Browse

You are looking at 1 - 10 of 23,531 items for :

  • Bulletin of the American Meteorological Society x
  • Refine by Access: Content accessible to me x
Clear All
Juhyeong Han, Inyoung Jang, Daein Kang, Minju Baek, Hideki Kanamaru, and Kwang-Hyung Kim
Full access
Callum Munday, Sebastian Engelstaedter, Gilbert Ouma, Geoffrey Ogutu, Daniel Olago, Dennis Ong’ech, Thomas Lees, Bonface Wanguba, Rose Nkatha, Clinton Ogalo, Roba Ali Gàlgalo, Abdi Jillo Dokata, Erick Kirui, Robert Hope, and Richard Washington

Abstract

The Turkana Low-level Jet (LLJ) is an intrinsic part of the African climate system. It is the principle conduit for water vapour transport to the African interior from the Indian Ocean, and droughts in East Africa tend to occur when the jet is strong. The only direct observations of the Turkana Jet come from manual tracking of pilot balloons in the 1980s. Now, modern reanalysis datasets disagree with one another over the strength of jet winds and underestimate the strength of the jet by 25-75% compared to the pilot balloon data. This article gives an overview of a month-long field campaign based in northwest Kenya - the Radiosonde Investigation For the Turkana Jet (RIFTJet) - which measured the Turkana Jet for the first time in forty years using modern technologies. Radiosonde data reveal a persistent low-level jet, which formed on every night of the campaign, with an average low-level maximum wind speed of 16.8 m.s-1 at 0300LT. One of the latest reanalysis datasets (ERA5) underestimates low-level wind speeds by an average of 24% (4.1 m.s-1) at 0300LT, and by 33% (3.6 m.s-1) at 1500LT. The measurements confirm the role of the Turkana LLJ in water vapor transport: mean water vapour transport at Marsabit is 172 kg.m.s-1. The dataset provides new opportunities to understand regional dynamics, and to evaluate models in one of the most data sparse regions in the world.

Full access
Huiling Ouyang, Xu Tang, Rajesh Kumar, Renhe Zhang, Guy Brasseur, Ben Churchill, Mozaharul Alam, Haidong Kan, Hong Liao, Tong Zhu, Emily Ying Yang Chan, Ranjeet Sokhi, Jiacan Yuan, Alexander Baklanov, Jianmin Chen, and Maria Katherina Patdu

Abstract

Air pollution is estimated to contribute to approximately 7 million premature deaths, of which around 4.5 million deaths are linked to ambient (outdoor) air pollution (Murray et al. 2020). The deaths attributed to air pollution rank the highest in the Asian Region and thus the implementation of the stricter World Health Organization (WHO) Global Air Quality Guidelines (AQGs) released on 22 Sep 2021 will generate the greatest health benefits in the Asian region. Here we present some key messages and recommendations at national, regional, and global level to promote the strategies for implementation of the ambitious WHO 2021 AQGs in the Asian region.

Full access
Chidong Zhang, John M. Wallace, Robert A. Houze, Edward J. Zipser, and Kerry A. Emanuel

Abstract

This article documents historically the planning of the Global Atmospheric Research Program's (GARP) Atlantic Tropical Experiment (GATE), the largest atmospheric field program of all time. In its earliest planning, GATE was called the Tropical Meteorological Experiment (TROMEX) and designed to be in the tropical western Pacific. For reasons including concerns of the U.S. Department of Defense, the international project was relocated to the tropical Atlantic and renamed GATE.

Full access
Nick Dunstone, Julia Lockwood, Balakrishnan Solaraju-Murali, Katja Reinhardt, Eirini E. Tsartsali, Panos J. Athanasiadis, Alessio Bellucci, Anca Brookshaw, Louis-Philippe Caron, Francisco J. Doblas-Reyes, Barbara Früh, Nube González-Reviriego, Silvio Gualdi, Leon Hermanson, Stefano Materia, Andria Nicodemou, Dario Nicolì, Klaus Pankatz, Andreas Paxian, Adam Scaife, Doug Smith, and Hazel E. Thornton

Abstract

The decadal timescale (˜1 –10 years) bridges the gap between seasonal predictions and longer-term climate projections. It is a key planning timescale for users in many sectors as they seek to adapt to our rapidly changing climate. Whilst significant advances in using initialized climate models to make skilful decadal predictions have been made in the last decades, including co-ordinated international experiments and multi-model forecast exchanges, few user-focussed decadal climate services have been developed. Here we highlight the potential of decadal climate services using four case studies from a project led by four institutions that produce real-time decadal climate predictions. Working in co-development with users in agriculture, energy, infrastructure and insurance sectors, four prototype climate service products were developed. This study describes the challenge of trying to match user needs with the current scientific capability. For example, the use of large ensembles (achieved via a multi-system approach) and skilfully predicted large-scale environmental conditions, are found to improve regional predictions, particularly in mid-latitudes. For each climate service, a two-page ‘product sheet’ template was developed that provides users with both a concise probabilistic forecast and information on retrospective performance. We describe the development cycle, where valuable feedback was obtained from a ‘showcase event’ where a wider group of sector users were engaged. We conclude that for society to take full and rapid advantage of useful decadal climate services, easier and more timely access to decadal climate prediction data is required, along with building wider community expertise in their use.

Full access
Lynn A. McMurdie, Gerald M. Heymsfield, John E. Yorks, Scott A. Braun, Gail Skofronick-Jackson, Robert M. Rauber, Sandra Yuter, Brian Colle, Greg M. McFarquhar, Michael Poellot, David R. Novak, Timothy J. Lang, Rachael Kroodsma, Matthew McLinden, Mariko Oue, Pavlos Kollias, Matthew R. Kumjian, Steven J. Greybush, Andrew J. Heymsfield, Joseph A. Finlon, Victoria L. McDonald, and Stephen Nicholls

Abstract

The Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) is a NASA-sponsored field campaign to study wintertime snowstorms focusing on East Coast cyclones. This large cooperative effort takes place during the winters of 2020–23 to study precipitation variability in winter cyclones to improve remote sensing and numerical forecasts of snowfall. Snowfall within these storms is frequently organized in banded structures on multiple scales. The causes for the occurrence and evolution of a wide spectrum of snowbands remain poorly understood. The goals of IMPACTS are to characterize the spatial and temporal scales and structures of snowbands, understand their dynamical, thermodynamical, and microphysical processes, and apply this understanding to improve remote sensing and modeling of snowfall. The first deployment took place in January–February 2020 with two aircraft that flew coordinated flight patterns and sampled a range of storms from the Midwest to the East Coast. The satellite-simulating ER-2 aircraft flew above the clouds and carried a suite of remote sensing instruments including cloud and precipitation radars, lidar, and passive microwave radiometers. The in situ P-3 aircraft flew within the clouds and sampled environmental and microphysical quantities. Ground-based radar measurements from the National Weather Service network and a suite of radars located on Long Island, New York, along with supplemental soundings and the New York State Mesonet ground network provided environmental context for the airborne observations. Future deployments will occur during the 2022 and 2023 winters. The coordination between remote sensing and in situ platforms makes this a unique publicly available dataset applicable to a wide variety of interests.

Full access
Mathias W. Rotach, Stefano Serafin, Helen C. Ward, Marco Arpagaus, Ioana Colfescu, Joan Cuxart, Stephan F. J. De Wekker, Vanda Grubišic, Norbert Kalthoff, Thomas Karl, Daniel J. Kirshbaum, Manuela Lehner, Stephen Mobbs, Alexandre Paci, Elisa Palazzi, Adriana Bailey, Jürg Schmidli, Christoph Wittmann, Georg Wohlfahrt, and Dino Zardi

Abstract

In this essay, we highlight some challenges the atmospheric community is facing concerning adequate treatment of flows over mountains and their implications for numerical weather prediction (NWP), climate simulations, and impact modeling. With recent increases in computing power (and hence model resolution) numerical models start to face new limitations (such as numerical instability over steep terrain). At the same time there is a growing need for sufficiently reliable NWP model output to drive various impact models (for hydrology, air pollution, agriculture, etc.). The input information for these impact models is largely produced by the boundary layer (BL) parameterizations of NWP models. All known BL parameterizations assume flat and horizontally homogeneous surface conditions, and their performance and interaction with resolved flows is massively understudied over mountains—hence their output may be accidentally acceptable at best. We therefore advocate the systematic investigation of the so-called “mountain boundary layer” (MoBL), introduced to emphasize its many differences to the BL over flat and horizontally homogeneous terrain.

An international consortium of scientists has launched a research program, TEAMx (Multi-Scale Transport and Exchange Processes in the Atmosphere over Mountains–Program and Experiment), to address some of the most pressing scientific challenges. TEAMx is endorsed by World Weather Research Programme (WWRP) and the Global Energy and Water Exchanges (GEWEX) project as a “cross-cutting project.” A program coordination office was established at the University of Innsbruck (Austria). This essay introduces the background to and content of a recently published white paper outlining the key research questions of TEAMx.

Full access
Neil P. Lareau, Nicholas J. Nauslar, Evan Bentley, Matthew Roberts, Samuel Emmerson, Brian Brong, Matthew Mehle, and James Wallman

Abstract

Fire-generated tornadic vortices (FGTVs) linked to deep pyroconvection, including pyrocumulonimbi (pyroCbs), are a potentially deadly, yet poorly understood, wildfire hazard. In this study we use radar and satellite observations to examine three FGTV cases during high-impact wildfires during the 2020 fire season in California. We establish that these FGTVs each exhibit tornado-strength anticyclonic rotation, with rotational velocity as strong as 30 m s−1 (60 kt), vortex depths of up to 4.9 km AGL, and pyroCb plume tops as high as 16 km MSL. These data suggest similarities to EF2+ strength tornadoes. Volumetric renderings of vortex and plume morphology reveal two types of vortices: embedded vortices anchored to the fire and residing within high-reflectivity convective columns and shedding vortices that detach from the fire and move downstream. Time-averaged radar data further show that each case exhibits fire-generated mesoscale flow perturbations characterized by flow splitting around the fire’s updraft and pronounced flow reversal in the updraft’s lee. All the FGTVs occur during deep pyroconvection, including pyroCb, suggesting an important role of both fire and cloud processes. The commonalities in plume and vortex morphology provide the basis for a conceptual model describing when, where, and why these FGTVs form.

Full access
Lexi Henny, Lauriana C. Gaudet, Kevin M. Lupo, Kenya Goods, Shadya Sanders, and Yanda Zhang

Abstract

The U.S.–Taiwan Partnership for International Research and Education (PIRE) “Building Extreme Weather Resiliency through Improved Weather and Climate Prediction and Emergency Response Strategies” was an NSF-funded grant between universities and institutions in the United States and Taiwan that intended to understand 1) weather forecast uncertainty during extreme precipitation events and 2) how emergency managers use such information to make decisions. In this reflective paper, graduate students from the project’s working groups, including climate, ensemble, microphysics, and decision science, share their experiences of being involved in this ambitious program. A notable strength of this PIRE was its opportunities for international collaboration and related cultural experiences; however, despite direct student involvement in PIRE, student experiences varied considerably (e.g., research experiences, cultural exposure). Recommendations for improvement are informed predominantly by U.S.-based graduate student experiences and are discussed with the intention of bolstering future interdisciplinary research for students and investigators. To this end, projects of this scale and scope could benefit from more frequent communication among leadership and research groups, as well as explicitly outlining and prioritizing interactions between groups to focus and strengthen collaboration toward the completion of interdisciplinary research goals.

Full access
James C. Fallon, Hannah C. Bloomfield, David J. Brayshaw, Sarah N. Sparrow, David C. H. Wallom, Tim Woollings, Kate Brown, Laura Dawkins, Erika Palin, Nikolaus Houben, Daniel Huppmann, and Bruno U. Schyska
Open access