Events (Upcoming & Past)

Past MMM Events

MMM Seminar - Thursday, October 3, 2019 - 3:30pm

Speaker: Susan Joslyn

Affiliation: Department of Psychology, University of Washington

How do everyday users understand weather forecast information? What is the best way to provide them with information that is relevant to critical decisions but not confusing? This talk will describe a psychological research program that investigates each of these questions using a cognitive-experimental approach. We show, in a series of experimental studies that including numeric uncertainty estimates (30% chance) in weather forecasts leads to better decisions and increases trust in the forecast when compared to deterministic forecasts. Surprisingly comprehending probabilistic expressions does not depend on the user's level of education. However, understanding depends critically on how uncertainty is expressed. Communication formats that take into account users' decision goals are much better understood than those that ignore the user's perspective. In addition some typical misunderstandings will be discussed, particularly those that occur when visualizations are used. Finally we will describe the evidence suggesting that forecast consistency may not be as important as was once thought. In sum, this line of research suggests that people can attain a “working understanding” of fairly complex and updating information as long as it is communicated in a way that is compatible with how people think about the issues.

Refreshments: 3:15 PM

Building:
Room Number: 
FL2-1022 - Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Monday, September 23, 2019 to Thursday, October 3, 2019
Calendar Timing: 
Thursday, October 3, 2019 - 3:30pm to 4:30pm
Nancy Sue
Kerner
8946

MMM Seminar - Thursday, October 10, 2019 - 3:30pm

Speaker: Wojciech W. Grabowski

Affiliation: Mesoscale and Microscale Meteorology Laboratory, NCAR

Representation of cloud microphysics is a key aspect of simulating clouds. From the early days of cloud modeling, numerical models have relied on an Eulerian approach for all cloud and thermodynamic and microphysics variables. Over time the sophistication of microphysics schemes has steadily increased, from simple single-moment bulk warm-rain schemes, through double- and triple-moment bulk warm-rain and ice schemes, to complex bin (spectral) schemes that predict the evolution of cloud and precipitation particle size distributions. As computational resources grow, there is a clear trend toward wider use of bin schemes, including their use as benchmarks to develop and test simplified bulk schemes. We argue that continuing on this path brings fundamental challenges due to the complexity of processes involved (especially for ice), the multiscale nature of atmospheric flows that Eulerian approaches are not able to cope with, conceptual issues with the Smoluchowski equation that is solved by bin schemes to predict evolution of the particle size distributions, and numerical problems when applying bin schemes in multidimensional cloud simulations. The Lagrangian particle-based probabilistic approach is a practical alternative in which the myriad of cloud and precipitation particles present in a natural cloud is represented by a judiciously selected ensemble of point particles called super-droplets or super-particles.  Advantages of the Lagrangian particle-based approach when compared to the Eulerian bin methodology will be explained and illustrated with computational examples. Prospects of applying the method to more comprehensive simulations involving clouds, for instance targeting deep convection or frontal cloud systems, will be discussed.

Refreshments: 3:15 PM

Building:
Room Number: 
FL2-1022 - Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Tuesday, September 24, 2019 to Thursday, October 10, 2019
Calendar Timing: 
Thursday, October 10, 2019 - 3:30pm to 4:30pm
Nancy Sue
Kerner
8946

RAL/MMM Joint Seminar - Distinguished Speaker Series  - Thursday, August 29, 2019 - 3:30pm

Speaker: Professor Kerry Emanuel

Affiliation: Massachusetts Institute of Technology, Cambridge, Massachusetts

I will present a linear model of the equatorial waveguide based on the assumptions of hydrostatic balance and a temperature profile that remains moist adiabatic at all times. As has been shown before, these assumptions reduce the primitive equations to the mathematical form of shallow water equations of the kind first explored by Matsuno. Some of the classical Matsuno modes are destabilized in this model by cloud-radiation and/or wind-surface-heat-flux feedbacks (WISHE); no instability arises purely from the interaction of convection with circulation.

Based on this and previous published work, I will argue that convectively coupled Kelvin waves are amplified WISHE while eastward propagating disturbances of nearly constant, low frequency are driven mostly by cloud-radiation feedback but driven eastward by WISHE. In addition, mixed-Rossby-gravity waves and equatorial Rossby waves can be destabilized and propagated by WISHE and/or cloud-radiation feedback. These feedbacks can be strong enough to drive the modes substantially far away from the Matsuno dispersion curves, calling for alternative descriptions of their physics.

Refreshments: 3:15 PM

Building:
Room Number: 
Large Auditorium, Room 1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Monday, August 26, 2019 to Thursday, August 29, 2019
Calendar Timing: 
Thursday, August 29, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
8946

MMM Seminar - Thursday, August 22, 2019 - 3:30pm

Speaker: Lian-Ping Wang

Affiliation: University of Delaware and Southern University of Science and Technology, China

Gas kinetic schemes (GKS’s) are a class of CFD methods based on the kinetic theory and have gained much success in flow simulations ranging from continuum compressible flows to rarefied non-equilibrium flows. As a mesoscopic CFD method, GKS’s can handle rich dynamics beyond the classical CFD methods based on the Euler and Navier-Stokes-Fourier equations. This lecture gives an introduction of the GKS methods, including the original GKS for continuum flows and its recent variants for multiscale flows. I will discuss how the details of GKS’s can be inversely designed to address different complex flow problems, as well as open research problems. Several examples of using gas kinetic schemes to solve complex flows will be provided, including an incompressible particle-laden flow, an immiscible two-phase flow and a compressible thermal flow. Indeed, this class of schemes have a lot to offer and could serve as a unified framework to simulate many different complex flows.

Refreshments: 3:15 PM

 

Building:
Room Number: 
FL2-1022 - Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Wednesday, August 21, 2019 to Thursday, August 22, 2019
Calendar Timing: 
Thursday, August 22, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
8946

MMM Seminar - Thursday, August 15, 2019 - 3:30pm

Speaker: McKenna Stanford

Affiliation: University of Utah

Models run within the convective “grey” zone (i.e. 1-3 km horizontal grid spacing) are unable to resolve the spectrum of updraft sizes produced by large eddy simulations (LESs). This deficiency results in updrafts in km-scale models being too wide, and since lateral mixing is inversely proportional to updraft width, leads to reduced dilution. Addressing this issue is becoming increasingly important as global models approach convection-permitting resolution but global LES remains intractable. Since shortcomings associated with the model’s effective resolution are inevitable, more sophisticated parameterizations are necessary to overcome the mixing problem. In this work, we allow for enhanced but variable mixing in time and space by applying a stochastic framework within a Smagorinsky-type first order turbulence closure. Specifically, a stochastic multiplicative factor is applied to the closure’s horizontal eddy diffusion coefficient, which controls lateral mixing. Conceptually, this framework allows some updrafts to mix vigorously with mid-level environmental air while also allowing other updrafts to remain relatively undilute.

The stochastic scheme is used to simulate a quasi-idealized squall line using a sounding from the pre-convective environment of an observed mesoscale convective system (MCS) that occurred during the Midlatitude Continental Convective Clouds Experiment (MC3E). Comparisons are made between stochastic simulations at 1-3 km grid spacing, baseline simulations using the standard Smagorinsky-type (non-stochastic) closure at the same grid spacing, and a LES run at 125 m grid spacing. These comparisons show that the stochastic scheme alters vertical profiles of mass flux and vertical velocity as well as other key squall line features such as cold pool strength and condensate mass spatial structure. Moreover, the stochastic scheme alters these features and structures in a manner not capable by simply diagnostically applying constant multiplicative factors to the diffusion coefficient. Finally, scale adaptability is discussed along with potential expansion of the scheme to non-idealized frameworks.

Refreshments: 3:15 PM

Building:
Room Number: 
FL2-1022 - Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Friday, August 9, 2019 to Thursday, August 15, 2019
Calendar Timing: 
Thursday, August 15, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
8946

MMM Seminar - Thursday, August 8, 2019 - 3:30pm

Speaker: Joshua J. Alland

Affiliation: Advanced Study Program, NCAR

To better understand how midlevel moisture and vertical wind shear (VWS) synergistically modulate tropical cyclone (TC) development via ventilation, a three-dimensional modeling framework is utilized to conduct a suite of experiments. Each experiment has a different combination of initial midlevel moisture and VWS environments. A strong, positive, linear relationship exists between the low-level vertical mass flux in the inner core and TC intensity. The linear increase in vertical mass flux with intensity is not due to an increased strength of upward motions, but instead, is due to an increased area of strong upward motions (w>0.5 m s-1). This relationship suggests that physical processes influencing the vertical mass flux, such as downdraft and radial ventilation, directly influence the intensity of a TC.

The three-dimensional structure of downdraft ventilation has different orientations and strengths, which are controlled by the vertical tilt of the vortex. The modulating effect of downdraft ventilation on TC development is the transport of low-equivalent potential temperature air left-of-shear and into the upshear semicircle from downdraft ventilation regions, which aids in reducing the area of strong upward motions, reducing the vertical mass flux in the inner core, and stunting TC development.

The three-dimensional structure of radial ventilation shows two pathways: the first pathway is associated with rainband activity at low- and mid-levels, and is co-located with downdraft ventilation; while the second pathway at mid- and upper-levels is associated with the vertical tilt of the vortex and, in stronger-sheared environments, storm-relative flow induced by VWS. The modulating effect of radial ventilation on TC development is the inward transport of low-equivalent potential temperature air left-of-shear and in the upshear semicircle at low- and mid-levels, and low-RH air upshear and right-of-shear at mid- and upper-levels, which aids in reducing the area of strong upward motions, reducing the vertical mass flux in the inner core, and stunting TC development.

Refreshments: 3:15 PM

 

Building:
Room Number: 
FL2-1022 - Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Thursday, August 1, 2019 to Thursday, August 8, 2019
Calendar Timing: 
Thursday, August 8, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
4978946

MMM Seminar - Thursday, July 25, 2019 - 3:30pm

Speaker: Hing Ong

Affiliation: University at Albany, State University of New York

The nontraditional Coriolis terms (NCTs) are omitted in most of the current global atmospheric models. However, NCTs are significant in tropical large-scale dynamics in the following four aspects. (1) NCTs coupled with diabatic forcing yield considerable Ertel potential vorticity (EPV) flux, using reanalysis data. At the zonal annual mean heating maximum in the tropics, NCT-diabatic and mean-advective EPV flux can yield about 2 m s–1 month–1 of westward and 5 m s–1 month–1 of eastward acceleration; the former is considerable using the latter as a reference. (2) Omitting NCTs causes considerable westerly bias in the response to prescribed diabatic forcing mimicking the intertropical convergence zone (ITCZ), using linearized forced-dissipative models. The westerly bias lies in the heating region. In terms of the ratio of the maximum westerly bias to the maximum westerly wind, a normalized zonal wind bias increases with a narrower ITCZ or an ITCZ closer to the equator; for example, the normal wind bias is 0.120 ± 0.007 given the width of 1000 km and the location of 600 km. (3) omitting the NCT in the hypsometric equation biases geopotential height estimation using rawinsonde data. It causes geopotential height error of ~ 1 m, which is considerable with respect to geopotential height variability of ~ 10 m associated with the Madden–Julian oscillation (MJO) or convectively coupled equatorial waves (CCEWs). (4) NCTs transmit meridional vorticity disturbances eastward given the vertically decreasing density, i.e., the compressional beta-effect, using linearized unforced models. With a statically neutral profile and initial large-scale disturbances given a half vertical wavelength spanning the troposphere on Earth, compressional Rossby waves are expected to propagate eastward at a phase speed of 0.24 m s–1. Aspect (1), (2), and (3) encourage restoring NCTs into global atmospheric models for more-accurate simulations of MJO, CCEWs, and ITCZ-forced flow. Aspect (4) can serve as a benchmark for development of deep atmospheric dynamical cores for Earth system models.

 

Building:
Room Number: 
Large Auditorium, Room 1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Monday, July 22, 2019 to Thursday, July 25, 2019
Calendar Timing: 
Thursday, July 25, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
8946

*MMM Seminar - Thursday, July 18, 2019 - 3:30pm

*PLEASE NOTE SPECIAL LOCATION: FL2-1001 Small Auditorium

Speaker:  Dale Barker

Affiliation: United Kingdom Meteorological Office

Global NWP capabilities at the Met Office are currently based on a 10/20km deterministic/ensemble configuration based on the Unified Model (UM), providing forecasts out to 7 days. Deterministic initial conditions are provided by a ‘hybrid 4DVar’ technique, with ensemble initial perturbations updated via an Ensemble Transform Kalman Fillter (ETKF). A major project in recent years has been to replace the ETKF with an ‘ensemble of 4DEnVar data assimilations’ (En4DEnVar), to be implemented together with a major upgrade to global model physics (GA7) in winter 2019/20. Latest results indicate a very significant (4-5%) improvement in ensemble (CRPS) performance. A review of this, and other recent upgrades, will be presented. 

High-resolution (km-scale) UK NWP utilizes hourly-cycling 4DVar feeding 1.5/2.2km deterministic/ensemble forecasts out to 5 days. Data assimilation research is currently focussed on the extension to ‘hybrid’ 4DVar and the direct assimilation of radar reflectivity in 4DVar. Model physics activities are focussed on the development of a single regional atmosphere (RA) configuration suitable for both mid-latitude and tropical application. An overview of an expanding range of research applications beyond the UK (e.g. US HWT ensemble, tropical SE Asia) will be given.

Weather Science is completely overhauling its NWP post-processing capabilities, creating a new ensemble-based system that will provide consistent gridded and site-specific calibrated, blended products for the web, app, etc. In recent months, the ‘IMPROVER’ team have explored the use of machine learning techniques to further improve the quality of post-processed weather forecast. Promising early results will be presented.

Refreshments: 3:15 PM  

Building:
Room Number: 
*FL2-1001 Small Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Tuesday, July 9, 2019 to Thursday, July 18, 2019
Calendar Timing: 
Thursday, July 18, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
8946

MMM Seminar - Distinguished Speaker Series  - Thursday, July 11, 2019 - 3:30pm

Speaker: Christoph Schär

Affiliation: ETH Zurich, Switzerland

Currently major efforts are underway towards refining the horizontal grid spacings of climate models to about 1 km, either by increasing the resolution of current GCMs, or by extending the computational domain of high-resolution RCMs. There is well-founded hope that this increase in resolution represents a quantum jump, as it enables replacing the parameterizations of moist convection and gravity-wave drag by explicit treatments. It is expected that this advance will improve the simulation of the water cycle and extreme events, and reduce uncertainties in climate projections. However, the development of such modeling strategies requires a concerted effort.

In exploring high-resolution climate models, we utilize an RCM that allows decade-long continental-scale simulations at 2 km resolution. The model employed is a version of the COSMO model that runs entirely on graphics processing units (GPUs). It is demonstrated that horizontal resolutions around 1 km enable the credible simulation of many mesoscale phenomena. Although cloud structures are not yet fully resolved, analyses suggest that there is convergence at grid resolutions around 2 km in a bulk sense.

On a technical level, it is argued that the output avalanche of high-resolution simulations will make it impractical or impossible to store the data. Rather, repeating the simulation and conducting online analyses may become more efficient. A prototype system of this type will be presented. An assessment will be provided of the potential of these novel approaches.

The presentation is largely based on a paper that is currently in review: Schär, C., O. Fuhrer, A. Arteaga, N. Ban, C. Charpilloz, S. Di Girolamo, L. Hentgen, T. Hoefler, X. Lapillonne, D. Leutwyler, K. Osterried, D. Panosetti, S. Ruedisuehli, L. Schlemmer, T. Schulthess, M. Sprenger, S. Ubbiali, H. Wernli, 2019: Kilometer-scale climate models: Prospects and challenges. Bull. American Meteorol. Soc., in review.

Refreshments: 3:15 PM

Building:
Room Number: 
Large Auditorium, Room 1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Monday, July 8, 2019 to Thursday, July 11, 2019
Calendar Timing: 
Thursday, July 11, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
8946

*Special MMM/RAL Joint Seminar - Monday, July 15, 2019 - 11:00am

*PLEASE NOTE SPECIAL DAY/TIME & LOCATION

Speaker: Jon Petch

Affiliation: United Kingdom Meteorological Office

I will present an overview of current and planned efforts to evaluate and develop the kilometre gird-scale regional modelling system in the Met Office. This will include current and longer term research and developments as well as specific results from recent evaluation activities.  I will also highlight the importance of science partnerships in the Met Office in underpinning this activity.

Refreshments: 10:45 AM

Building:
Room Number: 
*FL2-1001 Small Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Monday, July 1, 2019 to Monday, July 15, 2019
Calendar Timing: 
Monday, July 15, 2019 - 11:00am to 12:00pm
Nancy
Kerner
8946

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