bluuebunny/crossref_metadata_2025_split huggingface dataset:
On Climate Impacts of a Potential Expansion of Urban Land in Europe
Authors: Trusilova K. , Jung M. , Churkina G. 
Published: April 2009

Abstract
Over the last two decades, a disproportional increase of urban land area in comparison with the population growth has been observed in many countries of Europe, and this trend is predicted to continue. The conversion of vegetated land into urban land leads to a higher proportion of impervious surface area, to decline and change of vegetation cover, to artificial heat sources, and therefore to changes in climate. This study focuses on the implications of the expansion of urban land for the European climate at the local and regional scales. Regional climate simulations with the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) coupled to the Town Energy Budget model are used to isolate effects of urban land expansion on temperature and precipitation. The study suggests that the expansion of current urban land by 40% would lead to an enlargement of regions affected by thermal stress by a factor of 2, whereas the intensity of the thermal stress does not change significantly. Precipitation in urban areas would be reduced by 0.2 mm day−1 in summer as a result of disturbances of the water cycle caused by urban surfaces. The area in which precipitation was altered increased nearly linearly with the urban land increment.
Spectra, Spatial Scales, and Predictability in a Quasigeostrophic Model
Authors: Morss Rebecca E. , Snyder Chris , Rotunno Richard 
Published: April 2009

Abstract
Results from homogeneous, isotropic turbulence suggest that predictability behavior is linked to the slope of a flow’s kinetic energy spectrum. Such a link has potential implications for the predictability behavior of atmospheric models. This article investigates these topics in an intermediate context: a multilevel quasigeostrophic model with a jet and temperature perturbations at the upper surface (a surrogate tropopause). Spectra and perturbation growth behavior are examined at three model resolutions. The results augment previous studies of spectra and predictability in quasigeostrophic models, and they provide insight that can help interpret results from more complex models. At the highest resolution tested, the slope of the kinetic energy spectrum is approximately at the upper surface but −3 or steeper at all but the uppermost interior model levels. Consistent with this, the model’s predictability behavior exhibits key features expected for flow with a shallower than −3 slope. At the highest resolution, upper-surface perturbation spectra peak below the energy-containing scales, and the error growth rate decreases as small scales saturate. In addition, as model resolution is increased and smaller scales are resolved, the peak of the upper-surface perturbation spectra shifts to smaller scales and the error growth rate increases. The implications for potential predictive improvements are not as severe, however, as in the standard picture of flows exhibiting a finite predictability limit. At the highest resolution, the model also exhibits periods of much faster-than-average perturbation growth that are associated with faster growth at smaller scales, suggesting predictability behavior that varies with time.
The Late-Spring Maximum of Rainfall over the U.S. Central Plains and the Role of the Low-Level Jet
Authors: Wang Shih-Yu , Chen Tsing-Chang 
Published: April 2009

Abstract
The seasonal rainfall over the U.S. central plains features a late-spring maximum. A spring–fall annual mode revealed from the empirical orthogonal function analysis on rainfall delineates a maximum center over the central plains that coincides with the large late-spring rainfall. This paper examines the large-scale dynamical and hydrological processes in forming the rainfall center. The NCEP–Department of Energy (DOE) reanalysis 2 data reveal that the baroclinic structure of the continental-scale circulation during late spring (May and June) induces a vertically out-of-phase divergent circulation forming strong convergence of water vapor flux over the central plains. Such circulation features generate concentrated convective activity in this region. The upper-level anticyclone development with the North American monsoon in July replaces the late-spring baroclinic structure and, in turn, reduces the convective activity. The Great Plains low-level jet (LLJ) plays a role in the downscaling process that connects the continental-scale circulation to rainfall. The LLJ coupled with approaching baroclinic waves leads to stronger moisture convergence in the central plains than that occurring under the upper-level anticyclone. The former type of the LLJ occurs most frequently in late spring and contributes to more than 60% of the rainfall. During midsummer (July and August), such a coupling is hindered by the well-developed upper-level anticyclone, subsequently decreasing the rainfall.
Overturning and Dissipation Caused by Baroclinic Tidal Flow near the Sill of a Fjord Basin
Authors: Arneborg Lars , Liljebladh Bengt 
Published: April 2009

Abstract
Dissipation time series and moored velocity and density time series on the inner slopes of the Gullmar Fjord sill showed that the internal tides generated at the sill radiated to the head of the fjord, were reflected, and then radiated back to the sill, where they dissipated their energy mainly below sill level. A large amount of the dissipation was caused by a transitional flow at a particular phase of the internal tide, when the bottom layer descended down the sill slope and had to pass a constriction set up by a submarine hill. The inward, baroclinic bottom-layer flow transformed into a supercritical bottom jet, which separated from the bottom just downstream of the constriction. A large fraction of the dissipation took place in the successive rebounding region (the hydraulic jump) above the bottom jet, where overturns of the same size as the vertical extent of the rebounding region were observed. More than half of the dissipation was happening in the bottom boundary layer below the jet. During the transitional flow, there were clear pulsations of the jet with periods of about 15 min. The amount of diapycnal mixing caused by the turbulence was reduced by the large fraction of dissipation within the bottom boundary layer and perhaps also by the high-buoyancy Reynolds numbers within the rebounding region. When using a relatively new parameterization of mixing, the mixing was significantly reduced compared to using the traditional constant mixing efficiency method.
Interplay of Resonant and Quasi-Resonant Interaction of the Directional Ocean Waves
Authors: Waseda Takuji , Kinoshita Takeshi , Tamura Hitoshi 
Published: April 2009

Abstract
Recent experimental study of the evolution of random directional gravity waves in deep water provides new insight into the nature of the spectral evolution of the ocean waves and the relative significance of resonant and quasi-resonant wave interaction. When the directional angle containing half the total energy is broader than ∼20°, the spectrum evolves following the energy transfer that can be described by the four-wave resonant interaction alone. In contrast, in the case of a directionally confined spectrum, the effect of quasi-resonant wave–wave interaction becomes important, and the wave system becomes unstable. When the temporal change of the spectral shape due to quasi resonance becomes irreversible owing to energetic breaking dissipation, the spectrum rapidly downshifts. Under such extreme conditions, the likelihood of a freak wave is high.
Modeling Influence of Stratification on Lateral Circulation in a Stratified Estuary
Authors: Cheng Peng , Wilson Robert E. , Chant Robert J. , Fugate David C. , Flood Roger D. 
Published: April 2009

Abstract
The dynamics of lateral circulation in the Passaic River estuary is examined in this modeling study. The pattern of lateral circulation varies significantly over a tidal cycle as a result of the temporal variation of stratification induced by tidal straining. During highly stratified ebb tides, the lateral circulation exhibits a vertical two-cell structure. Strong stratification suppresses vertical mixing in the deep channel, whereas the shoal above the halocline remains relatively well mixed. As a result, in the upper layer, the lateral asymmetry of vertical mixing produces denser water on the shoal and fresher water over the thalweg. This density gradient drives a circulation with surface currents directed toward the shoal, and the currents at the base of the pycnocline are directed toward the thalweg. In the lower layer, the lateral circulation tends to reduce the tilting of isopycnals and gradually diminishes at the end of the ebb tide. A lateral baroclinic pressure gradient is a dominant driving force for lateral circulation during stratified ebb tides and is generated by differential diffusion that indicates a lateral asymmetry in vertical mixing. Over the thalweg, vertical mixing is strong during the flood and weak during the ebb. Over the shoal, the tidally periodical stratification shows an opposite cycle of that at the thalweg. Lateral straining tends to enhance stratification during flood tides and vertical diffusion maintains the relatively well-mixed water column over the shoal during the stratified ebb tides.
Numerical Simulations and Observations of Surface Wave Fields under an Extreme Tropical Cyclone
Authors: Fan Yalin , Ginis Isaac , Hara Tetsu , Wright C. Wayne , Walsh Edward J. 
Published: April 2009

Abstract
The performance of the wave model WAVEWATCH III under a very strong, category 5, tropical cyclone wind forcing is investigated with different drag coefficient parameterizations and ocean current inputs. The model results are compared with field observations of the surface wave spectra from an airborne scanning radar altimeter, National Data Buoy Center (NDBC) time series, and satellite altimeter measurements in Hurricane Ivan (2004). The results suggest that the model with the original drag coefficient parameterization tends to overestimate the significant wave height and the dominant wavelength and produces a wave spectrum with narrower directional spreading. When an improved drag parameterization is introduced and the wave–current interaction is included, the model yields an improved forecast of significant wave height, but underestimates the dominant wavelength. When the hurricane moves over a preexisting mesoscale ocean feature, such as the Loop Current in the Gulf of Mexico or a warm- and cold-core ring, the current associated with the feature can accelerate or decelerate the wave propagation and significantly modulate the wave spectrum.
On the Quantitative Low-Level Aerosol Measurements Using Ceilometer-Type Lidar
Authors: Sundström Anu-Maija , Nousiainen Timo , Petäjä Tuukka 
Published: April 2009

Abstract
The objective of this work is to investigate whether a commercial ceilometer-type lidar can be used as a quantitative aerosol measurement instrument. To this end, lidar backscattering measurements are compared with exact theoretical calculations of backscattering, which are based on in situ–measured size distributions and account for uncertainties in particle composition and shape. The results show that the differences between simulated and measured backscattering remain nearly constant and within the uncertainties involved. The differences are most plausibly explained by an error in the overlap function of the lidar and/or errors in the calibration of either the lidar or the in situ instruments used to measure the aerosol size distribution. Occasionally, large differences occur that are obviously connected to the unrepresentativeness of the in situ and lidar measurement volumes because of insufficient atmospheric mixing. The results imply that the absolute accuracy of the instrument investigated might be sufficient for quantitative aerosol measurements in some applications. A fix for the overlap function, however, would be desirable.
Overview of the CALIPSO Mission and CALIOP Data Processing Algorithms
Authors: Winker David M. , Vaughan Mark A. , Omar Ali , Hu Yongxiang , Powell Kathleen A. , Liu Zhaoyan , Hunt William H. , Young Stuart A. 
Published: April 2009

Abstract
The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is a two-wavelength polarization lidar that performs global profiling of aerosols and clouds in the troposphere and lower stratosphere. CALIOP is the primary instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite, which has flown in formation with the NASA A-train constellation of satellites since May 2006. The global, multiyear dataset obtained from CALIOP provides a new view of the earth’s atmosphere and will lead to an improved understanding of the role of aerosols and clouds in the climate system. A suite of algorithms has been developed to identify aerosol and cloud layers and to retrieve a variety of optical and microphysical properties. CALIOP represents a significant advance over previous space lidars, and the algorithms that have been developed have many innovative aspects to take advantage of its capabilities. This paper provides a brief overview of the CALIPSO mission, the CALIOP instrument and data products, and an overview of the algorithms used to produce these data products.
Next-Day Convection-Allowing WRF Model Guidance: A Second Look at 2-km versus 4-km Grid Spacing
Authors: Schwartz Craig S. , Kain John S. , Weiss Steven J. , Xue Ming , Bright David R. , Kong Fanyou , Thomas Kevin W. , Levit Jason J. , Coniglio Michael C. 
Published: April 2009

Abstract
During the 2007 NOAA Hazardous Weather Testbed (HWT) Spring Experiment, the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma produced convection-allowing forecasts from a single deterministic 2-km model and a 10-member 4-km-resolution ensemble. In this study, the 2-km deterministic output was compared with forecasts from the 4-km ensemble control member. Other than the difference in horizontal resolution, the two sets of forecasts featured identical Advanced Research Weather Research and Forecasting model (ARW-WRF) configurations, including vertical resolution, forecast domain, initial and lateral boundary conditions, and physical parameterizations. Therefore, forecast disparities were attributed solely to differences in horizontal grid spacing. This study is a follow-up to similar work that was based on results from the 2005 Spring Experiment. Unlike the 2005 experiment, however, model configurations were more rigorously controlled in the present study, providing a more robust dataset and a cleaner isolation of the dependence on horizontal resolution. Additionally, in this study, the 2- and 4-km outputs were compared with 12-km forecasts from the North American Mesoscale (NAM) model. Model forecasts were analyzed using objective verification of mean hourly precipitation and visual comparison of individual events, primarily during the 21- to 33-h forecast period to examine the utility of the models as next-day guidance. On average, both the 2- and 4-km model forecasts showed substantial improvement over the 12-km NAM. However, although the 2-km forecasts produced more-detailed structures on the smallest resolvable scales, the patterns of convective initiation, evolution, and organization were remarkably similar to the 4-km output. Moreover, on average, metrics such as equitable threat score, frequency bias, and fractions skill score revealed no statistical improvement of the 2-km forecasts compared to the 4-km forecasts. These results, based on the 2007 dataset, corroborate previous findings, suggesting that decreasing horizontal grid spacing from 4 to 2 km provides little added value as next-day guidance for severe convective storm and heavy rain forecasters in the United States.
Radar Refractivity Retrievals in Oklahoma: Insights into Operational Benefits and Limitations
Authors: Heinselman P. L. , Cheong B. L. , Palmer R. D. , Bodine D. , Hondl K. 
Published: April 2009

Abstract
The 2007 and 2008 spring refractivity experiments at KTLX investigated the potential utility of high-resolution, near-surface refractivity measurements to operational forecasting. During these experiments, forecasters at the Norman, Oklahoma, National Weather Service Forecast Office (NWSFO) assessed refractivity and scan-to-scan refractivity change fields retrieved from the Weather Surveillance Radar-1988 Doppler weather radar near Oklahoma City—Twin Lakes, Oklahoma (KTLX). Both quantitative and qualitative analysis methods were used to analyze the 41 responses from seven forecasters to a questionnaire designed to measure the impact of refractivity fields on forecast operations. The analysis revealed that forecasts benefited from the refractivity fields on 25% of the days included in the evaluation. In each of these cases, the refractivity fields provided complementary information that somewhat enhanced the forecasters’ capability to analyze the near-surface environment and boosted their confidence in moisture trends. A case in point was the ability to track a retreating dryline after its location was obscured by a weak reflectivity bloom caused by biological scatterers. Forecasters unanimously agreed, however, that the impact of this complementary information on their forecasts was too insignificant to justify its addition as an operational dataset. The applicability of these findings to other NWSFOs may be limited to locations with similar weather situations and access to surface data networks like the Oklahoma Mesonet.
Increasing Incidence of Medial Meniscal Tears in Nonoperatively Treated Anterior Cruciate Ligament Insufficiency Patients Documented by Serial Magnetic Resonance Imaging Studies
Authors: Yoo Jae Chul , Ahn Jin Hwan , Lee Sang Hak , Yoon Young Cheol 
Published: April 2009

Background No consensus has been reached with regard to the ideal timing of anterior cruciate ligament reconstruction in terms of reducing secondary meniscal tears in anterior cruciate ligament–deficient knees. Hypothesis Delay in anterior cruciate ligament reconstruction increases the incidence and severity of medial meniscal tears. Study Design Case series; Level of evidence, 4. Methods Thirty-one patients were evaluated with arthroscopic all-inside suturing of medial meniscal tears with concurrent anterior cruciate ligament reconstruction who had at least 2 preoperative magnetic resonance imaging studies. Patients were evaluated during the acute phase of injury, but anterior cruciate ligament reconstruction surgery was delayed at least 6 months. Mean interval between first and second imaging studies was 36.8 months. Subsequent medial meniscal tears were identified as longitudinal or bucket-handle types. Relationships between medial meniscal lesions and patient age, time interval between the date of initial injury and surgery, repetitive injury, and patient activity level were evaluated. Results During the first preoperative magnetic resonance imaging studies, 14 knees had no medial meniscal tear, 15 a longitudinal tear, and 2 a bucket-handle–type tear; during the second preoperative imaging studies, 5 knees had no medial meniscal tear, 19 a longitudinal tear, and 7 a bucket-handle–type tear. The incidence of medial meniscal tears increased from 55% in first studies to 84% in second studies for chronic anterior cruciate ligament–insufficient knees (P =. 0054). Eight knees without a tear during first studies had a longitudinal tear during second studies, 1 knee without a tear and 4 with a longitudinal tear in first studies had a bucket-handle–type tear in second studies. Thirteen knees (42%) had a worse meniscal status during the second studies. Conclusion Delayed anterior cruciate ligament reconstruction increases the likelihood of a medial meniscal tear, suggesting that early anterior cruciate ligament reconstruction should reduce or prevent additional medial meniscal injury. The findings show that further medial meniscal damage is common if surgery is delayed by 6 months or more.
Initial Outcomes of 3-Dimensional Imaging-Based Computer-Assisted Retrograde Drilling of Talar Osteochondral Lesions
Authors: Geerling Jens , Zech Stefan , Kendoff Daniel , Citak Musa , O'Loughlin Padhraig F. , Hüfner Tobias , Krettek Christian , Richter Martinus 
Published: April 2009

Background In operative treatment of Berndt and Harty stage 1 and stage 2 osteochondral lesions of the talus, the goal is revascularization. The use of computer-assisted guided retrograde drilling of osteochondral lesions has been described as a new technique with promising results. Purpose This study reports the follow-up assessment of patients treated with Iso-C-3D-navigated retrograde drilling. Its aim was to establish whether the greater precision of computer-assisted drilling results in satisfactory clinical outcomes. Study Design Case series; Level of evidence, 4. Methods Patients who underwent navigated Iso-C-3D-based retrograde drilling between June 1, 2003, and July 31, 2005, were included in the follow-up study. Clinical outcomes were measured using (1) the Ankle-Hindfoot Scale of the American Orthopaedic Foot and Ankle Society and (2) the Visual Analogue Scale—Foot and Ankle. Radiological outcomes were assessed via radiographs and magnetic resonance imaging. Surgeon satisfaction was assessed using a simple 0 to 10 rating scheme for feasibility, accuracy, and clinical benefit. Results Average follow-up time was 25 months (range, 20-34). Twenty patients satisfied the inclusion criteria: 12 men and 8 women; mean age, 35 years (range, 19-58). One patient was excluded because he required a cartilage restoration procedure. All scores improved at the time of follow-up—Ankle-Hindfoot Scale, from 76 to 90 (P < .001); Visual Analogue Scale—Foot and Ankle, from 79 to 92 (P < .001). The average ratings of the operating surgeons (n = 3) were as follows: feasibility 9.0 (range, 7.3-10.0); accuracy, 8.5 (range, 5.8-10.0); and clinical benefit, 8.5 (5.7-10.0). At follow-up, magnetic resonance imaging revealed an improvement of the Hepple score in 80% of patients. Conclusion Arthroscopic treatment of osteochondral lesions of the talus is well established. A retrograde approach does not breach the overlying intact talar cartilage. The results of this follow-up study of 3-dimensional computer navigated drilling are promising.