Atmospheric Physics Seminar
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2024-11-22 (Friday)
room B4.58, Pasteura 5 at 13:15 
prof. dr hab. Wojciech W. Grabowski (NSF National Center for Atmospheric Research, Boulder, Colorado, USA)Broadening of cloud droplet spectra through eddy hopping: Getting it right
Droplet spectra observed in adiabatic and close-to-adiabatic volumes of convective clouds are typically significantly wider than those predicted by an adiabatic parcel rising from the cloud base, 1-2 microns versus a couple tenths of a micron. Presence of cloud turbulence and its impact on the diffusional growth of cloud droplets has been often used as a possible explanation. The idea is that droplets arriving at a given location follow different trajectories through a turbulent cloud and they feature different growth histories. This is what we refer to as the “eddy hoping”. This mechanism has been investigated over the last two decades applying theory as well as numerical simulations using idealized frameworks of stochastic models, DNS, and scaled-up DNS. These studies suggest that eddy hopping can explain large spectral width of the adiabatic droplet spectra. However, as I discussed in my lecture in May, all those computational studies feature a fundamental flaw of droplets dispersing in the vertical direction, with the large spectral width because of the correlation between droplet radius and its vertical position. In this lecture, I will discuss a new extremely-high-resolution (grid length of 7.5 m) numerical simulation of a turbulent cumulus cloud applying Lagrangian particle-based microphysics. The simulation indeed shows spectral width up to 1 micron in adiabatic volumes not far from the cloud base. To understand these results, I will discuss an idealized framework of a kinematic one-dimensional vertical air plume that crosses the cloud base and forms a cloud. Without turbulence, the results are consistent with the adiabatic parcel model: the spectral width above the cloud base is close to 0.1 micron. However, with turbulence, the kinematic model predicts spectral widths between 1 and 2 microns. Physical mechanisms involved will be discussed.
Join Zoom Meeting
https://uw-edu-pl.zoom.us/j/98509018301?pwd=62UlZxbSPGKGo4rPMaXGI5cOUUObG2.1
Meeting ID: 985 0901 8301
Passcode: 428031
Join Zoom Meeting
https://uw-edu-pl.zoom.us/j/98509018301?pwd=62UlZxbSPGKGo4rPMaXGI5cOUUObG2.1
Meeting ID: 985 0901 8301
Passcode: 428031
2024-10-25 (Friday)
room B4.58, Pasteura 5 at 13:15
dr Konstantin Kuznetsov (GRASP Global - Space Services, Lille, France)Local scale Computational Fluid Dynamics modeling of aerosol transport over complex urban areas using CODE_SATURNE
Urban air pollution is a significant concern that affects the health andquality of life of city residents. The way pollutants spread through the air in cities is complicated by the intricate layout of buildings, streets, and other structures. In this seminar, we’ll dive into how we use Computational Fluid Dynamics (CFD) with code_saturne to model wind patterns and the movement of aerosols and other passive pollutants in cities like Paris and Warsaw.
We’ll share the details of our approach to building these high-resolution models (up to 1 meter resolution). This includes how we gather data about the city’s layout, create detailed meshes to represent complex urban geometries, and set up the right conditions for our simulations to run accurately. We’ll focus on how adding detailed features of the city into our models helps us better understand the subtle ways wind flows and pollutants move in densely built areas.
Additionally, we will present a comparative analysis between our simulation results and in-situ measurements from meteo stations. This comparison not only serves to validate our modeling approach but also highlights the effectiveness and limitations of CFD simulations in replicating real-world atmospheric conditions.
https://www.linkedin.com/in/kikuznetsov/edit/forms/next-action/after-connect-update-profile/
Join Zoom Meeting
https://uw-edu-pl.zoom.us/j/98630327949?pwd=dCnSGizv52gG8DiEC4iJZN6HRkL5WU.1
Meeting ID: 986 3032 7949
Passcode: 875971
We’ll share the details of our approach to building these high-resolution models (up to 1 meter resolution). This includes how we gather data about the city’s layout, create detailed meshes to represent complex urban geometries, and set up the right conditions for our simulations to run accurately. We’ll focus on how adding detailed features of the city into our models helps us better understand the subtle ways wind flows and pollutants move in densely built areas.
Additionally, we will present a comparative analysis between our simulation results and in-situ measurements from meteo stations. This comparison not only serves to validate our modeling approach but also highlights the effectiveness and limitations of CFD simulations in replicating real-world atmospheric conditions.
https://www.linkedin.com/in/kikuznetsov/edit/forms/next-action/after-connect-update-profile/
Join Zoom Meeting
https://uw-edu-pl.zoom.us/j/98630327949?pwd=dCnSGizv52gG8DiEC4iJZN6HRkL5WU.1
Meeting ID: 986 3032 7949
Passcode: 875971