bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intercalibrated Passive Microwave Rain Products from the Unified Microwave Ocean Retrieval Algorithm (UMORA)
Authors: Hilburn K. A. , Wentz F. J. 
Published: April 2008

AbstractThe Unified Microwave Ocean Retrieval Algorithm (UMORA) simultaneously retrieves sea surface temperature, surface wind speed, columnar water vapor, columnar cloud water, and surface rain rate from a variety of passive microwave radiometers including the Special Sensor Microwave Imager (SSM/I), the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), and the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). The rain component of UMORA explicitly parameterizes the three physical processes governing passive microwave rain retrievals: the beamfilling effect, cloud and rainwater partitioning, and effective rain layer thickness. Rain retrievals from the previous version of UMORA disagreed among different sensors and were too high in the tropics. These issues have been fixed with more realistic rain column heights and proper modeling of saturation and footprint-resolution effects in the beamfilling correction. The purpose of this paper is to describe the rain algorithm and its recent improvements and to compare UMORA retrievals with Goddard Profiling Algorithm (GPROF) and Global Precipitation Climatology Project (GPCP) rain rates. On average, TMI retrievals from UMORA agree well with GPROF; however, large differences become apparent when the instantaneous retrievals are compared on a pixel-to-pixel basis. The differences are due to fundamental algorithm differences. For example, UMORA generally retrieves higher total liquid water, but GPROF retrieves a higher surface rain rate for a given amount of total liquid water because of differences in microphysical assumptions. Comparison of UMORA SSM/I retrievals with GPCP shows similar spatial patterns, but GPCP has higher global averages because of greater amounts of precipitation in the extratropics. UMORA and GPCP have similar linear trends over the period 1988–2005 with similar spatial patterns.
Simulations of the Urban Planetary Boundary Layer in an Arid Metropolitan Area
Authors: Grossman-Clarke Susanne , Liu Yubao , Zehnder Joseph A. , Fast Jerome D. 
Published: April 2008

AbstractA modified version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) was applied to the arid Phoenix, Arizona, metropolitan region. The ability of the model to simulate characteristics of the summertime urban planetary boundary layer (PBL) was tested by comparing model results with observations from two field campaigns conducted in May/June 1998 and June 2001. The modified MM5 included a refined land use/cover classification and updated land use data for Phoenix and bulk approaches of characteristics of the urban surface energy balance. PBL processes were simulated by a version of MM5’s Medium-Range Forecast Model (MRF) scheme that was enhanced by new surface flux and nonlocal mixing approaches. Simulated potential temperature profiles were tested against radiosonde data, indicating that the modified MRF scheme was able to simulate vertical mixing and the evolution and height of the PBL with good accuracy and better than the original MRF scheme except in the late afternoon. During both simulation periods, it is demonstrated that the modified MM5 simulated near-surface air temperatures and wind speeds in the urban area consistently and considerably better than the standard MM5 and that wind direction simulations were improved slightly.
Evaluation of Limited-Area Models for the Representation of the Diurnal Cycle and Contrasting Nights in CASES-99
Authors: Steeneveld G. J. , Mauritsen T. , de Bruijn E. I. F. , Vilà-Guerau de Arellano J. , Svensson G. , Holtslag A. A. M. 
Published: April 2008

Abstract
This study evaluates the ability of three limited-area models [the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5), the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS), and the High-Resolution Limited-Area Model (HIRLAM)] to predict the diurnal cycle of the atmospheric boundary layer (ABL) during the Cooperative Atmosphere–Surface Exchange Study (CASES-99) experimental campaign. Special attention is paid to the stable ABL. Limited-area model results for different ABL parameterizations and different radiation transfer parameterizations are compared with the in situ observations. Model forecasts were found to be sensitive to the choice of the ABL parameterization both during the day and at night. At night, forecasts are particularly sensitive to the radiation scheme. All three models underestimate the amplitude of the diurnal temperature cycle (DTR) and the near-surface wind speed. Furthermore, they overestimate the stable boundary layer height for windy conditions and underestimate the stratification of nighttime surface inversions. Favorable parameterizations for the stable boundary layer enable rapid surface cooling, and they have limited turbulent mixing. It was also found that a relatively large model domain is required to model the Great Plains low-level jet. A new scheme is implemented for the stable boundary layer in the Medium-Range Forecast Model (MRF). This scheme introduces a vegetation layer, a new formulation for the soil heat flux, and turbulent mixing based on the local scaling hypothesis. The new scheme improves the representation of surface temperature (especially for weak winds) and the stable boundary layer structure.
A Basin- to Channel-Scale Unstructured Grid Hurricane Storm Surge Model Applied to Southern Louisiana
Authors: Westerink Joannes J. , Luettich Richard A. , Feyen Jesse C. , Atkinson John H. , Dawson Clint , Roberts Hugh J. , Powell Mark D. , Dunion Jason P. , Kubatko Ethan J. , Pourtaheri Hasan 
Published: April 2008

AbstractSouthern Louisiana is characterized by low-lying topography and an extensive network of sounds, bays, marshes, lakes, rivers, and inlets that permit widespread inundation during hurricanes. A basin- to channel-scale implementation of the Advanced Circulation (ADCIRC) unstructured grid hydrodynamic model has been developed that accurately simulates hurricane storm surge, tides, and river flow in this complex region. This is accomplished by defining a domain and computational resolution appropriate for the relevant processes, specifying realistic boundary conditions, and implementing accurate, robust, and highly parallel unstructured grid numerical algorithms.The model domain incorporates the western North Atlantic, the Gulf of Mexico, and the Caribbean Sea so that interactions between basins and the shelf are explicitly modeled and the boundary condition specification of tidal and hurricane processes can be readily defined at the deep water open boundary. The unstructured grid enables highly refined resolution of the complex overland region for modeling localized scales of flow while minimizing computational cost. Kinematic data assimilative or validated dynamic-modeled wind fields provide the hurricane wind and pressure field forcing. Wind fields are modified to incorporate directional boundary layer changes due to overland increases in surface roughness, reduction in effective land roughness due to inundation, and sheltering due to forested canopies. Validation of the model is achieved through hindcasts of Hurricanes Betsy and Andrew. A model skill assessment indicates that the computed peak storm surge height has a mean absolute error of 0.30 m.
Cluster Analysis for Object-Oriented Verification of Fields: A Variation
Authors: Marzban Caren , Sandgathe Scott 
Published: April 2008

Abstract
In a recent paper, a statistical method referred to as cluster analysis was employed to identify clusters in forecast and observed fields. Further criteria were also proposed for matching the identified clusters in one field with those in the other. As such, the proposed methodology was designed to perform an automated form of what has been called object-oriented verification. Herein, a variation of that methodology is proposed that effectively avoids (or simplifies) the criteria for matching the objects. The basic idea is to perform cluster analysis on the combined set of observations and forecasts, rather than on the individual fields separately. This method will be referred to as combinative cluster analysis (CCA). CCA naturally lends itself to the computation of false alarms, hits, and misses, and therefore, to the critical success index (CSI). A desirable feature of the previous method—the ability to assess performance on different spatial scales—is maintained. The method is demonstrated on reflectivity data and corresponding forecasts for three dates using three mesoscale numerical weather prediction model formulations—the NCEP/NWS Nonhydrostatic Mesoscale Model (NMM) at 4-km resolution (nmm4), the University of Oklahoma’s Center for Analysis and Prediction of Storms (CAPS) Weather Research and Forecasting Model (WRF) at 2-km resolution (arw2), and the NCAR WRF at 4-km resolution (arw4). In the small demonstration sample herein, model forecast quality is efficiently differentiated when performance is assessed in terms of the CSI. In this sample, arw2 appears to outperform the other two model formulations across all scales when the cluster analysis is performed in the space of spatial coordinates and reflectivity. However, when the analysis is performed only on spatial data (i.e., when only the spatial placement of the reflectivity is assessed), the difference is not significant. This result has been verified both visually and using a standard gridpoint verification, and seems to provide a reasonable assessment of model performance. This demonstration of CCA indicates promise in quickly evaluating mesoscale model performance while avoiding the subjectivity and labor intensiveness of human evaluation or the pitfalls of non-object-oriented automated verification.
Implications of the Form of the Ensemble Transformation in the Ensemble Square Root Filters
Authors: Sakov Pavel , Oke Peter R. 
Published: April 2008

Abstract
This paper considers implications of different forms of the ensemble transformation in the ensemble square root filters (ESRFs) for the performance of ESRF-based data assimilation systems. It highlights the importance of using mean-preserving solutions for the ensemble transform matrix (ETM). The paper shows that an arbitrary mean-preserving ETM can be represented as a product of the symmetric solution and an orthonormal mean-preserving matrix. The paper also introduces a new flavor of ESRF, referred to as ESRF with mean-preserving random rotations. To investigate the performance of different solutions for the ETM in ESRFs, experiments with two small models are conducted. In these experiments, the performances of two mean-preserving solutions, two non-mean-preserving solutions, and a traditional ensemble Kalman filter with perturbed observations are compared. The experiments show a significantly better performance of the mean-preserving solutions for the ETM in ESRFs compared to non-mean-preserving solutions. They also show that applying the mean-preserving random rotations prevents the buildup of ensemble outliers in ESRF-based data assimilation systems.
An Efficient Dual-Resolution Approach for Ensemble Data Assimilation and Tests with Simulated Doppler Radar Data
Authors: Gao Jidong , Xue Ming 
Published: April 2008

Abstract
A new efficient dual-resolution (DR) data assimilation algorithm is developed based on the ensemble Kalman filter (EnKF) method and tested using simulated radar radial velocity data for a supercell storm. Radar observations are assimilated on both high-resolution and lower-resolution grids using the EnKF algorithm with flow-dependent background error covariances estimated from the lower-resolution ensemble. It is shown that the flow-dependent and dynamically evolved background error covariances thus estimated are effective in producing quality analyses on the high-resolution grid.
The DR method has the advantage of being able to significantly reduce the computational cost of the EnKF analysis. In the system, the lower-resolution ensemble provides the flow-dependent background error covariance, while the single-high-resolution forecast and analysis provides the benefit of higher resolution, which is important for resolving the internal structures of thunderstorms. The relative smoothness of the covariance obtained from the lower 4-km-resolution ensemble does not appear to significantly degrade the quality of analysis. This is because the cross covariance among different variables is of first-order importance for “retrieving” unobserved variables from the radar radial velocity data.
For the DR analysis, an ensemble size of 40 appears to be a reasonable choice with the use of a 4-km horizontal resolution in the ensemble and a 1-km resolution in the high-resolution analysis. Several sensitivity tests show that the DR EnKF system is quite robust to different observation errors. A 4-km thinned data resolution is a compromise that is acceptable under the constraint of real-time applications. A data density of 8 km leads to a significant degradation in the analysis.
Typhoon Initialization in a Mesoscale Model—Combination of the Bogused Vortex and the Dropwindsonde Data in DOTSTAR
Authors: Chou Kun-Hsuan , Wu Chun-Chieh 
Published: April 2008

Abstract
Issues concerning the initialization and simulation of tropical cyclones by integrating both dropwindsonde data and a bogused vortex into a mesoscale model have been studied. A method is proposed to combine dropwindsonde data with a bogused vortex for tropical cyclone initialization and to improve track and intensity prediction. A clear positive impact of this proposed method on both the tropical cyclone track and intensity forecasts in a mesoscale model is demonstrated in three cases of typhoons, including Meari (2004), Conson (2004), and Megi (2004). The effectiveness of the proposed method in improving the track and intensity forecasts is also demonstrated in the evaluation of all 10 cases of Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR) missions in 2004. This method provides a useful and practical means to improve operational tropical cyclone prediction with dropwindsonde observations.
Comparison of Observed 10-m Wind Speeds to Those Based on Monin–Obukhov Similarity Theory Using IHOP_2002 Aircraft and Surface Data
Authors: Strassberg Diane , LeMone Margaret A. , Warner Thomas T. , Alfieri Joseph G. 
Published: April 2008

AbstractComparisons of 10-m above ground level (AGL) wind speeds from numerical weather prediction (NWP) models to point observations consistently show that model daytime wind speeds are slow compared to observations, even after improving model physics and going to smaller grid spacing. Previous authors have attributed the discrepancy to differences between the areas represented by model and observations, and the small surface roughness upstream of wind vanes compared with the corresponding model grid value. Using daytime fair-weather data from the May–June 2002 International H2O Experiment (IHOP_2002), the effect of wind-vane exposure is explored by comparing observed 10-m winds from nine surface-flux towers in well-exposed locations to modeled 10-m winds found by applying Monin–Obukhov (MO) similarity for unstable conditions to flight-track-averaged data collected by the University of Wyoming King Air over flat to rolling terrain with occasional trees and buildings. In the calculations, King Air winds and fluxes are supplemented with thermodynamic means and fluxes from the surface-flux towers. After exercising considerable care in characterizing and reducing biases in aircraft winds and fluxes, the authors found that MO-based surface winds averaged 0.5–0.7 ± 0.2 m s−1 less than those measured—about the same as the smaller reported discrepancies between NWP models and observed winds.
Atlantic Hurricane Season of 2006
Authors: Franklin James L. , Brown Daniel P. 
Published: April 2008

AbstractThe 2006 Atlantic hurricane season is summarized and the year’s tropical cyclones are described. A verification of National Hurricane Center official forecasts during 2006 is also presented. Ten cyclones attained tropical storm intensity in 2006. Of these, five became hurricanes and two became “major” hurricanes. Overall activity was near the long-term mean, but below the active levels of recent seasons. For the first time since 2001, no hurricanes made landfall in the United States. Elsewhere in the basin, hurricane-force winds were experienced in Bermuda (from Florence) and in the Azores (from Gordon). Official track forecast errors were smaller in 2006 than during the previous 5-yr period (by roughly 15%–20% out to 72 h), establishing new all-time lows at forecast projections through 72 h. Since 1990, 24–72-h official track forecast errors have been reduced by roughly 50%.
Chilled water circuit designs for in situ chiller performance measurement
Authors: Yik Francis W H 
Published: April 2008

Determining the full- and part-load performance of chillers through short-term in situ measurements requires complicated arrangements. It will take a long time if consistently logged performance data under normal plant operation are used instead. Chilled water circuit designs that allow the full- and part-load performance of chillers to be measured conveniently and expeditiously are presented in the paper. The circuit designs require just minor extra provisions, including the installation of supplementary pipes and fittings, and a few additional control devices. Besides making it possible to conduct full-load tests on chillers at most of the time in the year, simulation results based on a building model in Hong Kong show that part-load performance data that cover the entire capacity range of chillers can be captured in less than 2 weeks, both in hot and cold months. Practical application: With the proposed chilled water circuit designs, the time and effort required for measuring the full- and part-load performance of new or existing chillers can be largely reduced. The method will work provided that each chiller is connected in series with a dedicated chilled water pump and the return chilled water will flow from one end of the main return pipe to another with connections to all chiller branches in between. The circuit design can be incorporated easily into new plant designs. For existing buildings, the required pipe modification work will interrupt plant operation.
Epistemic demand analysis for fresh water supply of Chinese restaurants
Authors: Mui KW , Wong LT , Yeung MK 
Published: April 2008

In order to design a cost-effective and eco-efficient fresh water supply system for Chinese restaurants, a better understanding of the simultaneous water demands in these restaurants is essential. Taking the professional evaluation practice and actual on-site measurements into account, this study examines the probable maximum demands of the water supply system for some Chinese restaurants in Hong Kong using the Bayesian approach. The installed capacities, usage patterns, flow rates and `per customer' hourly demands of tea urns, dishwashers, kitchen sinks and washbasins employed in a typical Chinese restaurant were evaluated. With the assumption of normally distributed discharge probability, the fixture units of these appliances were estimated for local Chinese restaurants; comparisons with the existing design values were also made. The posterior results, which showed that the sinks for tea urn and dishwasher required bigger plant capacity, would be useful for updating the calculation of water demands in certain Chinese restaurants to justify the installation cost. Practical application: The probable maximum demands of the water supply system for some Chinese restaurants in Hong Kong were examined using the Bayesian approach; the fixture units of tea urns, dishwashers, kitchen sinks and washbasins employed in a typical Chinese restaurant were estimated for local Chinese restaurants. The results showed that the sinks for tea urn and dishwasher required bigger plant capacity, would be useful for updating the calculation of water demands in certain Chinese restaurants to justify the installation cost.
The Effect of Donor Age and Low-Dose Gamma Irradiation on the Initial Biomechanical Properties of Human Tibialis Tendon Allografts
Authors: Greaves Laura L. , Hecker Aaron T. , Brown Charles H. 
Published: April 2008

Background Most tissue banks recover and irradiate tibialis tendon allografts from donors aged up to 65 years. It is unknown whether donor age and low-dose gamma irradiation affect the initial biomechanical properties of tibialis allografts. Hypothesis Donor age up to 65 years and low-dose gamma irradiation do not significantly affect the initial biomechanical properties of tibialis allografts. Study Design Controlled laboratory study. Methods One hundred twenty-six tibialis tendon allografts (63 pairs, 37 human donors) were divided into 3 age groups: young (<45 years), middle (46-55 years), and old (56-65 years). Within each age group, half of the paired tendons underwent tensile testing as single-strand grafts and the other half as double-strand grafts. One tendon from each donor pair was randomly assigned to undergo terminal sterilization with an absorbed dose of 1.46 to 1.80 Mrad (14.6-18.0 kGy) gamma irradiation, whereas the other tendon received no irradiation. All tendon grafts were preconditioned with a cyclic load and tested to failure in tension. Results Irradiated single-strand tendons in the old age group had a longer displacement at failure compared to the middle but not the young age group. Nonirradiated double-strand tendons in the old age group had a lower failure stress. Single-strand irradiated old tendons had a lower stiffness, and all irradiated young tendons and old double-strand tendons had a higher failure stress compared to nonirradiated tendons. Conclusion Donor age up to 65 years does not significantly affect the initial failure load, stiffness, or displacement at failure of tibialis allografts. An age-related decrease in failure stress was observed among nonirradiated tendons but not in tendons subjected to irradiation. Clinical Relevance The results provide biomechanical evidence for use of tibialis allografts from donors up to 65 years of age. Low-dose gamma irradiation does not negatively influence the initial biomechanical properties of tibialis allografts. Further studies examining age and irradiation effects after submaximal cyclic loading conditions are recommended.