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755 results on '"A. Sledd"'

1. Nudging allows direct evaluation of coupled climate models with in situ observations: a case study from the MOSAiC expedition

Author

F. Pithan, M. Athanase, S. Dahlke, A. Sánchez-Benítez, M. D. Shupe, A. Sledd, J. Streffing, G. Svensson, and T. Jung

Subjects
Geology, QE1-996.5
Abstract

Comparing the output of general circulation models to observations is essential for assessing and improving the quality of models. While numerical weather prediction models are routinely assessed against a large array of observations, comparing climate models and observations usually requires long time series to build robust statistics. Here, we show that by nudging the large-scale atmospheric circulation in coupled climate models, model output can be compared to local observations for individual days. We illustrate this for three climate models during a period in April 2020 when a warm air intrusion reached the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in the central Arctic. Radiosondes, cloud remote sensing and surface flux observations from the MOSAiC expedition serve as reference observations. The climate models AWI-CM1/ECHAM and AWI-CM3/IFS miss the diurnal cycle of surface temperature in spring, likely because both models assume the snowpack on ice to have a uniform temperature. CAM6, a model that uses three layers to represent snow temperature, represents the diurnal cycle more realistically. During a cold and dry period with pervasive thin mixed-phase clouds, AWI-CM1/ECHAM only produces partial cloud cover and overestimates downwelling shortwave radiation at the surface. AWI-CM3/IFS produces a closed cloud cover but misses cloud liquid water. Our results show that nudging the large-scale circulation to the observed state allows a meaningful comparison of climate model output even to short-term observational campaigns. We suggest that nudging can simplify and accelerate the pathway from observations to climate model improvements and substantially extends the range of observations suitable for model evaluation.

Published
2023
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2. Clouds Increasingly Influence Arctic Sea Surface Temperatures as CO2 Rises

Author

A. Sledd, T. S. L’Ecuyer, J. E. Kay, and M. Steele

Subjects
Arctic, clouds, sea surface temperature, sea ice, Geophysics. Cosmic physics, QC801-809
Abstract

Abstract As Arctic sea ice retreats during the melt season, the upper ocean warms in response to atmospheric heat fluxes. Overall, clouds reduce these fluxes in summer, but how the radiative impacts of clouds on ocean warming could change as sea ice declines has not been documented. In global climate model simulations with variable CO2, the timing of sea ice retreat strongly influences the amplitude of cloud‐induced summer cooling at the ocean surface. Under pre‐industrial CO2 concentrations, summer clouds have little direct effect on maximum annual sea surface temperatures (SST). When CO2 concentrations increase, sea ice retreats earlier, allowing more solar radiation to warm the ocean. Clouds can counteract this summer warming by reflecting solar radiation back to space. Consequently, clouds explain up to 13% more variability in maximum annual SST under modern‐day CO2 concentrations. Maximum annual SST are three times more sensitive to summer clouds when CO2 concentrations are four times pre‐industrial levels.

Published
2023
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3. Asymptotic and Assouad-Nagata dimension of finitely generated groups and their subgroups

Author

Sledd, Levi

Subjects
Mathematics - Group Theory, Mathematics - Metric Geometry
Abstract

We prove that for all $k,m,n \in \mathbb N \cup \{\infty\}$ with $4 \leq k \leq m \leq n$, there exists a finitely generated group $G$ with a finitely generated subgroup $H$ such that the asymptotic dimension of $G$ is $k$, the Assouad-Nagata dimension of $G$ is $m$, and the Assouad-Nagata dimension of $H$ is $n$. This simultaneously answers two open questions in asymptotic dimension theory., Comment: 33 pages, 7 figures This paper is a sequel to "Assouad-Nagata dimension of C'(1/6) groups" (1909.06646). Some of the results from the previous paper have been shifted to this one, since their proofs use similar techniques. The author believes this reorganization will make both papers easier to read and greatly reduce their combined length

Published
2020

4. Assouad-Nagata dimension of finitely generated C'(1/6) groups

Author

Sledd, Levi

Subjects
Mathematics - Group Theory, Mathematics - Metric Geometry
Abstract

This paper is the first in a two-part series. In this paper, we prove that the Assouad-Nagata dimension of any finitely generated (but not necessarily finitely presented) $C'(1/6)$ group is at most 2. In the next paper, we use this result, along with techniques of classical small cancellation theory, to answer two open questions in the study of asymptotic and Assouad-Nagata dimension of finitely generated groups., Comment: 20 pages, 10 figures. Some of the results of this paper have now been moved to the sequel paper, "Assouad-Nagata dimension of finitely generated groups and their subgroups."

Published
2019

6. Postdoc Perspectives on Leadership and Matters of Equity and Inclusion in Polar Science.

Author

Goliber, Sophie, Coenen, Jason, Fair, Heather, Szesciorka, Angela R., Schulz, Kirstin, Harning, David J., Fernando, Benjamin, Ksenofontov, Stanislav Saas, Pacini, Astrid, Rivera, Marisol Juarez, Calmer, Radiance, Conroy, John A., Doting, Eva Lisa, Bergelin, Marie, Dunmire, Devon, Sánchez Montes, Maria Luisa, Ravelo, Alexandra M., Sledd, Anne, Stinchcomb, Taylor R., and Tibbett, Emily J.

Published
2024
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7. An Examination of University Agricultural Education Faculty Attitudes toward the Implementation of High Impact Learning Experiences

Author

Murphrey, Theresa Pesl, Odom, Summer F., and Sledd, James

Abstract

Meaningful learning is a goal across the broad field of agricultural education and high impact learning (HIL) experiences are a mechanism to facilitate that goal. The purpose of this study was to examine university agricultural education faculty attitudes toward the implementation of HIL. Faculty (n=85) from 10 agricultural education departments nationwide responded to a survey about perceptions of HIL experiences for undergraduate and graduate students. The majority of respondents reported that as a student they had participated in HIL experiences such as study abroad, research projects, internships, and student teaching. However, neither participation as a student nor current involvement in HIL activities influenced their perceptions of HIL. Characteristics that influenced perceptions included teaching experience and departmental support. Respondents with less teaching experience possessed a stronger perception of the benefit of HIL and those who perceived they had departmental support reported less concern for barriers (i.e., time and planning) to HIL implementation. Findings revealed a need for support and training related specifically to the implementation of study abroad activities.

Published
2016

11. Variations on Narrow Dots-and-Boxes and Dots-and-Triangles

Author

Jobson, Adam, Sledd, Levi, White, Susan C., and Wildstrom, D. Jacob

Subjects
Mathematics - Combinatorics, Computer Science - Computer Science and Game Theory
Abstract

We verify a conjecture of Nowakowski and Ottaway that closed $1 \times n$ Dots-and-Triangles is a first-player win when $n \neq 2$. We also prove that in both the open and closed $1 \times n$ Dots-and-Boxes games where $n$ is even, the first player can guarantee a tie., Comment: 8 pages, 11 figures, 1 table

Published
2015

12. Introduction

Author

Dunkerly, Judith M., primary, Poplin, Julia, additional, and Taylor, Valerie Sledd, additional

Published
2022
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18. An evaluation of the exposure in nadir observation of the JEM-EUSO mission

Author

Adams, J. H., Ahmad, S., Albert, J. -N., Allard, D., Ambrosio, M., Anchordoqui, L., Anzalone, A., Arai, Y., Aramo, C., Asano, K., Ave, M., Barrillon, P., Batsch, T., Bayer, J., Belenguer, T., Bellotti, R., Berlind, A. A., Bertaina, M., Biermann, P. L., Biktemerova, S., Blaksley, C., Blecki, J., Blin-Bondil, S., Bluemer, J., Bobik, P., Bogomilov, M., Bonamente, M., Briggs, M. S., Briz, S., Bruno, A., Cafagna, F., Campana, D., Capdevielle, J-N., Caruso, R., Casolino, M., Cassardo, C., Castellini, G., Catalano, O., Cellino, A., Chikawa, M., Christl, M. J., Connaughton, V., Cortes, J. F., Crawford, H. J., Cremonini, R., Csorna, S., D'Olivo, J. C., Dagoret-Campagne, S., de Castro, A. J., De Donato, C., de la Taille, C., del Peral, L., Dell'Oro, A., De Pascale, M. P., Di Martino, M., Distratis, G., Dupieux, M., Ebersoldt, A., Ebisuzaki, T., Engel, R., Falk, S., Fang, K., Fenu, F., Fernandez-Gomez, I., Ferrarese, S., Franceschi, A., Fujimoto, J., Galeotti, P., Garipov, G., Geary, J., Giaccari, U. G., Giraudo, G., Gonchar, M., Alvarado, C. Gonzalez, Gorodetzky, P., Guarino, F., Guzman, A., Hachisu, Y., Harlov, B., Haungs, A., Carretero, J. Hernandez, Higashide, K., Iguchi, T., Ikeda, H., Inoue, N., Inoue, S., Insolia, A., Isgrio, F., Itow, Y., Joven, E., Judd, E. G., Jung, A., Kajino, F., Kajino, T., Kaneko, I., Karadzhov, Y., Karczmarczyk, J., Katahira, K., Kawai, K., Kawasaki, Y., Keilhauer, B., Khrenov, B. A., Kim, Jeong-Sook, Kim, Soon-Wook, Kim, Sug-Whan, Kleifges, M., Klimov, P. A., Ko, S. H., Kolev, D., Kreykenbohm, I., Kudela, K., Kurihara, Y., Kuznetsov, E., La Rosa, G., Lee, J., Licandro, J., Lim, H., Lopez, F., Maccarone, M. C., Mannheim, K., Marcelli, L., Marini, A., Martin-Chassard, G., Martinez, O., Masciantonio, G., Mase, K., Matev, R., Maurissen, A., Medina-Tanco, G., Mernik, T., Miyamoto, H., Miyazaki, Y., Mizumoto, Y., Modestino, G., Monnier-Ragaigne, D., Rios, J. A. Morales de los, Mot, B., Murakami, T., Nagano, M., Nagata, M., Nagataki, S., Nakamura, T., Nam, J. W., Nam, S., Nam, K., Napolitano, T., Naumov, D., Neronov, A., Nomoto, K., Ogawa, T., Ohmori, H., Olinto, A. V., Orleanski, P., Osteria, G., Pacheco, N., Panasyuk, M. I., Parizot, E., Park, I. H., Pastircak, B., Patzak, T., Paul, T., Pennypacker, C., Peter, T., Picozza, P., Pollini, A., Prieto, H., Reardon, P., Reina, M., Reyes, M., Ricci, M., Rodriguez, I., Frias, M. D. Rodriguez, Ronga, F., Rothkaehl, H., Roudil, G., Rusinov, I., Rybczynski, M., Sabau, M. D., Cano, G. Saez, Saito, A., Sakaki, N., Sakata, M., Salazar, H., Sanchez, S., Santangelo, A., Cruz, L. Santiago, Palomino, M. Sanz, Saprykin, O., Sarazin, F., Sato, H., Sato, M., Schanz, T., Schieler, H., Scotti, V., Scuderi, M., Segreto, A., Selmane, S., Semikoz, D., Serra, M., Sharakin, S., Shibata, T., Shimizu, H. M., Shinozaki, K., Shirahama, T., Siemieniec-Ozieb, G., Lopez, H. H. Silva, Sledd, J., Slominska, K., Sobey, A., Sugiyama, T., Supanitsky, D., Suzuki, M., Szabelska, B., Szabelski, J., Tajima, F., Tajima, N., Tajima, T., Takahashi, Y., Takami, H., Takeda, M., Takizawa, Y., Tenzer, C., Tibolla, O., Tkachev, L., Tomida, T., Tone, N., Trillaud, F., Tsenov, R., Tsuno, K., Tymieniecka, T., Uchihori, Y., Vaduvescu, O., Valdes-Galicia, J. F., Vallania, P., Valore, L., Vankova, G., Vigorito, C., Villasenor, L., von Ballmoos, P., Wada, S., Watanabe, J., Watanabe, S., Watts, J., Weber, M., Weiler, T. J., Wibig, T., Wiencke, L., Wille, M., Wilms, J., Wlodarczyk, Z., Yamamoto, T., Yamamoto, Y., Yang, J., Yano, H., Yashin, I. V., Yonetoku, D., Yoshida, K., Yoshida, S., Young, R., Zamora, A., and Marchi, A. Zuccaro

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Observatory, on-board the Japanese Experiment Module of the International Space Station. Designed as a mission to explore the extreme energy Universe from space, JEM-EUSO will monitor the Earth's nighttime atmosphere to record the ultraviolet light from tracks generated by extensive air showers initiated by ultra-high energy cosmic rays. In the present work, we discuss the particularities of space-based observation and we compute the annual exposure in nadir observation. The results are based on studies of the expected trigger aperture and observational duty cycle, as well as, on the investigations of the effects of clouds and different types of background light. We show that the annual exposure is about one order of magnitude higher than those of the presently operating ground-based observatories., Comment: published in Astroparticle Physics by the JEM-EUSO Collaboration

Published
2013
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19. A Cloudier Picture of Ice-Albedo Feedback in CMIP6 Models

Author

Anne Sledd and Tristan S. L’Ecuyer

Subjects
arctic, climate change, solar absorption, clouds, sea ice, albedo, Science
Abstract

Increased solar absorption is an important driver of Arctic Amplification, the interconnected set of processes and feedbacks by which Arctic temperatures respond more rapidly than global temperatures to climate forcing. The amount of sunlight absorbed in the Arctic is strongly modulated by seasonal ice and snow cover. Sea ice declines and shorter periods of seasonal snow cover in recent decades have increased solar absorption, amplifying local warming relative to the planet as a whole. However, this Arctic albedo feedback would be substantially larger in the absence of the ubiquitous cloud cover that exists throughout the region. Clouds have been observed to mask the effects of reduced surface albedo and slow the emergence of secular trends in net solar absorption. Applying analogous metrics to several models from the 6th Climate Model Intercomparison Project (CMIP6), we find that ambiguity in the influence of clouds on predicted Arctic solar absorption trends has increased relative to the previous generation of climate models despite better agreement with the observed albedo sensitivity to sea ice variations. Arctic albedo responses to sea ice loss are stronger in CMIP6 than in CMIP5 in all summer months. This agrees better with observations, but models still slightly underestimate albedo sensitivity to sea ice changes relative to observations. Never-the-less, nearly all CMIP6 models predict that the Arctic is now absorbing more solar radiation than at the start of the century, consistent with recent observations. In fact, many CMIP6 models simulate trends that are too strong relative to internal variability, and spread in predicted Arctic albedo changes has increased since CMIP5. This increased uncertainty can be traced to increased ambiguity in how clouds influence natural and forced variations in Arctic solar absorption. While nearly all CMIP5 models agreed with observations that clouds delay the emergence of forced trends, about half of CMIP6 models suggest that clouds accelerate their emergence from natural variability. Isolating atmospheric contributions to total Arctic reflection suggests that this diverging behavior may be linked to stronger Arctic cloud feedbacks in the latest generation of climate models.

Published
2021
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20. The JEM-EUSO Mission: Status and Prospects in 2011

Author

Collaboration, The JEM-EUSO, Adams Jr, J. H., Ahmad, S., Albert, J. -N., Allard, D., Ambrosio, M., Anchordoqui, L., Anzalone, A., Arai, Y., Aramo, C., Asano, K., Barrillon, P., Batsch, T., Bayer, J., Belenguer, T., Bellotti, R., Berlind, A. A., Bertaina, M., Biermann, P. L., Biktemerova, S., Blaksley, C., Blecki, J., Blin-Bondil, S., Bluemer, J., Bobik, P., Bogomilov, M., Bonamente, M., Briggs, M. S., Briz, S., Bruno, A., Cafagna, F., Campana, D., Capdevielle, J-N., Caruso, R., Casolino, M., Cassardo, C., Castellini, G., Catalano, O., Cellino, A., Chikawa, M., Christl, M. J., Connaughton, V., Cortes, J. F., Crawford, H. J., Cremonini, R., Csorna, S., D'Olivo, J. C., Dagoret-Campagne, S., de Castro, A. J., De Donato, C., de la Taille, C., De Pascale, M. P., del Peral, L., Dell'Oro, A., Di Martino, M., Distrati, G., Dupieux, M., Ebersoldt, A., Ebisuzaki, T., Engel, R., Falk, S., Fang, K., Fenu, F., Ferrarese, S., Fernandez-Gomez, I., Franceschi, A., Fujimoto, J., Galeotti, P., Garipov, G., Geary, J., Giaccari, U. G., Giraudo, G., Gonchar, M., Alvarado, C. Gonzalez, Gorodetzky, P., Guarino, F., Guzman, A., Hachisu, Y., Harlov, B., Haungs, A., Carretero, J. Hernandez, Higashide, K., Iguchi, T., Ikeda, H., Inoue, N., Inoue, S., Insolia, A., Isgro, F., Itow, Y., Joven, E., Judd, E. G., Jung, A., Kajino, F., Kajino, T., Kaneko, I., Karadzhov, Y., Karczmarczyk, J., Katahira, K., Kawai, K., Kawasaki, Y., Keilhauer, B., Khrenov, B. A., Kim, Jeong-Sook, Kim, Soon-Wook, Kim, Sug-Whan, Kleifges, M., Klimov, P. A., Ko, S. H., Kolev, D., Kreykenbohm, I., Kudela, K., Kurihara, Y., Kuznetsov, E., La Rosa, G., Lee, J., Licandro, J., Lim, H., Lopez, F., Maccarone, M. C., Marcelli, L., Marini, A., Martin-Chassard, G., Martinez, O., Masciantonio, G., Mase, K., Matev, R., Maurissen, A., Medina-Tanco, G., Mernik, T., Miyamoto, H., Miyazaki, Y., Mizumoto, Y., Modestino, G., Monnier-Ragaigne, D., Rıos, J. A. Morales de los, Mot, B., Murakami, T., Nagano, M., Nagata, M., Nagataki, S., Nam, J. W., Nam, S., Nam, K., Napolitano, T., Naumov, D., Neronov, A., Nomoto, K., Ogawa, T., Ohmori, H., Olinto, A. V., Orleanski, P., Osteria, G., Pacheco, N., Panasyuk, M. I., Parizot, E., Park, I. H., Pastircak, B., Patzak, T., Paul, T., Pennypacker, C., Peter, T., Picozza, P., Pollini, A., Prieto, H., Reardon, P., Reina, M., Reyes, M., Ricci, M., Rodrıguez, I., Frıas, M. D. Rodrıguez, Ronga, F., Rothkaehl, H., Roudil, G., Rusinov, I., Rybczynski, M., Sabau, M. D., Cano, G. Saez, Saito, A., Sakaki, N., Sakata, M., Salazar, H., Sanchez, S., Santangelo, A., Cruz, L. Santiago, Palomino, M. Sanz, Saprykin, O., Sarazin, F., Sato, H., Sato, M., Schanz, T., Schieler, H., Scotti, V., Scuderi, M., Segreto, A., Selmane, S., Semikoz, D., Serra, M., Sharakin, S., Shibata, T., Shimizu, H. M., Shinozaki, K., Shirahama, T., Siemieniec-Ozieblo, G., Lopez, H. H. Silva, Sledd, J., Slominska, K., Sobey, A., Sugiyama, T., Supanitsky, D., Suzuki, M., Szabelska, B., Szabelski, J., Tajima, F., Tajima, N., Tajima, T., Takami, H., Nakamura, T., Takeda, M., Takahashi, Y., Takizawa, Y., Tenzer, C., Tkachev, L., Tomida, T., Tone, N., Trillaud, F., Tsenov, R., Tsuno, K., Tymieniecka, T., Uchihori, Y., Vaduvescu, O., Valdes-Galicia, J. F., Vallania, P., Valore, L., Vankova, G., Vigorito, C., Villasenor, L., von Ballmoos, P., Wada, S., Watanabe, J., Watanabe, S., Watts Jr, J., Weber, M., Weiler, T. J., Wibig, T., Wiencke, L., Wille, M., Wilms, J., Wlodarczyk, Z., Yamamoto, T., Yamamoto, Y., Yang, J., Yano, H., Yashin, I. V., Yonetoku, D., Yoshida, K., Yoshida, S., Young, R., Zamora, A., and Marchi, A. Zuccaro

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Contributions of the JEM-EUSO Collaboration to the 32nd International Cosmic Ray Conference, Beijing, August, 2011., Comment: 33 contributions plus index

Published
2012

23. Teaching English to the Disenfranchised: A Look Back.

Author

Sledd, James

Abstract

In this paper, the author/educator recalls a 1972 article that reviewed 11 books about the English to minorities. Over the years, teaching issues have been debated--one commonly discussed topic of the '90s being Ebonics. The author asserts that the public at large pays no attention to most academic writing. Exploitation of graduate students as teaching assistants was also discussed in the 60s; the Wyoming Resolution appeared in 1986, and many professional groups have promulgated codes of ethics. However, good professionals such as writing instructors get in the way of significant change. Academics should realize that there will never be unity among academic labor as long as the institution of tenure exists. Tenure supposedly protects academic freedom (for the tenured only), but the protection is not very effective. Administrators have lots of ways of controlling the tenured--denial of raises, punitive course assignments, etc. The real function of tenure now is to replicate the encompassing two-tiered society within the academy. So that an administrator might get a raise as big as the combined salaries of a married couple with long experience on staff. Academic workers should organize and battle for real change. The continued abuse of part-timers and TAs, and the unchanging insistence that "talking white" is talking right, should make it obvious to even the most submissive that tough action is necessary, not just good words. (NKA)

Published
1998

24. Composition and Civic Education.

Author

Sledd, James

Abstract

This paper addresses civic educators on the left, who "babble" about liberation and empowerment by transformative intellectuals. The paper argues that many of those "leftists" belong to the group that could be called "boss" compositionists, comfortable lower managers of a corrupt system, who never tire of denouncing the traditional or of advertising their own alleged revolution in composition. The paper states that (1) "boss" compositions can produce little evidence that they have improved students' writing more than their denigrated predecessors improved it; (2) the liberators and empowerers have done little to improve the lot of the graduate students and other contingent workers who actually teach composition; (3) the intellectual quality of their heralded discipline is unremarkable; (4) by their careerism, the boss compositions have duplicated the wider society's brutal division of haves and have nots; and (5) in consequence the deepest lesson of the revolution in composition is the lesson of upward mobility in the main stream, the lesson of going along to get along. The paper offers three brief examples to substantiate these points, two of which are recent books about the subject. (TB)

Published
1996

25. Sandra Stotsky's Civic Education: What Gets Taught.

Author

Sledd, James

Abstract

In this paper, James Sledd and his son Andrew Sledd respond, on seven distinct points, to Sandra Stotsky's "Connecting Civic Education and Language Education" and to her "College English" essay "Conceptualizing Writing as Moral and Civic Thinking," in both of which she attacks the Sledds for their criticism of E. D. Hirsch. According to the paper, Stotsky's technique is to lift short passages of academic prose from their explanatory contexts and then to praise or blame them according to her notions of scholarly responsibility. The paper notes that one of the qualities that Stotsky values highly is academic courtesy. The paper also states that, in both book and essay, Stotsky has called the Sledds' criticism of E. D. Hirsch irresponsible, racist, age-ist and immoral--and rude, too. In response, the Sledds affirm that, although they dislike being called racist, they are not primarily concerned with the personal attacks. In the paper they make three familiar but sometimes neglected propositions: (1) that the politic evasion of an opponent's evidence and arguments, though commonplace, is not an academic virtue; (2) that such criticism of "decontextualized" passages as Stotsky recommends is guaranteed to obscure issues really at stake; and (3) that the ancient rhetorical tradition of justified blame as well as praise should not be submerged in a rhetoric of identification for immediate persuasion. (TB)

Published
1994

26. The Dark and Bloody Mystery: Building Basic Writers' Confidence.

Author

Sledd, Robert

Abstract

While the roots of students' fear of writing go deep, students fear most the surface of writing. They fear that a person's language indicates the state not only of the mind but of the soul--thus their writing can make them look stupid and morally depraved. This fear of error and lack of confidence prevent students from developing a command of the written language and results in superficial treatment of superficial ideas. Using an inductive approach to analyzing writing can help students conquer the fear of surface errors that prevents them from tackling complex ideas in their work. An inductive approach which involves class discussion that analyzes samples of strong and weak writing has several benefits: (1) disagreement about which revision the class prefers undermines the notion that writing is "right" or "wrong," good" or "bad"; (2) students get reinforcement of the idea that writing involves choices among multiple alternatives, not a binary choice between "right" and "wrong"; (3) describing differences among alternative revisions and the original dispells the notions that the mysteries of writing are inaccessible to students; (4) discussion and description of the paragraphs make it necessary to get concepts like subject, verb, dependent clause under control; (5) the frequency of surface errors in student writing decreases; and (6) students begin to do more substantive stylistic revision to their own writing with the result that the content of their essays also improves. (Handouts intended to aid students in analyzing their own own and others' writing are presented in four attached appendixes.) (SAM)

Published
1993

28. Cosmic ray oriented performance studies for the JEM-EUSO first level trigger

Author

Abdellaoui, G., Abe, S., Acheli, A., Adams, J.H., Jr., Ahmad, S., Ahriche, A., Albert, J.-N., Allard, D., Alonso, G., Anchordoqui, L., Andreev, V., Anzalone, A., Aouimeur, W., Arai, Y., Arsene, N., Asano, K., Attallah, R., Attoui, H., Ave Pernas, M., Bacholle, S., Bakiri, M., Baragatti, P., Barrillon, P., Bartocci, S., Batsch, T., Bayer, J., Bechini, R., Belenguer, T., Bellotti, R., Belov, A., Belov, K., Benadda, B., Benmessai, K., Berlind, A.A., Bertaina, M., Biermann, P.L., Biktemerova, S., Bisconti, F., Blanc, N., Błȩcki, J., Blin-Bondil, S., Bobik, P., Bogomilov, M., Bonamente, M., Boudaoud, R., Bozzo, E., Briggs, M.S., Bruno, A., Caballero, K.S., Cafagna, F., Campana, D., Capdevielle, J.-N., Capel, F., Caramete, A., Caramete, L., Carlson, P., Caruso, R., Casolino, M., Cassardo, C., Castellina, A., Castellini, G., Catalano, C., Catalano, O., Cellino, A., Chikawa, M., Chiritoi, G., Christl, M.J., Connaughton, V., Conti, L., Contino, G., Cordero, G., Cotto, G., Crawford, H.J., Cremonini, R., Csorna, S., Dagoret-Campagne, S., De Donato, C., de la Taille, C., De Santis, C., del Peral, L., Di Martino, M., Djemil, T., Djenas, S.A., Dulucq, F., Dupieux, M., Dutan, I., Ebersoldt, A., Ebisuzaki, T., Engel, R., Eser, J., Fang, K., Fenu, F., Fernández-González, S., Fernández-Soriano, J., Ferrarese, S., Finco, D., Flamini, M., Fornaro, C., Forza, R., Fouka, M., Franceschi, A., Franchini, S., Fuglesang, C., Fujimoto, J., Fukushima, M., Galeotti, P., García-Ortega, E., Garipov, G., Gascón, E., Geary, J., Gelmini, G., Genci, J., Giraudo, G., Gonchar, M., González Alvarado, C., Gorodetzky, P., Guardone, N., Guarino, F., Guehaz, R., Guzmán, A., Hachisu, Y., Haiduc, M., Harlov, B., Haungs, A., Hernández Carretero, J., Hidber, W., Higashide, K., Ikeda, D., Ikeda, H., Inoue, N., Inoue, S., Insolia, A., Isgrò, F., Itow, Y., Jammer, T., Joven, E., Judd, E.G., Jung, A., Jochum, J., Kajino, F., Kajino, T., Kalli, S., Kaneko, I., Kang, D., Kanouni, F., Karadzhov, Y., Karczmarczyk, J., Karus, M., Katahira, K., Kawai, K., Kawasaki, Y., Kedadra, A., Khales, H., Khrenov, B.A., Kim, Jeong-Sook, Kim, Soon-Wook, Kim, Sug-Whan, Kleifges, M., Klimov, P.A., Kolev, D., Kreykenbohm, I., Kudela, K., Kurihara, Y., Kusenko, A., Kuznetsov, E., Lacombe, M., Lachaud, C., Lahmar, H., Lakhdari, F., Larsson, O., Lee, J., Licandro, J., Lim, H., López Campano, L., Maccarone, M.C., Mackovjak, S., Mahdi, M., Manfrin, M., Maravilla, D., Marcelli, L., Marcos, J.L., Marini, A., Martens, K., Martín, Y., Martinez, O., Masciantonio, G., Mase, K., Matev, R., Matthews, J.N., Mebarki, N., Medina-Tanco, G., Mehrad, L., Mendoza, M.A., Merino, A., Mernik, T., Meseguer, J., Messaoud, S., Micu, O., Mignone, M., Mimouni, J., Miyamoto, H., Miyazaki, Y., Mizumoto, Y., Modestino, G., Monaco, A., Monnier-Ragaigne, D., Morales de los Ríos, J.A., Moretto, C., Morozenko, V.S., Mot, B., Murakami, T., Nadji, B., Nagano, M., Nagata, M., Nagataki, S., Nakamura, T., Napolitano, T., Naumov, D., Nava, R., Neronov, A., Nomoto, K., Nonaka, T., Ogawa, T., Ogio, S., Ohmori, H., Olinto, A.V., Orleański, P., Osteria, G., Painter, W., Panasyuk, M.I., Panico, B., Parizot, E., Park, I.H., Park, H.W., Pastircak, B., Patzak, T., Paul, T., Pennypacker, C., Pérez-Grande, I., Perfetto, F., Peter, T., Picozza, P., Pierog, T., Pindado, S., Piotrowski, L.W., Piraino, S., Placidi, L., Plebaniak, Z., Pliego, S., Pollini, A., Popescu, E.M., Prat, P., Prévôt, G., Prieto, H., Putis, M., Rabanal, J., Radu, A.A., Rahmani, M., Reardon, P., Reyes, M., Rezazadeh, M., Ricci, M., Rodríguez Frías, M.D., Ronga, F., Roth, M., Rothkaehl, H., Roudil, G., Rusinov, I., Rybczyński, M., Sabau, M.D., Sáez Cano, G., Sagawa, H., Sahnoune, Z., Saito, A., Sakaki, N., Sakata, M., Salazar, H., Sanchez, J.C., Sánchez, J.L., Santangelo, A., Santiago Crúz, L., Sanz-Andrés, A., Sanz Palomino, M., Saprykin, O., Sarazin, F., Sato, H., Sato, M., Schanz, T., Schieler, H., Scotti, V., Segreto, A., Selmane, S., Semikoz, D., Serra, M., Sharakin, S., Shibata, T., Shimizu, H.M., Shinozaki, K., Shirahama, T., Siemieniec-Oziȩbło, G., Sledd, J., Słomińska, K., Sobey, A., Stan, I., Sugiyama, T., Supanitsky, D., Suzuki, M., Szabelska, B., Szabelski, J., Tahi, H., Tajima, F., Tajima, N., Tajima, T., Takahashi, Y., Takami, H., Takeda, M., Takizawa, Y., Talai, M.C., Tenzer, C., Tibolla, O., Tkachev, L., Tokuno, H., Tomida, T., Tone, N., Toscano, S., Traïche, M., Tsenov, R., Tsunesada, Y., Tsuno, K., Tymieniecka, T., Uchihori, Y., Unger, M., Vaduvescu, O., Valdés-Galicia, J.F., Vallania, P., Vankova, G., Vigorito, C., Villaseñor, L., Vlcek, B., von Ballmoos, P., Vrabel, M., Wada, S., Watanabe, J., Watanabe, S., Watts, J., Jr., Weber, M., Weigand Muñoz, R., Weindl, A., Weiler, T.J., Wibig, T., Wiencke, L., Wille, M., Wilms, J., Włodarczyk, Z., Yamamoto, T., Yamamoto, Y., Yang, J., Yano, H., Yashin, I.V., Yonetoku, D., Yoshida, S., Young, R., Zgura, I.S., Zotov, M.Yu., and Zuccaro Marchi, A.

Published
2017
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29. Meteor studies in the framework of the JEM-EUSO program

Author

Abdellaoui, G., Abe, S., Acheli, A., Adams, J.H., Jr., Ahmad, S., Ahriche, A., Albert, J.-N., Allard, D., Alonso, G., Anchordoqui, L., Andreev, V., Anzalone, A., Aouimeur, W., Arai, Y., Arsene, N., Asano, K., Attallah, R., Attoui, H., Ave Pernas, M., Bacholle, S., Bakiri, M., Baragatti, P., Barrillon, P., Bartocci, S., Batsch, T., Bayer, J., Bechini, R., Belenguer, T., Bellotti, R., Belov, A., Belov, K., Benadda, B., Benmessai, K., Berlind, A.A., Bertaina, M., Biermann, P.L., Biktemerova, S., Bisconti, F., Blanc, N., Błȩcki, J., Blin-Bondil, S., Bobik, P., Bogomilov, M., Bonamente, M., Boudaoud, R., Bozzo, E., Briggs, M.S., Bruno, A., Caballero, K.S., Cafagna, F., Campana, D., Capdevielle, J.-N., Capel, F., Caramete, A., Caramete, L., Carlson, P., Caruso, R., Casolino, M., Cassardo, C., Castellina, A., Castellini, G., Catalano, C., Catalano, O., Cellino, A., Chikawa, M., Chiritoi, G., Christl, M.J., Connaughton, V., Conti, L., Cordero, G., Crawford, H.J., Cremonini, R., Csorna, S., Dagoret-Campagne, S., De Donato, C., de la Taille, C., De Santis, C., del Peral, L., Di Martino, M., Djemil, T., Djenas, S.A., Dulucq, F., Dupieux, M., Dutan, I., Ebersoldt, A., Ebisuzaki, T., Engel, R., Eser, J., Fang, K., Fenu, F., Fernández-González, S., Fernández-Soriano, J., Ferrarese, S., Finco, D., Flamini, M., Fornaro, C., Fouka, M., Franceschi, A., Franchini, S., Fuglesang, C., Fujimoto, J., Fukushima, M., Galeotti, P., García-Ortega, E., Garipov, G., Gascón, E., Geary, J., Gelmini, G., Genci, J., Giraudo, G., Gonchar, M., González Alvarado, C., Gorodetzky, P., Guarino, F., Guehaz, R., Guzmán, A., Hachisu, Y., Haiduc, M., Harlov, B., Haungs, A., Hernández Carretero, J., Hidber, W., Higashide, K., Ikeda, D., Ikeda, H., Inoue, N., Inoue, S., Isgrò, F., Itow, Y., Jammer, T., Joven, E., Judd, E.G., Jung, A., Jochum, J., Kajino, F., Kajino, T., Kalli, S., Kaneko, I., Kang, D., Kanouni, F., Karadzhov, Y., Karczmarczyk, J., Karus, M., Katahira, K., Kawai, K., Kawasaki, Y., Kedadra, A., Khales, H., Khrenov, B.A., Kim, Jeong-Sook, Kim, Soon-Wook, Kim, Sug-Whan, Kleifges, M., Klimov, P.A., Kolev, D., Kreykenbohm, I., Kudela, K., Kurihara, Y., Kusenko, A., Kuznetsov, E., Lacombe, M., Lachaud, C., Lahmar, H., Lakhdari, F., Larsson, O., Lee, J., Licandro, J., Lim, H., López Campano, L., Maccarone, M.C., Mackovjak, S., Mahdi, M., Maravilla, D., Marcelli, L., Marcos, J.L., Marini, A., Martens, K., Martín, Y., Martinez, O., Masciantonio, G., Mase, K., Matev, R., Matthews, J.N., Mebarki, N., Medina-Tanco, G., Mehrad, L., Mendoza, M.A., Merino, A., Mernik, T., Meseguer, J., Messaoud, S., Micu, O., Mimouni, J., Miyamoto, H., Miyazaki, Y., Mizumoto, Y., Modestino, G., Monaco, A., Monnier-Ragaigne, D., Morales de los Ríos, J.A., Moretto, C., Morozenko, V.S., Mot, B., Murakami, T., Nadji, B., Nagano, M., Nagata, M., Nagataki, S., Nakamura, T., Napolitano, T., Nardelli, A., Naumov, D., Nava, R., Neronov, A., Nomoto, K., Nonaka, T., Ogawa, T., Ogio, S., Ohmori, H., Olinto, A.V., Orleański, P., Osteria, G., Painter, W., Panasyuk, M.I., Panico, B., Parizot, E., Park, I.H., Park, H.W., Pastircak, B., Patzak, T., Paul, T., Pennypacker, C., Perdichizzi, M., Pérez-Grande, I., Perfetto, F., Peter, T., Picozza, P., Pierog, T., Pindado, S., Piotrowski, L.W., Piraino, S., Placidi, L., Plebaniak, Z., Pliego, S., Pollini, A., Popescu, E.M., Prat, P., Prévôt, G., Prieto, H., Putis, M., Rabanal, J., Radu, A.A., Rahmani, M., Reardon, P., Reyes, M., Rezazadeh, M., Ricci, M., Rodríguez Frías, M.D., Ronga, F., Roth, M., Rothkaehl, H., Roudil, G., Rusinov, I., Rybczyński, M., Sabau, M.D., Sáez Cano, G., Sagawa, H., Sahnoune, Z., Saito, A., Sakaki, N., Sakata, M., Salazar, H., Sanchez, J.C., Sánchez, J.L., Santangelo, A., Santiago Crúz, L., Sanz-Andrés, A., Sanz Palomino, M., Saprykin, O., Sarazin, F., Sato, H., Sato, M., Schanz, T., Schieler, H., Scotti, V., Segreto, A., Selmane, S., Semikoz, D., Serra, M., Sharakin, S., Shibata, T., Shimizu, H.M., Shinozaki, K., Shirahama, T., Siemieniec-Oziȩbło, G., Sledd, J., Słomińska, K., Sobey, A., Stan, I., Sugiyama, T., Supanitsky, D., Suzuki, M., Szabelska, B., Szabelski, J., Tahi, H., Tajima, F., Tajima, N., Tajima, T., Takahashi, Y., Takami, H., Takeda, M., Takizawa, Y., Talai, M.C., Tenzer, C., Tibolla, O., Tkachev, L., Tokuno, H., Tomida, T., Tone, N., Toscano, S., Traïche, M., Tsenov, R., Tsunesada, Y., Tsuno, K., Tymieniecka, T., Uchihori, Y., Unger, M., Vaduvescu, O., Valdés-Galicia, J.F., Vallania, P., Vankova, G., Vigorito, C., Villaseñor, L., Vlcek, B., von Ballmoos, P., Vrabel, M., Wada, S., Watanabe, J., Watanabe, S., J. Watts Jr., Weber, M., Weigand Muñoz, R., Weindl, A., Weiler, T.J., Wibig, T., Wiencke, L., Wille, M., Wilms, J., Włodarczyk, Z., Yamamoto, T., Yamamoto, Y., Yang, J., Yano, H., Yashin, I.V., Yonetoku, D., Yoshida, S., Young, R., Zgura, I.S, Zotov, M.Yu., and Zuccaro Marchi, A.

Published
2017
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31. Modeling the Winter Heat Conduction Through the Sea Ice System During MOSAiC.

Author

Zampieri, Lorenzo, Clemens‐Sewall, David, Sledd, Anne, Hutter, Nils, and Holland, Marika

Subjects
SEA ice, HEAT conduction, GLOBAL warming, ARCTIC climate, CLIMATE feedbacks, ARCTIC exploration
Abstract

Models struggle to accurately simulate observed sea ice thickness changes, which could be partially due to inadequate representation of thermodynamic processes. We analyzed co‐located winter observations of the Arctic sea ice from the Multidisciplinary Drifting Observatory for the Study of the Arctic Climate for evaluating and improving thermodynamic processes in sea ice models, aiming to enable more accurate predictions of the warming climate system. We model the sea ice and snow heat conduction for observed transects forced by realistic boundary conditions to understand the impact of the non‐resolved meter‐scale snow and sea ice thickness heterogeneity on horizontal heat conduction. Neglecting horizontal processes causes underestimating the conductive heat flux of 10% or more. Furthermore, comparing model results to independent temperature observations reveals a ∼5 K surface temperature overestimation over ice thinner than 1 m, attributed to shortcomings in parameterizing surface turbulent and radiative fluxes rather than the conduction. Assessing the model deficiencies and parameterizing these unresolved processes is required for improved sea ice representation. Plain Language Summary: Numerical sea ice models rely on conceptual simplifications of the sea ice and snow conditions observed in the Arctic and Southern Ocean. In particular, we cannot account for the variations in sea ice thickness and snow depth at the meter scale because we have limited computing capabilities and lack a detailed understanding of the processes defining how the sea ice system evolves. Furthermore, when designing sea ice models, we assume that the heat can flow only vertically, while in reality, this exchange is also horizontal and depends on the local topography. Thanks to observations collected during the Multidisciplinary Drifting Observatory for the Study of Arctic Climate expedition, we can better quantify model errors when using thermodynamic approximations. Our findings suggest that slightly more heat flows through the sea ice system than we can simulate with a simplified sea ice model and that the surface temperature of the model is too warm for thin ice and snow conditions. Learning the nature of these errors is useful because we could formulate corrections for our models, investigate the occurrence of climate feedback mechanisms, and possibly provide more reliable predictions about the current state of the sea ice and its future evolution, which is currently heavily impacted by global warming. Key Points: Multidisciplinary Drifting Observatory for the Study of Arctic Climate observations enable improved thermodynamic process understanding and representation in sea ice modelsResolved meter‐scale ice and snow thickness heterogeneity and horizontal heat conduction enhance conductive heat flux by up to 10% in modelsA positive surface temperature model bias up to 5 K suggests a misrepresentation of the surface energy balance over thin ice [ABSTRACT FROM AUTHOR]

Published
2024
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32. Looking Backward, Looking Forward: MLA Members Speak

Author

Alliston, April, Ammons, Elizabeth, Arnold, Jean, Baym, Nina, Beckett, Sandra L., Beidler, Peter G., Berger, Roger A., Bermann, Sandra, Wilson, J. J., Boone, Troy, Booth, Alison, Booth, Wayne C., Phelan, James, Borroff, Marie, Hassan, Ihab, Bowen, Zack, Weisstein, Ulrich, Campbell, Jill, Campion, Dan, Caplan, Jay, Charney, Maurice, Clark, Beverly Lyon, Colby, Robert A., Coleman,, Thomas C., Cooley, Nicole, Dellamora, Richard, Dickstein, Morris, Dixon, Terrell, Elliott, Emory, Emerson, Caryl, Engar, Ann W., Engle, Lars, Hammermeister, Kai, Feltes, N. N., Ferguson, Mary Anne, Finch, Annie, Fishkin, Shelley Fisher, Flieger, Jerry Aline, Friedman, Norman, Garland-Thomson, Rosemarie, Gilbert, Sandra M., Grobman, Laurie, Guida, George, Gumpel, Liselotte, Gupta, R. K., Howe, Florence, Jrade, Cathy L., Kaye, Richard A., Winton, Calhoun, Krieger, Murray, Langbaum, Robert, Lanham, Richard A., Lindemann, Marilee, Lützeler, Paul Michael, Lynn, Thomas J., MacCannell, Juliet Flower, Massé, Michelle A., Massey, Irving, May, Georges, Hallstein, Christian W., May, Gita, McDiarmid, Lucy, Messer-Davidow, Ellen, Mitchell, Koritha, Smiles, Robin, Albeny, Kenyatta, Monteiro, George, Myerson, Joel, Nadel, Alan, Nichols, Ashton, Nishimura, Jeffrey, Oxenhandler, Neal, Palumbo-Liu, David, Pecora, Vincent P., Porter, David, Potter, Nancy, Rosbottom, Ronald C., Rivers, Elias L., Strasser, Gerhard F., Styan, J. L., Totten, Gary, van Leer, David, Varadharajan, Asha, Willis, Sharon, Wright, Louise E., Yates, Donald A., Yokota-Murakami, Takayuki, Zeikowitz, Richard E., Bammer, Angelika, Bauer, Dale, Beckson, Karl, Bowen, Betsy A., Donohue, Stacey, Emerson, Sheila, Foster, Gwendolyn Audrey, Halio, Jay L., Kroeber, Karl, Hawkes, Terence, Hunter, William B., Jacobus, Mary, King, Willard F., Miller, Nancy K., Norton, Jody, Pellegrini, Ann, Rosenbaum, S. P., Roth, Lorie, Scholes, Robert, Shattock, Joanne, VanArsdel, Rosemary T., Bendixen, Alfred, Brown, Alanna Kathleen, Kiskis, Michael J., Castillo, Debra A., Chow, Rey, Crossen, John F., Fleissner, Robert F., Gagnier, Regenia, Howe, Nicholas, Inge, M. Thomas, Mehring, Frank, Park, Hyungji, Ramazani, Jahan, Roemer, Kenneth M., Rogers, Deborah D., Schwartz, Regina M., Shawcross, John T., Silver, Brenda R., von Hendy, Andrew, Wexman, Virginia Wright, Zangen, Britta, Aldridge, A. Owen, Backscheider, Paula R., Bartel, Roland, Birnbaum, Milton, Bishop, Jonathan, Downing, Crystal, Ellis, Frank H., Forns-Broggi, Roberto, Giles, James R., Giles, Mary E., Green, Susan Blair, Gutwirth, Madelyn, Hieatt, Constance B., Adepitan, Titi, Knowlton,, Edgar C., Mussman, Emanuel, Nelson, Sally Todd, Preyer, Robert O., Rodriguez, David Diego, Stern, Guy, Thorpe, James, Wilson, Robert J., Beal, Rebecca S., Simutis, Joyce, Bowden, Betsy, Cooper, Sara, Dixon, Wheeler Winston, el Ariss, Tarek, Jewell, Richard, Kronik, John W., Martin, Wendy, McDougal, Stuart Y., Méndez-Ramírez, Hugo, Schweitzer, Ivy, Singer, Armand E., Tanselle, G. Thomas, Bishop, Tom, Caws, Mary Ann, Gutwirth, Marcel, Ippolito, Christophe, Kritzman, Lawrence D., Longenbach, James, McCracken, Tim, Molitor, Wolfe S., Quantic, Diane, Rabassa, Gregory, Tsagaris, Ellen M., Yu, Anthony C., Craige, Betty Jean, Harris, Wendell V., Miller, J. Hillis, Swan, Jesse G., Zimmer-Loew, Helene, Berek, Peter, Chandler, James, Charney, Hanna K., Cohen, Philip, Fetterley, Judith, Lindenberger, Herbert, Lupton, Julia Reinhard, Novak, Maximillian E., Ohmann, Richard, Perloff, Marjorie, Reynolds, Mark, Sledd, James, Turner, Harriet, Umeh, Marie, Alaya, Flavia, Barreca, Regina, Bieber, Konrad, Hanson, Ellis, Hyde, William J., Laird, Holly A., Leverenz, David, Michie, Allen, Miller, J. Wesley, Rosenberg, Marvin, Schwarz, Daniel R., Trahan, Elizabeth Welt, and Yellin, Jean Fagan

Published
2000
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35. Nudging allows direct evaluation of coupled climate models with in situ observations : a case study from the MOSAiC expedition

Author

Pithan, Felix, Athanase, Marylou, Dahlke, Sandro, Sánchez-Benítez, Antonio, Shupe, Matthew D., Sledd, Anne, Streffing, Jan, Svensson, Gunilla, Jung, Thomas, Pithan, Felix, Athanase, Marylou, Dahlke, Sandro, Sánchez-Benítez, Antonio, Shupe, Matthew D., Sledd, Anne, Streffing, Jan, Svensson, Gunilla, and Jung, Thomas

Abstract

Comparing the output of general circulation models to observations is essential for assessing and improving the quality of models. While numerical weather prediction models are routinely assessed against a large array of observations, comparing climate models and observations usually requires long time series to build robust statistics. Here, we show that by nudging the large-scale atmospheric circulation in coupled climate models, model output can be compared to local observations for individual days. We illustrate this for three climate models during a period in April 2020 when a warm air intrusion reached the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in the central Arctic. Radiosondes, cloud remote sensing and surface flux observations from the MOSAiC expedition serve as reference observations. The climate models AWI-CM1/ECHAM and AWI-CM3/IFS miss the diurnal cycle of surface temperature in spring, likely because both models assume the snowpack on ice to have a uniform temperature. CAM6, a model that uses three layers to represent snow temperature, represents the diurnal cycle more realistically. During a cold and dry period with pervasive thin mixed-phase clouds, AWI-CM1/ECHAM only produces partial cloud cover and overestimates downwelling shortwave radiation at the surface. AWI-CM3/IFS produces a closed cloud cover but misses cloud liquid water. Our results show that nudging the large-scale circulation to the observed state allows a meaningful comparison of climate model output even to short-term observational campaigns. We suggest that nudging can simplify and accelerate the pathway from observations to climate model improvements and substantially extends the range of observations suitable for model evaluation.

Published
2023
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36. Asymptotic and Assouad–Nagata dimension of finitely generated groups and their subgroups.

Author

Sledd, Levi

Subjects
*OPEN-ended questions
Abstract

We prove that for all k,m,n∈N∪{∞}$k,m,n \in \mathbb {N} \cup \lbrace \infty \rbrace$ with 4⩽k⩽m⩽n$4 \leqslant k \leqslant m \leqslant n$, there exists a finitely generated group G$G$ with a finitely generated subgroup H$H$ such that asdim(G)=k$\operatorname{asdim}(G) = k$, asdimAN(G)=m$\operatorname{asdim}_{\textnormal {AN}}(G) = m$, and asdimAN(H)=n$\operatorname{asdim}_{\textnormal {AN}}(H)=n$. This simultaneously answers two open questions in asymptotic dimension theory. [ABSTRACT FROM AUTHOR]

Published
2023
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39. Evaluating nudged coupled climate models against MOSAiC observations reveals weaknesses in the representation of clouds, boundary-layer turbulence and snow pack

Author

Felix Pithan, Marylou Athanase, Sandro Dahlke, Antonio Sánchez-Benítez, Matthew Shupe, Anne Sledd, Jan Streffing, Gunilla Svensson, and Thomas Jung

Abstract

Comparing the output of general circulation models to observations is essential for assessing and improving the quality of models. While numerical weather prediction models are routinely assessed against a large array of observations, comparing climate models and observations usually requires long time series to build robust statistics. Here, we show that by nudging the large-scale atmospheric circulation in coupled climate models, model output can be compared to local observations for individual days. We illustrate this for three climate models during a period in April 2020 when a warm air intrusion reached the MOSAiC expedition in the central Arctic. Radiosondes, cloud remote sensing and surface flux observations from the MOSAiC expedition serve as reference observations. The climate models AWI-CM1/ECHAM and AWI-CM3/IFS miss the diurnal cycle of surface temperature in spring, likely because both models assume the snow pack on ice to have a uniform temperature. CAM6, a model that uses three layers to represent snow temperature, represents the diurnal cycle more realistically. During a cold and dry period with pervasive thin mixed-phase clouds, AWI-CM1/ECHAM only produces partial cloud cover and overestimates downwelling shortwave radiation at the surface. AWI-CM3/IFS produces a closed cloud cover but misses cloud liquid water. All models overestimate downward turbulent heat fluxes under stable stratification, a long-standing issue in weather and climate models. Our results show that nudging the large-scale circulation to the observed state allows a meaningful comparison of climate model output even to short-term observational campaigns. We suggest that nudging can simplify and accelerate the pathway from observations to climate model improvements and substantially extends the range of observations suitable for model evaluation.

Published
2023
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40. Nudging allows direct evaluation of coupled climate models with in-situ observations: A case study from the MOSAiC expedition

Author

Felix Pithan, Marylou Athanase, Sandro Dahlke, Antonio Sánchez-Benítez, Matthew D. Shupe, Anne Sledd, Jan Streffing, Gunilla Svensson, and Thomas Jung

Subjects
General Medicine
Abstract

Comparing the output of general circulation models to observations is essential for assessing and improving the quality of models. While numerical weather prediction models are routinely assessed against a large array of observations, comparing climate models and observations usually requires long time series to build robust statistics. Here, we show that by nudging the large-scale atmospheric circulation in coupled climate models, model output can be compared to local observations for individual days. We illustrate this for three climate models during a period in April 2020 when a warm air intrusion reached the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in the central Arctic. Radiosondes, cloud remote sensing and surface flux observations from the MOSAiC expedition serve as reference observations. The climate models AWI-CM1/ECHAM and AWI-CM3/IFS miss the diurnal cycle of surface temperature in spring, likely because both models assume the snowpack on ice to have a uniform temperature. CAM6, a model that uses three layers to represent snow temperature, represents the diurnal cycle more realistically. During a cold and dry period with pervasive thin mixed-phase clouds, AWI-CM1/ECHAM only produces partial cloud cover and overestimates downwelling shortwave radiation at the surface. AWI-CM3/IFS produces a closed cloud cover but misses cloud liquid water. Our results show that nudging the large-scale circulation to the observed state allows a meaningful comparison of climate model output even to short-term observational campaigns. We suggest that nudging can simplify and accelerate the pathway from observations to climate model improvements and substantially extends the range of observations suitable for model evaluation.

Published
2023

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