Parametrization Research Papers - Academia.edu (original) (raw)

Abstract—Strong and stormy winds are the most dangerous weather phenomena in the resort region of Lake Balaton, and that is why the weather warnings are of great importance for the protection of life and property. In summer the wind... more

Abstract—Strong and stormy winds are the most dangerous weather phenomena in the resort region of Lake Balaton, and that is why the weather warnings are of great
importance for the protection of life and property. In summer the wind storms breaking out suddenly in the area of Lake Balaton are generally associated with thunderstorms. In wind forecasting, one of the most difficult tasks is to predict the degree of wind strengthening associated with thunderstorms, as it may vary according to the synoptic situation. This paper studies how correct and useful information is available in the products of the limited area numerical weather prediction model ALADIN for forecasting the spatial and temporal intensity of organised convection using an interactive nowcasting decisionmaking procedure. The procedure provides a more objective foundation for storm warnings at Lake Balaton. The obtained results are completed by the statistical investigation for the application of meteograms to the storm warning practice. Key-words: very short range forecast, nowcasting, storm warning, decision-making procedure, limited area numerical weather p

Shear strength is an important parameter for interpreting the stability of simulated snow covers. In the SNOWPACK model, snow shear strength is estimated as a function of snow density using expressions for different grain types. In the... more

Shear strength is an important parameter for interpreting the stability of simulated snow covers. In the SNOWPACK model, snow shear strength is estimated as a function of snow density using expressions for different grain types. In the model, shear strength changes discontinuously as grain type changes from rounded to faceted grains (and vice versa), but in nature, shear strength changes

This paper focuses on the study of certain classes of Boolean functions that have appeared in several different contexts. Nested canalyzing functions have been studied recently in the context of Boolean network models of gene regulatory... more

This paper focuses on the study of certain classes of Boolean functions that have appeared in several different contexts. Nested canalyzing functions have been studied recently in the context of Boolean network models of gene regulatory networks. In the same context, polynomial functions over finite fields have been used to develop network inference methods for gene regulatory networks. Finally, unate cascade functions have been studied in the design of logic circuits and binary decision diagrams. This paper shows that the class of nested canalyzing functions is equal to that of unate cascade functions. Furthermore, it provides a description of nested canalyzing functions as a certain type of Boolean polynomial function. Using the polynomial framework one can show that the class of nested canalyzing functions, or, equivalently, the class of unate cascade functions, forms an algebraic variety which makes their analysis amenable to the use of techniques from algebraic geometry and com...

This paper documents the sensitivity of the modeled evolution of the East Asian summer monsoon (EASM) to physical parameterization using the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM). To this end,... more

This paper documents the sensitivity of the modeled evolution of the East Asian summer monsoon (EASM) to physical parameterization using the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM). To this end, perfect boundary condition experiments driven by analysis data are designed for August 2003 to investigate the individual role of the surface processes, boundary layer, and convection parameterization on the simulated monsoon. Also, 10-yr June–August (JJA) simulations from 1996 to 2005 are performed to evaluate the overall impacts of these revisions on the simulated EASM climatology. The one-month simulation for August 2003 reveals that the experiment with a realistic distribution of land use conditions and vegetation and smaller thermal roughness length simulates higher temperature and geopotential height. On the other hand, in the experiment with an improved boundary layer scheme, the rainfall amount is slightly decreased due to reduced vertical m...

Three-dimensional simulations of the daytime thermally induced valley wind system for an idealized valley–plain configuration, obtained from nine nonhydrostatic mesoscale models, are compared with special emphasis on the evolution of the... more

Three-dimensional simulations of the daytime thermally induced valley wind system for an idealized valley–plain configuration, obtained from nine nonhydrostatic mesoscale models, are compared with special emphasis on the evolution of the along-valley wind. The models use the same initial and lateral boundary conditions, and standard parameterizations for turbulence, radiation, and land surface processes. The evolution of the mean along-valley wind (averaged over the valley cross section) is similar for all models, except for a time shift between individual models of up to 2 h and slight differences in the speed of the evolution. The analysis suggests that these differences are primarily due to differences in the simulated surface energy balance such as the dependence of the sensible heat flux on surface wind speed. Additional sensitivity experiments indicate that the evolution of the mean along-valley flow is largely independent of the choice of the dynamical core and of the turbule...

The Canadian Middle Atmosphere Model is used to examine the sensitivity of simulated climate to conservation of momentum in gravity wave drag parameterization. Momentum conservation requires that the parameterized gravity wave momentum... more

The Canadian Middle Atmosphere Model is used to examine the sensitivity of simulated climate to conservation of momentum in gravity wave drag parameterization. Momentum conservation requires that the parameterized gravity wave momentum flux at the top of the model be zero and corresponds to the physical boundary condition of no momentum flux at the top of the atmosphere. Allowing momentum flux to escape the model domain violates momentum conservation. Here the impact of momentum conservation in two sets of model simulations is investigated. In the first set, the simulation of present-day climate for two model-lid height configurations, 0.001 and 10 hPa, which are identical below 10 hPa, is considered. The impact of momentum conservation on the climate with the model lid at 0.001 hPa is minimal, which is expected because of the small amount of gravity wave momentum flux reaching 0.001 hPa. When the lid is lowered to 10 hPa and momentum is conserved, there is only a modest impact on t...

Meteorological model errors caused by imperfect parameterizations generally cannot be overcome simply by optimizing initial and boundary conditions. However, advanced data assimilation methods are capable of extracting significant... more

Meteorological model errors caused by imperfect parameterizations generally cannot be overcome simply by optimizing initial and boundary conditions. However, advanced data assimilation methods are capable of extracting significant information about parameterization behavior from the observations, and thus can be used to estimate model parameters while they adjust the model state. Such parameters should be identifiable, meaning that they must have a detectible impact on observable aspects of the model behavior, their individual impacts should be a monotonic function of the parameter values, and the various impacts should be clearly distinguishable from each other. A sensitivity analysis is conducted for the parameters within the Asymmetrical Convective Model, version 2 (ACM2) planetary boundary layer (PBL) scheme in the Weather Research and Forecasting model in order to determine the parameters most suited for estimation. A total of 10 candidate parameters are selected from what is, ...

Forecasts of southeast Pacific stratocumulus at 20°S and 85°W during the East Pacific Investigation of Climate (EPIC) cruise of October 2001 are examined with the ECMWF model, the Atmospheric Model (AM) from GFDL, the Community Atmosphere... more

Forecasts of southeast Pacific stratocumulus at 20°S and 85°W during the East Pacific Investigation of Climate (EPIC) cruise of October 2001 are examined with the ECMWF model, the Atmospheric Model (AM) from GFDL, the Community Atmosphere Model (CAM) from NCAR, and the CAM with a revised atmospheric boundary layer formulation from the University of Washington (CAM-UW). The forecasts are initialized from ECMWF analyses and each model is run for 3–5 days to determine the differences with the EPIC field observations. Observations during the EPIC cruise show a well-mixed boundary layer under a sharp inversion. The inversion height and the cloud layer have a strong and regular diurnal cycle. A key problem common to the models is that the planetary boundary layer (PBL) depth is too shallow when compared to EPIC observations. However, it is suggested that improved PBL depths are achieved with more physically realistic PBL schemes: at one end, CAM uses a dry and surface-driven PBL scheme an...

The South American low level jet (SALLJ) of the Eastern Andes is investigated with Regional Climate Model version 3 (RegCM3) simulations during the 2002–2003 austral summer using two convective parameterizations (Grell and Emanuel). The... more

The South American low level jet (SALLJ) of the Eastern Andes is investigated with Regional Climate Model version 3 (RegCM3) simulations during the 2002–2003 austral summer using two convective parameterizations (Grell and Emanuel). The simulated ...

The aim of any radiodiagnostic procedure is to obtain a high quality image while keeping the dose to the patients as low as practicable. Significant problems and wide variations in the current mammography practice could be avoided by... more

The aim of any radiodiagnostic procedure is to obtain a high quality image while keeping the dose to the patients as low as practicable. Significant problems and wide variations in the current mammography practice could be avoided by performing regularly a quality control programme (QCP). The technical QCP consists of tests on the characteristics of the X ray equipment, dose, image quality. dark room, sensitometry, and viewing conditions. The judgement of the overall effectiveness of a QCP is, in general, left to a subjective evaluation and sometimes fluctuations in the results are not easily interpreted. The aim of this paper is to introduce an objective evaluation of the impact of a QCP through a statistical analysis of the results of the measurements. The proposed statistical methods are a randomisation test named Shuffling Without Replacement and the Student-t test. Another application of the statistical tests is to validate the frequency of the measurements chosen for a single parameter by a centre performing a QCP.

A mosaic-type parameterization of subgrid-scale topography and land use ( SubBATS ) is applied for a high-resolution regional climate simulation over the Alpine region with a regional climate model (RegCM3). The model coarse-gridcell size... more

A mosaic-type parameterization of subgrid-scale topography and land use ( SubBATS ) is applied for a high-resolution regional climate simulation over the Alpine region with a regional climate model (RegCM3). The model coarse-gridcell size in the control simulation is 15 km while the subgridcell size is 3 km. The parameterization requires disaggregation of atmospheric variables from the coarse grid to the subgrid and aggregation of surface fluxes from the subgrid to the coarse grid. Two 10-yr simulations (1983–92) are intercompared, one without (CONT) and one with (SUB) the subgrid scheme. The authors first validate the CONT simulation, showing that it produces good quality temperature and precipitation statistics, showing in particular a good performance compared to previous runs of this region. The subgrid scheme produces much finer detail of temperature and snow distribution following the topographic disaggregation. It also tends to form and melt snow more accurately in response t...

ABSTRACT: Real cities are comprised of a diverse, random arrangement of building positions, shapes, and sizes. Yet most of the urban parameterisations thus far developed share the assumption that a city is made up of either a regular... more

ABSTRACT: Real cities are comprised of a diverse, random arrangement of building positions, shapes, and sizes. Yet most of the urban parameterisations thus far developed share the assumption that a city is made up of either a regular array of parallelepipeds or infinitely long canopies. The inputs to these models, which include street width, building width, building density and a statistical representation of building heights, are generally obtained through quantitative field surveys (which are very slow and time consuming to perform) or qualitative estimates from Digital Elevation Model. But in performing this geometric abstraction there is no way to ensure that the total built surfaces and volumes of the simplified geometry match those of the actual city, or more importantly, that the energy and momentum exchanges are equivalent. In this paper, we aim to test the central hypothesis that cities can be accurately represented by a regular array of parallelepipeds or canopies. For thi...

Transcranial Doppler (TCD) units measure blood velocity in the middle cerebral artery (MCA) and are used to examine the effects of pharmacological agents. The units actually measure the average of the maximum blood velocity envelope... more

Transcranial Doppler (TCD) units measure blood velocity in the middle cerebral artery (MCA) and are used to examine the effects of pharmacological agents. The units actually measure the average of the maximum blood velocity envelope (aveV(max)) and it is assumed that changes in aveV(max) follow changes in the true mean velocity (aveV(mean)). This may not be true if there are changes in velocity profile. Results from previous TCD studies using acetazolamide (ACZ) and caffeine were examined for evidence for changes in velocity profile. ACZ increased aveV(max) by 21% (95% CI 13 to 29%) and aveV(mean) by 14% (95% CI 9 to 19%). Caffeine decreased aveV(max) by 8% (95% CI 4 to 12%) and aveV(mean) by 5% (95% CI 4% increase to 13% decrease). In both cases, the true change, measured using aveV(mean) was lower, indicating possible changes in velocity profile. We conclude that the possibility of changes in velocity profile must be considered when using TCD to quantify changes in blood velocity.

The South American low level jet (SALLJ) of the Eastern Andes is investigated with Regional Climate Model version 3 (RegCM3) simulations during the 2002–2003 austral summer using two convective parameterizations (Grell and Emanuel). The... more

The South American low level jet (SALLJ) of the Eastern Andes is investigated with Regional Climate Model version 3 (RegCM3) simulations during the 2002–2003 austral summer using two convective parameterizations (Grell and Emanuel). The simulated ...