Atmospheric instability, cloud formation and precipitation processes

2004 ◽  
pp. 121-151
Keyword(s):  
Cloud Formation ◽  
Atmospheric Instability ◽  
Precipitation Processes

scholarly journals A process-based evaluation of the Intermediate Complexity Atmospheric Research Model (ICAR) 1.0.1

2020 ◽  
Author(s):  
Johannes Horak ◽  
Marlis Hofer ◽  
Ethan Gutmann ◽  
Alexander Gohm ◽  
Mathias W. Rotach
Keyword(s):  
Water Vapor ◽  
Wind Field ◽  
Wave Theory ◽  
Cloud Formation ◽  
Mountain Wave ◽  
Atmospheric Research ◽  
Intermediate Complexity ◽  
Precipitation Processes ◽  
The Right

Abstract. The verification of models in general is a non-trivial task and can, due to epistemological and practical reasons, never be considered as complete. As a consequence, a model may yield correct results for the wrong reasons, i.e. by a different chain of processes than found in observations. While in the atmospheric sciences guidelines and strategies exist to maximize the chances that models are correct for the right reasons, these are mostly applicable to full-physics models, such as numerical weather prediction models. The Intermediate Complexity Atmospheric Research (ICAR) model is an atmospheric model employing linear mountain wave theory to represent the wind field. In this wind field atmospheric quantities, such as temperature and moisture are advected and a microphysics scheme is applied to represent the formation of clouds and precipitation. This study conducts an in-depth process-based evaluation of ICAR, employing idealized simulations to increase the understanding of the model and develop recommendations to maximize the probability that its results are correct for the right reasons. To contrast the obtained results from the linear-theory-based ICAR model to a full-physics model, idealized simulations with the Weather Research and Forecasting (WRF) model are conducted. The impact of the developed recommendations is then demonstrated with a case study for the South Island of New Zealand. The results of this investigation suggest three modifications to improve different aspects of ICAR simulations. The representation of the wind field within the domain improves when the dry and the moist Brunt-Väisälä frequencies are calculated in accordance to linear mountain wave theory from the unperturbed base state rather than from the time-dependent perturbed atmosphere. Imposing boundary conditions at the upper boundary different to the standard zero gradient boundary condition is shown to reduce errors in the potential temperature and water vapor fields. Furthermore, the results show that there is a lowest possible model top elevation that should not be undercut to avoid influences of the model top on cloud and precipitation processes within the domain. The method to determine the lowest model top elevation is applied to both the idealized simulations as well as the real terrain case study. Notable differences between the ICAR and WRF simulations are observed across all investigated quantities such as the wind field, water vapor and hydrometeor distributions, and the distribution of precipitation. The case study indicates a large shift in the precipitation maximum for the ICAR simulation employing the developed recommendations in contrast to an unmodified version of ICAR. The cause for the shift is found in influences of the model top on cloud formation and precipitation processes in the ICAR simulations. Furthermore, the results show that when model skill is evaluated from statistical metrics based on comparisons to surface observations only, such analysis may not reflect the skill of the model in capturing atmospheric processes such as gravity waves and cloud formation.

scholarly journals A process-based evaluation of the Intermediate Complexity Atmospheric Research Model (ICAR) 1.0.1

2021 ◽  
Vol 14 (3) ◽  
pp. 1657-1680
Author(s):  
Johannes Horak ◽  
Marlis Hofer ◽  
Ethan Gutmann ◽  
Alexander Gohm ◽  
Mathias W. Rotach
Keyword(s):  
Water Vapor ◽  
Wind Field ◽  
Wave Theory ◽  
Cloud Formation ◽  
Mountain Wave ◽  
Atmospheric Research ◽  
Intermediate Complexity ◽  
Precipitation Processes ◽  
The Right

Abstract. The evaluation of models in general is a nontrivial task and can, due to epistemological and practical reasons, never be considered complete. Due to this incompleteness, a model may yield correct results for the wrong reasons, i.e., via a different chain of processes than found in observations. While guidelines and strategies exist in the atmospheric sciences to maximize the chances that models are correct for the right reasons, these are mostly applicable to full physics models, such as numerical weather prediction models. The Intermediate Complexity Atmospheric Research (ICAR) model is an atmospheric model employing linear mountain wave theory to represent the wind field. In this wind field, atmospheric quantities such as temperature and moisture are advected and a microphysics scheme is applied to represent the formation of clouds and precipitation. This study conducts an in-depth process-based evaluation of ICAR, employing idealized simulations to increase the understanding of the model and develop recommendations to maximize the probability that its results are correct for the right reasons. To contrast the obtained results from the linear-theory-based ICAR model to a full physics model, idealized simulations with the Weather Research and Forecasting (WRF) model are conducted. The impact of the developed recommendations is then demonstrated with a case study for the South Island of New Zealand. The results of this investigation suggest three modifications to improve different aspects of ICAR simulations. The representation of the wind field within the domain improves when the dry and the moist Brunt–Väisälä frequencies are calculated in accordance with linear mountain wave theory from the unperturbed base state rather than from the time-dependent perturbed atmosphere. Imposing boundary conditions at the upper boundary that are different to the standard zero-gradient boundary condition is shown to reduce errors in the potential temperature and water vapor fields. Furthermore, the results show that there is a lowest possible model top elevation that should not be undercut to avoid influences of the model top on cloud and precipitation processes within the domain. The method to determine the lowest model top elevation is applied to both the idealized simulations and the real terrain case study. Notable differences between the ICAR and WRF simulations are observed across all investigated quantities such as the wind field, water vapor and hydrometeor distributions, and the distribution of precipitation. The case study indicates that the precipitation maximum calculated by the ICAR simulation employing the developed recommendations is spatially shifted upwind in comparison to an unmodified version of ICAR. The cause for the shift is found in influences of the model top on cloud formation and precipitation processes in the ICAR simulations. Furthermore, the results show that when model skill is evaluated from statistical metrics based on comparisons to surface observations only, such an analysis may not reflect the skill of the model in capturing atmospheric processes like gravity waves and cloud formation.

Precipitation in silicon: Microanalysis

1988 ◽  
Vol 46 ◽  
pp. 474-475
Author(s):  
R.W. Carpenter
Keyword(s):  
Transition Metals ◽  
Spatial Resolution ◽  
Thin Foil ◽  
Precipitation Reaction ◽  
High Current ◽  
Reaction Products ◽  
Carbon And Nitrogen ◽  
Dielectric Layers ◽  
Precipitation Processes ◽  
Areas Of Interest

Interest in precipitation processes in silicon appears to be centered on transition metals (for intrinsic and extrinsic gettering), and oxygen and carbon in thermally aged materials, and on oxygen, carbon, and nitrogen in ion implanted materials to form buried dielectric layers. A steadily increasing number of applications of microanalysis to these problems are appearing. but still far less than the number of imaging/diffraction investigations. Microanalysis applications appear to be paced by instrumentation development. The precipitation reaction products are small and the presence of carbon is often an important consideration. Small high current probes are important and cryogenic specimen holders are required for consistent suppression of contamination buildup on specimen areas of interest. Focussed probes useful for microanalysis should be in the range of 0.1 to 1nA, and estimates of spatial resolution to be expected for thin foil specimens can be made from the curves shown in Fig. 1.

On the precipitation processes in commercial QE22 magnesium alloy

2007 ◽  
Vol 98 (6) ◽  
pp. 501-505 ◽  
Author(s):  
Osvaldo Agustin Lambri ◽  
Gabriel Julio Cuello ◽  
Werner Riehemann ◽  
Jose´ Lucioni
Keyword(s):  
Magnesium Alloy ◽  
Precipitation Processes

Part Eight

2017 ◽  
Author(s):  
Robert J. Fogelin
Keyword(s):  
Cloud Formation ◽  
Striking Similarity ◽  
Common Life ◽  
Natural Religion ◽  
Sextus Empiricus ◽  
Argument From Design

Philo expands on the nature of his objections to the natural religion of Cleanthes: far-fetched comparisons are dismissed in matters of common life, but are appropriate objections when we rise to the level of abstruse and remote reasoning. He offers a counterargument to the design-designer hypothesis, citing Epicurus. Constancy and change are discussed; cloud formation is one example. Philo’s critique of Cleanthes’ argument from design moves through stages, with striking similarity to Agrippa’s suspension of belief as presented by Sextus Empiricus.

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