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.

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.

Better downscaling results for the right reasons - A process based evaluation of the ICAR model

2021 ◽  
Author(s):  
Johannes Horak ◽  
Marlis Hofer ◽  
Alexander Gohm ◽  
Mathias W. Rotach
Keyword(s):  
Wind Field ◽  
Prediction Models ◽  
Weather Prediction ◽  
Wave Theory ◽  
Cloud Formation ◽  
Mountain Wave ◽  
Microphysics Scheme ◽  
The Right ◽  
The Impact

<p>The evaluation of models in general is a non-trivial task. Even a well established model may yield correct results for the wrong reasons, i.e. by a different chain of processes than found in observations. While guidelines and strategies exist to maximize the chances that results match measurements 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 a comparatively novel atmospheric model employed to downscale atmospheric fields. ICAR uses linear mountain wave theory to represent the wind field and advects atmospheric quantities, such as temperature and moisture in this wind field. Additionally a microphysics scheme is applied to represent the formation of clouds and precipitation.</p><p>We conducted an in-depth process-based evaluation of ICAR, employing idealized simulations to increase the understanding of the model and develop recommendations to improve its results. We contrast the ICAR simulations to Weather Research and Forecasting (WRF) model simulations and asses the impact of our recommendations with a case study for the South Island of New Zealand.</p><p>Our results suggest two key aspects relevant for ICAR to obtain the correct results for the right reasons. Firstly, 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. Secondly, 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. We analysed the causes for the differences between the idealized ICAR and WRF simulations and attribute them to the non-linearities in the WRF wind field and additional simplifications in the governing equations of ICAR. With our recommended ICAR setup applied to the real case study we find an upwind spatial shift of the precipitation maximum in comparison to the results obtained with the original ICAR setup. Additionally our 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.<br><br>Overall our findings have consequences for the interpretation of past results obtained with ICAR and suggest improvements to ICAR in future studies.</p>

Three recommendations to improve simulations with the Intermediate Complexity Atmospheric Research (ICAR) model

2020 ◽  
Author(s):  
Johannes Horak ◽  
Marlis Hofer ◽  
Alexander Gohm
Keyword(s):  
Water Vapor ◽  
Wind Field ◽  
Climate Models ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Complex Topography ◽  
Atmospheric Research ◽  
Mountainous Regions ◽  
Intermediate Complexity ◽  
Long Term Impact

<p>The output of general circulation models is too coarse to adequately capture the features influencing local climate and weather, particularly in complex topography. To asses the long-term impact of a changing global climate in mountainous regions, regional climate models need to be run on a fine spatial and temporal grid. Here the Intermediate Complexity Atmospheric Research (ICAR) model is a computationally frugal and physics based alternative to full physics regional climate models such as the Weather Research and Forecasting (WRF) model. A sizable portion of the computational efficiency of ICAR stems from its application of linear mountain wave theory to determine the wind field in the domain, thereby avoiding a numerical solution of the Navier-Stokes equations of motion. Heat, moisture and other atmospheric quantities are then advected in this wind field. Microphysical conversion processes between water vapor and various hydrometeor species are handled by a complex microphysics scheme. Altogether ICAR does not require measurements and enables computationally cheap downscaling, particularly in mountainous regions with complex topography, yielding a physically consistent set of atmospheric variables. However, in a real-world application and evaluation of ICAR we observed a strong sensitivity of the model performance to the elevation of the model top (Horak et al., 2019).<br><br>We present three recommendations, derived from idealized simulations, that improve different aspects of ICAR simulations. The simulations constitute an idealized ridge experiment with a non-dimensional mountain height of 0.5. The ridge is specified by a witch of Agnesi function and the sounding characterized by a saturated, horizontally and vertically homogeneous atmosphere with constant and stable stratification. The wind field calculated by ICAR is compared to the exact analytical solution. Furthermore, the water vapor, suspended hydrometeor and precipitating hydrometeor fields are used as proxies to identify inconsistencies in the model output, such as the dependence of the results on the elevation of the model top. To highlight the deviations of ICAR results from a full physics model, resulting from non-linearities in the wind field, the ICAR output was additionally compared to that of a WRF simulation. The results of our investigation strongly suggest that ICAR simulations can be significantly improved by (i) calculating the Brunt-Väisälä frequency from the forcing data set instead of the perturbed state of the atmosphere, (ii) setting the model top to an elevation of at least 11.4 km and, (iii) by applying a zero value boundary condition to the water vapor and hydrometeor species at the model top. To our knowledge none of the preceding studies employing ICAR satisfied these three conditions. Overall our investigation deepens the understanding of the ICAR model sensitivity to crucial model components, thereby increasing the potential of the model as a tool for long-term impact studies in data-sparse regions with complex topography.<br><br>References<br>Horak, J., Hofer, M., Maussion, F., Gutmann, E., Gohm, A., and Rotach, M. W. (2019), Assessing the added value of the Intermediate Complexity Atmospheric Research (ICAR) model for precipitation in complex topography. <em>Hydrology and Earth System Sciences</em>, 23(6), 2715-2734. </p>

Using the GOES-16 Split Window Difference to Detect a Boundary prior to Cloud Formation

2018 ◽  
Vol 99 (8) ◽  
pp. 1541-1544 ◽  
Author(s):  
Daniel T. Lindsey ◽  
Dan Bikos ◽  
Lewis Grasso
Keyword(s):  
Water Vapor ◽  
Infrared Spectrum ◽  
Temporal Resolution ◽  
Cloud Formation ◽  
Operational Forecast ◽  
Low Level ◽  
Spectral Bands ◽  
The Difference ◽  
Local Water

AbstractGeostationary Operational Environmental Satellite-16 (GOES-16) was launched into geostationary orbit in late 2016 and began providing unprecedented spatial and temporal resolution imagery early in 2017. Its Advanced Baseline Imager has additional spectral bands including two in the “clear” window and “dirty window” portion of the infrared spectrum, and the difference of these two bands, sometimes called the split window difference, provides unique information about low-level water vapor. Under certain conditions, low-level convergence along a boundary can cause local water vapor pooling, and the signal of this pooling can sometimes be detected by GOES-16 prior to any cloud formation. This case study from 15 June 2017 illustrates how the technique might be used in an operational forecast setting. A boundary in western Kansas was detected using the split window difference more than 2 h before the first cloud formed.

The Calculation of Turbulent Diffusion Coefficients in Aquatic Ecosystems

2019 ◽  
Vol 70 (11) ◽  
pp. 3903-3907
Author(s):  
Galina Marusic ◽  
Valeriu Panaitescu
Keyword(s):  
Transport Equation ◽  
Turbulent Diffusion ◽  
Diffusion Coefficients ◽  
Aquatic Ecosystems ◽  
Specific Area ◽  
Left Bank ◽  
The Right ◽  
Prut River

The paper deals with the issues related to the pollution of aquatic ecosystems. The influence of turbulence on the transport and dispersion of pollutants in the mentioned systems, as well as the calculation of the turbulent diffusion coefficients are studied. A case study on the determination of turbulent diffusion coefficients for some sectors of the Prut River is presented. A new method is proposed for the determination of the turbulent diffusion coefficients in the pollutant transport equation for specific sectors of a river, according to the associated number of P�clet, calculated for each specific area: the left bank, the right bank and the middle of the river.

Traditionalism and politics: A case study of Northern Nigeria

1967 ◽  
Vol 2 (4) ◽  
pp. 509-524 ◽  
Author(s):  
B. J. O. Dudley
Keyword(s):  
Social Change ◽  
Local Government ◽  
Status Quo ◽  
Political Elite ◽  
High Time ◽  
The Political ◽  
Northern Nigeria ◽  
The North ◽  
The Right

In the debate on the Native Authority (Amendment) Law of 1955, the late Premier of the North, Sir Ahmadu Bello, Sardauna of Sokoto, replying to the demand that ‘it is high time in the development of local government systems in this Region that obsolete and undemocratic ways of appointing Emirs’ Councils should close’, commented that ‘the right traditions that we have gone away from are the cutting off of the hands of thieves, and that has caused a lot of thieving in this country. Why should we not be cutting (off) the hands of thieves in order to reduce thieving? That is logical and it is lawful in our tradition and custom here.’ This could be read as a defence against social change, a recrudescence of ‘barbarism’ after the inroads of pax Britannica, and a plea for the retention of the status quo and the entrenched privilege of the political elite.

scholarly journals Fieldwork on epistemic authority markers: What we can learn from different types of data

2020 ◽  
Vol 54 (2) ◽  
pp. 405-445 ◽  
Author(s):  
Karolina Grzech
Keyword(s):  
Data Collection ◽  
Discourse Markers ◽  
Epistemic Modality ◽  
Linguistic Meaning ◽  
Epistemic Authority ◽  
Data Collection And Analysis ◽  
The Right To Know ◽  
Cognitive Study ◽  
The Right

AbstractEpistemicity in language encompasses various kinds of constructions and expressions that have to do with knowledge-related aspects of linguistic meaning (cf. Grzech, Karolina, Eva Schultze-Berndt and Henrik Bergqvist. 2020c. Knowing in interaction: an introduction. Folia Linguistica [this issue]). It includes some well-established categories, such as evidentiality and epistemic modality (Boye, Kasper. 2012. Epistemic meaning: A crosslinguistic and functional-cognitive study. Berlin: De Gruyter Mouton), but also categories that have been less well described to-date. In this paper, I focus on one such category: the marking of epistemic authority, i.e. the encoding of “the right to know or claim” (Stivers, Tanya, Lorenza Mondada & Jakob Steensig. 2011b. Knowledge, morality and affiliation in social interaction. In Stivers et al. 2011a). I explore how the marking of epistemic authority can be documented and analysed in the context of linguistic fieldwork. The discussion is based on a case study of Upper Napo Kichwa, a Quechuan language spoken in the Ecuadorian Amazon that exhibits a rich paradigm of epistemic discourse markers, encoding meanings related to epistemic authority and distribution of knowledge between discourse participants. I describe and appraise the methodology for epistemic fieldwork used in the Upper Napo Kichwa documentation and description project. I give a detailed account of the different tools and methods of data collection, showing their strengths and weaknesses. I also discuss the decisions made at the different stages of the project and their implications for data collection and analysis. In discussing these issues, I extrapolate from the case study, proposing practical solutions for fieldwork-based research on epistemic markers.

Unemployment in the Affective Economy: Exploring the Affective Governing of Young Unemployed People in the Danish Welfare State

2020 ◽  
Vol 66 (3) ◽  
pp. 335-361
Author(s):  
Sabina Pultz
Keyword(s):  
Welfare State ◽  
Complex Relationship ◽  
Field Observations ◽  
Unemployed People ◽  
Political Implications ◽  
Governmentality Studies ◽  
The Right ◽  
The Unemployed ◽  
The Ideal

Abstract This case study investigates the affective governing of young unemployed people, and it concludes that getting money in the Danish welfare state comes with an “affective price”. In the quest for a job, unemployed people have been increasingly responsibilized in order to live up to the ideal of the active jobseeker. Consequently, when faced with unemployment, they are encouraged to work harder on themselves and their motivation. Based on an interview study with young unemployed people (N=39) and field observations made at employment fund agencies in Denmark (2014–15), I explore how young unemployed people are governed by and through their emotions. By supplementing governmentality studies (Foucault et al. 1988, 2010) with the concept of “affective economy” from Ahmed (2014), I discuss how young unemployed people who receive money from the Danish state are placed in a situation of debt. The paper unfolds how this debt becomes visible as the unemployed people often describe feeling under suspicion for not doing enough, for not being motivated enough. Through an abundance of (pro) activity, they have to prove the suspicion of being lazy wrong, and through managing themselves as active jobseekers, they earn the right to get money from the state. Here motivation, passion and empowerment are key currencies. I discuss the intricate interplay between monetary and affective currencies as well as political implications in the context of the Danish welfare. The article contributes by making visible the importance of taking affective matters into account when investigating the complex relationship between politics and psychology.

HOUSEHOLD FORMATION IN 19TH-CENTURY CENTRAL ANATOLIA: THE CASE STUDY OF A TURKISH-SPEAKING ORTHODOX CHRISTIAN COMMUNITY

2002 ◽  
Vol 34 (3) ◽  
pp. 495-517
Author(s):  
Irini Renieri
Keyword(s):  
Central Anatolia ◽  
Household Formation ◽  
Greek Orthodox ◽  
Christian Community ◽  
Orthodox Christian ◽  
Complex Forms ◽  
The Right ◽  
Extended Households ◽  
The Village

This article explores household formation among the Greek Orthodox population of a mixed village of Cappadocia inhabited by Muslims, as well. The village, Çukur, was located on the right bank of the river Kızılırmak, 49 kilometers north–northwest of Kayseri.1 I aim to show that complex forms of household formation were the main type of social organization and were especially durable over time, with a high average household membership. I attempt to clarify whether the predominance of extended households—which, as other studies have shown, is not that common in the Asian portion of the Ottoman Empire—was related to the Christian character of this section of the Çukur population, or whether the agricultural basis of the village economy played a more important role.

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