass generates a very large acoustic wave response relative to the PV-equivalent injection of heat. However, the buoyancy wave response to these two injection types is quite similar.
The responses to injections of divergent momentum in the vertical and horizontal directions are also compared. It is shown that neither divergent momentum injection generates any PV and, thus, there is no steady-state response to these injections. The waves excited by these injections generally propagate their energy in the direction of the injection. Consequently, an injection of vertical momentum is an efficient generator of vertically propagating, horizontally trapped, high-frequency buoyancy waves. Such waves have a short time scale and are therefore very sensitive to the injection duration. Analogously, an injection of divergent horizontal momentum is an efficient generator of horizontally propagating, vertically trapped low-frequency buoyancy waves that are relatively insensitive to the injection duration. Because of this difference in the response to horizontal and vertical injections of momentum, the response to the injection of an isolated updraft differs depending on whether a compensating horizontal inflow/outflow is also specified. This additional specification of inflow/outflow helps filter acoustic waves and encourages a stronger updraft that is not removed as rapidly by the buoyancy waves. This finding is relevant to the initialization of updrafts in compressible numerical weather prediction models.
Injection of nondivergent momentum generates waves in the regions of convergence/divergence produced by the deflection of the current by Coriolis forces. The energy partitioning for such an injection is sensitive to the width and depth of the current relative to the Rossby radius of deformation, but the response is insensitive to the duration of injection for time scales shorter than several hours.
Regional Heat Sources and the Active and Break Phases of Boreal Summer Intraseasonal (30–50 Day) Variability*
Authors: Annamalai H. , Sperber K. R. 
Published: September 2005

AbstractThe boreal summer intraseasonal variability (BSISV) associated with the 30–50-day mode is represented by the coexistence of three components: poleward propagation of convection over the Indian and tropical west Pacific longitudes and eastward propagation along the equator. The hypothesis that the three components influence each other has been investigated using observed outgoing longwave radiation (OLR), NCEP–NCAR reanalysis, and solutions from an idealized linear model. The null hypothesis is that the three components are mutually independent. Cyclostationary EOF (CsEOF) analysis is applied on filtered OLR to extract the life cycle of the BSISV. The dominant CsEOF mode is significantly tied to the observed spatial rainfall pattern associated with the active/break phases over the Indian subcontinent. The components of the heating patterns from CsEOF analysis serve as prescribed forcings for the dry version of the linear model. This allows one to investigate the possible roles that the regional heat sources and sinks play in driving the large-scale monsoon circulation at various stages of the BSISV life cycle. To understand the interactive nature between convection and circulation, the moist version of the model is forced with intraseasonal SST anomalies.The linear models reproduce the major features of the BSISV seen in the reanalysis. The linear model suggests three new findings: (i) The circulation anomalies that develop as a Rossby wave response to suppressed convection over the equatorial Indian Ocean associated with the previous break phase of the BSISV results in low-level convergence and tropospheric moisture enhancement over the equatorial western Indian Ocean and helps trigger the next active phase of the BSISV. (ii) The development of convection over the tropical west Pacific forces descent anomalies to the west. This, in conjunction with the weakened cross-equatorial flow due to suppressed convective anomalies over the equatorial Indian Ocean, reduces the tropospheric moisture over the Arabian Sea and promotes westerly wind anomalies that do not recurve over India. As a result the low-level cyclonic vorticity shifts from India to Southeast Asia and break conditions are initiated over India. (iii) The circulation anomalies forced by equatorial Indian Ocean convective anomalies significantly influence the active/break phases over the tropical west Pacific.The model solutions support the hypothesis that the three components of the BSISV influence each other but do not imply that such an influence is responsible for the space–time evolution of the BSISV. Further, the applicability of the model results to the observed system is constrained by the assumption that linear interactions are sufficient to address the BSISV and that air–sea interaction and transient forcing are excluded.
On the Role of Moist Processes in Tropical Intraseasonal Variability: Cloud–Radiation and Moisture–Convection Feedbacks
Authors: Bony Sandrine , Emanuel Kerry A. 
Published: September 2005

Abstract
Recent observations of the tropical atmosphere reveal large variations of water vapor and clouds at intraseasonal time scales. This study investigates the role of these variations in the large-scale organization of the tropical atmosphere, and in intraseasonal variability in particular. For this purpose, the influence of feedbacks between moisture (water vapor, clouds), radiation, and convection that affect the growth rate and the phase speed of unstable modes of the tropical atmosphere is investigated.
Results from a simple linear model suggest that interactions between moisture and tropospheric radiative cooling, referred to as moist-radiative feedbacks, play a significant role in tropical intraseasonal variability. Their primary effect is to reduce the phase speed of large-scale tropical disturbances: by cooling the atmosphere less efficiently during the rising phase of the oscillations (when the atmosphere is moister) than during episodes of large-scale subsidence (when the atmosphere is drier), the atmospheric radiative heating reduces the effective stratification felt by propagating waves and slows down their propagation. In the presence of significant moist-radiative feedbacks, planetary disturbances are characterized by an approximately constant frequency. In addition, moist-radiative feedbacks excite small-scale disturbances advected by the mean flow. The interactions between moisture and convection exert a selective damping effect upon small-scale disturbances, thereby favoring large-scale propagating waves at the expense of small-scale advective disturbances. They also weaken the ability of radiative processes to slow down the propagation of planetary-scale disturbances. This study suggests that a deficient simulation of cloud radiative interactions or of convection-moisture interactions may explain some of the difficulties experienced by general circulation models in simulating tropical intraseasonal oscillations.
An Observational Case for the Prevalence of Roll Vortices in the Hurricane Boundary Layer*
Authors: Morrison Ian , Businger Steven , Marks Frank , Dodge Peter , Businger Joost A. 
Published: September 2005

Abstract
Doppler velocity data from Weather Surveillance Radar-1988 Doppler (WSR-88D) radars during four hurricane landfalls are analyzed to investigate the presence of organized vortices in the hurricane boundary layer (HBL). The wavelength, depth, magnitude, and track of velocity anomalies were compiled through analysis of Doppler velocity data. The analysis reveals alternating bands of enhanced and reduced azimuthal winds closely aligned with the mean wind direction. Resulting statistics provide compelling evidence for the presence of organized secondary circulations or boundary layer rolls across significant areas during four hurricane landfalls. The results confirm previous observations of the presence of rolls in the HBL. A potential limitation of the study presented here is the resolution of the WSR-88D data. In particular, analysis of higher-resolution data (e.g., from the Doppler on Wheels) is needed to confirm that data aliasing has not unduly impacted the statistics reported here. Momentum fluxes associated with the secondary circulations are estimated using the covariance between the horizontal and vertical components of the wind fluctuations in rolls, with resulting fluxes 2–3 times greater than estimated by parameterizations in numerical weather prediction models. The observational analysis presented here, showing a prevalence of roll vortices in the HBL, has significant implications for the vertical transport of energy in hurricanes, for the character of wind damage, and for improvements in numerical simulations of hurricanes.
Using Idealized Coherent Structures to Parameterize Momentum Fluxes in a PBL Mass-Flux Model
Authors: Lappen Cara-Lyn , Randall David A. 
Published: September 2005

Abstract
In 2001, the authors presented a higher-order mass-flux model called assumed distributions with higher-order closure (ADHOC), which represents the large eddies of the planetary boundary layer (PBL) in terms of an assumed joint distribution of the vertical velocity and scalars such as potential temperature or water vapor mixing ratio. ADHOC is intended for application as a PBL parameterization. It uses the equations of higher-order closure to predict selected moments of the assumed distribution, and diagnoses the parameters of the distribution from the predicted moments. Once the parameters of the distribution are known, all moments of interest can be computed.
The first version of ADHOC was incomplete in that the horizontal momentum equations, the vertical fluxes of horizontal momentum, the contributions to the turbulence kinetic energy from the horizontal wind, and the various pressure terms involving covariances between pressure and other variables were not incorporated into the assumed distribution framework. Instead, these were parameterized using standard methods.
This paper describes an updated version of ADHOC. The new version includes representations of the horizontal winds and momentum fluxes that are consistent with the mass-flux framework of the model. The assumed joint probability distribution is replaced by an assumed joint spatial distribution based on an idealized coherent structure, such as a plume or roll. The horizontal velocity can then be determined using the continuity equation, and the momentum fluxes and variances are computed directly by spatial integration. These expressions contain unknowns that involve the parameters of the assumed coherent structures. Methods are presented to determine these parameters, which include the radius of convective updrafts and downdrafts and the wavelength, tilt, and orientation angle of the convective rolls. The parameterization is tested by comparison with statistics computed from large-eddy simulations. In a companion paper, the results of this paper are built on to determine the perturbation pressure terms needed by the model.
Assimilation of Surface Pressure Observations Using an Ensemble Filter in an Idealized Global Atmospheric Prediction System
Authors: Anderson Jeffrey L. , Wyman Bruce , Zhang Shaoqing , Hoar Timothy 
Published: September 2005

Abstract
An ensemble filter data assimilation system is tested in a perfect model setting using a low resolution Held–Suarez configuration of an atmospheric GCM. The assimilation system is able to reconstruct details of the model’s state at all levels when only observations of surface pressure (PS) are available. The impacts of varying the spatial density and temporal frequency of PS observations are examined. The error of the ensemble mean assimilation prior estimate appears to saturate at some point as the number of PS observations available once every 24 h is increased. However, increasing the frequency with which PS observations are available from a fixed network of 1800 randomly located stations results in an apparently unbounded decrease in the assimilation’s prior error for both PS and all other model state variables. The error reduces smoothly as a function of observation frequency except for a band with observation periods around 4 h. Assimilated states are found to display enhanced amplitude high-frequency gravity wave oscillations when observations are taken once every few hours, and this adversely impacts the assimilation quality. Assimilations of only surface temperature and only surface wind components are also examined.
The results indicate that, in a perfect model context, ensemble filters are able to extract surprising amounts of information from observations of only a small portion of a model’s spatial domain. This suggests that most of the remaining challenges for ensemble filter assimilation are confined to problems such as model error, observation representativeness error, and unknown instrument error characteristics that are outside the scope of perfect model experiments. While it is dangerous to extrapolate from these simple experiments to operational atmospheric assimilation, the results also suggest that exploring the frequency with which observations are used for assimilation may lead to significant enhancements to assimilated state estimates.
The Impact of Model Resolution on Differences between Independent Column Approximation and Monte Carlo Estimates of Shortwave Surface Irradiance and Atmospheric Heating Rate
Authors: O’Hirok William , Gautier Catherine 
Published: September 2005

Abstract
Within general circulation models (GCMs), domain average radiative fluxes are computed using plane-parallel radiative transfer algorithms that rely on cloud overlap schemes to account for clouds not resolved at the horizontal resolution of a grid cell. These parameterizations have a strong statistical approach and have difficulty being applied well to all cloudy conditions. A more physically based superparameterization has been developed that captures subgrid cloud variability using an embedded cloud system resolving model (CSRM) within each GCM grid cell. While plane-parallel radiative transfer computations are generally appropriate at the scale of a GCM grid cell, their suitability for the much higher spatially resolved CSRMs (2–4 km) is unknown because they ignore photon horizontal transport effects. The purpose of this study is to examine the relationship between model horizontal resolution and 3D radiative effects by computing the differences between independent column approximations (ICA) and 3D Monte Carlo estimates of shortwave surface irradiance and atmospheric heating rate.
Shortwave radiative transfer computations are performed on a set of six 2D fields composed of stratiform and convective liquid water and ice clouds. To establish how 3D effects vary with the size of a grid cell, this process is repeated as the model resolution is progressively degraded from 200 to 20 km. For shortwave surface irradiance, the differences between the 3D and ICA results can reach 500 W m−2. At model resolutions of between 2.0 and 5.0 km the difference for almost all columns is reduced to a maximum of ±100 W m−2. For atmospheric heating rates assessed at the level of individual model cells, 3D radiative effects can approach a maximum value of ±1.2 K h−1 when the horizontal column size is 200 m. However, between model resolutions of 2.0 and 5.0 km, 3D radiative effects are reduced to well below ±0.1 K h−1 for a large majority of the cloudy cells. While this finding seems to bode well for the CSRM, the results ultimately need to be understood within the context of how 3D radiative effects impact not only heating rates but also cloud dynamics.
Destabilization of the Symmetric Vortex and Formation of the Elliptical Eye of Typhoon Herb
Authors: Oda Masahito , Itano Toshihisa , Naito Gen’ichi , Nakanishi Mikio , Tomine Kikuro 
Published: September 2005

Abstract
An elliptical eye was observed in Typhoon Herb during its passage around the Sakishima Islands located in the southwest of the Okinawa Islands in Japan on 30–31 July 1996. Later analysis showed that this elliptical eye had a structure with wavenumber 2 in the radar echo distribution, rainfall field, and pressure field. It is argued here that this structure is likely caused by a dynamic instability arising from radial shear in the tangential flow. To examine this possibility, a linear eigenvalue problem was set up using the asymmetric balance model in which the basic flow was based on the observed surface wind in Typhoon Herb, and the stability of the basic flow for both two- and three-dimensional perturbations was examined.
Although for large Rossby numbers, the asymmetric balance model is not formally valid for higher azimuthal wavenumber perturbations, results certainly show that an unstable mode appears with the perturbation with wavenumber 2. In particular, the largest growth rate of the perturbation with wavenumber 2 is shown to occur for the three-dimensional perturbation. The eigenmode structure and rotation period of this three-dimensional perturbation with wavenumber 2 are comparable with the observations. These results suggest that barotropic instability due to the radial shear of tangential flow is relevant to the formation of the elliptical eye of Typhoon Herb.
Analytic Green’s Function for Radiative Transfer in Plane-Parallel Atmospheres
Authors: Qin Yi , Box Michael A. 
Published: September 2005

Abstract
Green’s function is a widely used approach for boundary value problems. In problems related to radiative transfer, Green’s function has been found to be useful in land, ocean, and atmosphere remote sensing. It is also a key element in higher order perturbation theory. This paper presents an explicit expression of the Green’s function, in terms of the source and radiation field variables, for a plane-parallel atmosphere with either vacuum boundaries or a reflecting [atmosphere–bidirectional reflectance distribution function (BRDF)] surface. A FORTRAN 95 code, Green’s function and discrete ordinate method (GDOM), has been developed to efficiently compute the Green’s function. This code also integrates with an implementation of the discrete ordinate method with several extensions and improvements. Computing complexity of the Green’s function algorithm is analyzed, and validation of the code is discussed.
ZAP-70 expression in acute lymphoblastic leukemia: association with the E2A/PBX1 rearrangement and the pre-B stage of differentiation and prognostic implications
Authors: Chiaretti Sabina , Guarini Anna , De Propris Maria Stefania , Tavolaro Simona , Intoppa Stefania , Vitale Antonella , Iacobelli Simona , Elia Loredana , Ariola Cristina , Ritz Jerome , Foà Robin 
Published: September 2005

AbstractWe evaluated the expression of 2 members of the Syk family, ZAP-70 and Syk, in acute lymphoblastic leukemia (ALL) samples, using data derived from a series of 33 T-ALL and 95 B-lineage adult ALL patients analyzed by oligonucleotide arrays. Of the B-lineage ALL cases, 37 were BCR/ABL+, 10 were ALL1/AF4+, 5 were E2A/PBX1+, and 43 carried no known molecular abnormality. ZAP-70 was highly expressed in T-ALL. A high ZAP-70 expression was also found in a proportion of B-lineage ALL, the highest levels being associated with the E2A/PBX1+ group and the lowest with ALL1/AF4+ cases (P < .001). A higher ZAP-70 expression was also observed in the pre-B group (P < .001). Remarkably, Syk expression was always preserved, suggesting that ZAP-70 expression is not substitutive of Syk. At the protein level, ZAP-70 was evaluated on 39 newly diagnosed ALL patients (25 adults, 14 children) and was detected in 23 cases (59%). ZAP-70 expression was consistently found in Igμ+ cases. Evaluation of long-term outcome in cases without molecular abnormalities showed that the higher levels of ZAP-70 were coupled to a higher relapse rate. In ALL, ZAP-70 expression is associated with the E2A/PBX1 rearrangement and pre-B stage and may have a prognostic role and be a candidate molecule for targeted therapies.
FGF-2 binding to fibrin(ogen) is required for augmented angiogenesis
Authors: Sahni Abha , Khorana Alok A. , Baggs Raymond B. , Peng Hu , Francis Charles W. 
Published: September 2005

AbstractWe have shown previously that fibrin(ogen) binds fibroblast growth factor 2 (FGF-2) and potentiates stimulation of endothelial-cell (EC) proliferation. We have now used 2 FGF-2 mutants differing only in the 5 residues constituting the binding site to characterize the importance of this interaction in angiogenesis. The nonbinding (2212) and binding (221*2) mutants stimulated EC proliferation by 2.2 ± 0.4-fold and 2.9 ± 0.3-fold over control, respectively, and both were similar to wild-type (wt) FGF-2 (2.5 ± 0.3-fold). Proliferation was augmented by fibrinogen to 5.3 ± 1.2-fold and 4.8 ± 0.8-fold with wtFGF-2 and 221*2, whereas no augmentation occurred with 2212 and fibrinogen. Using a placental explant model in a fibrin matrix, wtFGF-2 resulted in 2.6 ± 0.9-fold more growth over control, and 221*2 increased growth 3.3 plus or minus 0.9-fold. Vessel outgrowth with 2212 was minimal and comparable to control. Similarly, fibrinogen potentiated wtFGF-2 or 221*2-mediated angiogenesis in the chicken chorioallantoic membrane model. In a mouse Matrigel implant model, fibrinogen significantly increased angiogenesis with either wtFGF-2 or 221*2, whereas there was no augmentation with 2212. These results demonstrate that binding of FGF-2 to fibrin(ogen) mediated by the 5-residue FGF-2-fibrin(ogen) interactive site is required for augmented angiogenesis.