104 research outputs found
GF-GMD/ccpp-physics: GMD-paper branch
No full textThe GF code for the part 3.1 "The trimodal characteristics revealed by single-column simulations" of "The Grell–Freitas (GF) convection parameterization: recent developments, extensions, and applications" by Saulo R. Freitas, Georg A. Grell, and Haiqin Li. Geosci. Model Dev., 14, 1–18, 2021 https://doi.org/10.5194/gmd-14-1-202
Review: Petra Grell (2006). Forschende Lernwerkstatt. Eine qualitative Untersuchung zu Lernwiderständen in der Weiterbildung
No full textPetra GRELL beschreibt ein gelungenes Beispiel einer partizipativen, problemorientierten qualitativen Sozialforschung, das sich mit dem in der Weiterbildung häufig anzutreffenden Problem von Lernwiderständen bei den Lehrgangsteilnehmenden auseinandersetzt. Um die verschiedenen Facetten und die Motivation hinter diesem Verhalten zu analysieren, greift die Autorin auf verschiedene qualitative Methoden zurück und integriert und reflektiert erfolgreich die Verwendung von bildgestützten Verfahren. Die Arbeit ist daher sowohl vom thematischen Fokus als auch von der methodischen Reflexion und Diskussion her sehr empfehlenswert.Petra GRELL describes an example of a successful participatory, problem-oriented qualitative social research project. The project dealt with resistance to learning in further education, a problem which is frequently observed. To show the different facets and the motivation behind this behaviour, the author uses a mixture of qualitative methods, and integrates and reflects on the successful use of image processes. The work is highly recommended both for its thematic focus and for the methodological reflection and discussion it contains.Petra GRELL describe el ejemplo de un exitoso proyecto de investigación cualitativa orientado al problema y participativo. El proyecto trata sobre la resistencia al aprendizaje en la educación superior, que es un problema observado frecuentemente. Para mostrar las diferentes facetas y la motivación detrás de esta conducta, el autor usa una mezcla de métodos cualitativos, integra y reflexiona acerca del exitoso uso de procesos de imagen. El trabajo es altamente recomendado tanto por su foco temático como por la reflexión metodológica y discusión que contiene
Impact of a Cold Pool Parameterization on the Diurnal Cycle and Intraseasonal Variability in the GEOS AGCM
No full textA gradual transition from shallow to deep convection may be important both to the continental diurnal cycle of precipitation and to the tropical Madden-Julian Oscillation. However, many existing convection parameterizations transition too readily, with corresponding diurnal and intraseasonal biases. High entrainment rates can be used to delay deep convection, but typically produce mean state biases; this is the "entrainment dilemma." Cold pools and sub-grid organization offer a potential solution to this dilemma, and recent work shows parameterized cold pools can effectively modulate deep convection, with improvements to the diurnal cycle and intraseasonal variability. Here we investigate the effects of a simple prognostic cold pool scheme coupled to the Grell-Freitas convection parameterization, in a set of global simulations with the NASA GEOS model. Air detrained from parameterized downdrafts is maintained in vertically resolved cold pools, which evolve with simplified dynamics. We test several options for cold pool feedbacks on convection, including modifications to deep convective entrainment rates, convective source air properties, and thermodynamic profiles, based on the level of cold pool activity. Cold pool impacts on the diurnal cycle are evaluated against TRMM, and moisture and moist static energy budgets are used to understand changes in tropical intraseasonal variability. Preliminary results show delays in the diurnal cycle of precipitation
The Grell-Freitas Convection Parameterization: Recent Developments and Applications Within the NASA GEOS Global Model
No full textWe implemented and began to evaluate an alternative convection parameterization for the NASA Goddard Earth Observing System (GEOS) global model. The parameterization is based on the mass flux approach with several closures, for equilibrium and non-equilibrium convection, and includes scale and aerosol awareness functionalities. Recently, the scheme has been extended to a tri-modal spectral size approach to simulate the transition from shallow, mid, and deep convection regimes. In addition, the inclusion of a new closure for non-equilibrium convection resulted in a substantial gain of realism in model simulation of the diurnal cycle of convection over the land. Here, we briefly introduce the recent developments, implementation, and preliminary results of this parameterization in the NASA GEOS modeling system
Reseña: Petra Grell (2006). Forschende Lernwerkstatt [Un taller de investigación acerca del aprendizaje. Una investigación cualitativa sobre la resistencia al aprendizaje en la educación superior]
No full textPetra GRELL beschreibt ein gelungenes Beispiel einer partizipativen, problemorientierten qualitativen Sozialforschung, das sich mit dem in der Weiterbildung häufig anzutreffenden Problem von Lernwiderständen bei den Lehrgangsteilnehmenden auseinandersetzt. Um die verschiedenen Facetten und die Motivation hinter diesem Verhalten zu analysieren, greift die Autorin auf verschiedene qualitative Methoden zurück und integriert und reflektiert erfolgreich die Verwendung von bildgestützten Verfahren. Die Arbeit ist daher sowohl vom thematischen Fokus als auch von der methodischen Reflexion und Diskussion her sehr empfehlenswert.
URN: urn:nbn:de:0114-fqs0902242Petra GRELL describes an example of a successful participatory, problem-oriented qualitative social research project. The project dealt with resistance to learning in further education, a problem which is frequently observed. To show the different facets and the motivation behind this behaviour, the author uses a mixture of qualitative methods, and integrates and reflects on the successful use of image processes. The work is highly recommended both for its thematic focus and for the methodological reflection and discussion it contains.
URN: urn:nbn:de:0114-fqs0902242Petra GRELL describe el ejemplo de un exitoso proyecto de investigación cualitativa orientado al problema y participativo. El proyecto trata sobre la resistencia al aprendizaje en la educación superior, que es un problema observado frecuentemente. Para mostrar las diferentes facetas y la motivación detrás de esta conducta, el autor usa una mezcla de métodos cualitativos, integra y reflexiona acerca del exitoso uso de procesos de imagen. El trabajo es altamente recomendado tanto por su foco temático como por la reflexión metodológica y discusión que contiene.
URN: urn:nbn:de:0114-fqs090224
Sandheden som fremmedlegeme? Helge Grell: Skaberordet og billedordet.
No full textTruth as a Foreign Body?The Creative Word and the Word as Image By Helge Grell. Reviewed by Hellmut Toftdahl.How and why is mankind able to speak truth about God? - That is the subject of this book, which addresses itself to theologians. Grell treats a large area of Grundtvig’s authorship from the period 1807-32, where he works his way out of speculative unified philosophy and the idealistic view of Christianity. For Grundtvig cognition of the creation concept and the word of God are very closely connected. Man is created in time and space and apprehends with the aid of his senses in images or imaginative thoughts. So the eternal and spiritual must reveal itself to man in temporal and sensuous images.Truth must have a body. On the basis of the material before him Grell analyses Grundtvig’s major dogma: God is at hand for mankind in the Word of God as Creator, Redeemer and Holy Spirit. Since Grundtvig is under the powerful influence of Schelling during this period, the book considers Schelling’s philosophy in a separate appendix. In his presentation of Grundtvig’s thought Grell emphasizes that Grundtvig accepts dualism as a condition for his understanding of existence and that mankind is unable to gain eternity through poetry and philosophy because of the Fall.One chapter deals with unpublished sermons from the beginning of the 1820’s. Grell sees them as an expression of the thoughts that Grundtvig later advanced with regard to the aim and content of sermons. The weakness in this method is that Grundtvig the poet does not receive his full due; for it is precisely in this period that Grundtvig gives free rein to the imagery in his sermons. The author is more on the wave-length of Grundtvig the analyser than Grundtvig the poetic preacher. He presents Grundtvig’s development as that of a systematic theologian and disregards his poetic development in the same period.Because the book stops at 1832 there is no explanation of the relationship between the young theorist and the older politician on the subject of the Church and cultural affairs. This lack has spurred the reviewer into a further consideration of Grundtvig as a preacher, particularly in the light of Søren Kierkegaard’s criticism. Toftdahl sees the essence of Grundtvig’s problem as a preacher lying in truth being subjected to the body’s conditions: that truth has to be mediated in time and space on given historical and political conditions. It therefore seems appropriate to put the preaching theories of the young Grundtvig into the perspective of the older Grundtvig’s major statements about the conditions God’s Word faces in the political reality of the Church and cultural affairs. At what points was Grundtvig a divinely-inspired preacher, and at what points was he, in the words of Kierkegaard, “a bellowing blacksmith” or a “jaunty, yodelling chap”?Later on in life Grundtvig was aware that not all salvation is legitimatelybased. There are words that create life; but there are also words that create something that is hardly distinguishable from life. What decides the case is the conscience, “which is Truth’s own witness in us about itse lf’ (Church Faith and School Teachings 1846) - (Kirke-Troen og Skole-Læren). In the same place Grundtvig distinguishes between “the Faith of Truth” and “the Faith of Falseness”.What is so exciting about Grundtvig as a preacher is to see how the preacher keeps a fairly tight rein on the poet, but without choking him. His genius is not that he had visions - every poet has them - but how he dealt with those visions so that they benefitted others as well as himself. Solidarity with the fellowship of baptism and Holy Communion is the prerequisite for his calling his inspired moments “true”. It is a delicate balance between what is basic and what is vulgar. He analyses this in Elementary Christian Teachings 1855-61 (Den Christne Børnelærdom), and it is reflected everywhere in his political work on cultural affairs.The cardinal point in Grundtvig’s theory of preaching and in his political programme was a separatism between the Church, the State and the School. He wanted a society in which growth of consciousness, politics and education all exist freely and independently of each other. Grundtvig thus represents an alternative to our present way of thinking, in which politics infiltrates both education and religion. With Grundtvig Truth’s body is present, in contrast to abstract ideologies: “these French and German free-hand drawings of castles in the air”, he calls them, protesting against the use of ideologies as a substitute for lost religious feeling. Only through the greatest possible comprehensiveness in education and the greatest possible political freedom can Truth be given fair conditions of existence; the Lie will reveal itself.A relevant cultural battle on Grundtvig’s terms must therefore consist of fighting ideological infiltration wherever it is to be found in the politics of the Church and of education. In a thoroughly politicised, technocratic and authoritarian world it is perhaps the individual congregation that is the last refuge for the scruples that the individual in Grundtvig and Kierkegaard’s time was still strong enough to manage as an isolated individual. The collective defence of the Truth of the message of conscience and love may be the Grundtvigian alternative to the brave new world.In a technocratic society Truth’s body will be diagnosed as a foreign body: either an insignificant splinter in the machine or an irritating mistake in the control-room. This will depend on what sort of impetus the Grundtvigian alternative to the brave new world is given. But a body will not let itself be quietly choked. It reacts violently when it is threatened. Often the will to live grows with the threat. The corporality of Truth adds to the gospel what is so characteristic of Grundtvig, namely the battle motif. The gospel is not merely a dogmatic or an aesthetic problem, but a vital, existential problem. It is in battle that Truth proves its life-power against the facile truth, the “castles in the air” of ideologies
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Semi-prognostic tests of cumulus parameterization schemes in the middle latitudes
No full textThe performance of three disparate cumulus parameterization schemes (Arakawa-Schubert, Kreitzberg-Perkey, and Kuo) was tested semi-prognostically in the mid-latitude environment of severe convective storms. With the aid of the analysis package of a mesoscale model, three independent rawin data sets were analyzed on different grid sizes (120 km, 45 km) to provide the larger scale variables and the verifying heat and moisture budgets. The terminology of dynamic control, static control, and feedback was used to separate different assumptions used by various cumulus parameterization schemes. These assumptions were then tested rigorously to find systematic errors and show possible improvements. For the Arakawa-Schubert parameterization heating and drying in the lower troposphere were systematically overpredicted. This problem was fixed by adding a simple parameterization of moist convective-scale downdrafts to the dynamic control, static control and feedback of the scheme. For the Kuo-type parameterizations, assumptions used by the feedback led to serious errors in predicting the vertical heating distribution. For the Kreitzberg-Perkey scheme assumptions used by the dynamic control led to an erroneous reproduction of rainfall patterns. Furthermore, assumptions used by the feedback of this scheme led to too much moistening and cooling in the middle and upper troposphere. For all schemes, it was shown that moist convective scale downdrafts, which play a vital role in the mid-latitude environment of severe convective storms, should probably be a part of the feedback in any cumulus parameterization scheme.</p
Atmospheric modeling of natural hazards
No full textDissertation (Ph.D.) University of Alaska Fairbanks, 2021Airborne hazards either in gaseous form or particulate matter can originate from a variety of sources. The most common natural airborne hazards are ash and SO₂ released during volcanic eruptions, smoke emitted caused by wildfires and dust storms. Once released into the atmosphere they can have a significant impact on different parts of the environment e.g. air quality, soil and water, as well as air traffic and ground transportation networks. This latter field is an important aspect of everyday life that is affected during hazardous events. Aviation is one of the most critical ways of transport in this century. Even short interruptions in flight schedules can lead to major economic damages. Volcanic eruptions comprise one of the most important airborne hazards to aviation. These are considered rare as compared to severe weather, but with an extremely high impact. This dissertation focusses on dispersion modeling tools and how they can support emergency response during different phases of volcanic eruption events. The impact of the volcanic ash cloud on the prediction of meteorological parameters and furthermore the dispersion of the ash is demonstrated by applying the Weather Research Forecasting (WRF) model with on-line integrated chemical transport (WRF-Chem) to simulate the 2010 Eyjafjallajökull eruption in Iceland. Comprehensive observational data sets have been collected to evaluate the model and to show the added value of integrating direct-feedback processes into the simulations. The case of the Eyjafjallajökull eruption showed the necessity to further develop the volcanic emission preprocessor of WRF-Chem which has been extended for flexible and complex ash and SO₂ source terms. Furthermore, the thesis describes how scientists could support operational centers to mitigate hazards during a large volcanic eruption event. The author of the dissertation coordinated a large exercise including experts across all Europe within a project funded by the European Union. The exercise aimed to develop and test new tools, models, and data to support real-time decision making in aviation flight planning during a volcanic crisis event. New state-of-the-art modeling applications were integrated into a flight planning software during a fictitious eruption of the Etna volcano in Italy with contributions from scientists, the military and the aviation community.Cooperative Institute for Alaska Research, National Oceanic and Atmospheric Administration cooperative agreement NA13OAR4320056 with the University of AlaskaChapter 1: Introduction --1.1 Airborne hazards and their impact on the environment and aviation -- 1.2 The volcanic risk mitigation system for aviation -- 1.3 Dispersion models support emergency response -- 1.4 Composition of the dissertation -- References. Chapter 2: The effects of simulating volcanic aerosol radiative feedbacks with WRF-Chem during the Eyjafjallajökull eruption, April and May 2010 -- Abstract -- 2.1 Introduction -- 2.2. Simulations setup -- 2.2.1. Model setup and case specifications -- 2.2.2. Volcanic emission preprocessor -- 2.3. Spatial and temporal evaluation of the location of the volcanic plume -- 2.4. Evaluation of meteorological parameters close to the surface -- 2.4.1. Meteorological observations -- 2.4.2. Average meteorological parameters at ground level -- 2.5. Aerosol radiative feedback effects in the model simulations -- 2.5.1. Radiative feedback effects close to the surface -- 2.5.2. Vertical profiles of wind speed and temperature -- 2.5.3. Influence of the radiative feedback effects on the atmospheric stability -- 2.6. The influence of considering the direct effect on the dispersion of the ash cloud -- 2.7. Summary and conclusions -- 2.8. Acknowledgments -- References. Chapter 3: Extension of the WRF-Chem volcanic emission preprocessor to integrate complex source terms and evaluation for different emission scenarios of the Grimsvötn 2011 eruption -- Abstract -- 3.1 Introduction -- 3.2 Extension of the volcanic preprocessor of the WRF-Chem model -- 3.3 WRF-Chem model simulations -- 3.3.1 Model setup -- 3.3.2 Volcanic emission scenarios -- 3.3.3 Model inter-comparison of predicted ash considering aviation regulation aspects -- 3.4 Evaluation of WRF-Chem simulations with observations -- 3.4.1. Comparison of volcanic ash and SO₂ with satellite data -- 3.4.2 Comparison with ground-based observations -- 3.4.2.1 Lidar profiles at selected stations -- 3.4.2.2 Comparison with PM10 observations at selected ground stations -- 3.5. Conclusions -- 3.6 Acknowledgements -- Glossary -- Appendix -- References. Chapter 4: A volcanic-hazard demonstration exercise to assess and mitigate the impacts of volcanic ash clouds on civil and military aviation -- Abstract -- 4.1 Introduction -- 4.2 International exercises -- 4.3 Overview of the EUNADICS-AV demonstration exercise set-up -- 4.3.1 General approach -- 4.3.1.1 The volcanic-eruption scenario -- 4.3.1.2 Data sharing and visualization -- 4.4 Data sets used for the demonstration exercise -- 4.4.1 Artificial observations -- 4.4.1.1 Simulations of the artificial plume evolution -- 4.4.1.2 Generation of artificial observations from SILAM simulations -- 4.4.2 The early-warning system (EWS) -- 4.4.2.1 Volcano observatory, Sicily -- 4.4.2.2 Synthetic ACTRIS EARLINET data -- 4.4.2.3 Synthetic satellite data simulated for IASI and MODIS -- 4.4.3 Model ensemble -- 4.5 The impact of the ash cloud on aviation for the Etna eruption scenario -- 4.5.1 Air navigation service provider -- 4.5.2 Austrian Armed Forces (AAF) -- 4.5.3 Rerouting of flights -- 4.6 Conclusion -- 4.7 Acknowledgements -- Glossary -- References. Chapter 5: Dissertation Summary and Conclusions -- 5.1 Extension and evaluation of the WRF-Chem model -- 5.2 Future perspectives -- References
Analysis Of Model And Observation Data For The Development Of A Public Pm2.5 Air-Quality Advisories Tool (Aquat)
No full textDissertation (Ph.D.) University of Alaska Fairbanks, 2012An air-quality advisory tool (AQuAT) that combines mobile measurements of particulate matter less than or equal to 2.5mum in diameter (PM2.5) with air-quality simulations performed with the Alaska adapted version of the Community Multiscale Air Quality (CMAQ) model was developed to interpolate PM2.5-measurements into unmonitored neighborhoods in Fairbanks, Alaska. AQuAT was developed as traditional interpolation methods of interpolating the mobile measurements were unsuccessful. Such a spatially differentiated air-quality advisory is highly desired in Fairbanks due to health concerns of PM2.5, and the need to improve the quality of life. The accuracy of AQuAT depends on the accuracy of the air-quality simulations used for its database. Evaluation of these simulations showed that they captured the observed relationships between PM2.5-concentrations and major meteorological fields (e.g., wind-speed, temperature, and surface-inversions) well. Skill scores for simulated PM2.5-concentrations fell in the range of modern models. The AQuAT database can include information on the nonlinear impacts of various emission sources on PM2.5-concentrations. This benefit was illustrated by investigating the impacts of emissions from point sources, uncertified wood-burning devices, and traffic on the distribution of PM 2.5-concentrations in the neighborhoods. Sensitivity studies on the effects of wood-burning device changeouts on the PM2.5-concentrations suggested that the emission inventory should be updated as soon as possible to capture recent changes in the emission situation in response to the changeout program. The performance of AQuAT was evaluated with PM2.5-measurements from mobile and stationary sites, and with simulated PM2.5-concentrations of winter 2010/2011 which were assumed to be "grand-truth" data. These evaluations showed that AQuAT captured the magnitudes and temporal evolutions of the PM 2.5-measurements and the "grand-truth" data well. The inclusion of wind-speed, wind-direction, and temperature in AQuAT did not improve its accuracy. This result may be explained by the fact that the relationships between meteorology and PM2.5-concentrations were already captured by the database. AQuAT allows quick spatial interpolation after the mobile measurements were made and provides error bars. It also allows for any route within the area for which a database of simulated concentrations exists. It was shown that AQuAT can be easily transferred for applications in other regions
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