Accuracy of Simulated Diurnal Valley Winds in the Swiss Alps: Influence of Grid Resolution, Topography Filtering, and Land Surface Datasets

We evaluate the near-surface representation of thermally driven winds in the Swiss Alps in a numerical weather prediction model at km-scale resolution. In addition, the influence of grid resolution (2.2 km and 1.1 km), topography filtering, and land surface datasets on the accuracy of the simulated valley winds is investigated. The simulations are evaluated against a comprehensive set of surface observations for an 18-day fair-weather summer period in July 2006. The episode is characterized by strong diurnal wind systems and the formation of shallow convection over the mountains, which transitions to precipitating convection in some areas. The near-surface winds (10 m above ground level) follow a typical diurnal pattern with strong daytime up-valley flow and weaker nighttime down-valley flow. At a 2.2 km resolution the valley winds are poorly simulated for most stations, while at a 1.1 km resolution the diurnal cycle of the valley winds is well represented in most large (e.g., Rhein valley at Chur and Rhone valley at Visp) and medium-sized valleys (e.g., Linth valley at Glarus). In the smaller valleys (e.g., Maggia valley at Cevio), the amplitude of the valley wind is still significantly underestimated, even at a 1.1 km resolution. Detailed sensitivity experiments show that the use of high-resolution land surface datasets, for both the soil characteristics as well as for the land cover, and reduced filtering of the topography are essential to achieve good performance at a 1.1 km resolution

Nonlinear bias correction for satellite data assimilation using Taylor series polynomials

Output from a high-resolution ensemble data assimilation system is used to assess the ability of an innovative nonlinear bias correction (BC) method that uses a Taylor series polynomial expansion of the observation-minus background departures to remove linear and nonlinear conditional biases from all-sky satellite infrared brightness temperatures. Univariate and multivariate experiments were performed in which the satellite zenith angle and variables sensitive to clouds and water vapor were used as the BC predictors. The results showed that even though the bias of the entire observation departure distribution is equal to zero regardless of the order of the Taylor series expansion, there are often large conditional biases that vary as a nonlinear function of the BC predictor. The linear 1st order term had the largest impact on the entire distribution as measured by reductions in variance; however, large conditional biases often remained in the distribution when plotted as a function of the predictor. These conditional biases were typically reduced to near zero when the nonlinear 2nd and 3rd order terms were used. The univariate results showed that variables sensitive to the cloud top height are effective BC predictors especially when higher order Taylor series terms are used. Comparison of the statistics for clear-sky and cloudy-sky observations revealed that nonlinear departures are more important for cloudy-sky observations as signified by the much larger impact of the 2nd and 3rd order terms on the conditional biases. Together, these results indicate that the nonlinear BC method is able to effectively remove the bias from all-sky infrared observation departures

Revisiting the latent heating contribution to foehn warming - Lagrangian analysis of two foehn events over the Swiss Alps

Foehn flows are typically associated with warm air temperatures. Though several theories for the so-called foehn air warming have been developed over the past century, no conclusion about the most important mechanism has been reached. The development of new methods to calculate accurate air-mass trajectories over complex topography has opened up a new perspective on this question. Air-mass-trajectories derived from wind-field data from COSMO model simulations with 20 s temporal resolution are used in this study to investigate the origin of the foehn air and the contribution of adiabatic and diabatic processes for two foehn events in the Swiss Alps, with a focus on the Rhine valley. The first foehn event investigated has no precipitation on the upstream side of the Alps. The majority of air parcels stem from upstream altitudes above 1.8 km and most of the foehn air warming is due to adiabatic descent (∼79%). In the second event investigated, significant upstream precipitation occurred. For this case, a significantly larger fraction of the foehn air parcels originate within the lowest 2 km of the upstream atmosphere (up to 70%). Adiabatic descent accounts for the largest part of the temperature change (∼70%), while moist diabatic processes explain about 60% of the potential temperature change. The vertical displacement across the Alpine range is correlated with the diabatic temperature change: parcels strongly heated by condensation, deposition and freezing are in general found at high altitudes above the foehn valley, while parcels affected by diabatic cooling through evaporation, sublimation and melting arrive closer to the valley floor. The high-resolution trajectories also indicate a much more complicated vertical and horizontal flow pattern than generally assumed, with several distinct air streams upstream of the mountain range and vertical ‘scrambling’ of air masses

Idealized large-eddy and convection-resolving simulations of moist convection over mountainous terrain

On summertime fair-weather days, thermally driven wind systems play an important role in determining the initiation of convection and the occurrence of localized precipitation episodes over mountainous terrain. This study compares the mechanisms of convection initiation and precipitation development within a thermally driven flow over an idealized double-ridge system in large-eddy (LESs) and convection-resolving (CRM) simulations. First, LES at a horizontal grid spacing of 200 m is employed to analyze the developing circulations and associated clouds and precipitation. Second, CRM simulations at horizontal grid length of 1 km are conducted to evaluate the performance of a kilometer-scale model in reproducing the discussed mechanisms. Mass convergence and a weaker inhibition over the two ridges flanking the valley combine with water vapor advection by upslope winds to initiate deep convection. In the CRM simulations, the spatial distribution of clouds and precipitation is generally well captured. However, if the mountains are high enough to force the thermally driven flow into an elevated mixed layer, the transition to deep convection occurs faster, precipitation is generated earlier, and surface rainfall rates are higher compared to the LES. Vertical turbulent fluxes remain largely unresolved in the CRM simulations and are underestimated by the model, leading to stronger upslope winds and increased horizontal moisture advection toward the mountain summits. The choice of the turbulence scheme and the employment of a shallow convection parameterization in the CRM simulations change the strength of the upslope winds, thereby influencing the simulated timing and intensity of convective precipitation

Elementos que Impactam a Construção de um Modelo de Governança Pública no Brasil: O Caso da Marinha do Brasil

This paper investigated the essential elements for building a public governance model in Brazil, with the objective of proposing an analytical framework with contributions from different theoretical lenses. The concepts and debates emerging from the literature were analyzed along with the normative instruments that guide the principles of public governance in Brazil, and, finally, empirical research was carried out in a Brazilian public organization (Brazilian Navy). The study found that, in the Brazilian context, external control bodies have been playing the role of giving rise to an increase in governance levels within the scope of public administration, restricting at first its application to the perspective of control, and involving, to a lesser extent, the concepts of governance as instruments for achieving political administrative effectiveness. This result corroborates the need to develop more comprehensive proposals related to public value creation involving the structuring of both political and administrative bodies in Brazil.Este artigo buscou investigar os elementos que impactam a construção de um modelo de governança pública no Brasil, com o objetivo de propor uma estrutura analítica (framework) com contribuições de diferentes lentes teóricas. Para isso, foram analisados os conceitos e debates emergentes da literatura, os instrumentos normativos que norteiam os princípios da governança pública no Brasil, e, por fim, foi realizada uma pesquisa empírica em uma organização pública brasileira (Marinha do Brasil). Como resultado, observou-se que, no contexto brasileiro, os órgãos de controle externo vêm exercendo o papel de ensejar um aumento dos níveis de governança no âmbito da administração pública, restringindo, em um primeiro momento, sua aplicação à perspectiva do controle, evoluindo em menor grau os conceitos da governança como instrumento para realização da efetividade político-administrativa. Esse resultado corrobora a necessidade de se pensar em propostas mais abrangentes relativas à criação de valor público, envolvendo tanto a estruturação política quanto administrativa brasileira

Elements That Impact Building a Public Governance Model in Brazil: The Case of the Brazilian Navy

This paper investigated the essential elements for building a public governance model in Brazil, with the objective of proposing an analytical framework with contributions from different theoretical lenses. The concepts and debates emerging from the literature were analyzed along with the normative instruments that guide the principles of public governance in Brazil, and, finally, empirical research was carried out in a Brazilian public organization (Brazilian Navy). The study found that, in the Brazilian context, external control bodies have been playing the role of giving rise to an increase in governance levels within the scope of public administration, restricting at first its application to the perspective of control, and involving, to a lesser extent, the concepts of governance as instruments for achieving political-administrative effectiveness. This result corroborates the need to develop more comprehensive proposals related to public value creation involving the structuring of both political and administrative bodies in Brazil

Avaliação de Fatores que Influenciam na Implantação de Programas de Gestão de Riscos e de Integridade da Marinha do Brasil

This study aimed to evaluate the factors that most influence the implementation of Risk Management (RMP) and Integrity (IMP) Programs in order to identify the main obstacles and strategies to face resistance to change. To this end, a Systematic Literature Review was conducted, followed by content analysis and categorization, which enabled the development and application of the questionnaire with 39 assertions about the implementation of the Programs, with 74 valid responses obtained. Due to the differences identified in the application of the Chi-square Test in the responses of the three groups of respondents, the quantitative study, using the t-Test, was carried out using the 48 valid responses of the members who work in the operation of the RMP. Despite the small sample size, the analysis of the results suggests that the Brazilian Navy is in the initial phase of implementing the RMP and IMP. The results suggest that Training is an obstacle to the implementation of the RMP, which may hinder the governance of the Program. The results also indicate the dependence of the IMP on the implementation of the RMP. Furthermore, factors related to leadership performance to support integrity, reduce failures in internal communication and barriers to transparency, and reduce failures in identifying, analyzing, and executing responses to risks suggest that these factors are still poorly consolidated, perhaps due to the characteristics of the military environment where secrecy and security are essential. The research also confirmed that strategies to reduce resistance to change related to having clear and constant communication, the involvement and participation of military and civilian personnel, practicing recognition and reward, and, most importantly, having leadership that sets an example are essential to implementing changes based on the RMP and IMP.Este estudo teve por objetivo avaliar os fatores que mais influenciam a implantação de Programas de Gestão de Riscos (PGR) e de Integridade (PGI) com vistas a identificar os principais obstáculos e as estratégias para enfrentar a resistência às mudanças. Para isso, foi conduzida  uma Revisão Sistemática de Literatura, seguida de análise de conteúdo e categorização, o que possibilitou o desenvolvimento e aplicação do questionário com 39 assertivas sobre a implantação dos Programas, sendo obtidas 74 respostas válidas. Devido às diferenças identificadas na aplicação do Teste Qui-quadrado nas respostas dos três grupos de respondentes, o estudo quantitativo, por meio o Teste t, foi feito utilizando as 48 respostas válidas dos membros que trabalham na operação do PGR. Apesar do pequeno tamanho da amostra, a análise dos resultados sugere que a Marinha do Brasil esteja na fase inicial da implantação dos PGI e PGR. Os resultados sugerem que a Capacitação é um obstáculo à implantação do PGR, o que pode dificultar a governança do Programa. Os resultados também indicam a dependência do PGI em relação à implantação do PGR. Além disso, os fatores relacionados à atuação das lideranças para apoiar a integridade, para reduzir as falhas na comunicação interna e as barreiras à transparência e reduzir as falhas na identificação, análise e execução das respostas aos riscos sugerem que esses fatores estejam ainda pouco consolidados, talvez devido a características próprias do ambiente militar onde é fundamental o sigilo e a segurança. A pesquisa confirmou ainda que as estratégias para reduzir a resistência às mudanças relacionadas a ter uma comunicação clara e constante, ao envolvimento e participação dos militares e civis, a praticar reconhecimento e recompensa e, principalmente, a contar com uma liderança que dá o exemplo são essenciais para implementar mudanças com base no PGR e PGI

The “Grey Zone” cold air outbreak global model intercomparison: A cross evaluation using large-eddy simulations

A stratocumulus-to-cumulus transition as observed in a cold air outbreak over the North Atlantic Ocean is compared in global climate and numerical weather prediction models and a large-eddy simulation model as part of the Working Group on Numerical Experimentation “Grey Zone” project. The focus of the project is to investigate to what degree current convection and boundary layer parameterizations behave in a scale-adaptive manner in situations where the model resolution approaches the scale of convection. Global model simulations were performed at a wide range of resolutions, with convective parameterizations turned on and off. The models successfully simulate the transition between the observed boundary layer structures, from a well-mixed stratocumulus to a deeper, partly decoupled cumulus boundary layer. There are indications that surface fluxes are generally underestimated. The amount of both cloud liquid water and cloud ice, and likely precipitation, are under-predicted, suggesting deficiencies in the strength of vertical mixing in shear-dominated boundary layers. But also regulation by precipitation and mixed-phase cloud microphysical processes play an important role in the case. With convection parameterizations switched on, the profiles of atmospheric liquid water and cloud ice are essentially resolution-insensitive. This, however, does not imply that convection parameterizations are scale-aware. Even at the highest resolutions considered here, simulations with convective parameterizations do not converge toward the results of convection-off experiments. Convection and boundary layer parameterizations strongly interact, suggesting the need for a unified treatment of convective and turbulent mixing when addressing scale-adaptivity

Minimizing the number of apertures in multileaf collimator sequencing with field splitting

In this paper we consider the problem of decomposing a given integer matrix A into an integer conic combination of consecutive-ones matrices with a bound on the number of columns per matrix. This problem is of relevance in the realization stage of intensity modulated radiation therapy (IMRT) using linear accelerators and multileaf collimators with limited width. Constrained and unconstrained versions of the problem with the objectives of minimizing beam-on time and decomposition cardinality are considered. We introduce a new approach which can be used to find the minimum beam-on time for both constrained and unconstrained versions of the problem. The decomposition cardinality problem is shown to be NP-hard and an approach is proposed to solve the lexicographic decomposition problem of minimizing the decomposition cardinality subject to optimal beam-on time