Events (Upcoming & Past)

Past MMM Events

Professor Dale DurranDepartment of Atmospheric SciencesUniversity of Washington

One important limitation on the accuracy of weather forecasts is imposed by unavoidable errors in the specification of the atmosphere's initial state. Much theoretical concern has been focused on the limits to predictability imposed by small-scale errors, potentially even those on the scale of a butterfly. Very modest errors at much larger scales may nevertheless pose a more important practical limitation. We demonstrate the importance of large-scale uncertainty by analyzing ensembles of idealized squall-line simulations. Our results imply that minimizing initial errors on scales around 100 km is more likely to extend the accuracy of forecasts at lead times longer than 3--4 hours than efforts to minimize initial errors on much smaller scales. These simulations also demonstrate that squall lines, triggered in a horizontally homogeneous environment with no initial background circulations, can generate a background mesoscale kinetic energy spectrum roughly similar to that observed in the atmosphere.

This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htm

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

Thursday, 5 November 2015, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory 3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Professor Dale Durran
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, November 5, 2015 - 3:30pm to 5:00pm

John AllenInternational Research Institute for Climate and Society, Columbia University

How can we gain a greater understanding of the year-to-year variability in severe thunderstorms and derive the capability for seasonal prediction? In this presentation, I will illustrate the limitations of observed occurrences of hail, and how hail and tornado ‘proxy' indices for the probability of occurrence as a function of convective parameters are used, along with carefully controlled observations, to identify robust linkages between El Niño Southern Oscillation (ENSO) and springtime hail and tornado frequency. Leveraging this relationship, I will demonstrate how this technique allowed development of a simple probabilistic seasonal forecast for severe thunderstorm activity in the spring of 2015 based on the ENSO state of the prior winter. Finally, I will discuss how this forecast performed, the potential contributions of other sources of variability, and outline future directions that will move us towards a better understanding of natural variability in severe thunderstorms.

This seminar will be webcast live at:

http://www.fin.ucar.edu/it/mms/fl2-live.htm

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

Friday, 23 October 2015, 1 PMRefreshments 12:45 PMNCAR-Foothills Laboratory 3450 Mitchell LaneBldg. FL 2, Small Auditorium, Room 1001

First Name: 
Yemaya
Last Name: 
Thayer
Phone Extension (4 digits): 
8207
Email: 
ythayer@ucar.edu
Presenter(s): 
John Allen
Building:
Room Number: 
1001
Host lab/program/group:
Type of event:
Calendar Timing: 
Friday, October 23, 2015 - 1:00pm to 2:00pm

Scott W. PowellUniversity of WashingtonSeattle, WA

Observations, reanalysis, and regional modeling simulations support a dynamic mechanism that explains onset of convectively active periods of the Madden-Julian Oscillation (MJO) over the Indian Ocean. Observations made during DYNAMO confirm that clouds moisten the middle troposphere prior to MJO onset over the Indian Ocean. Regional modeling (WRF) runs show that the moistening is caused directly by upward advection of moisture within cloud updrafts and divergence of the moisture away from cloud updrafts into the environment.

TRMM and SPOL observations during DYNAMO show that, in terms of depth, two modes of precipitating convection over the Indian Ocean exist. One is a congestus-like mode that exists mainly below 500 hPa and increases in areal coverage during a 3–7 day long transition period prior to MJO onset. The other is a deep mode of convection, whose widespread existence is dependent upon the moistening caused by the congestus mode. The question of what permits widespread deep convective events then boils down to why congestus-like convection becomes more likely to develop.

Upper-tropospheric velocity potential anomalies (anomalies of large-scale (LS) divergence) have long been linked to MJO convective activity. Using ERA-Interim reanalysis, the low zonal wavenumber (1–1.5), eastward-propagating structures of vertical and zonal motion associated with the divergence signal are shown. As LS positive anomalies of divergence in the upper-troposphere approach the Indian Ocean, LS subsidence throughout the troposphere, and thus adiabatic warming, decreases. Peak reduction in LS subsidence occurs near 500 hPa, acting to destabilize the lower half of the troposphere.

WRF successfully reproduces three convective regimes prior to October and November convective events: suppressed, transition, and active periods, during which, respectively, shallow and non-precipitating, congestus, and deep convection are common. More congestus mode convection develops when the mean 900–700 hPa buoyancy within cloud updrafts becomes less negative, which occurs because the mean environmental (updraft) temperature in that layer decreases (increases) by 0.05–0.2K over a week prior to MJO onset. The updraft and environmental temperatures appear sensitive to sea surface temperature and the magnitude of LS environmental subsidence, suggesting that elements of both the “discharge-recharge” and circumnavigating wave hypotheses for MJO onset were active during DYNAMO.This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htm

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

Thursday, 22 October 2015, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory 3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Scott W. Powell
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, October 22, 2015 - 3:30pm to 5:00pm

Use of In-Situ Observations for Quantifying Ice Cloud Microphysical Properties and Processes, and their Uncertainties

Greg McFarquhar

University of Illinois

Some of the most fundamental and complex problems in climate and weather research today are our poor understanding of the basic properties of clouds and our inability to determine quantitatively the many effects that clouds have on weather and climate. The representation of ice microphysical processes such as riming, sedimentation, aggregation, evaporation and deposition has large effects on quantitative precipitation forecasts and the representation of fallout and single-scattering properties affects cloud feedbacks in climate models, yet there are large uncertainties in how to best represent these processes. To better understand controls of ice clouds, not only are modeling studies required but also multi-platform observations that form the basis of model parameterizations.

In this presentation, in-situ observations obtained by the University of Illinois group in varying environmental conditions are used to characterize uncertainties in derived ice properties, such as number distribution functions, total concentrations, effective radii, and fallout velocities. Sources of uncertainty include both instrumental errors and uncertainties associated with the processing of the data. A framework for including these uncertainties in parameterization schemes appropriate for numerical models and retrieval schemes is introduced, and preliminary results using this framework to describe the dependence of ice crystal properties on environmental conditions is presented. To explore implications of this framework, an example of a stochastic parameterization scheme is presented. In addition, the impacts of uncertainties in the shapes and concentrations of small ice crystal shapes on the calculation of shortwave and long wave radiative fluxes is examined.  Plans for future research efforts to better constrain the representation of ice processes and properties and implications of these uncertainties finishes the presentation.

This seminar will be webcast live at:

HYPERLINK "http://www.fin.ucar.edu/it/mms/fl-live.htm" http://www.fin.ucar.edu/it/mms/fl-live.htm

Recorded seminar link can be viewed here:

https://www.mmm.ucar.edu/events/seminars

Thursday, 15 October, 2015, 3:30 PM

Refreshments 3:15 PM

NCAR-Foothills Laboratory

3450 Mitchell Lane

Bldg 2 Main Auditorium, Room 1022

First Name: 
Meghan
Last Name: 
Stell
Phone Extension (4 digits): 
2043
Email: 
meghan@ucar.edu
Presenter(s): 
Greg McFarquhar
Building:
Room Number: 
1022 - Main Auditorium
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, October 15, 2015 - 3:30pm to 4:30pm

Carl SchmittThe National Center for Atmospheric ResearchBoulder, Colorado

Glaciers in the tropical Andes have been rapidly losing mass since the 1970s. While rising temperatures are clearly having an impact, an increase in black carbon (BC) and other light-absorbing particles deposited on glaciers is also contributing to glacier loss. I will present the results of five years of snow sampling from glaciers in Peru, which is home to the largest extent of tropical glaciers in the world. During six research expeditions led by the American Climber Science Program, snow samples have been collected from numerous mountains ranging from 4800 to nearly 6800m in altitude. The snow samples were melted and filtered in the field and later analyzed using the Light Absorption Heating Method (LAHM), a new technique that measures the ability of particles on filters to absorb visible light. LAHM results have been calibrated using filters with known amounts of fullerene soot, a common industrial surrogate for black carbon. Beginning in 2013, snow samples have also been collected and kept frozen for analysis with a Single Particle Soot Photometer (SP2). Results from the LAHM analysis and the SP2 refractory BC results are well correlated. These results indicate that a substantial portion of the light-absorbing particles in the more polluted regions is BC. Results from the Cordillera Blanca show that mountains close to human population centers have substantially higher levels of BC (as high as 70 ng of BC per g snow) than remote glaciers (as low as 2.0 ng g−1 BC), indicating that population centers can influence local glaciers by sourcing BC. This amount of BC has been calculated to lead to an additional 0.5 to 1 meter of ice loss per year, a rate that has significant implications for water security in this region.

This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htm

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

Thursday, 8 October 2015, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory 3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Carl Schmitt
Organization(s):
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, October 8, 2015 - 3:30pm to 5:00pm

Characteristic Boundary-Layer Scales Defining the Vegetation-Cloud Interaction

Jordi Vila-Guerau de ArellanoMeteorology and Air Quality SectionWageningen University (The Netherlands)We study the interaction between grass and shallow cumulus cloud formation at diurnal scales. We place special emphasis on quantifying the changes in the characteristic length and time scales associated with thermals, shallow Cu and induced thermal circulation structures. A series of systematic numerical experiments are performed using a large-eddy simulation model coupled to an active vegetation model. We design four different experiments to disentangle the effects of shallow Cu on the surface and the response of clouds to these surface changes. The experiments include a ‘clear case’, ‘transparent clouds’, ‘shading clouds’ and a case with a prescribed uniform domain and reduced surface heat flux. Length and time scales are calculated using autocorrelation and two-dimensional spectral analysis.

We find that, in absence of background wind, shading controls by shallow Cu locally lowers surface temperatures and consequently reduces the sensible and latent heat fluxes, thus inducing spatial and temporal variability in these fluxes. The length scale of this surface heterogeneity is not sufficiently large to generate circulations that are superimposed on the boundary-layer scale, but the heterogeneity does disturb boundary-layer dynamics and generates a flow opposite to the normal thermal circulation. Besides this effect, shallow Cu shading reduces turbulent kinetic energy and lowers the convective velocity scale, thus reducing the mass flux. This hampers the thermal lifetime, resulting in a decrease in the shallow Cu residence time (from 11 to 7 min). This reduction in lifetime, combined with a decrease in mass flux, leads to smaller clouds. This is partially compensated for by a decrease in thermal cell size due to a reduction in turbulent kinetic energy. As a result, inter-cloud distance is reduced, leading to a larger population of smaller clouds, while maintaining cloud cover similar to the non-shading clouds experiment. We finish the presentation with preliminary results of the effect of a background wind in the vegetation-cloud system and an open discussion of how to integrate plant physiologic aspects in atmospheric boundary layer studies.

This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htmRecorded seminar link can be viewed here:https://www.mmm.ucar.edu/events/seminars

Thursday, 1 October 2015, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

**THIS SEMINAR IS SPONSORED BY GTP**

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Jordi Vila-Guerau de Arellano
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, October 1, 2015 - 3:30pm to 5:00pm

Paul FieldMet OfficeUnited Kingdom

The first WGNE/GASS Grey Zone Project case is using a cold air outbreak to explore i) how well mesoscale regional NWP models simulate a cold air outbreak? ii) What the effect of grid resolution is on that ability? And iii) what is the influence of parametrized convection across resolutions? Results from 8 Limited Area Models will be shown. Each model participant provided data from runs with and without convection schemes at grid resolutions of 16, 8,4,2,1km across a 1600km x 800km domain. Comparisons have been made between the models, remotely sensed and insitu observations. Conclusions will be provided about the behaviour of models across resolutions, with and without parametrized convection. Such comparisons raise questions about bias in aircraft observations used to test models – if the observations are biased by sampling larger clouds, for example, how large is this bias? And finally, precipitation in these systems is due to the presence of ice or snow – how important is the presence of ice and snow to the production of precipitation – globally?

This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htm

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

Friday, 25 September 2015, 11:00 AMRefreshments 10:45 AMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Paul Field
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Friday, September 25, 2015 - 11:00am to 12:15pm

Anthony J. IllingworthDepartment of Meteorology University of ReadingReading, United Kingdom

Polarization radars are now widespread and the benefits for operational networks have been demonstrated. Better data quality by rejection of non-meteorological returns together with improved corrections for attenuation have lead to more reliable estimates of rainfall rates. The use of the polarization parameters for hydrometeor identification has proved more elusive.  Four new parameters are available: differential reflectivity, differential phase shift, the co-polar correlation, and linear depolarisation ratio.  In this talk I will consider the performance of the various algorithms using the new parameters, starting with the easier problem for stratiform precipitation, then moving to the more challenging tasks such as the identification and sizing of hail and detecting supercooled water in convective clouds.  I will consider the accuracy required for these polarization parameters if the identification algorithms are to be trustworthy, and the implications for the scan strategy and the temporal and spatial resolution needed for various configurations of ground based and airborne radars.

This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htm

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

Thursday, 24 September 2015, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Anthony J. Illingworth
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, September 24, 2015 - 3:30pm to 5:00pm

Chris SnyderThe National Center for Atmospheric ResearchBoulder, Colorado

Particle filters offer an elegant solution to the problem of state estimation. They make no assumptions about the form of the underlying probability distributions and, in principle, are applicable in the presence of strong nonlinearity and non-Gaussianity. Driven in part by geophysical applications, much recent work has focussed on particle-filter algorithms for high-dimensional systems. I will give a basic tutorial on particle filters and then present a small sample of further topics: reasons that high-dimensional system are especially challenging for particle filters, a bound on the performance of an important class of particle filters, and potential paths toward more effective high-dimensional particle filters.

This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htm

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

Thursday, 17 September 2015, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory 3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Chris Snyder
Organization(s):
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, September 17, 2015 - 3:30pm to 5:00pm

Fanglin YangIMSG at Environmental Modeling CenterNational Centers for Environmental PredictionCollege Park, MD

The Global Forecast Systems (GFS) is the cornerstone of NCEP’s operational numerical weather forecast suite. This presentation will first review GFS development history and its forecast skills in the past few decades, with a focus on its recent performance. Major changes in GFS dynamics, physics and data assimilation schemes and significant improvements in GFS forecast skills in the past will be highlighted. The evaluation includes forecast skills of atmospheric large-scale flow pattern, precipitation and hurricane track and intensity. The performance of GFS will be compared with other international NWP models. The second part of this presentation will describe the development of GFS forecast evaluation tools. A portable NWP model verification package has been developed in recent years. It is now widely used by modelers and forecasters at NCEP and the community. Recent effort is focused on the evaluation of surface weather sensible elements and on the application of object-oriented verification methods. At the end, major issues and near-future development of the GFS and requirements for more advanced model evaluation tools will be discussed.

This seminar will be webcast live at:http://www.fin.ucar.edu/it/mms/fl-live.htm

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

Thursday, 13 August 2015, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022

First Name: 
Michelle
Last Name: 
Menard
Phone Extension (4 digits): 
8189
Email: 
menard@ucar.edu
Presenter(s): 
Fanglin Yang
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, August 13, 2015 - 3:30pm to 5:00pm

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