Speaker: Heather Lazrus, Mesoscale and Microscale Meteorology Laboratory, NCAR

Date: Thursday, 3 December 2020

Time: 3:30 pm - 4:30 pm

For Zoom viewing access contact Nancy Sue Kerner, nskerner@ucar.edu

Abstract:

Coupling advances in meteorological science with research on how people understand, experience, and respond to weather hazards can enhance hazard outcomes, particularly among those who are most vulnerable to extreme weather impacts. This presentation will share results of research conducted with people affected by hurricanes and will demonstrate novel approaches to interdisciplinary research that produces knowledge for and with society. Analysis of focus group conversations held with specific populations in communities affected by Superstorm Sandy (2012), Hurricane Matthew (2016), Hurricane Irma (2017), and Hurricane Harvey (2017) reveal how risk communication helps mediate societal vulnerability to hurricanes by influencing the information that people receive, their perceptions of approaching hurricane risks, and their behavioral responses. Related work analyzing Twitter data from Sandy shows that digital communication of informal weather risk information over social media builds capacity among people who may be especially at risk from hazardous weather. Together, these datasets demonstrate how meteorological information and risk communication before and during an extreme weather event play important roles in hazard outcomes. This presentation will also share why research that is co-constructed with people who have extensive experience or knowledge of local extreme events contributes to meteorological justice – the idea that relevant and effective meteorological science and risk communication systems are necessary, if not sufficient, dimension of addressing inequities in the potential for harm that some people experience disproportionately when extreme weather threatens.

Seminar will also be live webcast: https://operations.ucar.edu/live-mmm

Recorded seminar link can be viewed here: https://www.mmm.ucar.edu/events/seminars

Title: Understanding tornado risk perceptions and responses for improving tornado risk communication

Speaker: Julie Demuth, Mesoscale and Microscale Meteorology Laboratory, NCAR

Date: Thursday, 15 October 2020

Time: 3:30 pm - 4:30 pm

For Zoom viewing access contact Nancy Sue Kerner, nskerner@ucar.edu

Abstract:

Despite tremendous advances in meteorological observations, knowledge, and forecasts, people still experience significant harm to life, property, and well-being due to tornadoes. Reducing these negative effects in part requires better understanding what people think and do – and why – when tornadoes threaten. This presentation will discuss research efforts to investigate the different ways that people perceive tornado risks and respond to them, along with the factors that influence these processes. Particular attention will be given to the influence of probabilistic tornado warning information, which is being actively researched and characterized by the meteorological research community in order to convey more nuanced chances of exposure than current tornado warnings convey. Understanding how people interpret and use such risk information—as situated in the real-world context of their lives, including their past experiences, beliefs, and barriers—is essential for improving tornado risk communication and risk mitigation efforts.

Seminar will also be live webcast: https://operations.ucar.edu/live-mmm

Recorded seminar link can be viewed here: https://www.mmm.ucar.edu/events/seminars

MMM Seminar - Thursday, April 23, 2020 - 3:30pm

Speaker: Gary Lackmann

Affiliation: North Carolina State University

Extratropical persistent flow anomalies (PAs), a subset of which are known as “blocking” events, are often associated with high-impact weather. Flooding, wildfires, heat waves, droughts, and cold-air outbreaks can be associated with PAs. These events can take place throughout the annual cycle, therefore, methods for their objective identification must be effective in all seasons. Despite their importance to society, the question of how the frequency, intensity, and duration of PAs will respond to climate change remains an open question. This is due in part to the complexity of this multifaceted phenomenon. Previous work has proposed increases in blocking and PA activity due to Arctic amplification. We can also hypothesize that the subset of blocking events resulting from latent heat release would to increase in frequency and intensity with warming owing to larger vapor content. Other GCM-based studies have found decreases in the frequency of blocking in warmer climates, while several studies have identified serious deficiencies in GCM representation of blocking. How will PAs change in a warmer climate?

Here, we present a new PA index, extending the method of Dole and Gordon (1983) to increase versatility. We apply this index to a reanalysis dataset, seeking trends in PA activity. We next examine changes in PA characteristics between the present climate and projected end-of-century conditions using high-resolution time-slice simulations from the Model for Prediction Across Scales (MPAS). In the future MPAS simulations, the Arctic Ocean is nearly devoid of autumn sea ice, making these runs ideal for studying the influence of Arctic amplification on midlatitude PA activity. Finally, we use an idealized oceanic channel model to study bivariate sensitivity of PAs to domain-average temperature and to baroclinicity (jet strength).

Using the ERA Interim reanalysis, we identify only weak trends in both positive and negative PA activity, including both annual and seasonal values. Results from the MPAS and channel model experiments will be shared at the seminar, because we would not want the abstract to give away all of the punchlines!

virtual seminar https://www.ucar.edu/live?room=fl21022

Viewers may submit their questions throughout the presentation to: Judith Berner; berner@ucar.edu

MMM Seminar - Thursday, March 5, 2020 - 3:30pm

Speaker: Andrew C. Winters

Affiliation: University of Colorado

The atmosphere often exhibits a three-step pole-to-equator tropopause structure, with each break in the tropopause associated with a jet stream. The polar jet stream (PJ) typically resides in the break between the polar and subtropical tropopause and is positioned atop the strongly baroclinic, tropospheric-deep polar front at ~50°N. The subtropical jet stream (SJ) resides in the break between the subtropical and the tropical tropopause and is situated on the poleward edge of the Hadley cell at ~30°N. On occasion, the latitudinal separation between the PJ and the SJ vanishes, resulting in a vertical jet superposition. Prior case study work indicates that jet superpositions are often attended by a dynamical and thermodynamic environment that is particularly favorable for the development of high-impact weather. Furthermore, this prior work suggests that there is considerable variability among antecedent environments conducive to jet superpositions. These considerations motivate a comprehensive examination of the relative importance of dynamical processes that operate within the double-jet environment to produce jet superpositions.

This study focuses on the identification of North American jet superposition events in the Climate Forecast System Reanalysis dataset during November–March 1979–2010. Jet superposition events are classified into three characteristic types: “Polar Dominant” events consist of events during which only the PJ is characterized by a substantial excursion from its climatological latitude band; “Subtropical Dominant” events consist of events during which only the SJ is characterized by a substantial excursion from its climatological latitude band; and “Hybrid” events consist of events characterized by an excursion of both the PJ and SJ from their climatological latitude bands. Following their classification, frequency distributions are constructed to highlight the geographical locations most often associated with jet superpositions within each event type. Composite analyses are also constructed in an effort to illuminate the dominant dynamical processes that support the production of jet superpositions for each event type. Predicated on the results from the preceding analyses, the relevance of jet superpositions to the development of high-impact weather within a changing climate is discussed.

Refreshments: 3:15 PM