bluuebunny/crossref_metadata_2025_split huggingface dataset:
Climatology of Upper-Level Turbulence over the Contiguous United States
Authors: Wolff J. K. , Sharman R. D. 
Published: February 2008

AbstractClimatologies of the regional, seasonal, and temporal distributions of upper-level (18 000–60 000-ft MSL) turbulence over the contiguous United States (CONUS) are constructed using pilot reports (PIREPs) of aircraft turbulence encounters. The PIREP database used contains over two million entries, and encompasses 12 complete years of data, from January 1994 through December 2005. In spite of known variability in pilot reporting practices, it was found that PIREPs are very consistent among themselves for the null and moderate-or-greater (MOG) intensity categories. Air traffic pattern biases were accounted for by considering only statistics of MOG/total report ratios. Over the CONUS, regional maxima are evident in MOG/total ratios over mountainous regions in the west, over the south and southeast, and over the North Atlantic seaboard. Some additional investigations are presented to help to identify possible origins of the turbulence using a smaller time interval of PIREPs in comparison with archived 20-km Rapid Update Cycle (RUC) NWP model analyses, satellite and radar-based cloud-top and cloud-base analyses, and lightning flash data, as well as topography statistics.
Robust Automated Quality Assurance of Radiosonde Temperatures
Authors: Durre Imke , Vose Russell S. , Wuertz David B. 
Published: February 2008

Abstract
This paper presents a description of the fully automated quality-assurance (QA) procedures that are being applied to temperatures in the Integrated Global Radiosonde Archive (IGRA). Because these data are routinely used for monitoring variations in tropospheric temperature, it is of critical importance that the system be able to detect as many errors as possible without falsely identifying true meteorological events as erroneous. Three steps were taken to achieve such robust performance. First, 14 tests for excessive persistence, climatological outliers, and vertical and temporal inconsistencies were developed and arranged into a deliberate sequence so as to render the system capable of detecting a variety of data errors. Second, manual review of random samples of flagged values was used to set the “thresholds” for each individual check so as to minimize the number of valid values that are mistakenly identified as errors. The performance of the system as a whole was also assessed through manual inspection of random samples of the quality-assured data. As a result of these efforts, the IGRA temperature QA procedures effectively remove the grossest errors while maintaining a false-positive rate of approximately 10%.
Northern Annular Mode Effects on the Land Surface Phenologies of Northern Eurasia
Authors: de Beurs K. M. , Henebry G. M. 
Published: February 2008

Abstract
Land surface phenology (LSP) is the spatiotemporal development of the vegetated land surface as revealed by synoptic sensors. Modeling LSP across northern Eurasia reveals the magnitude, significance, and spatial pattern of the influence of the northern annular mode. Here the authors fit simple LSP models to two normalized difference vegetation index (NDVI) datasets and calculate the Spearman rank correlations to link the start of the observed growing season (SOS) and the timing of the peak NDVI with the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) indices. The relationships between the northern annular mode and weather station data, accumulated precipitation derived from the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) dataset, accumulated growing degree-days (AGDDs) derived from the NCEP–Department of Energy Atmospheric Model Intercomparison Project (AMIP-II) reanalysis, and the number of snow days from the National Snow and Ice Data Center are investigated.
The analyses confirm strong relationships between the temporal behavior of temperature and precipitation and large-scale climatic variability across Eurasia. The authors find widespread influence of the northern annular mode (NAM) on the land surface phenologies across northern Eurasia affecting 200–300 Mha. The tundra ecoregions were especially impacted with significant results for about a quarter of the biome. The influence of the AO was also extensive (&gt;130 Mha) for the boreal forests. The AO appears to affect the Asian part of northern Eurasia more strongly than the NAO, especially for the NDVI peak position as a function of AGDD. Significant responses of vegetation timing to NAO and AO in northeastern Russia have not been as well documented as the seasonal advancement in Europe. The two Advanced Very High Resolution Radiometer NDVI datasets yield fields of LSP model parameter estimates that are more similar in dates of peak position than in dates for SOS and more similar for AO than for NAO. As a result, the authors conclude that peak position appears to be a more robust characteristic of land surface phenology than SOS to link vegetation dynamics to variability and change in regional and global climates.
A New Two-Moment Bulk Stratiform Cloud Microphysics Scheme in the Community Atmosphere Model, Version 3 (CAM3). Part I: Description and Numerical Tests
Authors: Morrison Hugh , Gettelman Andrew 
Published: February 2008

Abstract
A new two-moment stratiform cloud microphysics scheme in a general circulation model is described. Prognostic variables include cloud droplet and cloud ice mass mixing ratios and number concentrations. The scheme treats several microphysical processes, including hydrometeor collection, condensation/evaporation, freezing, melting, and sedimentation. The activation of droplets on aerosol is physically based and coupled to a subgrid vertical velocity. Unique aspects of the scheme, relative to existing two-moment schemes developed for general circulation models, are the diagnostic treatment of rain and snow number concentration and mixing ratio and the explicit treatment of subgrid cloud water variability for calculation of the microphysical process rates.
Numerical aspects of the scheme are described in detail using idealized one-dimensional offline tests of the microphysics. Sensitivity of the scheme to time step, vertical resolution, and numerical method for diagnostic precipitation is investigated over a range of conditions. It is found that, in general, two substeps are required for numerical stability and reasonably small time truncation errors using a time step of 20 min; however, substepping is only required for the precipitation microphysical processes rather than the entire scheme. A new numerical approach for the diagnostic rain and snow produces reasonable results compared to a benchmark simulation, especially at low vertical resolution. Part II of this study details results of the scheme in single-column and global simulations, including comparison with observations.
On Estimates of Historical North Atlantic Tropical Cyclone Activity*
Authors: Vecchi Gabriel A. , Knutson Thomas R. 
Published: February 2008

Abstract
In this study, an estimate of the expected number of Atlantic tropical cyclones (TCs) that were missed by the observing system in the presatellite era (between 1878 and 1965) is developed. The significance of trends in both number and duration since 1878 is assessed and these results are related to estimated changes in sea surface temperature (SST) over the “main development region” (“MDR”). The sensitivity of the estimate of missed TCs to underlying assumptions is examined. According to the base case adjustment used in this study, the annual number of TCs has exhibited multidecadal variability that has strongly covaried with multidecadal variations in MDR SST, as has been noted previously. However, the linear trend in TC counts (1878–2006) is notably smaller than the linear trend in MDR SST, when both time series are normalized to have the same variance in their 5-yr running mean series. Using the base case adjustment for missed TCs leads to an 1878–2006 trend in the number of TCs that is weakly positive, though not statistically significant, with p ∼ 0.2. The estimated trend for 1900–2006 is highly significant (+∼4.2 storms century−1) according to the results of this study. The 1900–2006 trend is strongly influenced by a minimum in 1910–30, perhaps artificially enhancing significance, whereas the 1878–2006 trend depends critically on high values in the late 1800s, where uncertainties are larger than during the 1900s. The trend in average TC duration (1878–2006) is negative and highly significant. Thus, the evidence for a significant increase in Atlantic storm activity over the most recent 125 yr is mixed, even though MDR SST has warmed significantly. The decreasing duration result is unexpected and merits additional exploration; duration statistics are more uncertain than those of storm counts. As TC formation, development, and track depend on a number of environmental factors, of which regional SST is only one, much work remains to be done to clarify the relationship between anthropogenic climate warming, the large-scale tropical environment, and Atlantic TC activity.
Diurnal Cycle of Surface Flows during 2004 NAME and Comparison to Model Reanalysis
Authors: Ciesielski Paul E. , Johnson Richard H. 
Published: February 2008

Abstract
During the North American Monsoon Experiment (NAME), an unprecedented surface dataset was collected over the core monsoon region. Observations from 157 surface sites in this region along with twice-daily Quick Scatterometer (QuikSCAT) oceanic winds were quality controlled and processed into a gridded dataset covering the domain (15°–40°N, 90°–120°W) at 1-h, 0.25° resolution for the period from 1 July to 15 August. Using this dataset, the mean, temporal variability, and diurnal characteristics of the monsoon surface flow are documented with detail not previously possible. Being independent of model data over land, these objectively analyzed surface products are compared to similar analyses from a special North American Regional Reanlysis for NAME (NARR_NAME) that was produced for the same period.
Observed surface fields indicate that a robust land–sea breeze circulation is present over most of the Gulf of California (GoC) region in response to the strong diurnal heating of landmasses on both sides of the gulf. Many details of this land–sea breeze circulation are either missing (e.g., the nighttime/early morning land breeze) or poorly represented in the NARR_NAME. Observations from high elevation sites in the Sierra Madre Occidental (SMO) show weak downslope flows (∼0.5 m s−1), near-saturated conditions, and low cloud bases during nighttime hours. These observations are consistent with the notion that high-terrain nocturnal clouds limit radiational cooling and, thus, nocturnal downslope flows as well. Over land, a cool and dry bias is observed in the NARR_NAME surface fields. This dry bias appears to limit the formation of nighttime cloudiness at high elevations, resulting in stronger radiational cooling at night and slope flows in the NARR_NAME that are 2–3 times stronger than observed. In addition, the daytime transition to surface convergence and rising motion over the western slopes of the SMO occurs about 3 h earlier in the NARR_NAME than observed, which indicates the tendency in the reanalyses to initiate the daily convective cycle too early, similar to that observed in operational forecast models over this region.
Following significant rainfall events, increased soil moisture and evapotranspiration due to vegetative green-up result in a smaller diurnal temperature signal over land and weaker slope flows over the SMO. In response to this weaker heating cycle, the magnitude and offshore extent of the land–sea breeze circulation is observed to diminish as the monsoon progresses.
Analysis of Idealized Tropical Cyclone Simulations Using the Weather Research and Forecasting Model: Sensitivity to Turbulence Parameterization and Grid Spacing
Authors: Hill Kevin A. , Lackmann Gary M. 
Published: February 2008

Abstract
The Weather Research and Forecasting Advanced Research Model (WRF-ARW) was used to perform idealized tropical cyclone (TC) simulations, with domains of 36-, 12-, and 4-km horizontal grid spacing. Tests were conducted to determine the sensitivity of TC intensity to the available surface layer (SL) and planetary boundary layer (PBL) parameterizations, including the Yonsei University (YSU) and Mellor–Yamada–Janjic (MYJ) schemes, and to horizontal grid spacing. Simulations were run until a quasi-steady TC intensity was attained. Differences in minimum central pressure (Pmin) of up to 35 hPa and maximum 10-m wind (V10max) differences of up to 30 m s−1 were present between a convection-resolving nested domain with 4-km grid spacing and a parent domain with cumulus parameterization and 36-km grid spacing. Simulations using 4-km grid spacing are the most intense, with the maximum intensity falling close to empirical estimates of maximum TC intensity. Sensitivity to SL and PBL parameterization also exists, most notably in simulations with 4-km grid spacing, where the maximum intensity varied by up to ∼10 m s−1 (V10max) or ∼13 hPa (Pmin). Values of surface latent heat flux (LHFLX) are larger in MYJ than in YSU at the same wind speeds, and the differences increase with wind speed, approaching 1000 W m−2 at wind speeds in excess of 55 m s−1. This difference was traced to a larger exchange coefficient for moisture, CQ, in the MYJ scheme. The exchange coefficients for sensible heat (Cθ) and momentum (CD) varied by &lt;7% between the SL schemes at the same wind speeds. The ratio Cθ/CD varied by &lt;5% between the schemes, whereas CQ/CD was up to 100% larger in MYJ, and the latter is theorized to contribute to the differences in simulated maximum intensity. Differences in PBL scheme mixing also likely played a role in the model sensitivity. Observations of the exchange coefficients, published elsewhere and limited to wind speeds &lt;30 m s−1, suggest that CQ is too large in the MYJ SL scheme, whereas YSU incorporates values more consistent with observations. The exchange coefficient for momentum increases linearly with wind speed in both schemes, whereas observations suggest that the value of CD becomes quasi-steady beyond some critical wind speed (∼30 m s−1).
Evaluation of the Noah Land Surface Model Using Data from a Fair-Weather IHOP_2002 Day with Heterogeneous Surface Fluxes
Authors: LeMone Margaret A. , Tewari Mukul , Chen Fei , Alfieri Joseph G. , Niyogi Dev 
Published: February 2008

AbstractSources of differences between observations and simulations for a case study using the Noah land surface model–based High-Resolution Land Data Assimilation System (HRLDAS) are examined for sensible and latent heat fluxes H and LE, respectively; surface temperature Ts; and vertical temperature difference T0 − Ts, where T0 is at 2 m. The observational data were collected on 29 May 2002, using the University of Wyoming King Air and four surface towers placed along a sparsely vegetated 60-km north–south flight track in the Oklahoma Panhandle. This day had nearly clear skies and a strong north–south soil-moisture gradient, with wet soils and widespread puddles at the south end of the track and drier soils to the north. Relative amplitudes of H and LE horizontal variation were estimated by taking the slope of the least squares best-fit straight line ΔLE/ΔH on plots of time-averaged LE as a function of time-averaged H for values along the track. It is argued that observed H and LE values departing significantly from their slope line are not associated with surface processes and, hence, need not be replicated by HRLDAS. Reasonable agreement between HRLDAS results and observed data was found only after adjusting the coefficient C in the Zilitinkevich equation relating the roughness lengths for momentum and heat in HRLDAS from its default value of 0.1 to a new value of 0.5. Using C = 0.1 and adjusting soil moisture to match the observed near-surface values increased horizontal variability in the right sense, raising LE and lowering H over the moist south end. However, both the magnitude of H and the amplitude of its horizontal variability relative to LE remained too large; adjustment of the green vegetation fraction had only a minor effect. With C = 0.5, model-input green vegetation fraction, and our best-estimate soil moisture, H, LE, ΔLE/ΔH, and T0 − Ts, were all close to observed values. The remaining inconsistency between model and observations—too high a value of H and too low a value of LE over the wet southern end of the track—could be due to HRLDAS ignoring the effect of open water. Neglecting the effect of moist soils on the albedo could also have contributed.
A Diagnostic Verification of the Precipitation Forecasts Produced by the Canadian Ensemble Prediction System
Authors: Peel Syd , Wilson Laurence J. 
Published: February 2008

Abstract
A comparatively long period of relative stability in the evolution of the Canadian Ensemble Forecast System was exploited to compile a large homogeneous set of precipitation forecasts. The probability of exceedance of a given threshold was computed as the fraction of ensemble member forecasts surpassing that threshold, and verified directly against observations from 36 stations across the country. These forecasts were stratified into warm and cool seasons and assessed against the observations through attributes diagrams, Brier skill scores, and areas under receiver operating characteristic curves. These measures were deemed sufficient to illuminate the salient features of a forecast system. Particular attention was paid to forecasts of 24-h accumulation, especially the exceedance of thresholds in the upper decile of station climates. The ability of the system to forecast extended dry periods was also explored.
Warm season forecasts for the 90th percentile threshold were found to be competitive with, even superior to, those for the cool season when verifying across the sample lumping together all of the stations. The relative skill of the forecasts in the two seasons depends strongly on station location, however. Moreover, the skill of the warm season forecasts rapidly drops below cool season values as the thresholds become more extreme. The verification, particularly of the cool season, is sensitive to the calibration of the gauge reports, which is complicated by the inclusion of snow events in the observational record.
Verification of an MSG Image Forecast Model: METCAST
Authors: Delgado Germán , de Valk Paul , Redaño Ángel , van der Veen Sibbo , Lorente Jerónimo 
Published: February 2008

Abstract
A validation of a very short-range forecast model is presented: the Meteosat Cloud Advection System (METCAST). The model forecasts IR (10.8 μm) images based on Meteosat Second Generation (MSG) data and uses ouput from the Royal Netherlands Meteorological Institute’s [Koninklijk Nederlands Meteorologisch Instituut (KNMI)] NWP model, the High Resolution Limited Area Model (HIRLAM). METCAST advects clouds and takes into account the evaporation–condensation processes in the atmosphere. To assimilate the satellite images into METCAST, an MSG image is converted to a modified image with coarser resolution. The relative performance of METCAST is evaluated, comparing the model results with persistence and a second nowcasting model called CineSat.
Two statistical techniques are used to evaluate the forecasts: (a) the computation of the BIAS, RMSE, and Hanssen and Kuiper (HK) discriminant for a cloud mask selected in the modified and forecast images and (b) the contiguous rain areas (CRAs) technique, which permits a decomposition of the mean-squared error (MSE) of cloud clusters in three components: displacement, intensity, and shape.
Five months of data, from June to November 2006 (August was not available), are used for this study. METCAST BIAS shows poor skill in comparison to CineSat and persistence. METCAST performs better in terms of the RMSE and HK discriminant. The CRA application reveals that although METCAST has a greater MSE volume component than CineSat, its displacement error component is smaller. Two interesting conclusions can be drawn: METCAST performs well when advecting cloudy pixels, but improvement in the atmospheric physics of the nowcast model may be required.
Operational Implementation of COSMIC Observations into NCEP’s Global Data Assimilation System
Authors: Cucurull L. , Derber J. C. 
Published: February 2008

Abstract
The next generation of NCEP’s Global Data Assimilation System became operational on 1 May 2007. This system incorporates the assimilation of global positioning system (GPS) radio occultation (RO) profiles from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission launched in April 2006. Roughly 1 yr after the launch of COSMIC, NCEP has begun operational use of this new dataset.
A preliminary assessment of this observation type was performed with an earlier version of NCEP’s analysis at a lower resolution. These experiments showed positive impact when GPS RO soundings from the Challenging Minisatellite Payload (CHAMP) mission were assimilated into the system in non–real time. In these earlier studies, two different forward operators for the GPS RO profiles were evaluated: one for refractivity and another one for bending angle.
In this paper, the data assimilation experiments with COSMIC observations that led NOAA/NCEP to assimilate COSMIC data into operations are described. The experiments were conducted with the current operational version of the code and at full operational resolution. Based on the results of the experiments analyzed here, profiles of refractivity were selected as the type of GPS RO observation to be assimilated. Further enhancement to the assimilation of bending angles is currently being evaluated at NCEP.
The results show a significant improvement of the anomaly correlation skill and a global reduction of the NCEP model bias and root-mean-square errors when COSMIC observations are assimilated into the system. The improvement is found for the temperature, geopotential heights, and moisture variables. Larger benefits are found in the Southern Hemisphere extratropics, although a significant positive impact is also found in the Northern Hemisphere extratropics and the tropics. Even if GPS RO observations cannot produce direct impact on the wind field through the adjoint of the forward operator, a slight benefit is found in the wind components.
The Little District That Could: The Process of Building District-School Trust
Authors: Chhuon Vichet , Gilkey Elizabeth M. , Gonzalez Margarita , Daly Alan J. , Chrispeels Janet H. 
Published: February 2008

Purpose: This article describes how trust emerged as an issue in one school district and the processes by which central office administrators enhanced trust with its school site leaders. Method: This exploratory participant observer case study uses multiple sources of data including surveys, interviews, observations, and documents collected during a 4-year period from central office and school site leaders. Findings: The article illustrates how a university partner can play a critical role in surfacing and bringing forth action on an undiscussable issue—trust between the central office and its schools—and the actions taken by the central office to address specific facets of trust: openness, communication, risk, and integrity. The site administrators' response to these actions revealed that trust can be developed at both the relational and organizational leadership levels. Significance to the Field: The study is significant in illustrating that building trust between the central office and school sites can be an essential step in an underperforming district and can serve as a resource in achieving and sustaining school district reform. It also shows that attending to specific facets of trust can be useful when examining the development of trust between school sites and the district office.