bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variational retrieval of cloud profile from ATOVS observations
Authors: Chevallier F. , Bauer P. , Mahfouf J.‐F. , Morcrette J.‐J. 
Published: January 2003

AbstractRadiation observations such as those from the Advanced Tiros Operational Vertical Sounder (ATOVS) on board the National Oceanic and Atmospheric Administration satellites provide information about cloud systems. However, like the other cloud observations they are not used in global data assimilation systems.As an essential step towards the assimilation of such data, a fast infrared and microwave radiation model and its linearized version (tangent linear and adjoint operators) have been developed for the computation of model‐equivalent cloud‐affected satellite radiances. They are used in a global one‐dimensional variational (1DVar) analysis of ATOVS radiances over open oceans. In non‐precipitating areas, it is shown that the 1D‐Var can remove, create and modify the cloud variables in each model layer to fit the observed radiances. The retrieved profiles have a degree of realism that will improve with better background constraint. This study is a first step towards the assimilation of clouds by variational analysis of clouds and dynamics at once, and will be further continued. Copyright © 2002 Royal Meteorological Society
Impact of new measurements of oxygen collision‐induced absorption on estimates of short‐wave atmospheric absorption
Authors: Chagas J. C. S. , Newnham D. A. , Smith K. M. , Shine K. P. 
Published: January 2003

AbstractA new set of laboratory measurements of the 1.06 µm and 1.27 µm collision‐induced bands of gaseous oxygen is presented. Absorption by pure oxygen and mixtures of oxygen with nitrogen and argon was observed using a Fourier transform spectrometer for temperatures between 230 and 295 K and pressures between 1 and 5 bar. Binary cross‐sections derived from the measurements were used to estimate the impacts on estimates of clear‐sky climatological absorption of solar irradiance. Monthly climatological atmospheric profiles averaged over 10° latitude belts were used to study the temporal and annual variation of the impacts. The global‐ and annual‐mean clear‐sky extra‐absorption was 0.58 W m−2 (about 1% of the absorption by water vapour and ozone), 0.42 W m−2 due to the 1.27 µm band and 0.16 W m−2 due to the 1.06 µm band. If estimates for other oxygen collision‐induced bands taken from previous studies are added, an overall impact of about 1 W m−2 results. Copyright © 2002 Royal Meteorological Society
Entropy as a basis for comparing and blending forecasts
Authors: Delsole Timothy 
Published: January 2003

AbstractThe use of Shannon's entropy for comparing forecasts, and for blending the forecasts into a single forecast with higher skill, is discussed. The basic idea is to examine the difference in the entropy of the error distributions. A particularly appealing approach is to decompose the entropy difference into a complete set of vectors in phase space that maximize or minimize the entropy difference. This decomposition identifies the patterns that the first model predicts with less error variance than the second, and those that the second model predicts with less error variance than the first. A ‘blended’ forecast with higher skill than either of the original forecasts can be constructed by an appropriate superposition of these patterns. In contrast to a linear regression correction, which minimizes only the total mean square error, the blended forecast predicts every pattern, and every local region, with less (or equal) error variance than either of the original forecasts. A filtering procedure is introduced to deal with the problem that, at long lead times, error variance fails to be an appropriate measure of skill.The above procedure is used to compare the 1 to 8‐day forecast skill of 500 hPa geopotential height predicted by the National Centers for Environmental Prediction (NCEP) reanalysis forecast model over a 40‐year period, against the forecast skill of a 200‐variable linear inverse model. The results show that the NCEP model predicts virtually every pattern with less error variance than the linear inverse model, provided that the pattern can be predicted with skill by at least one of the models. The best predicted patterns of each model (in an error variance sense) also have the longest decorrelation times, suggesting a strong relation between predictability and persistence. Copyright © 2002 Royal Meteorological Society
Empirical predictability study of October–December East African rainfall
Authors: Philippon N. , Camberlin P. , Fauchereau N. 
Published: January 2003

AbstractRelationships between September atmospheric dynamics over the global tropics and the East Africa short rains over the domain 4°S–4°N,30–39°E were investigated to define a seasonal rainfall forecasting scheme. From total and partial correlation analyses over the period 1968–97, three major and useful signals appear in September.
Precursor components of the October–December east–west circulation cell appear over the equatorial Indian Ocean (EIO). They were discovered through various indices of sea‐surface temperature (SST), zonal wind, vertical velocity and moist static energy computed over the western, central and eastern parts of the EIO. Principal component analyses were applied to these indices to form two synthetic indices which discriminate ocean–atmosphere variability in the eastern and western parts of the basin.
The Indian monsoon dynamics control the SSTs off the Somalia coast which are known to play an important role in the variability of the short rains.
Ridge–trough systems develop off South Africa which, when persistent enough, drive SST anomalies in the eastern tropical and equatorial Atlantic; these in turn are associated with anomalies in the middle levels over an equatorial band ranging from the Guinea Gulf to the western Indian Ocean.
The three September signals used as predictors in a multiple linear regression model explain 64% of the rainfall variance; a comparable efficiency is also achieved with a linear discriminant analysis model. Copyright © 2002 Royal Meteorological Society
A note on the occurrence of cloud in meteorologically sensitive areas and the implications for advanced infrared sounders
Authors: McNally A. P. 
Published: January 2003

AbstractThe geographical distribution and persistence of meteorologically sensitive areas (derived using adjoint forecast‐error tracking techniques) are investigated with respect to the occurrence of cloud. Using sensitivity patterns and cloud structures simulated from the ECMWF forecast model a high degree of correlation is found which, if realistic, could limit the ability of space‐based advanced infrared sounders to measure important meteorological features. The result underlines the need to develop techniques to use infrared sounder observations in the presence of cloud. Copyright © 2002 Royal Meteorological Society
A two‐dimensional numerical study of effects of vertical diffusion in frontal zones
Authors: Håkansson Måns 
Published: January 2003

AbstractParametrization of vertical diffusion tends to cause excessive smoothing of free‐troposphere frontal‐zone gradients in several forecast models. It has been observed that these models produce frontal structures that are diffuse, and that the dynamic stability of the frontal zones is higher in forecasts than in the corresponding analyses. Because of their inherent characteristics, frontal zones are sensitive to the way turbulent diffusion is parametrized in the model calculations. In several models, the estimation of vertical diffusion is based on the theory for mixing within boundary layers, assuming that the free‐tropospheric turbulent exchanges may be determined by an extension of boundary‐layer theory. This is an unrealistic assumption and consequently the observed model deficiency in describing upper frontal zones may to some significant degree be attributed to the crudeness of the vertical‐diffusion scheme. To address the problem, and in an effort to achieve further understanding of instabilities and turbulent fluxes associated with frontal dynamics, a two‐dimensional, semi‐geostrophic, nearly adiabatic model describing a vertical cross‐section through an idealized frontal zone is presented. The model utilizes the same kind of vertical‐diffusion scheme as numerous operational forecast models. Different types of instability generated in the model's interpretation of the frontogenesis process are presented and discussed in the context of vertical diffusion. Results show that turbulent diffusion as described by the parametrization scheme plays an important role in smoothing the frontal gradients, especially within the shear zone below the jet stream. Furthermore, the scheme shows sensitivity to the choice of parameters. Extreme values of wind shear and temperature gradient in frontal zones are likely to be weakened by the parametrized turbulent fluxes. These effects impact on short‐range forecasts but may also affect the results when modelling future climatological scenarios. Copyright © 2002 Royal Meteorological Society
Comparison of an axisymmetric hurricane model with the corresponding slab‐symmetric ITCZ model
Authors: Ulrich Wolfgang , Smith Roger K. , Chi Mai Nguyen 
Published: January 2003

AbstractWe examine the difference between the evolution of a hurricane‐like vortex in an axisymmetric model and that of an intertropical convergence‐zone‐ like disturbance in a slab‐symmetric model, starting from an initial disturbance with the same lateral structure. The main calculations are carried out using a hurricane model similar to that formulated by DeMaria and Pickle (1988), supplemented by a few calculations using a recently developed model by Nguyen et al. (2002). We show that, although the two flow configurations have many similarities, the slab‐symmetric model does not provide a dynamical surrogate for the hurricane. The main difference can be attributed to a geometrical factor in the formula for the conservation of absolute angular momentum in the axisymmetric model, which for an inward‐moving air parcel permits much larger tangential wind speeds to be attained than in the slab‐symmetric model. As a result, the sea‐surface latent‐heat flux, which is wind‐speed dependent, is much larger in the axisymmetric model, providing a larger energy supply to the growing disturbance per unit area than in the slab‐symmetric case. A further geometrical effect is that for the same inflow velocity profile in the boundary layer, there is larger convergence in the axisymmetric model. Because this convergence determines the deep cumulus mass flux in the DeMaria and Pickle model, the cumulus heating is larger in the axisymmetric configuration. The non‐development of the slab‐symmetric perturbation is a feature also of calculations using the Nguyen et al. (2002) model, even though two of the closures on the deep‐cumulus mass flux used do not depend on the mass convergence in the boundary layer. A few numerical details of the main model are described, including the method of solution, which differs from that used by DeMaria and Pickle (1988). Copyright © 2002 Royal Meteorological Society
Micrometeorological measurements of particle deposition velocities to moorland vegetation
Authors: Nemitz Eiko , Gallagher Martin W. , Duyzer Jan H. , Fowler David 
Published: January 2003

AbstractSize‐segregated particle number flux measurements using a micrometeorological technique, over the diameter (dp) range 0.1 to 3 µm and total particle number fluxes (dp>11 nm), are reported for Scottish moorland vegetation. Mean particle deposition velocities (Vd) range from 0.3 mm s−1 for 0.1 µm particles to more than 10 mm s−1 for 3 µm particles. On average, the measured size‐dependence of Vd is almost identical with the prediction by the widely used Slinn model, using the original parameters derived from wind‐tunnel studies. Within each size‐band Vd increased linearly with the friction velocity (u*). Total particle number fluxes measured with a condensation particle counter are dominated by the high concentration of small particles; therefore, this provides the first estimate of Vd for particles smaller than those that can be sized by optical techniques, for short vegetation. Values of Vd ranged from 0.2 to 0.6 mm s−1 as u* increased from 0.15 to 0.55 m s−1. These deposition rates are one order of magnitude smaller than have been observed for a pine forest stand. The analysis shows that, at least for super‐micron particles, the emission fluxes that were frequently observed at the study site need to be included in the computation of average values. At this site, upward fluxes are therefore more likely to be an artefact due to statistical constraints than a systematic physical phenomenon. Copyright © 2002 Royal Meteorological Society
Synoptic‐scale variability of the polar and subpolar tropopause: Data analysis and idealized PV inversions
Authors: Zängl G. , Wirth V. 
Published: January 2003

AbstractThe synoptic‐scale variability of the polar and subpolar tropopause is investigated based on radiosonde and European Centre for Medium‐Range Weather Forecasts Reanalysis data in combination with idealized potential vorticity (PV) inversions. A regression analysis is performed to examine the relationship between the relative vorticity at tropopause level, the tropopause displacement, the static stability above the tropopause, and the anomalies of tropopause temperature and potential temperature. The results are compared with regression coefficients computed from a large number of PV inversions. Generally, a cyclonically influenced tropopause is lower, warmer and potentially colder than average, and the static stability above the tropopause is reduced. The opposite is true under anticyclonic influence. Typically, a cyclonic vorticity of 10−5s−1 is associated with a decrease of the tropopause height by 150–200 m. Correspondingly, the mean vertical temperature gradient in the lowermost 2 km above the tropopause decreases by 0.2– 0.3 K km−1. Moreover, an increase of the tropopause height by 1 km is associated with a temperature decrease by 3–5 K and an increase of the potential temperature by 6–8 K. Except for the last one, these values do not depend significantly on the strength and the sign of the tropopause anomaly. Distinct annual cycles are observed in parts of the polar regions. Most of the relations found in the data can be reproduced with the PV inversions, except for the observed linearity for large tropopause displacements which is not always reproduced very well. The annual cycles can be partly explained with the aid of the PV inversions. Copyright © 2002 Royal Meteorological Society
Simulations of fall and early winter in the stratosphere
Authors: Manney G. L. , Lahoz W. A. , Sabutis J. L. , O'neill A. , Steenman‐Clark L. 
Published: January 2003

AbstractMechanistic model simulations of fall/early winter in the northern (November and December) and southern (May and June) stratosphere are compared with observational analyses to examine the skill of the model in simulating the state of the stratosphere, including both means and variability in key fields, during six winters. While detailed success varies from year to year, the model produces a realistic climatology of and variability in the evolution of winds, geopotential heights, temperatures and wave propagation in the early‐winter stratosphere. The variability and mean fields agree well with those in longer data records. The northern hemisphere (NH) simulations show a small cold bias when averaged over the 6 years, while the southern hemisphere (SH) simulations show a larger warm bias. Greater detailed success in simulations of alternate NH winters suggests the possibility of greater model skill during the westerly quasi‐biennial oscillation phase, although the short record and complexity of interactions between tropics and high latitudes preclude definitive identification of such a relationship. A prominent failing of the model when using Rayleigh friction to parametrize gravity‐wave drag is an inability to correctly reproduce the latitudinal structure of the stratospheric jet above about 7 hPa; this failing can be alleviated by using a non‐orographic gravity‐wave drag parametrization, at the expense of frequently degrading agreement of planetary‐wave phases and amplitudes. The success of the model in reproducing realistic climatology and variability makes these simulations useful for more detailed studies of transport and vortex evolution in early winter.Interhemispheric comparisons show that the early‐winter circulations are qualitatively similar in the NH and SH: they are dominated by a strengthening vortex, with most wave activity being in wave 1; they both have minor warmings in a preferred location and clustered around a preferred time—early December (early June) in the NH (SH); variability in the flow shows a crescent pattern of maximum variations near 60–80° latitude centred at the location of the minor warmings (over the dateline in the NH and in the South Pacific in the SH). Interhemispheric differences are primarily in the magnitude of the variability, with a more symmetric circulation and weaker minor warmings in the SH; this is in contrast to later in the winter, when large qualitative interhemispheric differences have been seen. Copyright © 2002 Royal Meteorological Society
Dynamic Portfolio Selection of NPD Programs Using Marginal Returns
Authors: Loch Christoph H. , Kavadias Stylianos 
Published: January 2003

Selecting program portfolios within a budget constraint is an important challenge in the management of new product development (NPD). Optimal portfolios are difficult to define because of the combinatorial complexity of project combinations. However, at the aggregate level of the strategic allocation of resources across product lines, investment in a program is not an all-or-nothing decision, but can be adjusted, resulting in a higher or lower program benefit (e.g., higher or lower quality). In some cases, resources can be adjusted even for individual projects.With this insight, one can use marginal analysis to optimally allocate the scarce budget. This article develops a dynamic model of resource allocation, taking into account multiple interacting factors, such as independent or correlated, uncertain market payoffs that change over time, increasing or decreasing returns from the NPD investment, carry-over of the investment benefit over multiple periods, and interactions across market segments. We characterize optimal policies in closed form and derive qualitative decision rules for managers.
Investigating the Effects of Store-Brand Introduction on Retailer Demand and Pricing Behavior
Authors: Chintagunta Pradeep K. , Bonfrer André , Song Inseong 
Published: January 2003

Researchers have recently been interested in studying the drivers of store-brand success as well as factors that motivate retailers to introduce store brands. In this paper, we study the effects of the introduction of a store-brand into a particular product category. Specifically, we are interested in the effect of store-brand introduction on the demand as well as on the supply side. On the demand side, we investigate the changes in preferences for the national brands and price elasticities in the category. On the supply side, we study the effects of the new entrant on the interactions between the national brand manufacturers and the retailer introducing the store brand, including how these interactions influence the retailer's pricing behavior. In doing so, we are also able to test whether the observed data are consistent with some of the commonly used assumptions regarding retailer pricing behavior. For the demand specification we use a random coefficients logit model that allows for consumer heterogeneity. The model parameters are estimated using aggregate data while explicitly accounting for endogeneity in retail prices. Our empirical results obtained from the oats product category based on store-level data from a multistore retail chain indicate that the store-brand introduction generates notable changes within the category. The store-brand introduction coincides with an increase in the retailer's margins for the national brand. We find that the preferences for the national brand are relatively unaffected by the introduction of the store-brand. While consumers are, in general, more price sensitive (in terms of elasticities) than they were prior to store-brand introduction, a statistical test of the differences in mean price elasticities across stores and between the two regimes fails to reject the hypothesis of no change in these elasticities. Elasticities in specific stores however, do increase after the store brand is introduced. We also find that there is considerable heterogeneity in the preferences for the store-brand. On the supply side, we test several forms of manufacturer-retailer interactions to identify retailer pricing behavior most consistent with the data. Our results indicate that the data reject several, commonly imposed, forms of interactions. In examining the nature of manufacturer interactions with the retailer, we find that the manufacturer of the national brand appears to take a softer stance in its interactions with the retailer subsequent to store-brand entry. This finding is consistent with academic research and with articles in the popular press which suggest that the store brand enhances the retailer's bargaining ability vis-à-vis the manufacturers of the national brands. We also provide results from a second product category frozen pasta) that are largely consistent with those found in the oats category.
Augmenting Conjoint Analysis to Estimate Consumer Reservation Price
Authors: Jedidi Kamel , Zhang Z. John 
Published: January 2003

Consumer reservation price is a key concept in marketing and economics. Theoretically, this concept has been instrumental in studying consumer purchase decisions,competitive pricing strategies,and welfare economics. Managerially,knowledge of consumer reservation prices is critical for implementing many pricing tactics such as bundling,tar get promotions,nonlinear pricing,and one-to-one pricing,and for assessing the impact of marketing strategy on demand. Despite the practical and theoretical importance of this concept, its measurement at the individual level in a practical setting proves elusive. We propose a conjoint-based approach to estimate consumer-level reservation prices. This approach integrates the preference estimation of traditional conjoint with the economic theory of consumer choice. This integration augments the capability of traditional conjoint such that consumers' reservation prices for a product can be derived directly from the individuallevel estimates of conjoint coefficients. With this augmentation,we can model a consumer's decision of not only which product to buy,but also whether to buy at all in a category. Thus, we can simulate simultaneously three effects that a change in price or the introduction of a new product may generate in a market: the customer switching effect,the cannibalization effect,and the market expansion effect. We show in a pilot application how this approach can aid product and pricing decisions. We also demonstrate the predictive validity of our approach using data from a commercial study of automobile batteries.