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Francisco J. Tapiador
,
Rémy Roca
,
Anthony Del Genio
,
Boris Dewitte
,
Walt Petersen
, and
Fuqing Zhang

Abstract

Precipitation has often been used to gauge the performances of numerical weather and climate models, sometimes together with other variables such as temperature, humidity, geopotential, and clouds. Precipitation, however, is singular in that it can present a high spatial variability and probably the sharpest gradients among all meteorological fields. Moreover, its quantitative measurement is plagued with difficulties, and there are even notable differences among different reference datasets. Several additional issues sometimes lead to questions about its usefulness in model validation. This essay discusses the use of precipitation for model verification and validation and the crucial role of highly precise and reliable satellite estimates, such as those from NASA’s Global Precipitation Mission Core Observatory.

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Bart Geerts
,
David J. Raymond
,
Vanda Grubišić
,
Christopher A. Davis
,
Mary C. Barth
,
Andrew Detwiler
,
Petra M. Klein
,
Wen-Chau Lee
,
Paul M. Markowski
,
Gretchen L. Mullendore
, and
James A. Moore

Abstract

Recommendations are presented for in situ and remote sensing instruments and capabilities needed to advance the study of convection and turbulence in the atmosphere. These recommendations emerged from a community workshop held on 22–24 May 2017 at the National Center for Atmospheric Research and sponsored by the National Science Foundation. Four areas of research were distinguished at this workshop: i) boundary layer flows, including convective and stable boundary layers over heterogeneous land use and terrain conditions; ii) dynamics and thermodynamics of convection, including deep and shallow convection and continental and maritime convection; iii) turbulence above the boundary layer in clouds and in clear air, terrain driven and elsewhere; and iv) cloud microphysical and chemical processes in convection, including cloud electricity and lightning.

The recommendations presented herein address a series of facilities and capabilities, ranging from existing ones that continue to fulfill science needs and thus should be retained and/or incrementally improved, to urgently needed new facilities, to desired capabilities for which no adequate solutions are as yet on the horizon. A common thread among all recommendations is the need for more highly resolved sampling, both in space and in time. Significant progress is anticipated, especially through the improved availability of airborne and ground-based remote sensors to the National Science Foundation (NSF)-supported community.

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Christopher W. Landsea
and
John P. Cangialosi

Abstract

The tropical cyclone is the largest single-day-impact meteorological event in the United States and worldwide through its effects from storm surge, extreme winds, freshwater flooding, and embedded tornadoes. Fortunately, over the last three decades there have been incredible advances in forecast accuracy, especially for the track of the tropical cyclone’s center. Errors have been cut by two-thirds in just 25 years due to global modeling advances, data assimilation improvements, dramatic increases in observations primarily derived from satellite platforms, and use of ensemble forecast techniques. These four factors have allowed for highly accurate synoptic-scale atmospheric initial conditions and forecasts of the steering flow out through several days into the future. However, such improvements cannot continue indefinitely. It is well known in the atmospheric sciences that there exists an inherent “limit of predictability” because of errors at the smallest scales (microscale—meters and seconds) that eventually cascade up to the largest scales (synoptic scale—thousands of kilometers and several days). While there have been estimates of the limits of predictability for tropical cyclone track prediction in the past, our current capabilities have exceeded those somewhat pessimistic earlier outlooks. This essay discusses the current state of the art for tropical cyclone track prediction and reassesses whether reaching the “limit of predictability” is imminent. The ramifications of this eventual conclusion—whether in the short-term or still decades away—could be critical for all users of tropical cyclone track forecast information, including the emergency management community/governments, the media, the private sector, and the general public.

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Alan Thorpe
and
David Rogers

Abstract

The Global Weather Enterprise (GWE) encompasses the scientific research, technology, observations, modeling, forecasting, and forecast products that need to come together to provide accurate and reliable weather information and services that save lives, protect infrastructure, and enhance economic output. It is a value chain from weather observations to, ultimately, the creation of actionable analysis-and-forecast weather information of huge benefit to society. The GWE is a supreme exemplar of the value of international cooperation, public–private engagement, and scientific and technological know-how. It has been a successful enterprise, but one that has ever-increasing requirements for continual improvement as population density increases and climate change takes place so that the impacts of weather hazards can be mitigated as far as possible. However, the GWE is undergoing a period of significant change arising, for example, from the growing need for more accurate and reliable weather information, advances coming from science and technology, and the expansion of private sector capabilities. These changes offer real opportunities for the GWE but also present a number of obstacles and risks that could, if not addressed, stifle this development, adversely impacting the societies it aims to serve. This essay aims to catalyze the GWE to address the issues collectively, by dialogue, engagement, and mutual understanding.

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Daniel E. Wolfe
and
R. J. Lataitis
Open access
A. K. Pavlov
,
A. Meyer
,
A. Rösel
,
L. Cohen
,
J. King
,
P. Itkin
,
J. Negrel
,
S. Gerland
,
S. R. Hudson
,
P. A. Dodd
,
L. de Steur
,
S. Mathisen
,
N. Cobbing
, and
M. A. Granskog

Abstract

Effective science communication is essential to share knowledge and recruit the next generation of researchers. Science communication to the general public can, however, be hampered by limited resources and a lack of incentives in the academic environment. Various social media platforms have recently emerged, providing free and simple science communication tools to reach the public and young people especially, an audience often missed by more conventional outreach initiatives. While individual researchers and large institutions are present on social media, smaller research groups are underrepresented. As a small group of oceanographers, sea ice scientists, and atmospheric scientists at the Norwegian Polar Institute, we share our experience establishing, developing, and maintaining a successful Arctic science communication initiative (@oceanseaicenpi) on Instagram, Twitter, and Facebook. The initiative is run entirely by a team of researchers with limited time and financial resources. It has built a broad audience of more than 7,000 followers, half of which is associated with the team’s Instagram account. To our knowledge, @oceanseaicenpi is one of the most successful Earth sciences Instagram accounts managed by researchers. The initiative has boosted the alternative metric scores of our publications and helped participating researchers become better writers and communicators. We hope to inspire and help other research groups by providing some guidelines on how to develop and conduct effective science communication via social media.

Open access
Jason A. Otkin
,
Mark Svoboda
,
Eric D. Hunt
,
Trent W. Ford
,
Martha C. Anderson
,
Christopher Hain
, and
Jeffrey B. Basara

Abstract

Given the increasing use of the term “flash drought” by the media and scientific community, it is prudent to develop a consistent definition that can be used to identify these events and to understand their salient characteristics. It is generally accepted that flash droughts occur more often during the summer owing to increased evaporative demand; however, two distinct approaches have been used to identify them. The first approach focuses on their rate of intensification, whereas the second approach implicitly focuses on their duration. These conflicting notions for what constitutes a flash drought (i.e., unusually fast intensification vs short duration) introduce ambiguity that affects our ability to detect their onset, monitor their development, and understand the mechanisms that control their evolution. Here, we propose that the definition for “flash drought” should explicitly focus on its rate of intensification rather than its duration, with droughts that develop much more rapidly than normal identified as flash droughts. There are two primary reasons for favoring the intensification approach over the duration approach. First, longevity and impact are fundamental characteristics of drought. Thus, short-term events lasting only a few days and having minimal impacts are inconsistent with the general understanding of drought and therefore should not be considered flash droughts. Second, by focusing on their rapid rate of intensification, the proposed “flash drought” definition highlights the unique challenges faced by vulnerable stakeholders who have less time to prepare for its adverse effects.

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Jun-Ichi Yano
,
Michał Z. Ziemiański
,
Mike Cullen
,
Piet Termonia
,
Jeanette Onvlee
,
Lisa Bengtsson
,
Alberto Carrassi
,
Richard Davy
,
Anna Deluca
,
Suzanne L. Gray
,
Víctor Homar
,
Martin Köhler
,
Simon Krichak
,
Silas Michaelides
,
Vaughan T. J. Phillips
,
Pedro M. M. Soares
, and
Andrzej A. Wyszogrodzki

Abstract

After extensive efforts over the course of a decade, convective-scale weather forecasts with horizontal grid spacings of 1–5 km are now operational at national weather services around the world, accompanied by ensemble prediction systems (EPSs). However, though already operational, the capacity of forecasts for this scale is still to be fully exploited by overcoming the fundamental difficulty in prediction: the fully three-dimensional and turbulent nature of the atmosphere. The prediction of this scale is totally different from that of the synoptic scale (103 km), with slowly evolving semigeostrophic dynamics and relatively long predictability on the order of a few days.

Even theoretically, very little is understood about the convective scale compared to our extensive knowledge of the synoptic-scale weather regime as a partial differential equation system, as well as in terms of the fluid mechanics, predictability, uncertainties, and stochasticity. Furthermore, there is a requirement for a drastic modification of data assimilation methodologies, physics (e.g., microphysics), and parameterizations, as well as the numerics for use at the convective scale. We need to focus on more fundamental theoretical issues—the Liouville principle and Bayesian probability for probabilistic forecasts—and more fundamental turbulence research to provide robust numerics for the full variety of turbulent flows.

The present essay reviews those basic theoretical challenges as comprehensibly as possible. The breadth of the problems that we face is a challenge in itself: an attempt to reduce these into a single critical agenda should be avoided.

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Mathew Stiller-Reeve
and
Zakia Naznin

Abstract

In our climate research project in Bangladesh, we work closely with local rural communities. The communities have designed their own citizen science projects in close dialogue with the project’s climate scientists. The climate scientists have also directed their research based on the stories the communities previously shared in longer narrative interviews. In order for the citizen science to be a success, a sense of community and good team spirit is essential. We collaborated with a Bangladeshi artist to achieve some important goals. Not only did we want to create new and exciting outreach materials, but, more importantly, we also wanted to see how the artistic process could nurture a sense of community for the local participants. Despite being limited by time, we saw some promising outcomes from the collaboration. The artist successfully interacted with the project researchers and the local participants. The final artwork was a real collaboration between the artist and the participants, who felt pride and ownership in the results.

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Simone M. S. Costa
,
Renato G. Negri
,
Nelson J. Ferreira
,
Timothy J. Schmit
,
Nelson Arai
,
Wagner Flauber
,
Juan Ceballos
,
Daniel Vila
,
Jurandir Rodrigues
,
Luiz A. Machado
,
Sérgio Pereira
,
Marcus Jorge Bottino
,
Raffi Agop Sismanoglu
, and
Pedro Langden

Abstract

This paper summarizes the successful use of Geostationary Operational Environmental Satellite-10 (GOES-10) and -12 (GOES-12), mainly beyond their retirement as operational satellites in the United States, in support of meteorological activities in South America (SA). These satellites were maneuvered by the National Oceanic and Atmospheric Administration (NOAA) to approximately 60°W, enabling other countries in Central and South America to benefit from their ongoing measurements. The extended usefulness of GOES-10 and -12 was only possible as a result of a new image geolocalization system developed by NOAA for correcting image distortions and evaluated in collaboration with the Brazilian National Institute for Space Research. The extension allowed GOES-10 and -12 to monitor SA for an additional 7 years proving the efficiency of this navigation capability implemented for the first time in the GOES series well beyond the expected satellites’ lifetime. Such successful capability is incorporated in the new-generation GOES-R series. This practical and technological experience shows the importance of communication between scientists from the United States and SA for advancing Earth’s monitoring system through the development of novel software and derived products. For SA in particular, GOES-10 and -12 were employed operationally to monitor dry spells, relevant for agriculture and forest fire management and to nowcast severe weather for flash flood warnings. Additionally, GOES-12 detected the first registered tropical hurricane over the Brazilian coast. This paper describes some of the technical and operational challenges faced in extending the GOES-10 and -12 missions to provide coverage over South America and emphasizes the usefulness of their ongoing measurements benefiting Brazilian environmental monitoring.

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