bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of High-Resolution Satellite Observations to Evaluate Cloud and Precipitation Statistics from Cloud-Resolving Model Simulations. Part I: South China Sea Monsoon Experiment
Authors: Zhou Y. P. , Tao W.-K. , Hou A. Y. , Olson W. S. , Shie C.-L. , Lau K.-M. , Chou M.-D. , Lin X. , Grecu M. 
Published: December 2007

Abstract
Cloud and precipitation simulated using the three-dimensional (3D) Goddard Cumulus Ensemble (GCE) model are compared to Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR) rainfall measurements and Clouds and the Earth’s Radiant Energy System (CERES) single scanner footprint (SSF) radiation and cloud retrievals. Both the model simulation and retrieved parameters are based upon observations made during the South China Sea Monsoon Experiment (SCSMEX) field campaign. The model-simulated cloud and rain systems are evaluated by systematically examining important parameters such as the surface rain rate, convective/stratiform percentage, rain profiles, cloud properties, and precipitation efficiency.
It is demonstrated that the GCE model is capable of simulating major convective system development and reproduces the total surface rainfall amount as compared to rainfall estimated from the SCSMEX sounding network. The model yields a slightly higher total convective rain/stratiform rain ratio than the TMI and PR observations. The GCE rainfall spectrum exhibits a greater contribution from heavy rains than those estimated from PR or TMI observations. In addition, the GCE simulation produces much greater amounts of snow and graupel than the TRMM retrievals. The model’s precipitation efficiency of convective rain is close to the observations, but the precipitation efficiency of stratiform rain is much lower than the observations because of large amounts of slowly falling simulated snow and graupel. Compared to observations, the GCE produces more compact areas of intense convection and less anvil cloud, which are consistent with a smaller total cloud fraction and larger domain-averaged outgoing longwave radiation.
Is a Real Cyclogenesis Case Explained by Generalized Linear Baroclinic Instability?
Authors: Descamps L. , Ricard D. , Joly A. , Arbogast P. 
Published: December 2007

Abstract
Midlatitude cyclogenesis is currently often explained as resulting from the baroclinic instability of a jet flow. The present formulation of the theory, essentially resulting from the deep revision performed by Farrell, associates incipient cyclones with amplifying singular vectors of a linear propagator operator obtained by linearizing the relevant model equations (balanced or not) about a trajectory representing the jet flow alone. A major difficulty for transposing the theoretical framework to a real case, and then opening the way to quantitative verifications of the theory, is this separation of an actual realization of cyclogenesis into the cyclone as a perturbation on one side and its environment on the other. A methodology to obtain such a separation in a reasonably objective and dynamically consistent way is presented. It enables obtaining two diabatic primitive equation solutions about the 26 December 1999 intense storm, one that has the event and the other that has most of the characteristics of the exceptional baroclinic environment of that case, except the storm itself. It is then possible to employ the theoretical framework without further approximation and to compare the predicted unstable modes with the storm representing itself as a perturbation. Two aspects of the theory are especially studied. One is a comparison of the properties of the real and predicted systems, focusing on their structures. The other deals with the idea that precursor structures, although very different from the theoretical modes, trigger the cyclogenesis by exciting these modes. It appears that the classical predictions (scales, etc.) of such a theory are, for most of them, far away from the observed properties. It is clear that the structure of a singular vector has little to share with that of a real cyclone. Yet, a weaker, slower storm does occur as a result of applying the theory to the stormless trajectory.
On the Occurrence of Hollow Bullet Rosette– and Column-Shaped Ice Crystals in Midlatitude Cirrus
Authors: Schmitt C. G. , Heymsfield A. J. 
Published: December 2007

AbstractCirrus clouds in mid- and high latitudes are frequently composed of bullet rosette– and column-shaped ice crystals, which can have hollow ends. Bullet rosette–shaped ice crystals are composed of a number of bullets radiating from a central point. Research has shown that the light-scattering properties of ice particles with hollow ends are different from the scattering properties of solid ice particles. Knowledge of the frequency of occurrence of hollow particles is important to more accurately calculate the radiative properties of cirrus clouds.This note presents the results of a survey of cirrus cloud ice crystal replicas imaged from balloon-borne Formvar (polyvinyl formal) replicators. Fifty percent to 80% of the replicated bullet rosette– and column-shaped particles had hollow ends. In bullets longer than 150 μm in length, the length of the hollows of the bullets averaged 88% of the total length of the bullet. The combined length of both hollow portions of column-shaped ice crystals varied from 50% of the length of the column for 30-μm-long columns to 80% of the length of the columns longer than 200 μm. Asymmetry parameter values estimated from cirrus cloud aircraft particle size distributions are higher by 0.014 when hollow crystals are considered. This difference leads to a 2.5 W m−2 increase for hollow crystals at the surface for a 0.5 optical depth cloud, demonstrating the importance of the incorporation of hollow particle scattering characteristics into radiative transfer calculations.
The Spacing of Orographic Rainbands Triggered by Small-Scale Topography
Authors: Kirshbaum Daniel J. , Rotunno Richard , Bryan George H. 
Published: December 2007

Abstract
A combination of idealized numerical simulations and analytical theory is used to investigate the spacing between convective orographic rainbands over the Coastal Range of western Oregon. The simulations, which are idealized from an observed banded precipitation event over the Coastal Range, indicate that the atmospheric response to conditionally unstable flow over the mountain ridge depends strongly on the subridge-scale topographic forcing on the windward side of the ridge. When this small-scale terrain contains only a single scale (λ) of terrain variability, the band spacing is identical to λ, but when a spectrum of terrain scales are simultaneously present, the band spacing ranges between 5 and 10 km, a value that is consistent with observations. Based on the simulations, an inviscid linear model is developed to provide a physical basis for understanding the scale selection of the rainbands. This analytical model, which captures the transition from lee waves upstream of the orographic cloud to moist convection within it, reveals that the spacing of orographic rainbands depends on both the projection of lee-wave energy onto the unstable cap cloud and the growth rate of unstable perturbations within the cloud. The linear model is used in tandem with numerical simulations to determine the sensitivity of the band spacing to a number of environmental and terrain-related parameters.
Snow Size Distribution Parameterization for Midlatitude and Tropical Ice Clouds
Authors: Field Paul R. , Heymsfield Andrew J. , Bansemer Aaron 
Published: December 2007

Abstract
Many microphysical process rates involving snow are proportional to moments of the snow particle size distribution (PSD), and in this study a moment estimation parameterization applicable to both midlatitude and tropical ice clouds is proposed. To this end aircraft snow PSD data were analyzed from tropical anvils [Tropical Rainfall Measuring Mission/Kwajelein Experiment (TRMM/KWAJEX), Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE)] and midlatitude stratiform cloud [First International Satellite Cloud Climatology Project Research Experiment (FIRE), Atmospheric Radiation Measurement Program (ARM)]. For half of the dataset, moments of the PSDs are computed and a parameterization is generated for estimating other PSD moments when the second moment (proportional to the ice water content when particle mass is proportional to size squared) and temperature are known. Subsequently the parameterization was tested with the other half of the dataset to facilitate an independent comparison. The parameterization for estimating moments can be applied to midlatitude or tropical clouds without requiring prior knowledge of the regime of interest. Rescaling of the tropical and midlatitude size distributions is presented along with fits to allow the user to recreate realistic PSDs given estimates of ice water content and temperature. The effects of using different time averaging were investigated and were found not to be adverse. Finally, the merits of a single-moment snow microphysics versus multimoment representations are discussed, and speculation on the physical differences between the rescaled size distributions from the Tropics and midlatitudes is presented.
Inertia–Gravity Waves Generated within a Dipole Vortex
Authors: Snyder Chris , Muraki David J. , Plougonven Riwal , Zhang Fuqing 
Published: December 2007

Abstract
Vortex dipoles provide a simple representation of localized atmospheric jets. Numerical simulations of a synoptic-scale dipole in surface potential temperature are considered in a rotating, stratified fluid with approximately uniform potential vorticity. Following an initial period of adjustment, the dipole propagates along a slightly curved trajectory at a nearly steady rate and with a nearly fixed structure for more than 50 days. Downstream from the jet maximum, the flow also contains smaller-scale, upward-propagating inertia–gravity waves that are embedded within and stationary relative to the dipole. The waves form elongated bows along the leading edge of the dipole. Consistent with propagation in horizontal deformation and vertical shear, the waves’ horizontal scale shrinks and the vertical slope varies as they approach the leading stagnation point in the dipole’s flow. Because the waves persist for tens of days despite explicit dissipation in the numerical model that would otherwise damp the waves on a time scale of a few hours, they must be inherent features of the dipole itself, rather than remnants of imbalances in the initial conditions. The wave amplitude varies with the strength of the dipole, with waves becoming obvious once the maximum vertical vorticity in the dipole is roughly half the Coriolis parameter. Possible mechanisms for the wave generation are spontaneous wave emission and the instability of the underlying balanced dipole.
Sling Effect in Collisions of Water Droplets in Turbulent Clouds
Authors: Falkovich Gregory , Pumir Alain 
Published: December 2007

Abstract
The effect of turbulence on the collision rate between droplets in clouds is investigated. Because of their inertia, water droplets can be shot out of curved streamlines of the turbulent airflow. The contribution of such a “sling effect” in the collision rate of the same-size water droplets is described and evaluated. It is shown that already for turbulence with the dissipation rate 103 cm2 s−3, the sling effect gives a contribution to the collision rate of 15-μm droplets comparable to that due to the local velocity gradient. That may explain why the formulas based on the local velocity gradient consistently underestimate the turbulent collision rate, even with the account of preferential concentration.
A Large Annual Cycle in Ozone above the Tropical Tropopause Linked to the Brewer–Dobson Circulation
Authors: Randel William J. , Park Mijeong , Wu Fei , Livesey Nathaniel 
Published: December 2007

Abstract
Near-equatorial ozone observations from balloon and satellite measurements reveal a large annual cycle in ozone above the tropical tropopause. The relative amplitude of the annual cycle is large in a narrow vertical layer between ∼16 and 19 km, with approximately a factor of 2 change in ozone between the minimum (during NH winter) and maximum (during NH summer). The annual cycle in ozone occurs over the same altitude region, and is approximately in phase with the well-known annual variation in tropical temperature. This study shows that the large annual variation in ozone occurs primarily because of variations in vertical transport associated with mean upwelling in the lower stratosphere (the Brewer–Dobson circulation); the maximum relative amplitude peak in the lower stratosphere is collocated with the strongest background vertical gradients in ozone. A similar large seasonal cycle is observed in carbon monoxide (CO) above the tropical tropopause, which is approximately out of phase with ozone (associated with an oppositely signed vertical gradient). The observed ozone and CO variations can be used to constrain estimates of the seasonal cycle in tropical upwelling.
The Extratropical Tropopause Inversion Layer: Global Observations with GPS Data, and a Radiative Forcing Mechanism
Authors: Randel William J. , Wu Fei , Forster Piers 
Published: December 2007

Abstract
Global characteristics of the extratropical tropopause inversion layer identified in radiosonde observations by Birner are studied using high vertical resolution temperature profiles from GPS radio occultation measurements. The GPS data are organized according to the height of the thermal tropopause in each profile, and a temperature inversion layer above the tropopause (with an average magnitude of 3–5 K) is found to be a ubiquitous, climatological feature. The GPS data show that the inversion layer is present for all seasons in both hemispheres, spanning the subtropics to the pole, and there is not strong longitudinal structure. Dependence of the inversion layer on upper-troposphere vorticity is studied; while anticyclones exhibit a substantially stronger inversion than cyclones (as expected from balanced dynamics), the inversion is evident for all circulation types. Radiative transfer calculations indicate that strong gradients in both ozone and water vapor near the tropopause contribute to the inversion. Significant absorption of both longwave and shortwave radiation by ozone occurs, warming the region above the tropopause. Water vapor near and immediately above the tropopause contributes to cooling, effectively enhancing the inversion.
Analysis of Wave Height Variability Using Altimeter Measurements: Application to the Mediterranean Sea
Authors: Queffeulou Pierre , Bentamy Abderrahim 
Published: December 2007

Abstract
Altimeter significant wave height (SWH) measurement data from six satellite missions covering 14 yr were analyzed over the Mediterranean Sea. First, data correction and screening were performed using the same method for the six altimeters [European Remote Sensing Satellites (ERS-1 and ERS-2), Ocean Topography Experiment (TOPEX), Geosat Follow-On, Jason, and Environmental Satellite (Envisat)]. The data from the TOPEX and Jason missions enabled the construction of seasonal maps of along-track SWH mean values and standard deviations. These reveal the regional short-scale sea state features associated with the specific meteorological patterns of the various geographical basins. Time series of monthly SWH mean values and standard deviations from each satellite and over the whole Mediterranean Sea were calculated and seen to be in good agreement, thus demonstrating interannual variability. The six altimeter missions used together enable the investigation of the monthly annual cycle at the short scales of the various subbasins. Significant differences are observed between the western and eastern parts of the Mediterranean Sea. The annual SWH cycle changes in both shape and amplitude depending on the subbasin. Analysis of the seasonal interannual variability confirms the existence of some degree of independence between the subbasins. Thanks to multisatellite missions and homogeneous corrections of the altimeter data, SWH time and space characteristics were able to be obtained at regional short scales. These results are independent of numerical wind and wave models. This method can be applied to any geographical region.
A Doppler Radar Emulator with an Application to the Detectability of Tornadic Signatures
Authors: May Ryan M. , Biggerstaff Michael I. , Xue Ming 
Published: December 2007

AbstractA Doppler radar emulator was developed to simulate the expected mean returns from scanning radar, including pulse-to-pulse variability associated with changes in viewing angle and atmospheric structure. Based on the user’s configuration, the emulator samples the numerical simulation output to produce simulated returned power, equivalent radar reflectivity, Doppler velocity, and Doppler spectrum width. The emulator is used to evaluate the impact of azimuthal over- and undersampling, gate spacing, velocity and range aliasing, antenna beamwidth and sidelobes, nonstandard (anomalous) pulse propagation, and wavelength-dependent Rayleigh attenuation on features of interest.As an example, the emulator is used to evaluate the detection of the circulation associated with a tornado simulated within a supercell thunderstorm by the Advanced Regional Prediction System (ARPS). Several metrics for tornado intensity are examined, including peak Doppler velocity and axisymmetric vorticity, to determine the degradation of the tornadic signature as a function of range and azimuthal sampling intervals. For the case of a 2° half-power beamwidth radar, like those deployed in the first integrated project of the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), the detection of the cyclonic shear associated with this simulated tornado will be difficult beyond the 10-km range, if standard metrics such as azimuthal gate-to-gate shear from a single radar are used for detection.
The USDA Natural Resources Conservation Service Soil Climate Analysis Network (SCAN)
Authors: Schaefer Garry L. , Cosh Michael H. , Jackson Thomas J. 
Published: December 2007

AbstractSurface soil moisture plays an important role in the dynamics of land–atmosphere interactions and many current and upcoming models and satellite sensors. In situ data will be required to provide calibration and validation datasets. Therefore, there is a need for sensor networks at a variety of scales that provide near-real-time soil moisture and temperature data combined with other climate information for use in natural resource planning, drought assessment, water resource management, and resource inventory. The U.S. Department of Agriculture (USDA)–Natural Resources Conservation Service (NRCS)–National Water and Climate Center has established a continental-scale network to address this need, called the Soil Climate Analysis Network (SCAN). This ever-growing network has more than 116 stations located in 39 states, most of which have been installed since 1999. The stations are remotely located and collect hourly atmospheric, soil moisture, and soil temperature data that are available to the public online in near–real time. New stations are located on benchmark soils when possible. Future plans for the network include increasing the number of stations, improving on user-friendly data summaries, increasing data quality, and scaling the stations to the surrounding region.
Divergence and Vorticity from Aircraft Air Motion Measurements
Authors: Lenschow Donald H. , Savic-Jovcic Verica , Stevens Bjorn 
Published: December 2007

Abstract
This paper considers the accuracy of divergence estimates obtained from aircraft measurements of the horizontal velocity field and points out an error that appears in these estimates that has heretofore not been addressed. A procedure for eliminating this error is presented. The divergence and vorticity are estimated from the coefficients of a least squares fit to a wind field obtained from the Second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) circular flight legs. These estimates are compared with estimates from numerical models and satellites and with airplane estimates based on tracer budgets and the temporal changes in cloud-top height. The estimates are consistent with expectations and estimates using other methods, albeit somewhat high. Furthermore, significant differences occur among the cases, likely due to the large differences in the techniques. The results indicate that the wind field technique is a viable approach for estimating mesoscale divergence if the wind measurements are accurate. The largest source of wind field systematic error may be the result of flow distortion effects on the air velocity measurement and limitations of in-flight calibrations. Because of flow distortion, the only way the current systems can be calibrated is by flight maneuvers, which assume a steady-state homogeneous nonturbulent atmosphere. Analysis of the errors in this technique suggests that wind field measurements with minimal systematic errors should provide estimates of divergence with much greater accuracy than is now possible with other existing methods.
Stratéole/Vorcore—Long-duration, Superpressure Balloons to Study the Antarctic Lower Stratosphere during the 2005 Winter
Authors: Hertzog Albert , Cocquerez Philippe , Guilbon René , Valdivia Jean-Noël , Venel Stéphanie , Basdevant Claude , Boccara Gillian , Bordereau Jérôme , Brioit Bernard , Vial François , Cardonne Alain , Ravissot Alain , Schmitt Éric 
Published: December 2007

Abstract
In September and October 2005, the Stratéole/Vorcore campaign flew 27 superpressure balloons from McMurdo, Antarctica, into the stratospheric polar vortex. Long-duration flights were successfully achieved, 16 of those flights lasting for more than 2 months. Most flights were terminated because they flew out of the authorized flight domain or because of energy shortage in the gondola. The atmospheric pressure (1-Pa precision) was measured every minute during the flights, whereas air temperature observations (0.25-K accuracy) and balloon positions (absolute GPS observations, 10-m accuracy) were obtained every 15 min. Fifteen-minute-averaged horizontal velocities of the wind were deduced from the successive balloon positions with a corresponding accuracy ≲0.1 m s−1. The collected dataset (more than 150 000 independent observations) provides a thorough high-resolution sampling of the polar lower stratosphere in the Southern Hemisphere from its wintertime state up to the establishment of the summer circulation in December–January. Most of the balloons stayed inside the vortex until its final breakdown, although a few were ejected toward the midlatitudes in November during filamention events associated with an increase in planetary wave activity. The balloons behaved as quasi-Lagrangian tracers during the first part of the campaign (quiescent vortex) and after the vortex breakdown in early December. Large-amplitude mountain gravity waves were detected over the Antarctic Peninsula and caused one flight termination associated with the sudden burst in the balloon superpressure.