| Date | Time | Seminar TItle | Presenter(s) | Affiliation/Contact | Location |
|---|---|---|---|---|---|
| Jul 7, 2022 (Thu) | 2:00pm | No seminar scheduled - date is available | No seminar scheduled - date is available | No seminar scheduled - date is available | |
| Jul 14, 2022 (Thu) | 2:00pm | TBD | Andy Heymsfield | MMM/NCAR | Hybrid - Seminar will be held onsite in FL2/1022 and Live-Webcast |
| Jul 21, 2022 (Thu) | 2:00pm | TBD | Alex Mitchell and Tyler Leicht | SUNY | Hybrid - FL2-1022 and also live webcast |
Speaker: Edward G. Patton, Mesoscale and Microscale Meteorology Laboratory, NCAR
Date: Thursday, 7 January 2021
Time: 3:30PM - 4:30PM (MST)
For Zoom viewing access contact Nancy Sue Kerner, nskerner@ucar.edu
Abstract:
Forests cover a significant fraction of Earth’s land surface and play a critical role in Earth’s climate through their influence on energy, water, and carbon cycles, as well as through exchanges of reactive species that place stringent controls on the atmosphere’s oxidative capacity [or cleansing ability]. Therefore, understanding and representing the processes controlling turbulent exchange of energy, momentum, and scalars between the vegetation and the atmosphere is of critical importance for accurate weather, air quality, and climate prediction.
Canopies interact with the atmosphere through a number of pathways. Momentum absorption occurring over the distributed height range of canopy elements produces turbulence qualitatively different to that over other rough surfaces. The distributed canopy elements also absorb/scatter radiation ensuring that the leaf-level exchange of heat, moisture, and other trace gases vary spatially depending on the elemental heat capacity, atmospheric demand, and physiological controls. Canopy-induced modification of turbulence characteristics, spatially varying radiation absorption/scattering, and leaf-level emission/deposition also influence within-canopy reactant evolution.
Relying on a combination of measurements and models, this talk will: 1) present our current understanding of biosphere-atmosphere exchange, 2) highlight some new insights into atmospheric stability’s role in determining the spatial structure and distribution of motions controlling turbulent transfer at the canopy-atmosphere interface, and 3) discuss implications for parameterization of biosphere-atmosphere exchange in weather, air pollution, and climate models.
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
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: Tropical Cyclogenesis Predictability and Shallow Cumulus Organization from the Perspective of Multiscale Processes
Speaker: Pornampai (Ping-Ping) Narenpitak, NOAA Earth System Research Laboratories
Date: Thursday, 29 October 2020
Time: 3:30 pm - 4:30 pm
For Zoom viewing access contact Nancy Sue Kerner, nskerner@ucar.edu
Abstract:
Convective organization occurs at various scales in different cloud systems. The spatial inhomogeneity of the clouds suggests that convective organization can be viewed as interactions of multiscale processes. This seminar combines my recent and ongoing studies that use the System of Atmospheric Modeling (SAM) with different domain sizes and resolutions to study tropical cyclogenesis predictability and explore mesoscale organization of marine shallow cumuli from this perspective.
In the first part, a near-global aquaplanet cloud-resolving model (NGAqua) is used to investigate tropical cyclogenesis and its predictability. This study analyzes an ensemble of three 20-day NGAqua simulations, with initial white-noise perturbations of low-level humidity. Tropical cyclones (TCs) in NGAqua develop spontaneously from the northern edge of the intertropical convergence zone (ITCZ), where interactions between large-scale flows and tropical convection provide necessary conditions for barotropic instability. Zonal bands of positive low-level absolute vorticity organize into cyclonic vortices, some of which develop into TCs. A vortex-following framework analysis shows that vertical stretching of absolute vorticity due to convective heating contributes positively to TCs’ vorticity spinup. A case study and composite analyses suggest that sufficient humidity is key for convective development. Tropical cyclogenesis in these three NGAqua simulations undergoes the same series of interactions. The locations of cyclonic vortices are broadly predetermined by planetary-scale circulation and humidity patterns associated with ITCZ breakdown, which are predictable up to 10 days. Whether and when the cyclonic vortices become TCs depend on the somewhat more random feedback between convection and vorticity, which occurs at a much smaller scale.
In the second part, Lagrangian large eddy simulations of trade cumulus organization observed during the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) are presented. ATOMIC was designed to understand the relationship between shallow convection and large-scale environments in the trade wind region. It is the U.S. counterpart of the European field campaign called EUREC4A and took place in January – February 2020. The simulations presented here are driven with ERA5 reanalysis large-scale meteorology and ATOMIC in-situ aerosol data. The results are used to explore different states of trade cumulus organization and address the transition between different states from the perspective of multiscale processes.
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
Title: Current Advances in Urban Hydrometeorological Research at the University of Georgia
Speaker: Dr. Marshall Shepherd, University of Georgia
Date: Thursday, 16 July 2020
Time: 3:30pm - 4:30pm MST
If you would like to join us by Zoom, please contact Nancy Sue Kerner for access, nskerner@ucar.edu.
Abstract:
Dr. Shepherd is a leading scholar studying aspects of hydrometeorological extremes, urban climate, and societal implications. Dr. Shepherd has advanced understanding of how urbanization, precipitation and convection are related. For this work, he has received the 2004 Presidential Early Career Award for Scientists and Engineers (PECASE) and the 2018 Helmut Landsberg Award. In this lecture, Dr. Shepherd will layout what we know about urban effects on precipitation and convective processes and where the research is headed in the future. He'll draw on past literature, research, and ongoing projects. Where relevant, Dr. Shepherd will also tie the basic research together with opportunities for applications and assessment of societal risk.
For more information contact Nancy Sue Kerner, nskerner@ucar.edu.
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 12, 2020 - 3:30pm
Speaker: Janice Coen
Affiliation: NCAR/MMM
Large, destructive wildfires have become prevalent across the western U.S. and other fire-prone areas yet the mechanisms through which a specific fire became large and what environmental factors were important, particularly in light of varying climate, are frequently not understood. The most extreme events frequently lie at an end of a spectrum. At one end, fire growth is driven by strong ambient winds and is characterized by practitioners as a "wind-driven" event. At the other end of the spectrum, fire growth amplifies due to an internal feedback loop in which winds are generated by heat released by the fire itself ("plume-driven" events). The limitations of current generation operational fire models in simulating extreme fires in particular has enhanced perceptions that fire behavior has become more unpredictable.
Progress has been made in understanding and predicting fire behavior by recognizing wildland fires and the atmosphere in which they occur as a fluid dynamical system. We draw from convective-scale (hundreds of meters horizontal grid spacing) simulations of the weather leading up to and fire growth during exceptional wildfire events exemplifying each type with the CAWFE? coupled weather-wildland fire modeling system using satellite active fire detection data and airborne fire mapping to initialize and evaluate event simulations. Results show that even extreme fire behavior may be modeled, provided that fine-scale circulations are well represented and fire feedbacks upon circulations are included. Large, destructive wildfires may be driven by internal feedbacks or small-scale circulations thus may surprise due to the lack of apparent ambient triggers or exceptional conditions. In fires occurring during California wind events, while mesoscale weather forecasts capture broad spatial patterns of accelerated winds, CAWFE simulations that refine to convective scales show common factors such as a shallow river of fast-moving stable air but several different types of dynamic microscale flow regimes, where ignitions and rapid early fire growth appear linked to microscale phenomena and wind extrema coincident with ignitions attributed to electrical system anomalies. We examine our collective ability to reproduce extreme events and the challenges and limitations in our remote sensing systems, fire prediction tools, and meteorological models that add to events' mystery and apparent unpredictability.
Refreshments: 3:15 PM
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
MMM Seminar - Thursday, February 27, 2020 - 3:30pm
Speaker: Zeljka Fuchs-Stone
Affiliation: Director, Climate and Water Consortium, New Mexico Tech
The OTREC (Organization of Tropical East Pacific Convection) field project took place from August 5 to October 3, 2019. The operational center was in Liberia, Costa Rica. During OTREC, we performed 127 research flight hours in the area of the Eastern Pacific and Southwest Caribbean. We deployed 665 dropsondes in a grid to evaluate mesoscale thermodynamic and vorticity budges. We also used the Hiaper Cloud Radar to determine the characteristics of cloud populations. Both of these tools were deployed from the NSF/NCAR Gulfstream V aircraft.
The Eastern Pacific has a strong meridional gradient in sea surface temperature. The southwest Caribbean exhibits uniform ocean temperatures. The two regions together provide a broad range of atmospheric conditions and a great deal of diversity in convective behavior.
The main goal of the project was to study deep convection in diverse environments to improve global weather and climate models. In this talk I will present an overview of OTREC, the highlights of the field project and the preliminary results that include the thermodynamics of the environment and the vertical mass flux profiles.
*MMM Seminar - Thursday, February 20, 2020 - 3:30pm
*Please note special location - FL2-1001/Small Auditorium
Speaker: Samuel Childs
Affiliation: Colorado State University
Eastern Colorado is one of the most active hail regions in the U.S., and recent damaging events have affirmed the need for improved prediction of hailstorm characteristics and effective warning communication. This work offers a multidisciplinary synthesis of eastern Colorado (37-41°N, 102-105.3°W) hailstorms. Climatologically, severe (1.0 in+) hail reports and days are increasing across the domain since 1997, although hail is preferentially reported where people live or drive. Still, the upward trend in hail days is not seen in the national record. To estimate how the frequency and spatial distribution of hailstorms across eastern Colorado may change by the end of the 21st century, threshold exceedances of convective proxies for severe hail reports are compared between control and future high-resolution dynamically-downscaled WRF simulations. An increase of up to 3 severe hail days per year is projected by the period 2071-2100, with the highest increase across the north-central eastern Plains. These projections, paired with high-resolution population projections taken from the Shared Socioeconomic Pathways, are input into a Hail Monte Carlo model, which predicts an increase in human exposure up to 178% by 2100. Results are sensitive to the overlap between future population and meteorological projections, however, and simulations that predict decreasing human exposure have a corresponding increase in agricultural exposure due to hailstorm frequency increasing most in places where population is not expected to grow. An interview study conducted in Summer 2019 with eastern Colorado agriculturalists revealed feelings of anxiety and dejection from hailstorms due to the financial losses incurred. Farmers also highlighted that small hail, either in large volume or driven by a strong wind, is most damaging to crops, which is contrast to the 1.0 in severe threshold used by the NWS. Results from this work are bringing awareness of the vulnerabilities faced by the agricultural sector and inspiring continued research into hail prediction.
Refreshments: 3:15 PM
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