AMS Science Preview: The “Black Swan” heatwave; volcanic chillers; tornadogenesis
Early online research from journals of the American Meteorological Society
The American Meteorological Society continuously publishes research on climate, weather, and water in its 12 journals. Many of these articles are available for early online access–they are peer-reviewed, but not yet in their final published form.
Below is a selection of articles published early online recently. To view full article text, members of the media can contact kpflaumer@ametsoc.org for press login credentials.
Searching for the Most Extreme Temperature Events in Recent History
Bulletin of the American Meteorological Society
Ranking the world’s most extreme recent heat/cold events. The authors developed a novel method to identify and rank abnormally extreme (i.e., locally unusual) heat waves and cold spells. Scanning global data from 2003 to 2022, they found the three most extreme heatwaves occurred in Fujian, Hunan, and Jiangxi, China (2003); Alberta, Canada (2021); and Chongqing and Sichuan, China (2022). The most extreme cold spells occurred in south Québec, Canada (2014); western South Africa (2014); and Nord-du Québec, Canada (2015).
The Pacific Northwest Heat Wave of 25-30 June 2021: Synoptic/Mesoscale Conditions and Climate Perspective
Weather and Forecasting
2021 Pacific Northwest heatwave was a chaotic “Black Swan,” global warming played only a minor role. A heatwave over the Pacific Northwest and southwest Canada on 25-30 June 2021 broke previous temperature records by a large margin and led to hundreds of deaths. While anthropogenic warming may have contributed up to 1°C to this heatwave, it was largely due to other factors including a record-breaking high-pressure ridge in the troposphere over British Columbia. Yearly high temperatures in the region are only increasing at the baseline rate of global warming; such all-time record-breaking temperature events have not become more frequent.
“It appears that the extreme Pacific Northwest heatwave of June 2021 was a Black Swan event … global warming may have made a small contribution, but an extreme heatwave, driven by natural variability, would have occurred in any case.”
—Clifford Mass et al. (paper authors)
A New Pathway for Tornadogenesis Exposed by Numerical Simulations of Supercells in Turbulent Environments
Journal of the Atmospheric Sciences
Simulations reveal previously unknown path for tornado formation. Computer simulations have been vital to understanding tornadogenesis, but until now, those models have not been sensitive enough, nor the data fine enough, to recreate turbulence at the boundary layer (near Earth's surface) as it interacts with a supercell storm. Simulations have therefore been based on the assumption of non-turbulent flow at this level. A new study using a model that incorporates boundary-layer turbulence has identified streaks of vertical spin that serve as a new way that a tornado-like vortex can form—which, if it translates to real life, could provide a new, alternative explanation for how tornadoes form from supercell storms.
Late-Winter and Springtime Temperature Variations throughout New Jersey in a Warming Climate
Journal of Applied Meteorology and Climatology
Shifting spring temperatures could harm New Jersey farmers, ecosystems. Many sites in New Jersey, especially the agriculturally intensive south and coastal plain, have experienced an increase since 1950 in spring daytime temperature variation—specifically the number of times that the temperature warms above 60°F (encouraging plant growth), then plunges below freezing again. At three-quarters of measured sites, spring variation in maximum daily temperature has increased since the 1950s.
Irrigated Agriculture Significantly Modifies Seasonal Boundary Layer Atmosphere and Lower Tropospheric Convective Environment
Journal of Applied Meteorology and Climatology
Turning Great Plains grasslands into irrigated agriculture has noticeable effects on weather and climate. Data from the Great Plains Irrigation Experiment (GRAINEX) in Nebraska demonstrate that compared with nearby grassland, large areas of irrigation significantly alter near-surface atmospheric characteristics, including cooling the local air, and create favorable conditions for clouds and convection to develop during the growing season.
Severe Global Cooling after Volcanic Super-eruptions? The Answer Hinges on Unknown Aerosol Size
Journal of Climate
Volcanic super-eruptions may not be global freezers after all. It’s theorized that volcanic super-eruptions could trigger massive global cooling events—the eruption of the volcano Toba 74,000 years ago, for example, purportedly threatened human survival—yet the evidence is sketchy. A new study finds that the particle size of emitted sulfate aerosols plays a key role in how much global cooling (or even global warming) an eruption causes, and that even super-eruptions may be incapable of cooling the globe by more than 1.5°C.
The Circum-global Transport of Massive African Dust and its Impacts on the Regional Circulation in Remote Atmosphere
Bulletin of the American Meteorological Society
2020 Saharan dust traveled all around the globe, altered climates far away. This paper demonstrates that a June 2020 North African dust event traveled worldwide and decreased rain over northeastern India and central North America, showing that such events can have a broad impact on the global atmosphere. Attempts to model future climate change should also include the impact of African dust.
The Respective Roles of Ocean Heat Transport and Surface Heat Fluxes in Driving Arctic Ocean Warming and Sea-Ice Decline
Journal of Climate
Influx of warm water will become the biggest driver of Arctic sea ice loss. During the 20th and early 21st centuries, the loss of Arctic Ocean sea ice has been primarily driven by atmospheric heat; however, repeated model simulations suggest that over time, the influx of warm water (especially through the Barents Sea Opening) will play a larger role in warming the Arctic Ocean and melting ice.
Atmospheric Rivers Are Responsible for Cyclicity in Sierra Nevada Precipitation
Journal of Climate
Sierra Nevada precipitation proves unpredictable. An important component of California’s water resources, precipitation in the Sierra Nevada mountains appears to show wet and dry cycles over years and decades. The authors attribute these apparent cycles to variations in the number of “atmospheric river” storms each year. However, they could not find any larger scale ocean-atmosphere patterns that would drive cyclical variation in atmospheric rivers, suggesting that observed cycles may not be useful for predicting future precipitation.
Drivers of Widespread Floods in Indian River Basins
Journal of Hydrometeorology
India’s Narmada and Mahanadi rivers are most prone to widespread flooding. A study of widespread flooding in Indian river basins found that basins in South India/peninsular India tend to be the most vulnerable, especially during the summer monsoon, when India receives 80% of its rainfall. In a given year, the Narmada River basin had a 59% chance of experiencing widespread floods, and the Mahanadi River a 50% chance; both are likely to have uniformly high rainfall and soil moisture during the summer, a key factor that makes flooding more likely.
Why Livelihoods Matter in The Gendering of Household Water Insecurity
Weather, Climate, and Society
Water awareness isn’t just about gender. Research has suggested women are more aware of/vulnerable to household water insecurity, but the divide isn’t so simple for households in rural Burkina Faso. In households focused on farming crops, this study found that women perceive more water insecurity; however, in households focused on livestock husbandry, men (usually responsible for securing water for animals) perceived greater water insecurity.
You can view all research published in AMS Journals at journals.ametsoc.org.
About the American Meteorological Society
The American Meteorological Society advances the atmospheric and related sciences, technologies, applications, and services for the benefit of society. Founded in 1919, AMS has a membership of around 12,000 professionals, students, and weather enthusiasts. AMS publishes 12 atmospheric and related oceanic and hydrologic science journals—in print and online; sponsors more than 12 conferences annually; and offers numerous programs and services. Visit us at www.ametsoc.org/.
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