Wydział Fizyki UW > Badania > Seminaria i konwersatoria > Środowiskowe Seminarium Fizyki Atmosfery

Środowiskowe Seminarium Fizyki Atmosfery

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Zapraszamy do sali B4.58, ul. Pasteura 5 o godzinie 13:15

dr Dariusz B. Baranowski (Institute of Geophysics, Polish Academy of Sciences)

Coupling between atmosphere and ocean on diurnal time scale: can we measure physical properties of atmosphere and ocean across an undisturbed air-sea interface

Interactions across an air-sea interface are fundamental features of Earth’s climate system with substantial implications for ecosystems. The diurnal variations of local exchange between atmosphere and ocean impact both environments and rectifies into longer and larger scale through the interactions with mesoscale circulation. Therefore, such local processes can potentially influence the evolution of weather patterns as well as properties of an ocean’s circulation. At the same time, atmosphere and ocean models struggle with the realistic representation of diurnal variations across an air-sea interface. The gaps in our understating of physical mechanisms behind these interactions stems from the fact that collocated, reliable measurements within coupled atmosphere and ocean environment, spanning across an air-sea interface are rare.The exchange of physical properties, including but not limited to, energy and momentum across an air-sea interface depends on the environment within the air-sea transition zone, which can be defined as an area between the bottom of the oceanic mixed layer (~100m depth) and the top of the atmospheric boundary layer (~1000m). Thus, measurements of stratifications across are required to characterize coupled variability of the atmosphere and ocean, especially on a diurnal time scale. Although many observational techniques have been devised to observe stratification (e.g., vertical profiles of physical properties) within atmospheric and oceanic environments, they can rarely be applied at the same place or time in both environments without disturbing it. The emergence of the Uncrewed Aircraft Systems (UAS) enables a new opportunity for sampling across air-sea interface. A multirotor UAS equipped with atmosphere and/or ocean measurement capabilities can be launched from a vessel and perform measurements in its vicinity, in flow but not obstructed by the ship’s structure.In my presentation I will discuss the opportunities provided by UAV-based measurement conducted in combination with other ship-borne observations to perform seamless observations across the air-sea transition zone. To that end, observations characterizing diurnal evolution of atmospheric and oceanic environments collected over tropical and subtropical Atlantic Ocean will be presented. Collected observations of atmospheric temperature, humidity, and winds profiles (surface to 500m) combined with observations of temperature in the top layer (top 10m) of the ocean can be used to identify the effect of air-sea fluxes on local variability in both environments. Results demonstrate the capability of ocean and atmosphere sensing UAS to measure coupled variability across an air-sea interface. Opportunities to expand such measurements in the future to other global basins and marginal seas (e.g., Baltic Sea) will be discussed as well.Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/98517197453?pwd=d2tqRk5zTm80eTJoWjk0R09ueGtrZz09Meeting ID: 985 1719 7453Passcode: 039135

Zapraszamy do sali B4.58, ul. Pasteura 5 o godzinie 13:15

prof. dr hab. Wojciech W. Grabowski (National Center for Atmospheric Research NCAR)

Nimbostrophy

Fluid mechanics use simple concepts that help understanding and appreciate balances stemming from the governing fluid motion equations. Such concepts highlight underlying physical processes and provide guidance for physical interpretations. Classical examples for the atmospheric and oceanic fluid dynamics are the hydrostatic balance, the cyclostrophy, or the geostrophy. This presentation will discuss simple balances appropriate for the cloud dynamics that we refer to as the "nimbostrophy". The simplest one is to assume that air flow within a cloud maintains water saturation (or ice saturation in very cold temperatures). Such an assumption privides a simple and computationally efficient methodology in cloud modeling. It does not allow, however, to appropriately model cloud microphysics, especially the role of cloud condensation nuclei and ice-forming nuclei in cloud and precipitation formation. The more accurate approach is to assume that the supersaturation inside a cloud is in a quasi-equilibrium between the forcing due to cloud updraft and the sink due growth of cloud particles (droplets or ice crystals). This pedagogical presentation will discuss the two approaches in the context of key cloud physics problems in modeling and predicting weather and climate.Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/95210132783

Zapraszamy do sali B4.58, ul. Pasteura 5 o godzinie 13:15

mgr inż. Grzegorz Florczyk (IGF UW)

How to model the evolution of the polluted PBL? - Exploring a new approach

Zapraszamy do sali B4.58, ul. Pasteura 5 o godzinie 13:15

mgr inż. Stanisław Król (IGF UW)

Ultra fast measurements of temperature at Methane-to-go-Poland campaign

A measurement campaign called "Methane-To-Go Poland" took place in October 2022 in Bielsko Biała. The main focus of the campaign was to measure methane emitted from the ventillation shafts of coal mines in Upper Silesia region. The data was gathered using a specially designed platform called "HELiPOD", on which sensors such as Li-7700, Picarro and 5-hole probe were installed. There was also a contribution from the Institute of Geophysics in the form of the Ultra Fast Thermometer. The platform was suspended below a helicopter, and plume penetrations on different heights and distances were performed in order to determine the flux of methane coming from the shaft.During the seminar, I will sketch the measurement strategy, briefly summarize the collected data and present examples of preliminary results Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/94390099976?pwd=eldZSjlwZVBMbzdGSExGdDk0RlhpQT09Meeting ID: 943 9009 9976Passcode: 171190

Zapraszamy do sali B4.58, ul. Pasteura 5 o godzinie 13:15

dr Victor Avsarkisov (Leibniz Institute of Atmospheric Physics, University of Rostock)

On the presence of stratified turbulence in the middle atmosphere

During this talk, the evidence that stratified turbulence is present in the middle atmosphere will be presented. The study is based on the results of General Circulation Model simulations and observational data, such as radar and rocket-borne measurements. In particular, it will be shown that mesoscale dynamics in the middle atmosphere is not always dominated by gravity waves, and layered vortical structures can play a significant role, as well.The importance of stratified turbulence in the formation of the cold summer mesopause at mid to high latitudes will also be discussed.// Join Zoom Meetinghttps://us05web.zoom.us/j/82239898147?pwd=UVhENEdNc1dnUjFJQ1dVbkZ6TUtTdz09// Meeting ID: 822 3989 8147// Passcode: Q8SM3F

Zapraszamy do sali B4.58, ul. Pasteura 5 o godzinie 13:15

dr Jun-Ichi Yano (Meteo-France, Toulouse)

Intermittency, coherency, pulse: wavelet-based analyses

Standard classical turbulence theories assume homogeneity and isotropy. However, turbulence found in reality, including those in the atmosphere (not only in the boundary layer), hardly satisfies those conditions. Instead, typical turbulence involves extensive intermittencies, associated with coherencies, with the latter often take pluse-like structures.Unfortunately, a standard analysis method based on Fourier transform is often not appropriate to quantify those realistic turbulence characteristics, due to its "global" nature of quantifications.In this talk, I propose the wavelet as an alternative methodology for the quantifications by exploiting its capacity of both the scales and the localizations of the structures.// Join Zoom Meetinghttps://us05web.zoom.us/j/89996287079?pwd=UnRxNmFFeFlqckhWTi95a0xNOFlHdz09// Meeting ID: 899 9628 7079// Passcode: 6Hy6FK

Zapraszamy do sali B0.14, ul. Pasteura 5 o godzinie 13:15

prof. dr hab. Wojciech W. Grabowski (National Center for Atmospheric Research NCAR)

Evolution of cloud droplet spectral width: A new look at an old problem

Spectral width of the cloud droplet spectrum is important for radiative properties and drizzle/rain development in warm ice-free clouds. We use an adiabatic rising parcel framework to study activation and diffusional growth of cloud droplets, focusing on the spectral width evolution, and contrasting clean and polluted environments. A comprehensive droplet growth equation is used that includes kinetic, solute, and surface tension effects. We show that those effects have an appreciable impact on the spectral width evolution above the cloud base. Without those effects, the droplet area standard deviation should not change once activation is completed. In contrast, simulation results show that the area standard deviation does increase with height, especially for weak updrafts and polluted environments. Implications of those results for cloud modeling, especially applying conventional bin microphysics, are discussed.Join Zoom Meeting // https://us05web.zoom.us/j/81851898071?pwd=VmdPbDBhbEhRZHU1WjNUR3FTeFNiQT09Meeting ID: 818 5189 8071Passcode: 9smiS9

Zapraszamy na spotkanie o godzinie 13:15

Prof. Dr.-Ing. Bettina Frohnapfel (Karlsruhe Institute of Technology, Institute of Fluid Mechanics)

The influence of heterogeneous surfaces on forced and mixed convection

The concept of an equivalent surface roughness provides an established procedure of how to include homogeneous surface roughness into large scale flow predictions of forced convection flows.This seminar presentation addresses the question whether the drag of heterogeneous rough surfaces can be included in this type of predictive correlation. Heterogeneous surfaces are often present as boundary conditions for the atmospheric boundary layer and may impact the Obukhov length scale.In terms of forced convection we consider results from laboratory experiments with different surface topologies. Moreover, the effect of spanwise heterogeneous surfaces on mixed convection is discussed based on Direct Numerical Simulations (DNS) data. It is shown that the flow organization classically found for smooth-surface mixed convection conditions can be influenced by the presence of heterogeneous surfaces. For example, streamwise aligned ridges favor the transition from streamwise rolls to convective cells at significantly lower Richardson number than in the smooth surface case.Join Zoom Meeting // https://us05web.zoom.us/j/82334366290?pwd=SWNoYkRlRngrWUlVNTZSRitTWXNrUT09Meeting ID: 823 3436 6290Passcode: 2B45ZX

Zapraszamy do sali B0.14, ul. Pasteura 5 o godzinie 13:15

prof. dr Piotr Smolarkiewicz (National Center for Atmospheric Research NCAR)

Richardson preconditioners for elliptic problems in numerical models of weather and climate

Numerical models for integrating partial-differential equations of weather and climate (W&C) often involve elliptic boundary value problems (BVPs). Solution of such BVPs amounts to inverting a sparse N x N matrix, with N being a total number of nodes discretizing the W&C model domain. With numerical weather prediction aiming at horizontal resolutions O(1)~km globally, N can be on the order of 109. The best suited methods for handling such large linear problems are the matrix-free Krylov-subspace algorithms, with the conjugate gradient scheme being a prominent example. Krylov schemes may be viewed as pseudo-time integrations of the damped oscillations equations, with a variable time step and damping scales determined variationally by minimizing the solution departures from the solution attainable in the stationary limit of the successive iterations. Notwithstanding their virtues of simplicity and robustness, Krylov schemes lose the efficacy for stiff problems characterized by the multiplicity of scales. To aid their performance, while retaining the virtues, the vanilla schemes incorporate operator preconditioning that amounts to solving efficiently a part of the governing BVP problem and reduce its stiffness. The present lecture discusses a suite of preconditioners steaming from the Richardson's (1910) seminal idea of augmenting an elliptic BVP with a transient diffusion equation. Exploiting this idea for mixed explicit-implicit pseudo-time-stepping schemes leads to a broad suite of stationary (as opposed to variational) iteration solvers, including the many classical algorithms. The high-performance all-scale EULAG model [J. Comput. Phys. 263 (2014) 185-205], with a flexible three-dimensional decomposition of MPI tasks, is furnished with the preconditioners akin to the classical alternating-direction-implicit (ADI) algorithms, generalized to optional permutations of parallel tridiagonal inversions.Given the availability of the article underlying this lecture [J. Comput. Phys. 463 (2022) 111296], I will only highlight key theoretical aspects of the BVPs in W&C models and focus on revealing the relative efficiency and accuracy gains attainable with the developed preconditioners in simulations of atmospheric flows across scales from planetary to cloud and laboratory. // Zoom Meeting: https://us05web.zoom.us/j/84243968806?pwd=bkhXSHQ0dmhlT3VYQ083VEhBd0dGUT09 // Meeting ID: 842 4396 8806 // Passcode: 2wQyTm