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Rasmus Wiuff

Abstract

In October 1941, Nazi Germany’s High Command realized that the war against the Soviet Union could not be ended before winter. The German professor Franz Baur prepared a long-range weather forecast for the winter of 1941/42. Baur never revealed anything about this forecast. However, according to an article published ten years after Baur’s death, Baur predicted that the winter of 1941/42 would be normal or milder than normal, primarily based on the main argument that the previous two winters had been very severe and never in climatic history had more than two severe winters occurred in a row. The winter ended up being one of the worst.

Today, Baur’s prognoses from wartime are public. In this article, it is shown that the previous description of Baur’s prognosis for the winter of 1941/42 is incorrect. Baur had a problematic relationship with his colleagues, so it is possible that the story of his prognosis is incorrect due to personal and professional contradictions. Baur’s postulated prognosis for the winter of 1941/42 destroyed his reputation. Based on the original prognoses from wartime and Baur’s scientific and personal history, this article shows that this judgment was too harsh and unfair.

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Daniel M. Hueholt
,
Sandra E. Yuter
, and
Matthew A. Miller

Abstract

Ice habit diagrams published prior to 2009—and many since—do not accurately describe in situ observations of ice shapes as a function of temperature and moisture. Laboratory studies and analysis of field observations by Bailey and Hallett in a series of papers in 2002, 2004, and 2009 corrected several errors from earlier studies, but their work has not been widely disseminated. We present a new, simplified diagram based on Bailey and Hallett’s work that focuses on several ice growth forms arising from the underlying surface processes by which mass is added to a crystal: tabular, columnar, branched, side branched, two types of polycrystalline forms, and a multiple growth regime at low ice supersaturations. To aid interpretation for a variety of applications, versions of the ice growth diagram are presented in terms of relative humidity with respect to water as well as the traditional formats of relative humidity with respect to ice and vapor density excess. These diagrams are intended to be understandable and useful in classroom settings at the sophomore undergraduate level and above. The myriad shapes of pristine snow crystals can be described as the result of either a single growth form or a sequence of growth forms. Overlays of data from upper-air soundings on the ice growth diagrams aid interpretation of expected physical properties and processes in conditions of ice growth.

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Julie M. Thériault
,
Nicolas R. Leroux
,
Ronald E. Stewart
,
André Bertoncini
,
Stephen J. Déry
,
John W. Pomeroy
,
Hadleigh D. Thompson
,
Hilary Smith
,
Zen Mariani
,
Aurélie Desroches-Lapointe
,
Selina Mitchell
, and
Juris Almonte

Abstract

The Canadian Rockies are a triple-continental divide, whose high mountains are drained by major snow-fed and rain-fed rivers flowing to the Pacific, Atlantic, and Arctic Oceans. The objective of the April–June 2019 Storms and Precipitation Across the continental Divide Experiment (SPADE) was to determine the atmospheric processes producing precipitation on the eastern and western sides of the Canadian Rockies during springtime, a period when upslope events of variable phase dominate precipitation on the eastern slopes. To do so, three observing sites across the divide were instrumented with advanced meteorological sensors. During the 13 observed events, the western side recorded only 25% of the eastern side’s precipitation accumulation, rainfall occurred rather than snowfall, and skies were mainly clear. Moisture sources and amounts varied markedly between events. An atmospheric river landfall in California led to moisture flowing persistently northward and producing the longest duration of precipitation on both sides of the divide. Moisture from the continental interior always produced precipitation on the eastern side but only in specific conditions on the western side. Mainly slow-falling ice crystals, sometimes rimed, formed at higher elevations on the eastern side (>3 km MSL), were lifted, and subsequently drifted westward over the divide during nonconvective storms to produce rain at the surface on the western side. Overall, precipitation generally crossed the divide in the Canadian Rockies during specific spring-storm atmospheric conditions although amounts at the surface varied with elevation, condensate type, and local and large-scale flow fields.

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Il-Ju Moon
,
Thomas R. Knutson
,
Hye-Ji Kim
,
Alexander V. Babanin
, and
Jin-Yong Jeong

Abstract

Tropical cyclones operate as heat engines, deriving energy from the thermodynamic disequilibrium between ocean surfaces and atmosphere. Available energy for the cyclones comes primarily from upper-ocean heat content. Here, we show that eastern North Pacific hurricanes reach a given intensity 15% faster on average than western North Pacific typhoons despite having half the available ocean heat content. Eastern North Pacific hurricanes also intensify on average 16% more with a given ocean energy (i.e., air–sea enthalpy flux) than western North Pacific typhoons. As efficient intensifiers, eastern Pacific hurricanes remain small during their intensification period, tend to stay at lower latitudes, and are affected by relatively lower vertical wind shear, a colder troposphere, and a drier boundary layer. Despite a shallower warm upper-ocean layer in the eastern North Pacific, average hurricane-induced sea surface cooling there is only slightly larger than in the western North Pacific due to the opposing influences of stronger density stratification, smaller size, and related wave-interaction effects. In contrast, western North Pacific typhoons encounter a more favorable oceanic environment for development, but several factors cause typhoons to greatly increase their size during intensification, resulting in a slow and inefficient intensification process. These findings on tropical cyclones’ basin-dependent characteristics contribute toward a better understanding of TC intensification.

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Samuel T. Buisán
,
Roberto Serrano-Notivoli
,
John Kochendorfer
, and
Francisco J. Bello-Millán

Abstract

On January 2021, the heaviest snowfall in five decades hit central Spain, especially affecting Madrid. The city’s Barajas International Airport closed, along with a number of roads, and all trains to and from Madrid were cancelled. This storm was named Filomena by the Spanish Meteorological Agency (AEMET), and produced continuous snowfall in Spain on 7–10 January. The observed snow depth was around 50 cm in 24 h in Madrid, and even higher in other areas of Spain. However, the measured accumulation of national precipitation gauges was not consistent with the observed accumulated snow on the ground and with the modeled weather forecast. The undercatch of solid precipitation was the primary reason for this inconsistency. This undercatch was quantified using transfer functions developed from the World Meteorological Organization (WMO) Solid Precipitation Intercomparison Experiment (SPICE). Results show that an underestimation of 20%–30% of solid precipitation in large areas of Spain was observed, with some areas experiencing even larger differences. Without adjustments, it was impossible to accurately validate the model forecast. The adjusted precipitation was also more realistically distributed, and it was more consistent with all the damage that occurred. The same methods can be applied to other snowfall events occurring anywhere in the world, and also using different precipitation gauges and/or models. This an example of the type of extreme events that modelers, forecasters, and climatologists should be aware of to avoid misinterpreting differences between modeled precipitation, observed precipitation, and nowcasting.

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John A. Knox

Abstract

Data on the number and economic status of bachelor’s degree recipients are harder to access for the atmospheric sciences than for other similar fields. The U.S. Department of Education’s College Scorecard provides a new, comprehensive, and annually updated way to obtain this data. Five years of College Scorecard data are analyzed, revealing that from 2015 to 2019 the number of bachelor’s recipients in the U.S. was at least 700 annually, with a downward trend of about 13% over the period. Institution-specific data allow for a ranking of undergraduate programs by number of bachelor’s recipients that has been impossible to compile since the demise of the American Meteorological Society (AMS)-University Corporation for Atmospheric Research (UCAR) Curricula publication in the mid-2000s. Early-career earnings data for federally aided students from larger programs compiled in the College Scorecard indicate that median first-year annual salaries by the end of the 2010s averaged about $35,000, with an increase to $45,000 by the third year. Median debt at graduation during the same period averaged slightly less than $25,000. In the future, College Scorecard data could be used to provide regular updates on atmospheric sciences students, graduates, and early-career professionals at all degree levels. The AMS should partner with the American Institute of Physics’ Statistical Research Center to create and disseminate such reports.

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Denis S. Willett
,
Brian White
,
Tom Augspurger
,
Jonathan Brannock
,
Jenny Dissen
,
Patrick Keown
,
Otis B. Brown
, and
Adrienne Simonson
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Nadir Jeevanjee
,
Isaac Held
, and
V. Ramaswamy

Abstract

Syukoro (Suki) Manabe’s Nobel Prize in Physics was awarded largely for his early work on one-dimensional models of “radiative–convective equilibrium” (RCE), which produced the first credible estimates of Earth’s climate sensitivity. This article reviews that work and tries to identify those aspects that make it so distinctive. We argue that Manabe’s model of RCE contained three crucial ingredients. These are (i) a tight convective coupling of the surface to the troposphere, (ii) an assumption of fixed relative humidity rather than fixed absolute humidity, and (iii) a sufficiently realistic representation of greenhouse gas radiative transfer. Previous studies had separately identified these key ingredients, but none had properly combined them. We then discuss each of these ingredients in turn, highlighting how subsequent research in the intervening decades has only cemented their importance for understanding global climate change. We close by reflecting on the elegance of Manabe’s approach and its lasting value.

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J. T. Pasquier
,
R. O. David
,
G. Freitas
,
R. Gierens
,
Y. Gramlich
,
S. Haslett
,
G. Li
,
B. Schäfer
,
K. Siegel
,
J. Wieder
,
K. Adachi
,
F. Belosi
,
T. Carlsen
,
S. Decesari
,
K. Ebell
,
S. Gilardoni
,
M. Gysel-Beer
,
J. Henneberger
,
J. Inoue
,
Z. A. Kanji
,
M. Koike
,
Y. Kondo
,
R. Krejci
,
U. Lohmann
,
M. Maturilli
,
M. Mazzolla
,
R. Modini
,
C. Mohr
,
G. Motos
,
A. Nenes
,
A. Nicosia
,
S. Ohata
,
M. Paglione
,
S. Park
,
R. E. Pileci
,
F. Ramelli
,
M. Rinaldi
,
C. Ritter
,
K. Sato
,
T. Storelvmo
,
Y. Tobo
,
R. Traversi
,
A. Viola
, and
P. Zieger

Abstract

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Ålesund, Svalbard. The campaign’s primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications.

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Anamaria Bukvic
,
Kyle Mandli
,
Donovan Finn
,
Talea Mayo
,
Gabrielle Wong-Parodi
,
Alexis Merdjanoff
,
Joshua Alland
,
Christopher Davis
,
Rebecca Haacker
,
Rebecca Morss
,
Cassandra O’Lenick
,
Olga Wilhelmi
, and
Danica Lombardozzi

Abstract

The authors introduce the National Center for Atmospheric Research’s Early-Career Faculty Innovator Program and present lessons learned about advancing interdisciplinary and convergent science with and for society. The Innovator Program brings together faculty and students from the social sciences with NCAR researchers to conduct interdisciplinary and convergent research on problems motivated by societal challenges in the face of climate change and environmental hazards. This article discusses aspects of program structure and the research being conducted. The article also emphasizes the challenges and successes of the research collaborations within the Innovator Program, along with lessons learned about engaging in highly interdisciplinary, potentially convergent work, particularly from the early-career perspective. Many projects involve faculty PIs from racially, ethnically, or otherwise minoritized groups, and minority serving institutions (MSIs), or those who engage with marginalized communities. Hence, the Innovator Program is contributing to the development of a growing research community pursuing science with and for society that also broadens participation in research related to the atmospheric sciences.

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