May 2025 - Particle-based-cloud-modelling

Fwd: Postdoc position at Notre Dame in air-sea interaction and droplet microphysics
by Sylwester Arabas 21 May '25

21 May '25

-------- Forwarded Message -------- Subject: Postdoc position at Notre Dame in air-sea interaction and droplet microphysics Date: Tue, 20 May 2025 20:44:41 -0400 From: David Richter <David.Richter.26(a)nd.edu> Dear colleagues, I am hiring a postdoctoral researcher at the broad intersection of air-sea interaction, wave-induced turbulence, and spray/marine aerosol/cloud microphysics. The specific goals and scientific questions will depend on the expertise of the candidate, but the idea is to use LES and Lagrangian droplet modeling to investigate process-level questions in the areas of fluxes, droplet-turbulence interaction, and wave influences on surface layer turbulence and droplet/aerosol transport. I have attached an advertisement here, and I would greatly appreciate it if you could forward this to or recommend anyone you know who might be eligible and interested. Many thanks, -- David Richter Professor Department of Civil and Environmental Engineering and Earth Sciences University of Notre Dame 120A Cushing Hall Office: 574-631-4839 Email: David.Richter.26(a)nd.edu <mailto:David.Richter.26@nd.edu> Website: http://nd.edu/~drichte2 <http://nd.edu/~drichte2>

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Axel Seifert's webinar on May 21-st 4 pm CET (@uni-mainz.de)
by Sylwester Arabas 19 May '25

19 May '25

-------- Forwarded Message -------- Subject: [EXT] Seminar mathematics and atmospheric physics on May 21 Date: Mon, 19 May 2025 09:17:06 +0200 From: Peter Spichtinger <spichtin(a)uni-mainz.de> Dear all, this is a kind reminder for the next talk in our monthly seminar on mathematics and atmospheric physics. On Wednesday, May 21, Axel Seifert (German Weather Service) will talk about Ice microphysics in higher dimensions: super-particles and the geometry of snowflakes Abstract: Understanding snowflake formation requires modeling the interplay between complex microphysical processes and environmental conditions. In this talk, I will present ice microphysics in a higher-dimensional phase space using a stochastic super-particle approach, where each numerical particle represents an ensemble of real ice crystals. Building on the McSnow modeling framework—which includes detailed habit prediction for ice particles—we extend the representation of snowflake geometry to more realistically capture particle growth and aggregation. In the first part of the talk, I introduce an ML-based coarse-graining method that enables the derivation of a multi-moment, P3-like bulk microphysics scheme directly from super-particle simulations—providing a systematic link between Lagrangian and Eulerian modeling frameworks. In the second part, the focus shifts to the variability in the geometry of aggregate snowflakes. We show that the maximum dimension of aggregates — given fixed mass and monomer count — follows a lognormal distribution, revealing the stochastic nature of the aggregation process. This rigorous treatment offers new insights into the morphological diversity of snowflakes and contributes to improved representations of ice particles in weather and climate models. And even if it doesn’t make the forecasts any better—or solve the problem of climate change—we gain a deeper understanding of clouds, and have some fun doing applied math along the way. The seminar will start at 16:00 local time (i.e. 14 UTC). The zoom link is provided below (starting already at 15:45 local time). The next dates for the seminar are as follows June 4 Jana de Wiljes, TU Ilmenau Please also check the homepage of the seminar: https://www.staff.uni-mainz.de/spichtin/seminar.html Best, Peter PS: Please feel free to distribute the announcement to others Reminder: The registration and abstract submission for the SCALES conference https://model.uni-mainz.de/scales-conference-2025/ are still open ... ----------------------- Peter Spichtinger is inviting you to a scheduled Zoom meeting. Topic: Seminar Mathematics and Atmospheric Physics Time: May 21, 2025 03:45 PM Amsterdam, Berlin, Rome, Stockholm, Vienna Join Zoom Meeting https://uni-mainz-de.zoom.us/j/68522641413?pwd=SX2azpaqe4yBP0Cy907rvhVk27Ky… Meeting ID: 685 2264 1413 Passcode: 293629 --- One tap mobile +496950500952,,68522641413#,,,,*293629# Germany -- ---------------------------------------------------------------- Prof. Dr. Peter Spichtinger Theoretical cloud physics Institute for Atmospheric Physics (IPA) Johannes Gutenberg University Mainz J.-J.-Becherweg 21, 55128 Mainz, Germany Office: 05-163 Phone: +49 (0) 6131 39 - 23157 Fax: +49 (0) 6131 39 - 23532 email:spichtin@uni-mainz.de https://www.staff.uni-mainz.de/spichtin/ https://theoryofclouds.ipa.uni-mainz.de/ https://binary.uni-mainz.de/ https://model.uni-mainz.de/ ----------------------------------------------------------------

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Fwd: [IGF] webinar 2025-05-16 13:15 CET ... online via Zoom (Emma Ware)
by Sylwester Arabas 14 May '25

14 May '25

Univ. Warsaw webinar by Emma Ware (UCDavis & agh.edu.pl) Fri May 16 at 1:15 pm CET (8:15 pm in Japan, 7:15 am East Coast) title: Adaptive Time-Stepping within the Super-Droplet Method Monte-Carlo Coagulation Scheme zoom link: https://uw-edu-pl.zoom.us/j/92869816385?pwd=OGGyBBxKufiLUNw1jbRmriWoWGKYQE.1 (Meeting ID: 928 6981 6385 Passcode: 447840) -------- Forwarded Message -------- Subject: [IGF] Seminarium, 2025-05-16 13:15, [...] and online via Zoom Date: Wed, 14 May 2025 08:00:06 -0000 To: zfa_seminarium(a)fuw.edu.pl *Adaptive Time-Stepping within the Super-Droplet Method Monte-Carlo Coagulation Scheme* https://www.igf.fuw.edu.pl/pl/seminars/presentation/adaptive-time-stepping-… Emma Ware Akademia Górniczo-Hutnicza We are presenting an analysis on an adaptive time-stepping scheme for the Super-Droplet Method (SDM) introduced in prior work to improve the efficiency and accuracy of probabilistic droplet coalescence in cloud microphysics. Superdroplets are computational particles that represent weighted ensembles of real cloud droplets, enabling high-fidelity representations of microphysical processes like collision–coalescence. SDM, first introduced by Shima et al. (2009), is a Monte Carlo algorithm that selects superdroplet pairs linearly within each timestep and simulation volume to test for collisions. The algorithm also includes logic that allows multiple collisions between the same candidate pair, accounting for the likelihood of repeated interactions within a single timestep. Adaptive time-stepping dynamically adjusts simulation time steps to control the coalescence deficit: a quantifiable error that arises when the available droplet population within superdroplet candidate pairs is not large enough to undergo the expected collision events. While SDM exhibits inherent statistical spread due to its probabilistic nature, the deficit represents a systemic underestimation bias of collision events. To validate the adaptive scheme, we implement it independently in two open-source models, PySDM and Droplets.jl. The results demonstrate consistency across platforms. Using the classical Golovin test case, we compare SDM and adaptive SDM scheme in terms of convergence, computational cost, and fidelity. We also draw conceptual parallels to the Weighted Flow Algorithm (WFA) Monte Carlo algorithm employed in PyPartMC, which employs analogous adaptive logic for eliminating the deficit within a different coalescence framework. Our convergence analysis spans a range of timesteps, superdroplet counts, and initialization methods, examining how the deficit scales and exploring the trade-off between efficiency and error mitigation when adaptive time-stepping is implemented. We show that the substepping procedure maintains a computational cost similar to that of the original SDM using the “parent” timestep, while achieving accuracy comparable to smaller fixed timesteps. Overall, our results demonstrate that adaptive time stepping provides a more efficient path to reducing coalescence error than uniformly decreasing the timestep, with implications for large-scale cloud and precipitation modeling. While we focus on warm-phase microphysics, the results are also applicable to cold and mixed-phase systems, as well as other coagulation problems outside atmospheric science. Join Zoom Meeting https://uw-edu-pl.zoom.us/j/92869816385?pwd=OGGyBBxKufiLUNw1jbRmriWoWGKYQE.1 <https://www.google.com/url?q=https://uw-edu-pl.zoom.us/j/92869816385?pwd%3D…> Meeting ID: 928 6981 6385 Passcode: 447840 /Koordynator seminarium: / /prof. dr hab. Hanna Pawłowska/ /e-mail: hanna.pawlowska(a)igf.fuw.edu.pl/ /telefon: +48 22 55 32 035/ Wysłano dnia: 14-05-2025 10:00 (c) 2025 UW, WF, Instytut Geofizyki, www.igf.fuw.edu.pl /This email has been sent automatically, please do not reply./ /If you see an error or if you are not the correct recipient, please contact: sekretariat.IGF(a)fuw.edu.pl/

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