bluuebunny/crossref_metadata_2025_split huggingface dataset:
Boundary Layer Characteristics over Homogeneous and Heterogeneous Surfaces Simulated by MM5 and DALES
Authors: Braam Miranda , Vilà-Guerau de Arellano Jordi , Górska Monica 
Published: February 2011

AbstractThe multiple-single-column approach is proposed as a new concept to study the boundary layer parameterization scheme in the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5). The results are compared with the Dutch Atmospheric Large-Eddy Simulation Model (DALES). Numerical experiments were performed over homogeneous and heterogeneous surfaces under clear convective boundary layer conditions. Identical simulations using MM5 and DALES were performed, which enabled an evaluation of the MM5 boundary layer scheme with DALES results. From the experiment with a homogeneous surface, MM5 shows a slightly shallower, colder, and moister boundary layer than DALES. This result is produced by an underestimation of turbulent mixing near the surface and less-vigorous entrainment of heat and dry air in MM5. In the heterogeneous surface experiment, the domain is divided into dry and wet patches, with the result that both models produce a mesoscale circulation. However, relative to the homogeneous case, larger differences were found between the models in the representation of the boundary layer dynamics. In DALES, the surface heterogeneity influenced the turbulent motions, making the mesoscale circulation much stronger (wmax is 6 times as large) than in MM5. Because of this stronger circulation, the boundary layer height, bulk temperature, and humidity also displayed differences in time and spatial patterns. Because of the land–atmosphere coupling in MM5, the mesoscale circulation strengthened the surface flux heterogeneity. Cold and moist air advection close to the surface from the wet patch to the dry patch increased the sensible heat flux above the dry patch and thus the induced mesoscale flow.
Cross Validation of Spaceborne Radar and Ground Polarimetric Radar Aided by Polarimetric Echo Classification of Hydrometeor Types
Authors: Wen Yixin , Hong Yang , Zhang Guifu , Schuur Terry J. , Gourley Jonathan J. , Flamig Zac , Morris K. Robert , Cao Qing 
Published: February 2011

AbstractGround-based polarimetric weather radar is arguably the most powerful validation tool that provides physical insight into the development and interpretation of spaceborne weather radar algorithms and observations. This study aims to compare and resolve discrepancies in hydrometeor retrievals and reflectivity observations between the NOAA/National Severe Storm Laboratory “proof of concept” KOUN polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D) and the spaceborne precipitation radar (PR) on board NASA’s Tropical Rainfall Measuring Mission (TRMM) platform. An intercomparison of PR and KOUN melting-layer heights retrieved from 2 to 5 km MSL shows a high correlation coefficient of 0.88 with relative bias of 5.9%. A resolution volume–matching technique is used to compare simultaneous TRMM PR and KOUN reflectivity observations. The comparisons reveal an overall bias of <0.2% between PR and KOUN. The bias is hypothesized to be from non-Rayleigh scattering effects and/or errors in attenuation correction procedures applied to Ku-band PR measurements. By comparing reflectivity with respect to different hydrometeor types (as determined by KOUN’s hydrometeor classification algorithm), it is found that the bias is from echoes that are classified as rain–hail mixture, wet snow, graupel, and heavy rain. These results agree with expectations from backscattering calculations at Ku and S bands, but with the notable exception of dry snow. Comparison of vertical reflectivity profiles shows that PR suffers significant attenuation at lower altitudes, especially in convective rain and in the melting layer. The attenuation correction performs very well for both stratiform and convective rain, however. In light of the imminent upgrade of the U.S. national weather radar network to include polarimetric capabilities, the findings in this study will potentially serve as the basis for nationwide validation of space-based precipitation products and also invite synergistic development of coordinated space–ground multisensor precipitation products.
A Confirmatory Snowfall Enhancement Project in the Snowy Mountains of Australia. Part I: Project Design and Response Variables
Authors: Manton Michael J. , Warren Loredana , Kenyon Suzanne L. , Peace Andrew D. , Bilish Shane P. , Kemsley Karen 
Published: February 2011

AbstractThe Snowy Precipitation Enhancement Research Project (SPERP) was undertaken from May 2005 to June 2009 in the Snowy Mountains of southeastern Australia with the aim of enhancing snowfall in westerly flows associated with winter cold fronts. Building on earlier field studies in the region, SPERP was developed as a confirmatory experiment of glaciogenic static seeding using a silver-chloroiodide material dispersed from ground-based generators. Seeding of 5-h experimental units (EUs) was randomized with a seeding ratio of 2:1. A total of 107 EUs were undertaken at suitable times, based on surface and upper-air observations. Indium (III) oxide was released during all EUs for comparison of indium and silver concentrations in snow in seeded and unseeded EUs to test the targeting of seeding material. A network of gauges was deployed at 44 sites across the region to detect whether precipitation was enhanced in a fixed target area of 832 km2, using observations from a fixed control area to estimate the natural precipitation in the target. Additional measurements included integrated supercooled liquid water at a site in the target area and upper-air data from a site upwind of the target.
A Confirmatory Snowfall Enhancement Project in the Snowy Mountains of Australia. Part II: Primary and Associated Analyses
Authors: Manton Michael J. , Warren Loredana 
Published: February 2011

AbstractThe Snowy Precipitation Enhancement Research Project (SPERP) was undertaken in winters from May 2005 to June 2009 in the Snowy Mountains region of southeastern Australia. Part I of this paper describes the design and implementation of the project, as well as the characteristics of the key datasets collected during the field phase. The primary analysis in this paper (Part II) shows an unequivocal impact on the targeting of seeding material, with the maximum level of silver in snow samples collected from the primary target area found to be significantly greater in seeded than unseeded experimental units (EUs). A positive but not statistically significant impact on precipitation was found. Further analysis shows that a substantial source of uncertainty in the estimation of the impacts of seeding on precipitation is associated with EUs where the seeding generators operated for relatively few hours. When the analysis is repeated using only EUs with more than 45 generator hours, the increase in precipitation in the primary target area is 14% at the 8% significance level. When applying that analysis to the overall target area, the precipitation increase is 14% at the 3% significance level. A secondary analysis of the ratio of silver to indium in snow supports the hypothesis that seeding material affected the cloud microphysics. Other secondary analyses reveal that seeding had an impact on virtually all of the physical variables examined in a manner consistent with the seeding hypothesis.
The Modified Gamma Size Distribution Applied to Inhomogeneous and Nonspherical Particles: Key Relationships and Conversions
Authors: Petty Grant W. , Huang Wei 
Published: February 2011

Abstract
The four-parameter modified gamma distribution (MGD) is the most general mathematically convenient model for size distributions of particle types ranging from aerosols and cloud droplets or ice particles to liquid and frozen precipitation. The common three-parameter gamma distribution, the exponential distribution (e.g., Marshall–Palmer), and power-law distribution (e.g., Junge) are all special cases. Depending on the context, the particle “size” used in a given formulation may be the actual geometric diameter, the volume- or area-equivalent spherical diameter, the actual or equivalent radius, the projected or surface area, or the mass.
For microphysical and radiative transfer calculations, it is often necessary to convert from one size representation to another, especially when comparing or utilizing distribution parameters obtained from a variety of sources. Furthermore, when the mass scales with Db, with b &lt; 3, as is typical for snow and ice and other particles having a quasi-fractal structure, an exponential or gamma distribution expressed in terms of one size parameter becomes an MGD when expressed in terms of another. The MGD model is therefore more fundamentally relevant to size distributions of nonspherical particles than is often appreciated.
The central purpose of this paper is to serve as a concise single-source reference for the mathematical properties of, and conversions between, atmospheric particle size distributions that can expressed as MGDs, including exponential and gamma distributions as special cases.
For illustrative purposes, snow particle size distributions published by Sekhon and Srivastava, Braham, and Field et al. are converted to a common representation and directly compared for identical snow water content, allowing large differences in their properties to be discerned and quantified in a way that is not as easily achieved without such conversion.
Orogenic Propagating Precipitation Systems over the United States in a Global Climate Model with Embedded Explicit Convection
Authors: Pritchard Michael S. , Moncrieff Mitchell W. , Somerville Richard C. J. 
Published: February 2011

Abstract
In the lee of major mountain chains worldwide, diurnal physics of organized propagating convection project onto seasonal and climate time scales of the hydrologic cycle, but this phenomenon is not represented in conventional global climate models (GCMs). Analysis of an experimental version of the superparameterized (SP) Community Atmosphere Model (CAM) demonstrates that propagating orogenic nocturnal convection in the central U.S. warm season is, however, representable in GCMs that use the embedded explicit convection model approach [i.e., multiscale modeling frameworks (MMFs)]. SP-CAM admits propagating organized convective systems in the lee of the Rockies during synoptic conditions similar to those that generate mesoscale convective systems in nature. The simulated convective systems exhibit spatial scales, phase speeds, and propagation speeds comparable to radar observations, and the genesis mechanism in the model agrees qualitatively with established conceptual models. Convective heating and condensate structures are examined on both resolved scales in SP-CAM, and coherently propagating cloud “metastructures” are shown to transcend individual cloud-resolving model arrays. In reconciling how this new mode of diurnal convective variability is admitted in SP-CAM despite the severe idealizations in the cloud-resolving model configuration, an updated discussion is presented of what physics may transcend the re-engineered scale interface in MMFs. The authors suggest that the improved diurnal propagation physics in SP-CAM are mediated by large-scale first-baroclinic gravity wave interactions with a prognostic organization life cycle, emphasizing the physical importance of preserving “memory” at the inner resolved scale.
A Latent Heat Retrieval and Its Effects on the Intensity and Structure Change of Hurricane Guillermo (1997). Part I: The Algorithm and Observations
Authors: Guimond Stephen R. , Bourassa Mark A. , Reasor Paul D. 
Published: February 2011

Abstract
Despite the fact that latent heating in cloud systems drives many atmospheric circulations, including tropical cyclones, little is known of its magnitude and structure, largely because of inadequate observations. In this work, a reasonably high-resolution (2 km), four-dimensional airborne Doppler radar retrieval of the latent heat of condensation/evaporation is presented for rapidly intensifying Hurricane Guillermo (1997). Several advancements in the basic retrieval algorithm are shown, including 1) analyzing the scheme within the dynamically consistent framework of a numerical model, 2) identifying algorithm sensitivities through the use of ancillary data sources, and 3) developing a precipitation budget storage term parameterization. The determination of the saturation state is shown to be an important part of the algorithm for updrafts of ~5 m s−1 or less.
The uncertainties in the magnitude of the retrieved heating are dominated by errors in the vertical velocity. Using a combination of error propagation and Monte Carlo uncertainty techniques, biases are found to be small, and randomly distributed errors in the heating magnitude are ~16% for updrafts greater than 5 m s−1 and ~156% for updrafts of 1 m s−1. Even though errors in the vertical velocity can lead to large uncertainties in the latent heating field for small updrafts/downdrafts, in an integrated sense the errors are not as drastic.
In Part II, the impact of the retrievals is assessed by inserting the heating into realistic numerical simulations at 2-km resolution and comparing the generated wind structure to the Doppler radar observations of Guillermo.
Regionalization of Present-Day Precipitation in the Greater Monsoon Region of Asia*
Authors: Conroy Jessica L. , Overpeck Jonathan T. 
Published: February 2011

Abstract
The spatial domain of the Asian monsoon has been defined by the intensity, seasonal concentration, and annual range of precipitation. Monsoon subdomains, such as the Indian monsoon, East Asian monsoon, and western North Pacific monsoon, have also been identified based on seasonal wind reversals as well as the timing and source of monsoon moisture. However, precipitation across the Asian monsoon region is heterogeneous and spatially complex and may have influences farther north than commonly assumed, particularly if scientists consider records of past variability spanning the current interglacial period. This paper presents an additional means of identifying the Asian monsoon domain and monsoon subsystems using an empirical orthogonal function (EOF)-based regionalization of gridded precipitation values. Regions of unique precipitation variability for the Asian monsoon region are determined using monthly precipitation anomalies from the Climate Prediction Center Merged Analysis of Precipitation (CMAP) gridded precipitation dataset from 1979 to 2009. From these regions, an area of Asian monsoon influence extending from the Arabian Sea eastward to the western North Pacific Ocean is defined, similar to other studies. One key difference is that this region of monsoon influence penetrates farther north into the Tibetan Plateau and northern China. Thus, paleoclimate observations of wetter conditions in these northern arid regions may suggest an intensification of monsoon moisture, rather than a northward shift in the boundary of the monsoon. In contrast, the Arabian Peninsula, largely removed from monsoon precipitation today, likely saw a shift of monsoon influence inland earlier in the Holocene. Also identified are different subdomains of distinct precipitation variability in southeastern Asia, the western North Pacific, and the East Asian monsoon region of northeastern China that agree with previous studies. Not identified in the paper is a single Indian summer monsoon region. Instead, the Arabian Sea was found to have unique precipitation variability relative to the Indian subcontinent. Summers with enhanced precipitation over the Arabian Sea coincide with decreased summer precipitation in the western North Pacific. This relationship is likely a result of the El Niño–Southern Oscillation (ENSO)-induced development of the Philippine Sea anticyclone. Local and remote sea surface temperatures were generally found to covary with regional precipitation, but not all regions respond similarly to the remote climate variability associated with ENSO. There is some evidence that the EOF-defined regions were stable … through the Holocene, although additional regionalization analyses of paleorecords and model simulations of past precipitation variability are needed to reconstruct past regions of coherent precipitation variability.
Statistics of Cloud Optical Properties from Airborne Lidar Measurements
Authors: Yorks John E. , Hlavka Dennis L. , Hart William D. , McGill Matthew J. 
Published: February 2011

Abstract
Accurate knowledge of cloud optical properties, such as extinction-to-backscatter ratio and depolarization ratio, can have a significant impact on the quality of cloud extinction retrievals from lidar systems because parameterizations of these variables are often used in nonideal conditions to determine cloud phase and optical depth. Statistics and trends of these optical parameters are analyzed for 4 yr (2003–07) of cloud physics lidar data during five projects that occurred in varying geographic locations and meteorological seasons. Extinction-to-backscatter ratios (also called lidar ratios) are derived at 532 nm by calculating the transmission loss through the cloud layer and then applying it to the attenuated backscatter profile in the layer, while volume depolarization ratios are computed using the ratio of the parallel and perpendicular polarized 1064-nm channels. The majority of the cloud layers yields a lidar ratio between 10 and 40 sr, with the lidar ratio frequency distribution centered at 25 sr for ice clouds and 16 sr for altocumulus clouds. On average, for ice clouds the lidar ratio slightly decreases with decreasing temperature, while the volume depolarization ratio increases significantly as temperatures decrease. Trends for liquid water clouds (altocumulus clouds) are also observed. Ultimately, these observed trends in optical properties, as functions of temperature and geographic location, should help to improve current parameterizations of extinction-to-backscatter ratio, which in turn should yield increased accuracy in cloud optical depth and radiative forcing estimates.
Life Cycle Study of a Diabatic Rossby Wave as a Precursor to Rapid Cyclogenesis in the North Atlantic—Dynamics and Forecast Performance
Authors: Boettcher Maxi , Wernli Heini 
Published: February 2011

Abstract
The life cycle of a North Atlantic cyclone in December 2005 that included a rapid propagation phase as a diabatic Rossby wave (DRW) is investigated by means of operational analyses and deterministic forecasts from the ECMWF. A quasigeostrophic omega diagnostic has been applied to assess the impact of upper-level forcing during the genesis, propagation, and intensification phase, respectively. The system was generated in the Gulf of Mexico as a mesoscale convective vortex (MCV) influenced by vertical motion forcing from a nearby upper-level trough. The DRW propagation phase was characterized by a shallow, low-level, diabatically produced potential vorticity (PV) anomaly that rapidly propagated along the southern border of an intense baroclinic zone. No significant upper-level forcing could be identified during this phase of the development. Eventually, explosive intensification occurred as the region of vertical motion forced by an approaching upper-level trough reached the position of the DRW. The rapid intensification of 34 hPa in 24 h led to a mature extratropical cyclone in the central North Atlantic with marked frontal structures associated with a pronounced PV tower.
The performance of four operational deterministic ECMWF forecasts has been investigated for the DRW propagation and cyclone intensification. The forecasts showed a highly variable skill. Despite the fact that the DRW was initially well represented in all forecasts, two of them failed to capture the explosive intensification. By applying a DRW tracking tool, the low-level baroclinicity downstream of the DRW and the moisture supply to the south of the DRW could be identified as the key environmental parameters during DRW propagation. The subsequent cyclone intensification went wrong in two of the forecasts because of the missing interaction of the DRW and the upper-level trough. It is shown that this interaction can fail if the intensity of the DRW and/or the approaching upper-level wave are too weak, or in case of an erroneous structure of the upper-level trough leading to a phasing problem of the vertical interaction with the DRW. Therefore, the DRW intensification bears similar characteristics and forecast challenges as the extratropical reintensification of tropical cyclones.
Playing-related musculoskeletal problems in child instrumentalists: The influence of gender, age and instrument exposure
Authors: Ranelli Sonia , Smith Anne , Straker Leon 
Published: February 2011

Playing-related musculoskeletal problems (PRMP) are common in adult musicians. The limited available evidence suggests PRMP are common in children and adolescents and that risk factors may be similar. The aim of this study was to determine the prevalence of PRMP in children and adolescents and their associations with female gender, age and instrument exposure. The study surveyed 731 children learning musical instruments (460 females) ranging in age from 7—17 years. Lifetime symptoms, monthly symptoms and monthly disorders (the inability to play an instrument as usual) were examined. Logistic regression evaluated the independent association of these potential risk factors with PRMP prevalences. A total of 67% students reported PRM symptoms at some point, 56% reported PRM symptoms within the last month and 30% reported an inability to play as usual within the last month. Female gender was significantly associated with PRMP (OR 1.38—1.56, p = 0.004—0.046), as was age (OR 1.19—0.23, p < 0.001). After adjustment for gender and age, type of instrument (upper and lower strings, woodwind and brass) were significantly associated with all PRMP ( p < 0.005) and playing three instruments was protective against monthly symptoms (OR 0.43, p = 0.05). The study concludes that the high prevalence and disabling impact of playing-related musculoskeletal problems is clearly an important issue for child and adolescent health with gender, age and instrument exposure important factors for risk management.