U-ENGAGE is proud to announce UCAR's Annual Holiday Market is taking place on Thursday November 14th from 9:00 AM - 2:00 PM in the Center Green Auditorium. Please join us for this festtive event! You'll find hand crafted gifts, unique services, and yummy treats from up to 30 staff/family/friend vendors!
Vendors! There's still a few slots left - if you'd like to join in the fun, please email Lisa Packard at lpackard@ucar.edu.
Title: Predictability of the North Atlantic Oscillation
Speaker: Adam Scaife, UK Met Office
Date: Tuesday, 19 November 2019
Time: 11 am - 12 pm
*Refreshments at 10:45*
Location: Mesa Lab, Main Seminar Room, ML - 132
Abstract:This seminar reviews the latest evidence for long range predictability of the winter North Atlantic Oscillation (NAO) and hence European and North American winters. Retrospective hindcasts and recent real time predictions suggest that the winter NAO is predictable at seasonal and longer lead times. In this seminar I show that much of this predictability originates in the tropics and the stratosphere. High predictability of tropical rainfall is first demonstrated for current prediction systems and this is shown to lead to clear stationary Rossby waves that propagate into the extratropics, into the Atlantic sector and project onto the NAO. We estimate that this mechanism can explain around half of the forecast variance in the NAO. Secondly, we show that initial atmospheric conditions are also important for seasonal prediction of the NAO. Initial anomalies in stratospheric winds at the start of winter propagate downwards into the troposphere on subseasonal timescales where they lead to anomalies in the winter mean sea level pressure. Together, these mechanisms potentially explain the majority of forecast variance in the winter NAO. I also show some of the remaining errors in seasonal forecasts of tropical rainfall and discuss the unresolved signal-to-noise paradox, whereby ensemble forecasts are better at predicting the real observed NAO than the they are at predicting their own simulations of the NAO.
For more information contact Tracy Baker, tbaker@ucar.edu, 303-497-1366
Title: Teleconnection processes linking the intensity of the Atlantic Multidecadal Vaiability to the climate impacts over Europe in boreal winter
Speaker: Christophe Cassou, Cerfacs
Date: Tuesday, 3 December 2019
Time: 11 am - 12 pm
*Refreshments at 10:45*
Location: Mesa Lab, Main Seminar Room, ML - 132
Abstract:The response of the European climate to the Atlantic Multidecadal Variability (AMV) remain difficult to isolate over the observational historical period in presence of pronounced internal variability on top of anthropogenically-forced signals. We here use targeted model sensitivity experiments proposed within the CMIP6/DCPP-C framework to investigate the physical processes at play in the teleconnection between the AMV and temperature and precipitation over Europe in winter. Large ensembles of pacemaker-type simulations, which consist in restoring the modeled North Atlantic Sea Surface Temperature (SST) to an anomalous pattern that is representative of the observed AMV, have been conducted using the CNRM-CM5 global circulation model. To evaluate the sensitivity of the model response to the intensity of the AMV, twin experiments with AMV-forcing pattern multiplied by 2 and 3 (hereafter 2xAMV and 3xAMV, respectively) are performed in complement to the reference ensemble (1xAMV).
Based on a flow analog method, we show that the AMV-forced atmospheric circulation tends to cool down the European continent, whereas the residual signal mostly including thermodynamical processes contributes to warming. In 1xAMV, both terms cancel each over, which explains the overall weak AMV-forced signals in both temperature and precipitation. In 2xAMV and 3xAMV, the thermodynamical contribution clearly overcomes the dynamical cooling and is primarily responsible for milder and wetter conditions found at large-scale over Europe. The thermodynamical term includes the advection of warmer and more humid oceanic air penetrating inland as well as the modification of surface radiative fluxes linked to altered cloudiness and snow-cover reduction acting as a positive feedback with the AMV amplitude. The dynamical anomalous circulation corresponds to the combination of (i) a remote response to enhanced diabatic heating acting as a Rossby-wave source in the western tropical Atlantic and (ii) a local response associated with warmer SST over the subpolar gyre that favors the presence of anomalous High between Greenland and Northern Europe. The extratropical influence is reinforced by polar amplification due to sea ice melting in all the Subarctic Seas. The respective weight between the tropical-extratropical processes and associated feedbacks is speculated to explain part of the nonlinear sensibility of model response to the AMV-forcing amplitude. Our findings challenge the use of so-called pattern-scaling technique to evaluate teleconnectivity and related impacts associated with AMV-type of variability.
For more information contact Tracy Baker, tbaker@ucar.edu, 303-497-1366
Title: Fire, Climate and Humans: A Combustive Combination
Speaker: Natalie Kehrwald, USGS
Date: Tuesday 17 December, 2019
Time: 11 am - 12 pm
*Refreshments at 10:45*
Location: Mesa Lab, Main Seminar Room, ML - 132
Abstact: Humans have accidentally and purposefully been lighting fires for at least one million years. As the past one million years encompasses multiple glacial-interglacial cycles with accompanying vegetation changes, climate has dominated the fire history over this time period, even with the contributions of humans. However, over the past 5000 years, human activity can overwhelm the contribution of climate to regional fire activity. Ice cores from northern Greenland (NEEM; 77°27'N; 51°3.6'W), demonstrate a peak in fire activity centered around ~2500 yr BP. This centennial-scale peak in fire activity is determined from the specific biomarkers levoglucosan, mannosan, and galactosan, which can only be produced by cellulose combustion. Fire data from the JSBACH-Spitfire model over the past 5000 years demonstrates that a climate-only scenario would not increase biomass burning in high northern latitudes for the past 5000 years, while NEEM ice core and regional pollen records demonstrate both increased fire activity and land use change that may be ascribed to human activity. New Zealand sediment cores demonstrate a “burn and bolt” strategy, where small bands of humans were able to deforest ~40% of the South Island within a single century. The arrival of the Māori to New Zealand ~800 yr BP introduced fire to a region with essentially no natural biomass burning. Here, we use fecal sterols in lake sediments to determine when people were in an individual watershed, and establish that the increased presence of Māori in an area corresponds with intensified fire activity. Peaks in fecal sterols and biomass burning occur at a single location for approximately two decades. Fire activity and human presence both drop to almost background levels after this initial burning period but then peak in other regional watersheds, demonstrating the migration of groups of people and associated biomass burning. This human-caused increase in New Zealand fire activity is quantifiable in locations as far away as the EPICA Dome C ice core in East Antarctica (75°06'S; 123°21'E). Due to the specificity of these biomarkers, levoglucosan and its isomers can help differentiate between the deposition of fire aerosols versus fossil fuel combustion products on to the surface of glaciers such as the Juneau Icefield (58° 35' N; 134° 29'W). This combination of specific biomarkers, other proxy data, and model output can help determine the relative impact of humans versus climate factors on regional fire activity.
For more information contact Tracy Baker, tbaker@ucar.edu, 303-497-1366
On Long Timescale Recurrent Active Region Coronal Jets: The Coronal Geyser Structure
The seminar will overview our recent findings on active region coronal jets. During its solar disk transit the solar active region 11302 showcased a vast display of coronal jets identified in extreme-ultraviolet imaging.
We describe multiple co-temporal jet phenomenology: (1) The jets exhibit a strand-like morphology undergoing untwisting motions which suggest torsional waves may propagate along open magnetic fields during eruptions; (2) We recover the thermal and non-thermal properties of the eruptions and compared the physical properties of the plasma simultaneously at the base brightpoint and along the jets outflow using multiple techniques in both extreme-ultraviolet and X-ray emission; (3) To further pursue the non-thermal manifestations of jet eruptions, we combined multiple observations and models aiming to reveal the physically fundamented relation between jets, their flaring brightpoints, and interplanetary type-III radio bursts. (4) We study the lower photosphere and reconstruct magnetic structures in order to assess the emission mechanism(s) responsible for generating the identified set of recurrent eruptions.
We report the identification of arched structures in the lower solar atmosphere which undergo through multiple magnetic reconnections and are the main trigger of solar jets. These sites are classified as “Coronal Geysers”. To our knowledge, the long term jet recurrence and its association with a persistent erupting structure, identified as the "geyser structure", was not previously discussed. The data analysis of this phenomenon provides new information for theoretical modeling of jets and allows for a better assessment of the hypothesis that jet eruptions are triggered by recurring small-scale filament eruptions
Spectroscopic Investigation of the Solar Atmosphere
The solar chromosphere plays a critical role in most of the open questions of solar physics, from coronal heating to the acceleration of the solar wind. It spans only 2000 km, but nine pressure scale heights, while the temperature increases by some two orders of magnitude. This layer is the location of most of the solar radiative losses, with the emission dominated by singly ionized ions. Despite its modest dimensions, the plasma properties make interpretation challenging, because most lines originating here are optically thick and formed in non-LTE.
We present an exploration of the chromospheric emission, from quiet to flaring solar conditions, using spectroscopic data from the IRIS instrument. The main focus of this study is the variability of the Mg II resonance lines, investigating how their profiles change based on the emitting solar structure. The extraction of the different spectral features from the observed emission profile is detailed and general trends are discussed.
Using quiet sun datasets we investigate potential characteristics that provide better contrast for distinguishing Coronal Holes from quiet sun in chromospheric emission. Thus we explore if any profile feature is more sensitive to the slightly different magnetic morphology, given that coronal holes are dominated by open field lines contributing to the solar wind acceleration.
We also explore the enhanced emission and wide variation of profiles in more active conditions leading up, during, and after a strong solar flare. For a complete picture of the flaring event, we also include information covering the surrounding solar atmosphere, using data from IRIS, SDO, and RHESSI. The slow rise and eventual destabilization of a filament is found to be preceding the flare. In the descending phase of the flare, we identified an extended coronal rain episode that persisted for more than an hour and was characterized by peculiarly wide profiles in both chromospheric and TR emission lines.
You are cordially invited to join us for the fourth 2019 NCAR Explorer Series Lecture, “Keeping an eye on the Sun's magnetism,” by Dr. Rebecca Centeno, that will be held Wednesday, November 13 at 7:00 pm, and Saturday, November 16 at 2:00 pm at the NCAR Mesa Lab.
The talk will be live-streamed and can be viewed at: http://ucarconnect.ucar.edu/live
This free, public event requires registration. Please see the links below for event times and location. For more information about Dr. Centeno and this topic, please visit our website: NCAR Explorer Series
Abstract: Space weather is driven by the Sun's magnetism; invisible yet powerful magnetic forces, created within the Sun itself, determine when and where the next solar storm is going to happen. Large solar storms can put our increasingly technological society at risk. In this talk, NCAR scientist, Rebecca Centeno discusses how advances in solar telescopes allow scientists to monitor the Sun in a lot more detail than ever before and quantify the underlying magnetism that drives its activity. Learn about the science that helps us understand solar storms and space weather.
"Planetary metabolism in a changing climate", Wednesday, November 13, 7:00 - 8:00 p.m. with Q&A to follow. Get tickets here
"Planetary metabolism in a changing climate", Saturday, November 16, 2:00 - 3:00 p.m. with Q&A to follow. Get tickets here
You are cordially invited to join us for the fourth 2019 NCAR Explorer Series Lecture, “Keeping an eye on the Sun's magnetism,” by Dr. Rebecca Centeno, that will be held Saturday, November 16 at 2:00 pm at the NCAR Mesa Lab.
The talk will be live-streamed and can be viewed at: http://ucarconnect.ucar.edu/live
This free, public event requires registration. Please see the links below for event times and location. For more information about Dr. Centeno and this topic, please visit our website: NCAR Explorer Series
Abstract: Space weather is driven by the Sun's magnetism; invisible yet powerful magnetic forces, created within the Sun itself, determine when and where the next solar storm is going to happen. Large solar storms can put our increasingly technological society at risk. In this talk, NCAR scientist, Rebecca Centeno discusses how advances in solar telescopes allow scientists to monitor the Sun in a lot more detail than ever before and quantify the underlying magnetism that drives its activity. Learn about the science that helps us understand solar storms and space weather.
"Planetary metabolism in a changing climate", Saturday, November 16, 2:00 - 3:00 p.m. with Q&A to follow. Get tickets here
Review Open Enrollment changes for the upcoming calendar year.
Review Open Enrollment changes for the upcoming calendar year.
HR Benefits staff providing assistance to employees who need help stepping through the open enrollment process in Workday.
HR Benefits staff providing assistance to employees who need help stepping through the open enrollment process in Workday.
HR Benefits staff providing assistance to employees who need help stepping through the open enrollment process in Workday.
HR Benefits staff providing assistance to employees who need help stepping through the open enrollment process in Workday.
Learn tips and tricks for creating cleaner, more compelling presentation slides! Seasoned graphic designer Simmi Sinha with NCAR|UCAR Communications will share design principles that can help you give a more effective scientific presentation and better deliver your key messages. While the presentation will focus on translating complex scientific into visually appealing slides and graphics, all interested staff are invited to join.
When: 3 - 4:30 pm on Wednesday, Nov. 13 Where: FL2-1001
If you have questions, please email Simmi at simmi@ucar.edu.
Due to the snow and campus closures on October 29th, we rescheduled our K12 Education and Public Outreach Working Group Meeting to Wednesday, November 20th from 2:30-3:45 pm in the Damon Room (Room 239) at the Mesa Lab.
During this meeting, we'll share updates on education and outreach efforts happening across the organization, discuss ideas for collaborations across groups, and discuss new ideas for education and outreach efforts we want to consider doing in the future. To RSVP, please send an email to Shaun Bush at sbush@ucar.edu and you'll be added to the calendar invite.
You do not need to re-RSVP if you were planning on attending the October 29th meeting. The calendar invite has already been updated.
In addition, if you haven't already signed up for the email list for this group (k12@ucar.edu) please email Emily Snode-Brenneman at emilysb@ucar.edu and let her know that you would like to be added to the list to get notifications about education and outreach efforts you can participate in.
We hope to see you on November 20th!
*Special MMM/GTP Joint Seminar - Thursday, November 14, 2019 - 3:30pm
*Please note special location - FL2/1001 Small Auditorium
Speaker: Shaun Lovejoy
Affiliation: McGill University, Montréal, Québec
A hundred years ago, Lewis Fry Richardson made the first numerical weather forecast, founding the field of numerical weather prediction (NWP). Based on deterministic continuum mechanics, today it is not only ubiquitous in daily weather forecasts, but has been extended to seasonal predictions through to multidecadal climate projections.
But Richardson also pioneered the development of high level turbulent laws. In 1926 he proposed the “Richardson 4/3 law” of turbulent diffusion, a law that wasn’t vindicated until 2013. Whereas NWP attempts to account for every whirl, cloud, eddy, structure, the 4/3 law exploits the idea of scaling to statistically account for the collective outcome of billions upon billions of structures jointly acting from millimetres up to the size of the planet.
The idea that high-level statistical laws could explain the actions of myriads of vortices, cells and structures was shared by successive generations of turbulence scientists. Unfortunately, they faced monumental mathematical difficulties largely connected to turbulent intermittency: the fact that most of the activity (e.g. energy flux) is inside tiny, violently active regions, themselves buried in a hierarchy of structures within structures. The application of turbulence theory to the atmosphere, encounters an additional obstacle: stratification that depends on scale.
The 1980’s marked a turning point when Richardson’s deterministic and statistical strands parted company, the unity of the atmospheric sciences was broken. On the one hand, computers revolutionized NWP, on the other hand, the nonlinear revolution promised to tame chaos itself, including turbulent chaos with its fractal structures within structures.
In this talk, I summarize four decades of work attempting to understand atmospheric variability that occurs over an astonishing range of scales: from millimetres to the size of the planet, from milliseconds to billions of years. The variability is so large that standard ways of dealing with it are utterly inadequate: in 2015, it was found that classical approaches had underestimated the variability by the astronomical factor of a quadrillion. The new understanding allows us to finally reunite Richardson’s strands.
For example, I show that the deterministic weather models respect the stochastic scaling laws very well. I explain “macroweather” and how it sits in between the weather and climate, finally settling the question: “What is Climate”? I answer the question “how big is a cloud?” and show that Mars is our statistical twin and why this shouldn’t surprise us. I explain how the multifractal butterfly effect gives rise to events that are so extreme that they have been called “black swans”.
By using data from the real world – not model – climate, and with the help of the Fractional Energy Balance Equation (FEBE), I explain how the emergent scaling laws can make accurate monthly to decadal (macroweather) forecasts by exploiting an unsuspected but huge memory in the atmosphere-ocean system itself. I show how the FEBE can help to significantly reduce the large uncertainties in our current climate projections to 2050 and 2100.
Refreshments: 3:15 PM
*Special RAL/MMM Joint Seminar - Wednesday, November 20, 2019 - 3:30pm
*Please note special day - Wednesday
Speaker: Prasanth Prabhakaran
Affiliation: Michigan Technological University
The formation of ice in mixed-phase clouds greatly impacts Earth’s hydrologic cycle. The intensity, distribution, and frequency of precipitation as well as radiative properties of clouds in the mid-latitudes are strongly influenced by the number concentration of ice particles. A long-standing riddle in cold clouds is the frequent observation of measured ice particle concentrations several orders of magnitude higher than measured ice-nucleating particle concentrations. Here, we report laboratory observations of copious cloud droplets and ice crystals formed in the wake of a warm, falling water drop. Aerosols were activated in the transient regions of very high supersaturation due to evaporative mixing in the wake. We extend these results to typical mixed-phase atmospheric conditions, and our calculations show that the induced evaporative supersaturation may significantly enhance the activated ice nuclei concentration in the particle’s wake.
Refreshments: 3:15 PM
TIAA Individual Counseling Sessions
11/20/19 - ML Chapman Room 245
Consultant: Rhett Belcher
NCAR is managed by the nonprofit University Corporation for Atmospheric Research on behalf of NSF and the UCAR university community.
