Events (Upcoming & Past)

Past MMM Events

Special MMM/RAL Joint Seminar - Thursday, June 27, 2019 - 3:30pm

Speaker: Bert Holtslag

Affiliation: Wageningen University, the Netherlands

Urbanization affects human thermal comfort and health, especially for vulnerable groups such as the elderly and people with established health issues. To mitigate heat stress and accompanying excess mortality there is an urgent need of urban weather observations as well as updated tools for fine scale weather forecasting on short to medium-range time scales. In this presentation first an overview will be given of weather observations made within Dutch cities of variable size. Subsequently, experiences with the setup and use of a high-resolution forecasting system for urban areas will be discussed. The forecasting system is based on the Weather Research & Forecasting (WRF) model, which is used to make forecasts for the city of Amsterdam on a very high spatial resolution of 100 meter and which is driven by extensive and very detailed land surface information. The forecasting system has been used to make 48-hourly daily forecasts for the urban and surrounding areas for the summer period of 2015. The forecasts are validated with observations that were taken at 25 automated weather stations at different locations within the city of Amsterdam. Validation is done for parameters that are important for the well-being of citizens in cities such as the temperature, the evening temperature, the humidity and Wet Bulb Globe Temperatures (WGBT). The potential of future use and improvements of the forecasting system will be discussed.

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: 
Wednesday, June 12, 2019 to Thursday, June 27, 2019
Calendar Timing: 
Thursday, June 27, 2019 - 3:30pm to 4:30pm
Nancy
Kerner
8946

*Special MMM/CGD Joint Seminar *Please note Special Day and Time

Title: Mesoscale Eddy Momentum Flux in a 7km Mesh Global Atmosphere Model

Presenter: Brian Mapes, University of Miami

Abstract:  A two-year global nonhydrostatic atmosphere simulation on a 7km mesh (G5NR from NASA’s GEOS-5 model) is queried for one of its most unique strengths: What is the vertical momentum flux (u’w’ and v’w') by explicit air motions in the mesoscale (7-444 km) scale range? After motivating this classic question, especially in light of the hypothesis that organized convection can act as an upscale energy transfer (via upgradient flux, a “negative viscosity”), we address it comprehensively with the data. A global climatology indicates that these mesoscale motions overall act as positive viscosity (damping the shear kinetic energy SKE), except perhaps for some grid points with steep topography. However, cases of positive SKE tendency are also seen. We drill down into full-resolution data for selected situations to expose the nature of the calculation and the phenomena involved. Cyclones in shear are especially prodigious in producing convection-momentum interactions, of both signs, through preferential sampling of non-average low-level momentum. 

*Special Day and Time: Friday, August 17, 2018, 11:30am Refreshments 11:15am FL2-1022 Large Auditorium, Live webcast http://ucarconnect.ucar.edu/live

Thursday, August 9, 2018 to Friday, August 17, 2018

Building:
Room Number: 
Main Auditorium, Room 1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Thursday, August 9, 2018 to Friday, August 17, 2018
Calendar Timing: 
Friday, August 17, 2018 - 11:30am to 12:30pm

Speaker: Jordi Vilà-Guerau de Arellano

Affiliation:  Wageningen University, The Netherlands

In regional and global models uncertainties arise due to our incomplete understanding of the coupling between biochemical and physical processes. Representing their impact depends on our ability to calculate these processes using physically sound parameterizations, since they are unresolved at scales smaller than the grid size. More specifically over land, the coupling between evapotranspiration, turbulent transport of heat and moisture, and clouds lacks a combined representation to take these sub-grid scales interactions into account. Our approach is based on understanding how radiation, surface exchange, turbulent transport and moist convection are interacting from the leaf-to the cloud scale. We therefore place special emphasis on plant stomatal aperture as the main regulator of CO2-assimilation and water transpiration, a key source of moisture source to the atmosphere.

Plant functionality is critically modulated by interactions with atmospheric conditions occurring at very short spatiotemporal scales such as cloud radiation perturbations or water vapour turbulent fluctuations. By explicitly resolving these processes, the LES (large-eddy simulation) technique is enabling us to characterize and better understand the interactions between canopies and the local atmosphere. This includes the adaption time of vegetation to rapid changes in atmospheric conditions driven by turbulence or the presence of cumulus clouds. Our LES experiments are based on explicitly coupling the diurnal atmospheric dynamics to a plant physiology model. Our general hypothesis is that different partitioning of direct and diffuse radiation leads to different responses of the vegetation. As a result there are changes in the water use efficiencies and shifts in the partitioning of sensible and latent heat fluxes under the presence of clouds.

Our presentation is as follows. First, we discuss the ability of LES to reproduce the surface energy balance including photosynthesis and CO2 soil respiration coupled to the dynamics of a convective boundary layer. Second, we perform systematic numerical experiments under a wide range of background wind conditions and stomatal aperture response time. Our analysis unravel how thin clouds, characterized by lower values of the cloud optical depth, have a different impact on evapotranspiration compared to thick clouds due to differences in the partitioning between direct and diffuse radiation at canopy level. Related to this detailed simulation, we discuss how new instrumental techniques, e.g. scintillometery, might enable us to obtain new observational insight of the coupling between clouds and vegetation. We will close the presentation with open questions regarding the need to include parameterizations for these interactions at short spatiotemporal scales in regional or climate models.

Refreshments 3:15 PM

 

Building:
Room Number: 
Main Auditorium, Room 1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
Thursday, August 16, 2018
Calendar Timing: 
Thursday, August 16, 2018 - 3:30pm to 4:30pm

Speaker:  Jean-Pierre Chaboureau

Affiliation: Laboratoire d'Aérologie, Université de Toulouse, CNRS, UPS, Toulouse, France

Convection-permitting simulations (CPSs) and large-eddy simulations (LESs) have been long used for process-oriented case studies because of their ability in resolving the details of complex atmospheric circulation. This allows one to focus on convective objects, i.e. mesoscale convective systems (MCSs), convective updrafts and overshoots. Such gain in resolving fine-scale processes was also found when running convection-permitting models over longer time periods. The added value of such simulations was demonstrated using usual metrics such as the diurnal cycle of precipitation or the occurrence of extreme events, for example. This opens up new possibilities in exploring convective objects over a much larger sampling. Examples will be given from current on-going studies over the Tropics. In a Giga-LES (more than 1 billion grid points with 100 m spacing) of the Australian thunderstorm Hector the convector, the 10-km wide updrafts that overshoot into the stratosphere are characterized by a weak dilution. The km-scale eddies at the top of the overshoots produce the irreversible mixing with the stratospheric air and finally the hydration. In a CPS over northern Africa, the tracking of the MCSs shows a remarkable realism of terms of precipitation and deep convective activity when considering the radiative effect of dust. Too numerous MCSs are however predicted with a lack of organization for the longest-lived MCSs. Challenges in the CPM and LES approaches will be discussed.

Refreshments: 3:15 PM

Building:
Room Number: 
Main Auditorium, Room 1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Thursday, August 9, 2018 - 3:30pm to 4:30pm

Thursday, 2 August 2018, 3:30PM 

Speaker: Xiquan Dong

Affiliation: University of Arizona  

MCSs have regions of both convective and stratiform precipitation where significant different microphysical and thermodynamical features are observed. In a recent study, a classification method has been developed to objectively identify components of MCS as convective rain (CR, heavy rain), stratiform rain (SR, moderate-light rain), and anvil clouds (AC, no rain) using ground-based NEXRAD radar reflectivity, which provides a thorough means for studying the lifecycle of MCSs’ components, as well as their associated cloud and precipitation properties. We also developed a tracking algorithm using GOES IR temperature and tracked and analyzed a total of 4221 MCSs during two warm seasons from 2010 to 2011 over the central US and found that the CR precipitation intensity is an order higher than the SR one, but the SR coverage is much larger than the CR one.   

The DOE Atmospheric Radiation Measurement (ARM) conducted a field campaign, the Midlatitude Continental Convective Clouds Experiment (MC3E), at the ARM Southern Great Plains site from April to June 2011. During the MC3E field campaign, the University of North Dakota (UND) Citation II research aircraft carried out the major in situ measurements of cloud microphysical properties. This study investigates microphysical properties at ice-phase layer using the measurements collected by UND Citation II aircraft and the focus is on the correction of cloud ice water content (IWC) and the reconstruction of particle size distribution (PSD) based on multiple sensors measurements.   
 
To investigate the NSSL WRF simulated the warm season (April-September) precipitation over the Great Plains (GP), we use long-term (NCEP) Stage IV data over the Great Plains (GP).  Specifically, two subdomains, namely the Southern Great Plains (SGP, 99.985o W to 94.985o W, 34.66o N to 38.66o N) and Northern Great Plains (NGP, 100.75o W to 95.75o W, 45o N to 49o N) are selected. By using Self-Organizing-Map (SOM) method, a total of 808 convective systems during the period 2007-2014 are objectively classified into 6 classes according to the integrative analysis of synoptic characteristics over each sub-domain respectively.  Despite the difference in regional climatology, both regions demonstrate prominent seasonal contrast in dominant synoptic patterns.  The early summer convective systems are more impacted by the extratropical cyclone, while the late summer/early fall events are strongly associated with subtropical ridge.  Based on the SOM results, the real-time weather forecast product generated by the National Oceanic and Atmospheric Administration (NOAA) National Severe Storms Laboratory (NSSL) is evaluated using NCEP Stage IV data for each individual SOM class over each region.
 
Refreshments 3:15PM

 

Building:
Room Number: 
Main Auditorium, Room 1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Thursday, August 2, 2018 - 3:30pm to 4:30pm

Thursday, 26 July 2018, 3:30PM (*Please note Special Location: FL2-1001 Small Seminar Room) Speaker: Paul Stoy  Affiliation: Montana State University 

The northern North American Great Plains (NNAGP) have seen massive land use changes over the past half-century. Increases in agricultural intensity are consistent with observed cooling and increases in precipitation during the vegetative growing season. Have land managers responded to these climate changes in a way that further cools growing season climate, creating a positive feedback? Here, I review decadal changes in land management, hydrology, and climate in the NNAGP and demonstrate that it has experienced globally unique hydroclimate trends. Increases in evapotranspiration at the expense of sensible heat flux (a decrease in the Bowen ratio) have increased convective precipitation likelihood. The surface-atmosphere coupling framework used to quantify these changes also indicate that convective precipitation was anomalously unlikely weeks before the onset of the 2017 “flash” drought. Surface-atmosphere feedbacks in the NNAGP appear to be tipping toward a more closely coupled state, with both advantageous and deleterious effects on human livelihoods. From these results, I will argue that understanding the mechanisms underlying human-climate feedbacks in the NNAGP provides a framework for quantifying regional climate services across the globe.

Refreshments: 3:15 PM

 

Building:
Room Number: 
FL2-1001 Small-Seminar Room
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Thursday, July 26, 2018 - 3:30pm to 4:30pm

The Capacity Center for Climate and Weather Extremes (C3WE/MMM) is hosting a Climate and Weather Extremes Tutorial designed for students, researchers, and professionals who are interested in climate and weather extremes. The Tutorial will cover approaches to analyzing and modeling extremes, as well as methods to understand and characterize uncertainty. The Tutorial will also feature a clinic focused on workflows for accelerated science discoveries and overcoming barriers to understanding and predicting weather and climate extremes.

The Tutorial consists of both lectures and hands-on laboratory exercises, which will be taught by a team of NCAR climate scientists and members of the NSF Earthcube ASSET (Accelerating Scientific WorkflowS using Earthcube Technologies) project.

The Climate and Weather Extremes Tutorial will be offered over a 3-day period from Wednesday August 1– Friday August 3, 2018 at the NCAR Foothills Laboratory, Boulder, Colorado. 

Topics include:

  • Extremes under climate change: State of the science
  • Approaches to characterizing and predicting extremes
    • Dynamical modeling frameworks for extremes
    • Statistical modeling of extreme values and characteristics
  • Evaluating and validating extremes in climate models
  • Understanding sources of uncertainty
  • Challenges and advances in convective extremes
  • Improving workflows to accelerate science & discovery
Building:
Room Number: 
1022-Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
No
Calendar Timing: 
Wednesday, August 1, 2018 - 8:30am to Friday, August 3, 2018 - 5:00pm
MODEL FOR PREDICTION ACROSS SCALES – ATMOSPHERE (MPAS-A) TUTORIAL

30- 31 July 2018

NCAR Foothills Lab, Boulder, CO

OVERVIEW

The Mesoscale and Microscale Meteorology (MMM) Laboratory of the National Center for Atmospheric Research (NCAR) will be hosting a Tutorial on the Model for Prediction Across Scales – Atmosphere (MPAS-A). The tutorial will be held 30 – 31 July 2018 at NCAR’s Foothills Laboratory at 3450 Mitchell Lane in Boulder, Colorado. The tutorial will cover the basics of how to set-up, run, and post-process stand-alone MPAS-A simulations, and topics that will be covered will include:

  1. Horizontal (uniform and variable resolution) mesh configuration
  2. Real-data and idealized case initialization
  3. MPAS-A dynamical solver and numerical methods
  4. MPAS-A physics
  5. Software framework and MPAS infrastructure
  6. Post-processing tools

The primary audience for this tutorial is new or beginning users of MPAS-Atmosphere. Basic knowledge of atmospheric science and numerical modeling, as well as experience working within a Unix computing environment, is required for the tutorial.

Building:
Room Number: 
1022-Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
No
Calendar Timing: 
Monday, July 30, 2018 - 8:30pm to Tuesday, July 31, 2018 - 5:00pm

The Weather Research and Forecasting (WRF) model Tutorial will be held at the NCAR Foothills Laboratory (FL2) located at 3450 Mitchell Lane, Boulder, Colorado from July 23-27, 2018.

The Basic tutorial will consist of lectures on various components of the WRF modeling system along with hands-on practice sessions. The topics include:

  1. WRF Pre-processing System
  2. WRF Dynamics and Numerics
  3. WRF Physics
  4. WRF Software Framework
  5. WRF Post-processing and Graphical Tools

Basic knowledge of atmospheric science and numerical modeling, as well as experience working with a Unix computer environment, is required for the class. WRF Tutorial participants are strongly encouraged to work through the WRF-ARW online tutorial, especially if you have not used the model before. Reviewing the online tutorial will provide an overview of the system, which can help enhance your learning experience once you are here (even if you cannot compile and run the code physically).

Building:
Room Number: 
1022-Large Auditorium
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
No
Calendar Timing: 
Monday, July 23, 2018 - 8:30am to Friday, July 27, 2018 - 4:00pm

Speaker: Professor Lian-Ping Wang

Affiliation: Department of Mechanics and Aerospace Engineering, SUSTech

 

Since the 1980s, direct numerical simulations have served as a vital research tool to probe flow structures and nonlinear dynamics in complex flows such as multiphase flows and turbulent flows. Most of these simulations were performed based on the continuum (conventional or macroscopic) Navier-Stokes equation. In recent years, mesoscopic methods based on the Boltzmann equation, such as the lattice Boltzmann method and gas kinetic schemes, have been developed and applied to these complex flows. In this talk, I will discuss some recent advances in applying mesoscopic methods for rigorous simulations of such complex flows. Three specific examples will be considered: (a) turbulent channel flow laden with finite-size moving particles, (b) hydrodynamic interactions of cloud droplets, and (c) compressible turbulent flow.  A few implementation issues in these simulations will be discussed. The purpose is to expose the capabilities of these mesoscopic methods, open research issues, and their potentials for various complex flow problems.

Building:
Room Number: 
FL3-2072 MMM Conference Room
Type of event:
Calendar Timing: 
Monday, July 16, 2018 - 11:00am to 12:00pm

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