bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hurricane Alley SST Variability in 2005 and 2006*
Authors: Chiodi Andrew M. , Harrison Don E. 
Published: January 2008

Abstract
The North Atlantic hurricane seasons of 2005 and 2006 were dramatically different for the Gulf Coast and eastern seaboard of the United States. The 2005 hurricane season was one of the most destructive seasons in history, whereas there was limited impact in 2006. Hurricane activity had been forecast to be above normal in 2006, but it was not. One of the conspicuous differences in environmental conditions between these two years was sea surface temperature anomaly (SSTA) over a region of the western Atlantic and Caribbean (15°–30°N, 70°–40°W), which is important for hurricane formation and intensification. SSTA was more than 1.5 standard deviations warmer during the 2005 hurricane season, but it was much less in 2006 through most of its hurricane season. The intent of this study is to determine the mechanisms responsible for this SSTA difference. It is shown that the difference can be reproduced using a simple one-dimensional (1D) ocean mixed layer model forced with surface fluxes from the NCEP–NCAR reanalysis project. It is found that there are two causes of SSTA difference over this region during July through September: the first is latent heat flux variability caused by wind speed effects, and the second is nonlinear ocean warming caused by submonthly atmospheric variability. The observed SSTA difference is reproduced by our model even though solar forcing damps the observed difference, contrary to previous hypotheses.
Asymmetry of the Indian Ocean Dipole. Part I: Observational Analysis
Authors: Hong Chi-Cherng , Li Tim , LinHo  , Kug Jong-Seong 
Published: January 2008

The physical mechanism for the amplitude asymmetry of SST anomalies (SSTA) between the positive and negative phases of the Indian Ocean dipole (IOD) is investigated, using Simple Ocean Data Assimilation (SODA) and NCAR–NCEP data. It is found that a strong negative skewness appears in the IOD east pole (IODE) in the mature phase [September–November (SON)], while the skewness in the IOD west pole is insignificant. Thus, the IOD asymmetry is primarily caused by the negative skewness in IODE. A mixed-layer heat budget analysis indicates that the following two air–sea feedback processes are responsible for the negative skewness. The first is attributed to the asymmetry of the wind stress–ocean advection–SST feedback. During the IOD developing stage [June–September (JJAS)], the ocean linear advection tends to enhance the mixed-layer temperature tendency, while nonlinear advection tends to cool the ocean in both the positive and negative events, thus contributing to the negative skewness in IODE. The second process is attributed to the asymmetry of the SST–cloud–radiation (SCR) feedback. For a positive IODE, the negative SCR feedback continues with the increase of warm SSTA. For a negative IODE, the same negative SCR feedback works when the amplitude of SSTA is small. After reaching a critical value, the cold SSTA may completely suppress the mean convection and lead to cloud free conditions; a further drop of the cold SSTA does not lead to additional thermal damping so that the cold SSTA may grow faster. A wind–evaporation–SST feedback may further amplify the asymmetry induced by the aforementioned nonlinear advection and SCR feedback processes.
Estimates of Net Atmospheric Moisture Flux Convergence over the Amazon Basin: A Comparison of Reanalysis Products
Authors: Karam Hanan N. , Bras Rafael L. 
Published: January 2008

Abstract
Estimates of the net convergence of atmospheric moisture flux over the Amazon Basin, [C], derived using data products from three global reanalyses, the NCEP–NCAR reanalysis (NCEP-1), the NCEP/Department of Energy reanalysis (NCEP-2), and the 40-yr ECMWF Re-Analysis (ERA-40), are compared. Two types of uncertainty in these [C] estimates are distinguished and quantified: “model-associated uncertainty,” which necessarily arises from imperfections in the numerical weather models or data assimilation algorithms, and “postprocessing uncertainty” introduced by operations performed on the original reanalysis data products to compute [C], particularly the finite-difference approximation of divergence. Model-associated uncertainty is found to overwhelm the postprocessing error. A closer look at the time series of this field extending over the period 1980–2001, and their comparison to basin-averaged precipitation and runoff data, reveals the signatures of two potential sources of model-associated errors. 1) ERA-40 estimates of [C] exhibit an artificial shift in 1987, possibly produced by the start of assimilation of Special Sensor Microwave Imager (SSM/I) data. The estimates preceding 1988 are negatively biased relative to the remaining time series, and hence subsequent analysis is limited to the 14-yr period 1988–2001. 2) NCEP-1 and NCEP-2 estimates of [C] show a negative bias over the period 1992–98, which likely originates in biased Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) data assimilated by these reanalyses. A measure of the random error in the [C] time series produced by each reanalysis, computed using river discharge data as reference, indicates that ERA-40 gives the most accurate estimates of net atmospheric moisture flux convergence for the aforementioned 14-yr period.
Energetics of the Global Ocean: The Role of Layer-Thickness Form Drag
Authors: Aiki Hidenori , Richards Kelvin J. 
Published: January 2008

Abstract
Understanding the role of mesoscale eddies in the global ocean is fundamental to gaining insight into the factors that control the strength of the circulation. This paper presents results of an analysis of a high-resolution numerical simulation. In particular, the authors perform an analysis of energetics in density space. Such an approach clearly demonstrates the role of layer-thickness form drag (residual effects of hydrostatic pressure perturbations), which is hidden in the classical analysis of the energetics of flows. For the first time in oceanic studies, the global distribution of layer-thickness form drag is determined. This study provides direct evidence to verify some basic characteristics of layer-thickness form drag that have often been assumed or speculated about in previous theoretical studies. The results justify most of the previous assumptions and speculations, including those associated with (i) the presence of an oceanic energy cycle explaining the relationship between layer-thickness form drag and wind forcing, (ii) the manner in which layer-thickness form drag removes the energy of vertically sheared geostrophic currents, and (iii) the reason why the work of layer-thickness form drag nearly balances the work of eddy-induced overturning circulation in each vertical column. However, the result of the analysis disagrees with speculation in previous studies that the layer-thickness form drag in the Antarctic Circumpolar Current is the agent that transfers the wind-induced momentum near the sea surface downward to the bottom layers. The authors present a new interpretation: the layer-thickness form drag reduces (and thereby cancels) the vertical shear resulting from the eddy-induced overturning circulation (rather than the vertical shear resulting from the surface wind stress). This interpretation is consistent with the results of the energy analysis conducted in this study.
Dry Bias in Vaisala RS90 Radiosonde Humidity Profiles over Antarctica
Authors: Rowe Penny M. , Miloshevich Larry M. , Turner David D. , Walden Von P. 
Published: January 2008

Abstract
Middle to upper tropospheric humidity plays a large role in determining terrestrial outgoing longwave radiation. Much work has gone into improving the accuracy of humidity measurements made by radiosondes. Some radiosonde humidity sensors experience a dry bias caused by solar heating. During the austral summers of 2002/03 and 2003/04 at Dome C, Antarctica, Vaisala RS90 radiosondes were launched in clear skies at solar zenith angles (SZAs) near 83° and 62°. As part of this field experiment, the Polar Atmospheric Emitted Radiance Interferometer (PAERI) measured downwelling spectral infrared radiance. The radiosonde humidity profiles are used in the simulation of the downwelling radiances. The radiosonde dry bias is then determined by scaling the humidity profile with a height-independent factor to obtain the best agreement between the measured and simulated radiances in microwindows between strong water vapor lines from 530 to 560 cm−1 and near line centers from 1100 to 1300 cm−1. The dry biases, as relative errors in relative humidity, are 8% ± 5% (microwindows; 1σ) and 9% ± 3% (line centers) for SZAs near 83°; they are 20% ± 6% and 24% ± 5% for SZAs near 62°. Assuming solar heating is minimal at SZAs near 83°, the authors remove errors that are unrelated to solar heating and find the solar-radiation dry bias of 9 RS90 radiosondes at SZAs near 62° to be 12% ± 6% (microwindows) and 15% ± 5% (line centers). Systematic errors in the correction are estimated to be 3% and 2% for microwindows and line centers, respectively. These corrections apply to atmospheric pressures between 650 and 200 mb.
Cloud Detection with MODIS. Part I: Improvements in the MODIS Cloud Mask for Collection 5
Authors: Frey Richard A. , Ackerman Steven A. , Liu Yinghui , Strabala Kathleen I. , Zhang Hong , Key Jeffrey R. , Wang Xuangi 
Published: January 2008

Abstract
Significant improvements have been made to the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask (MOD35 and MYD35) for Collection 5 reprocessing and forward stream data production. Most of the modifications are realized for nighttime scenes where polar and oceanic regions will see marked improvement. For polar night scenes, two new spectral tests using the 7.2-μm water vapor absorption band have been added as well as updates to the 3.9–12- and 11–12-μm cloud tests. More non-MODIS ancillary input data have been added. Land and sea surface temperature maps provide crucial information for mid- and low-level cloud detection and lessen dependence on ocean brightness temperature variability tests. Sun-glint areas are also improved by use of sea surface temperatures to aid in resolving observations with conflicting cloud versus clear-sky signals, where visible and near-infrared (NIR) reflectances are high, but infrared brightness temperatures are relatively warm. Day and night Arctic cloud frequency results are compared to those created by the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder-Extended (APP-X) algorithm. Day versus night sea surface temperatures derived from MODIS radiances and using only the MODIS cloud mask for cloud screening are contrasted. Frequencies of cloud from sun-glint regions are shown as a function of sun-glint angle to gain a sense of cloud mask quality in those regions. Continuing validation activities are described in Part II of this paper.
Vertical 2-μm Heterodyne Differential Absorption Lidar Measurements of Mean CO2 Mixing Ratio in the Troposphere
Authors: Gibert Fabien , Flamant Pierre H. , Cuesta Juan , Bruneau Didier 
Published: January 2008

Abstract
Vertical mean CO2 mixing ratio measurements are reported in the atmospheric boundary layer (ABL) and in the lower free troposphere (FT), using a 2-μm heterodyne differential absorption lidar (HDIAL). The mean CO2 mixing ratio in the ABL is determined using 1) aerosol backscatter signal and a mean derivative of the increasing optical depth as a function of altitude and 2) optical depth measurements from cloud target returns. For a 1-km vertical long path in the ABL, 2% measurement precision with a time resolution of 30 min is demonstrated for the retrieved mean CO2 absorption. Spectroscopic calculations are reported in details using new spectroscopic data in the 2-μm domain and the outputs of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5). Then, using both aerosols in the ABL and midaltitude dense clouds in the free troposphere, preliminary HDIAL measurements of mean CO2 mixing ratio in the free troposphere are also presented. The 2-μm HDIAL vertical measurements are compared to ground-based and airborne in situ CO2 mixing ratio measurements and discussed with the atmospheric synoptic conditions.
Upper-Ocean Thermal Structure and the Western North Pacific Category 5 Typhoons. Part I: Ocean Features and the Category 5 Typhoons’ Intensification
Authors: Lin I-I. , Wu Chun-Chieh , Pun Iam-Fei , Ko Dong-Shan 
Published: January 2008

Abstract
Category 5 cyclones are the most intense and devastating cyclones on earth. With increasing observations of category 5 cyclones, such as Hurricane Katrina (2005), Rita (2005), Mitch (1998), and Supertyphoon Maemi (2003) found to intensify on warm ocean features (i.e., regions of positive sea surface height anomalies detected by satellite altimeters), there is great interest in investigating the role ocean features play in the intensification of category 5 cyclones. Based on 13 yr of satellite altimetry data, in situ and climatological upper-ocean thermal structure data, best-track typhoon data of the U.S. Joint Typhoon Warning Center, together with an ocean mixed layer model, 30 western North Pacific category 5 typhoons that occurred during the typhoon season from 1993 to 2005 are systematically examined in this study.
Two different types of situations are found. The first type is the situation found in the western North Pacific south eddy zone (SEZ; 21°–26°N, 127°–170°E) and the Kuroshio (21°–30°N, 127°–170°E) region. In these regions, the background climatological warm layer is relatively shallow (typically the depth of the 26°C isotherm is around 60 m and the upper-ocean heat content is ∼50 kJ cm−2). Therefore passing over positive features is critical to meet the ocean’s part of necessary conditions in intensification because the features can effectively deepen the warm layer (depth of the 26°C isotherm reaching 100 m and upper-ocean heat content is ∼110 kJ cm−2) to restrain the typhoon’s self-induced ocean cooling. In the past 13 yr, 8 out of the 30 category 5 typhoons (i.e., 27%) belong to this situation.
The second type is the situation found in the gyre central region (10°–21°N, 121°–170°E) where the background climatological warm layer is deep (typically the depth of the 26°C isotherm is ∼105–120 m and the upper-ocean heat content is ∼80–120 kJ cm−2). In this deep, warm background, passing over positive features is not critical since the background itself is already sufficient to restrain the self-induced cooling negative feedback during intensification.
Dry-Season Precipitation in Tropical West Africa and Its Relation to Forcing from the Extratropics
Authors: Knippertz Peter , Fink Andreas H. 
Published: January 2008

Abstract
Precipitation is a major socioeconomic factor in the Guineo-Soudanian zone of tropical West Africa with its distinct summer rainy season from May to October. Albeit rare, precipitation during the dry season can have substantial impacts on the local hydrology and human activities reaching from the rotting of harvests to improved grazing conditions. This study provides an observationally based synoptic and dynamical analysis of an abundant rainfall event during the dry season of 2003/04 that affected the countries of Nigeria, Benin, Togo, and Ghana. The results point to a forcing of the rainfalls from the extratropics in the following ways: 1) Upper-level clouds and moisture to the east of a weak, quasi-stationary extratropical disturbance enhance the greenhouse effect over the Sahel and the adjacent Sahara, and thereby cause a net-column warm anomaly and falling surface pressure. 2) One day before the precipitation event, negative pressure tendencies are further enhanced through warm advection and subsidence associated with the penetration of a more intense upper-trough into Algeria. 3) The resulting northward shift and intensification of the weak wintertime heat low allows low-level moist southerlies from the Gulf of Guinea to penetrate into the Soudanian zone. 4) Finally, daytime heating of the land surface and convective dynamics initiate heavy rainfalls. Operational forecasts of this event were promising, pointing to a strong control by the comparatively well-predicted extratropical upper-level circulation.
Downscaling of ECMWF Ensemble Forecasts for Cases of Severe Weather: Ensemble Statistics and Cluster Analysis
Authors: Branković Čedo , Matjačić Blaženka , Ivatek-Šahdan Stjepan , Buizza Roberto 
Published: January 2008

Abstract
Dynamical downscaling has been applied to global ensemble forecasts to assess its impact for four cases of severe weather (precipitation and wind) over various parts of Croatia. It was performed with the Croatian 12.2-km version of the Aire Limitée Adaptation Dynamique Développement International (ALADIN) limited-area model, nested in the ECMWF TL255 (approximately 80 km) global ensemble prediction system (EPS). The 3-hourly EPS output was used to force the ALADIN model over the central European/northern Mediterranean domain.
Results indicate that the identical clustering algorithm may yield differing results when applied to either global or to downscaled ensembles. It is argued that this is linked to the fact that a downscaled, higher-resolution ensemble resolves more explicitly small-scale features, in particular those strongly influenced by orographic forcing. This result has important implications in limited-area ensemble prediction, since it implies that downscaling may affect the interpretation or relevance of the global ensemble forecasts; that is, it may not always be feasible to make a selection (or a subset) of global lower-resolution ensemble members that might be representative of all possible higher-resolution evolution scenarios.
A Dual-Polarization-Radar-Based Assessment of the 8 May 2003 Oklahoma City Area Tornadic Supercell
Authors: Romine Glen S. , Burgess Donald W. , Wilhelmson Robert B. 
Published: January 2008

Abstract
On 8 May 2003, a tornadic supercell tracked through portions of the Oklahoma City, Oklahoma, metropolitan area and produced violent damage along portions of its path. This storm passed through the dense in situ radar network in central Oklahoma and provided close-range operational, prototype polarimetric and terminal Doppler weather radar observations of the storm as it made the transition into the tornadic phase. The time-evolving polarimetric features were scrutinized with regard to storm morphology, particularly as related to the development of a rear-flank downdraft pulse within the storm immediately preceding the long-track tornado event. Two new polarimetric terms are introduced, the Zdr shield and Kdp foot, along with a discussion of the orientation of the Zdr and Kdp columns relative to midlevel rotation signatures. Storm downdraft and gust front characteristics are discussed relative to polarimetric fields and background environment characteristics. Highlighted for this event are a “warm” forward-flank downdraft and a particularly cold rear-flank downdraft. Emphasis is also placed on demonstrating key polarimetric field characteristics relative to traditional features at low and midlevels defined in familiar conceptual models of severe storms.
An Unusual Hailstorm on 24 June 2006 in Boulder, Colorado. Part I: Mesoscale Setting and Radar Features
Authors: Schlatter Paul T. , Schlatter Thomas W. , Knight Charles A. 
Published: January 2008

AbstractAn unusual, isolated hailstorm descended on Boulder, Colorado, on the evening of 24 June 2006. Starting with scattered large, flattened, disk-shaped hailstones and ending with a deluge of slushy hail that was over 4 cm deep on the ground, the storm lasted no more than 20 min and did surprisingly little damage except to vegetation. Part I of this two-part paper examines the meteorological conditions preceding the storm and the signatures it exhibited on Weather Surveillance Radar-1988 Doppler (WSR-88D) displays. There was no obvious upper-tropospheric forcing for this storm, vertical shear of the low-level wind was minimal, the boundary layer air feeding the storm was not very moist (maximum dewpoint 8.5°C), and convective available potential energy calculated from a modified air parcel was at most 1550 J kg−1. Despite these handicaps, the hail-producing storm had low-level reflectivity exceeding 70 dBZ, produced copious low-density hail, exhibited strong rotation, and generated three extensive bounded weak-echo regions (BWERs) in succession. The earliest of these filled with high reflectivities as the second one to the south poked up through precipitation-filled air. This has implications for low-density hail growth, as discussed in Part II.
Control of Laxity in Knees with Combined Posterior Cruciate Ligament and Posterolateral Corner Deficiency
Authors: Apsingi Sunil , Nguyen Trung , Bull Anthony M. J. , Unwin Andrew , Deehan David J. , Amis Andrew A. 
Published: January 2008

Background Although many posterior cruciate ligament (PCL) injuries are in combination with posterolateral corner (PLC) injuries, there has been little research on combined injury reconstruction; the literature includes differing recommendations. Hypothesis Combined PCL plus PLC reconstruction corrects the abnormal posterior translation, varus, and external rotation laxities caused by combined PCL plus PLC deficiency. Furthermore, double-bundle PCL plus PLC reconstruction restores laxity closer to normal than single-bundle PCL plus PLC reconstruction. Study Design Controlled laboratory study. Methods Cadaveric knee kinematics were measured electromagnetically in 9 knees with posterior drawer, external rotation, and varus rotation loads applied at sequential stages: intact, PCL-deficient, PCL plus PLC-deficient, double-bundle PCL plus modified Larson PLC reconstruction, and single-bundle PCL plus modified Larson PLC reconstruction. Each graft was tensioned using a laxity-matching protocol. Results There was no significant difference between single-bundle and double-bundle PCL reconstruction, in combination with the modified Larson reconstruction, at any angle of flexion. Both combined reconstructions restored posterior drawer, external rotation, and varus laxity so that they did not differ significantly from normal. Conclusion In combined PCL plus PLC deficiency, combined PCL plus PLC reconstruction restored all major laxity limits to normal across the range of knee flexion examined. Double-bundle PCL reconstruction was not better than single-bundle reconstruction in this context. Clinical Relevance The added complexity of double-bundle reconstruction does not seem to be justified by these results. In combined PCL plus PLC-deficient knees, combined single-bundle PCL plus modified Larson PLC reconstruction was sufficient to restore posterior drawer, external rotation, and varus laxity to normal.
High Ligation of the Saphenofemoral Junction in Endovenous Obliteration of Varicose Veins
Authors: Boros Michael J. , O'Brien Sean P. , McLaren James T. , Collins John T. 
Published: January 2008

Background Endovenous radiofrequency (RF) ablation of the greater saphenous vein has become an accepted treatment modality. This study examines if it is necessary to perform high ligation of the saphenous vein to insure success of the procedure. Study design A retrospective chart analysis was conducted on 219 patients who underwent RF ablation for venous insufficiency. All procedures were performed by 3 board-certified vascular surgeons. One surgeon always ligated the saphenofemoral junction (SFJ), the second never ligated, and the third ligated selectively. Demographic data were collected and analyzed. Results A total of 77 patients underwent RF ablation with ligation of the SFJ (group I), and 142 patients underwent ablation without ligation (group II). Both groups had similar ablation success rates ( P = .0960), 92% (group I) and 84% (group II). Conclusion Saphenofemoral junction ligation is not indicated on a routine basis to achieve success with endovascular ablation of the greater saphenous vein.