Bulletin of the American Meteorological Society

Mylne, Ken; Roberts, Nigel; Walters, David; Barciela, Rosa; Petch, Jon; Wells, Oak; Willington, Steve; Suri, Dan; Steele, Edward; Titley, Helen; Gray, Mike; Williams, Keith; Piccolo, Chiara; Davies, Paul; Skea, Alasdair; Sachon, Patrick; Howard, Teil; McCabe, Anne; Robins, Ric

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0183.1

AbstractEnsemble Numerical Weather Prediction (NWP) systems have been used operationally for over 30 years, mainly supplementing higher resolution “deterministic” forecasts. Recognizing the greater forecast skill of ensembles, some centers are moving towards completely ensemble-based NWP, which broadens the variety of applications and use cases and has implications for developers and users. Ensembles offer a considerable increase in forecast information that can bring substantial benefits if used appropriately, but also bring increased cost and overheads. Applications range from picking preferred or representative members to exploiting the full probability distribution, enabling synthesis of either selected storylines (e.g. most likely or highest impact) or estimating the forecast uncertainty, depending on the decisions to be supported. To help users exploit ensembles effectively, we present a “classification of use cases”. The most appropriate class for a particular user and application will depend on the nature of the decision(s) to be taken, the risk appetite (or tolerance) of the user, and their vulnerability to weather impacts. The use cases are not fundamentally new, but by classifying them we aim to help users and service providers identify the best approaches to address their needs. We also highlight how we should be developing and processing ensemble data to deliver to these use cases, to ensure that the maximum benefits from ensemble NWP are pulled through for the whole of society.

Kirtman, B. P.; Arcodia, M. C.; Becker, E. J.; Besong, K.; Boyd, J. S.; Daher, H.; Gifford, I.; Infanti, J.; Kaiser, J.; Kramer, S.; Larson, S. M.; Laurindo, L. C.; Lopez, H.; Malloy, K.; Martinez, C.; Papazian, K.; Pegion, K.; Perlin, N.; Schuler, C.; Schoenwald, V.; Siqueira, L. S. P.; Zavadoff, B.; Zhang, W.

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0196.1

AbstractSimplified global atmospheric general circulation models are important tools for understanding basic climate dynamics and diagnosing more complete modeling systems. We have developed a simple, single-model framework with non-linear primitive equations that can be run via an interactive Python Jupyter notebook. This framework was developed as an educational tool for students to experiment with the model, as it is straightforward to impose forcing, post-process data, and visualize results in one notebook. However, experienced scientists can also use the model for original research.We have implemented three distinct innovations. First, the underlying dynamic core is entirely based in Python (as opposed to Fortran with a Python wrapper), making the model more accessible to both undergraduate and graduate students. The model can easily be run on a laptop without concerns such as compiler options or operating systems, thus removing common technical barriers to access. Second, the background state can be specified within the same framework as “strong,” where the model equations have been modified into an anomaly model, or “weak,” where the original full-field model is relaxed to the background state. Third, the “forcing” is described in terms of prescribed latent heat release in the troposphere, the topography, and the background state. Forcing and resolution changes are easily implemented using one preprocessing script that supports a wide range of hypothesis-driven experimentation options. This paper includes an exploration of the model’s mean state, some sensitivity experiments, and an example diagnosis of ENSO teleconnections.

Liu, Dongwei; Tan, Jianguo; Wang, Yadong; Shi, Jun; Ao, Xiangyu; He, Xiaochuan; He, Qianshan; Mu, Haizhen; Hou, Wenxuan; Sun, Juan; Peng, Jie; Liu, Miaomiao

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0186.1

AbstractSunshine duration is an important parameter to characterize local climatology and has been observed for a long time. We propose a novel method for observing sunshine duration using video images, based on a Large Vision-Language Model (LVLM) named ViLT (Vision-and-Language Transformer). The method can directly identify weather phenomena from video images without the need for fine-tuning, and can determine whether sunshine is present based on ViLT’s assessment of whether it is a sunny day or not. Evaluation results indicate that the cumulative percentage errors of the annual sunshine duration derived from video observations are 1.3% and 1.1% at the Chongming and Xujiahui stations, respectively. These errors are well below the WMO’s achievable measurement uncertainty for sunshine duration (2% or 0.1 h). Since the method only requires images from standard video equipment as input, it offers a cost-effective and convenient technology for observing sunshine duration, particularly in areas lacking sunshine observations but with available video data. Further studies demonstrate that when combined with the Ångström-Prescott formula, the method can be utilized to estimate total solar radiation from video data. Compared to observations from solar radiometers, the percentage error in the estimated total annual solar radiation is around 4.3%, indicating promising applications of the method in solar resource assessment and climate studies.

Wang, Zhuo; Rios-Berrios, Rosimar; Stern, Daniel P.; Baker, Alexander J.; Beucler, Tom; Camargo, Suzana J.; Duvel, Jean-Philippe; Feng, Xiangbo; Lee, Chia-Ying; Leroux, Marie-Dominique; Li, Hui; Macholl, Joshua; Molina, Maria J.; Ocasio, Kelly M. Núñez; Ramsay, Hamish A.; Ritchie, Elizabeth A.; Schenkel, Benjamin A.; Stansfield, Alyssa M.; Ayar, Pradeebane Vaittinada; Wisinski, Emily

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0200.1

Gaviria Pabón, América R.; Krocak, Makenzie J.; Ripberger, Joseph T.; Trujillo-Falcón, Joseph E.

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0199.1

AbstractThe U.S. National Weather Service issues forecasts and warnings to protect life and property. To fulfill this mission, the public must not only receive these warnings but also understand their meaning and take appropriate protective actions. While several studies have explored how English speakers receive, understand, and respond to forecasts and warnings, there is limited research on these concepts within the rapidly growing Spanish-speaking diaspora in the U.S. This gap is concerning, as past research indicates that this population can be particularly vulnerable to extreme weather events. Drawing on data from 14,341 individuals collected through both the English and Spanish versions of the Severe Weather and Society Survey (2018-2023), this article addresses this gap by comparing tornado forecast and warning reception, comprehension, and response between Spanish and English speakers. The results reveal significant differences between the two groups across all three dimensions. On average, Spanish speakers are less likely than English speakers to receive, understand, and respond to tornado forecasts and warnings. The article concludes by exploring possible explanations for these disparities and offering suggestions for improving forecast and warning reception, comprehension, and response in Spanish-speaking populations.

Miglietta, Mario Marcello; Flaounas, Emmanouil; González-Alemán, Juan Jesús; Panegrossi, Giulia; Gaertner, Miguel Angel; Pantillon, Florian; Pasquero, Claudia; Schultz, David M.; D’Adderio, Leo Pio; Dafis, Stavros; Husson, Romain; Ricchi, Antonio; Carrió, Diego Saúl Carrió; Davolio, Silvio; Fita, Lluís; Picornell, Maria Angeles; Pytharoulis, Ioannis; Raveh-Rubin, Shira; Scoccimarro, Enrico; Bernini, Lisa; Cavicchia, Leone; Conte, Dario; Ferretti, Rossella; Flocas, Helena; Gutiérrez-Fernández, Jesús; Hatzaki, Maria; Santaner, Victor Homar; Jansà, Agusti; Patlakas, Platon

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0289.1

AbstractThe term “Mediterranean tropical-like cyclone” or “medicane” has been used in different ways by different authors. Identification of medicanes has been based on features observed from satellite imagery or on diagnostics applied to numerical weather prediction model outputs. In the absence of an official definition, medicanes are generally considered to be cyclones over the Mediterranean sharing physical processes with tropical cyclones. Nevertheless, recent studies on the dynamics of several systems widely recognized as medicanes show different underlying development mechanisms. A commonly agreed definition is critical and necessary to assess their climatology in past and future climates, as well as to consistently identify such systems in weather forecasts. The scientific community working on Mediterranean cyclones hereby proposes a definition, which is based solely on Earth observations: “A medicane is a mesoscale cyclone that develops over the Mediterranean Sea and displays tropical-like cyclone characteristics: a warm core extending into the upper troposphere, an eye-like feature in its center with spiral cloud bands around, an almost windless center surrounded by nearly-symmetric sea-surface wind circulation with maximum wind speed within a few tens of km from the center.”

LIU, Yan-An; Huang, Hung-Lung

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-25-0013.1

AbstractLow Earth Orbit (LEO) meteorological satellite constellations, operated by international weather agencies such as the National Oceanic and Atmospheric Administration (NOAA) in the USA and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), provide critical weather and environmental observations. These data are made freely available to the public through inter-agency collaboration, coordination, and standardization efforts led by the World Meteorological Organization (WMO). The goal is to ensure effective and timely utilization of these data for weather monitoring and maintaining climate records. The satellite-based direct broadcast system (DBS), established in the early 1970s, is a product of these historical and ongoing international efforts. DBS enables continuous access to satellite observations without political restrictions. This study explores the use of NOAA’s Joint Polar Satellite System (JPSS) and EUMETSAT’s METOP satellite series, highlighting their contributions to regional weather and environmental monitoring. We demonstrate how these assets, combined with DBS technology, NOAA’s Community Satellite Processing Package (CSPP), and sustained operational and educational efforts, support weather forecasting and environmental monitoring. The study reviews the NOAA JPSS and EUMETSAT METOP LEO sensors, observations, and DBS systems. It also highlights unique regional applications in the greater Shanghai area, showcasing how this end-to-end infrastructure can prepare society and commerce for the lasting impacts of extreme weather and environmental changes.

Fogt, Ryan L.; Ziegler, Ashlee N.; King, John; Jones, Julie M.

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0208.1

AbstractEndurance, one of the main vessels of the Imperial Trans-Antarctic Expedition of 1914-1917, became stuck and eventually crushed by sea ice, sinking to the bottom of the Weddell Sea; yet miraculously, every member of the expedition returned safely home. Nonetheless, it still is not clear what role the weather of 1914-1915 may have played in the ship becoming beset and destroyed by the ice conditions, forcing the need for a heroic survival.Through examining the weather observations from Endurance in a climatological perspective, two key elements emerge that may have compromised the expedition. First, the austral summer of 1914-1915 was marked with more extensive sea ice in the Weddell Sea both in the context of satellite observations and estimates from the 20th century, consistent with an ongoing El Niño event. Once the ship became beset in the ice, persistent near record minimum daily mean temperatures lasted through the remainder of the summer of 1914-1915, offering little opportunity before winter to become dislodged. Second, the austral spring season of 1915 was marked with persistent high pressure anomalies in the Weddell Sea, confirmed by nearby observations and reconstructions. This extensive, persistent high pressure delayed ice breakup in the Weddell Sea and moved the ship into heavier multi-year ice, ultimately limiting opportunities for an early escape from the ice. While it is impossible to conclusively prove these exceptional conditions sealed the fate of Endurance, neighboring years do not show such extreme conditions, which may have led to a different outcome altogether.

Nicholson, Lindsey; Stiperski, Ivana; Nitti, Giordano; Prinz, Rainer; Georgi, Alexander; Groos, Alexander R.; Shaw, Thomas E.; Sauter, Tobias; Haugeneder, Michael; Mott, Rebecca; Sicart, Jean-Emmanuel; Brock, Ben W.; Albers, Roland; Allegri, Balthazar; Barral, Hélène; Biron, Romain; Charrondiere, Claudine; Coulaud, Catherine; Fischer, Alexander; Reynolds, Dylan; Richter, Niklas; Schroeder, Marie; Vettori, Phillip; Voordendag, Annelies; Wydra, Carlos

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-24-0010.1

AbstractMountain glaciers offer opportunities to observe boundary layer exchanges in conditions characterized by predominantly stable stratification, thermally driven winds and varying surface roughness. Logistical challenges involved in instrumenting glacier surfaces mean that insitu observations remain relatively scarce, limiting the use of this outdoor laboratory. The second HinterEisFerner EXperiment (HEFEX II) was carried out on an Austrian Alpine glacier during summer 2023. This collaborative endeavor, involving twelve institutions from Austria, France, Germany, Switzerland, and the UK, represents an unprecedented set of observations of glacier microclimate. Instrumentation on the glacier surface consisted of eight 3 m and two 5 m weather stations equipped with multilevel eddy covariance systems and auxiliary instrumentation, and eight additional lower specification weather stations. These operated successfully for 26 days with minimal data gaps. During a three day intensive observational period, additional instrumentation was deployed: a short-path ultrasonic anemometer installed very close to the glacier surface; a high speed thermal camera capturing high-resolution boundary layer heat transport at the glacier centerline on a synthetic screen; 3D sampling of the glacier boundary layer using two meteorological UAVs; a StreamLine XR Doppler LiDAR capturing the structure of the above-valley atmosphere. These novel datasets are valuable for improving understanding of glacier-atmosphere exchange processes, the role of glaciers in valley circulation, and how both might be affected by continued climate change and glacier recession. Here we detail the scientific goals and implementation of the campaign, describe the general weather conditions and first insights into what the observations reveal about the glacier boundary layer features observed during the campaign.

Jensen, Michael P.; Flynn, James H.; Gonzalez-Cruz, Jorge E.; Judd, Laura M.; Kollias, Pavlos; Kuang, Chongai; McFarquhar, Greg M.; Powers, Heath; Ramamurthy, Prathap; Sullivan, John; Aiken, Allison C.; Alvarez, Sergio L.; Argay, Peter; Argrow, Brian; Bell, Tyler M.; Boyer, Doug; Brooks, Sarah D.; Bruning, Eric C.; Brunner, Kelcy; Butterworth, Brian; Calmer, Radiance; Cappa, Christopher D.; Chakrabarty, Rajan K.; Chandrasekar, V.; Chao, Chun-Ying; Chen, Bo; China, Swarup; Collins, Don R.; Collis, Scott M.; Crowell, Sean; Porto, Rachael Dal; Boer, Gijs de; Deng, Min; Dexheimer, Darielle; Drager, Aryeh J.; Du, Xuanlin; Dubey, Manvendra K.; Dzambo, Andrew M.; Etten-Bohm, Montana; Fan, Jiwen; Farley, Ryan; Feng, Ya-Chien; Feng, Yan; Fenn, Marta; Ferrare, Richard E.; Flusche, Samuel; Fridlind, Ann M.; Galewsky, Joseph; Gamarro, Harold; Gardner, Samuel; Ghate, Virendra P.; Giangrande, Scott E.; Griffin, Robert J.; Griggs, Travis; Gronoff, Guillaume P.; Grover, Maxwell; Gaugenti, Meghan; Guo, Fangzhou; Gupta, Siddhant; Hu, Jiaxi; Huang, Yongjie; Jackson, Robert C.; Hair, Jonathan W.; Johnson, Karen L.; Kasparoglu, Sabin; Klein, Petra; Kotsakis, Alexander E.; Kumar, Joshin; Kumjian, Matthew R.; Lamer, Katia; Lappin, Francesca M.; Lei, Ziying; Li, Jing; Li, Ron; Li, Yuezhi; Logan, Timothy; Lombardo, Kelly; Luke, Edward P.; Mages, Zackary; Matthews, Alyssa A.; Matthews, Brianna H.; Mayol-Bracero, Olga; Matsui, Toshihisa; McKeown, Katherine E.; Mehra, Manisha; Mei, Fan; Meskidzhe, Nicholas; Nguyen, Cuong; Nielsen, Erik R.; Nowotarski, Christopher J.; Oaks, David; Oktem, Rusen; Oue, Mariko; Park, Jungmin M.; Partida, Nadia; Patil, Suarabh; Pena, Jean Carlos; Petters, Markus D.; Phoenix, Daniel B.; Puthserry, Joseph V.; Rapp, Anita D.; Romps, David M.; Roots, Maurice; Rosenfeld, Daniel; Saleeby, Stephen M.; Savala, Paul; Sedlacek, Arthur J.; Sharma, Milind; Sheesley, Rebeccca; Shingler, Taylor J.; Shrestha, Sujan; Singh, Ashish; Smith, Elizabeth N.; Smith, James N.; Smith, Scott; Snyder, Jeffrey; Spicer, Elizabeth; Spinei, Elena; Spychala, Mark; Steir, Philip; Storm, Michelle R.; Subba, Tamanna; Treserras, B. Puigdomenech; Trojanowski, Rebecca; Theisen, Adam; Thompson, Seth A.; Twigg, Laurence; Uin, Janek; Ulinski, Alexandra R.; van den Heever, Susan; van Lier-Walqui, Marcus; Varble, Adam C.; Wagner, Timothy J.; Wakeen, Jeremy; Wales, Nathan A.; Walter, Paul J.; Wang, Die; Wang, Jian; Wood, Lance; Wang, Yuxuan; Wolde, Mengistu; Yoon, Subin; Young, Michael H.; Zawadowicz, Maria A.; Zhang, Qi; Zhou, Aifang; Zhu, Zeen; Zhu, Zihan

2025 Bulletin of the American Meteorological Society

doi: 10.1175/bams-d-23-0331.1

AbstractA multi-agency succession of field campaigns was conducted in southeastern Texas during July 2021 through October 2022 to study the complex interactions of aerosols, clouds and air pollution in the coastal urban environment. As part of the Tracking Aerosol Convection interactions Experiment (TRACER), the TRACER- Air Quality (TAQ) campaign the Experiment of Sea Breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) and the Convective Cloud Urban Boundary Layer Experiment (CUBE), a combination of ground-based supersites and mobile laboratories, shipborne measurements and aircraft-based instrumentation were deployed. These diverse platforms collected high-resolution data to characterize the aerosol microphysics and chemistry, cloud and precipitation micro- and macro-physical properties, environmental thermodynamics and air quality-relevant constituents that are being used in follow-on analysis and modeling activities. We present the overall deployment setups, a summary of the campaign conditions and a sampling of early research results related to: (a) aerosol precursors in the urban environment, (b) influences of local meteorology on air pollution, (c) detailed observations of the sea breeze circulation, (d) retrieved supersaturation in convective updrafts, (e) characterizing the convective updraft lifecycle, (f) variability in lightning characteristics of convective storms and (g) urban influences on surface energy fluxes. The work concludes with discussion of future research activities highlighted by the TRACER model-intercomparison project to explore the representation of aerosol-convective interactions in high-resolution simulations.