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Atmospheric Physics Seminar

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room B4.58, Pasteura 5 at 13:15

prof. dr hab. Wojciech W. Grabowski (NCAR, Boulder, Colorado, USA)

Broadening of cloud droplet spectra through eddy hopping: Why did we all have it wrong?

The impact of turbulence on diffusional growth of cloud droplets has a long history in cloud physics research. Cooper (J. Atmos. Sci. 1989) argues that droplet spectrum observed at a given location within a cloud comes from different droplet trajectories through a turbulent cloud and thus different droplet growth histories. This is what we refer to as the “eddy hoping” mechanism. This mechanism has been investigated over the last two decades applying theory and numerical simulations using idealized frameworks of stochastic models, DNS, and scaled-up DNS. The theory advanced by Sardina et al. (Phys. Rev. Let. 2015), supported by their numerical simulations, suggests that the spectral width should continuously increase in time due to eddy hopping in homogeneous isotropic turbulence, with the spectral width of the radius squared distribution increasing as the square root of time. That scaling has been confirmed in several subsequent studies. However, we show that all those studies feature a fundamental flaw of droplets dispersing in the vertical direction, and the spectral width increase resulting from the correlation of the droplet radius with its vertical position. In fact, the square root of time scaling is the same as the scaling of the droplet position standard deviation in the random walk model. When droplet dispersion is accounted for, the spectral width at a given height or a small height range remains approximately constant in time, with the width dependent on the vertical depth over which droplet statistics are gathered (and arguably on the initial spectral width during cloud droplet formation through activation of cloud condensation nuclei). This presentation will review the theory and past numerical studies showing the square root of time scaling of the droplet radius squared distribution, and discuss results of numerical simulations where the impact of the droplet vertical dispersion is accounted for.Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/95502757086?pwd=RHpudG1YOUk0TFJ2UGlUcjZXVTFPQT09Meeting ID: 955 0275 7086Passcode: 416856

room B4.58, Pasteura 5 at 13:15

prof. Cédric Jamet (Université du Littoral-Côte d'Opale, Laboratoire d'Océanologie et de Géosciences)

Observation of the Ocean Color: Benefit of Lidar Technique

Active remote sensing of global ocean plankton properties presents a renewed opportunity for overcoming some of the major limitations of passive ocean color data that have challenged the community for decades. Passive remote sensing of ocean color observations has revolutionized our understanding of global plankton ecosystems and provide multi-spectral retrievals at many advantages: multiple wavelength bands, good spatial resolution (300-1000 meters) and on high repetitive cycles (~2 days). However, the ocean color signal is limited to the very near surface layer, provides no information on plankton vertical structure, is extremely limited in polar regions, suffers from cloud cover and absorbing aerosols, and provides no information on day-night changes in plankton properties. Active remote sensing, such as Lidar, can address some of these challenges and would provide an exceptional complement to passive remote observations. In the last decade, lidar systems applied to ocean color have reached maturity thanks to field deployments of multiple airborne and in-situ sensors and to recent studies using lidar measurements from atmospheric satellite missions to obtain significant scientific results in the ocean color field. These advances make the transition to an ocean-optimized satellite system foreseeable in the next generation of missions. This seminar will showcase what has been done so far with lidar through examples of successes in the field and from airborne, in-situ and satellite active sensors and to discuss potential avenues for further advances for ocean application. Additionally, the seminar will open discussion for which features a future ocean-optimized Lidar should possess, such as blue laser, High-Spectral Resolution Lidar, among others.Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/96415619204?pwd=eHdlTkMvU25MSUhoZjJySHZLak9Fdz09Meeting ID: 964 1561 9204Passcode: 893600

room B4.58, Pasteura 5 at 13:15

dr Florian Oschmann (Czech Academy of Sciences)

Rigorous derivation of magneto-Boussinesq approximation with non-local term

We derive rigorously the magneto-Boussinesq system for a gaseous star as done formally by Spiegel and Weiss ("Magnetic Buoyancy and the Boussinesq Approximation'', 1982). In contrast to their result, we take also into account the boundary conditions for the temperature, leading to an additional non-local temperature term in the limit. We shall then give physical meaning to our "mathematical'' system compared to the "physical'' Spiegel-Weiss system. This is joint work with Piotr Gwiazda and Aneta Wróblewska-Kamińska (both IMPAN).Join Zoom Meetinghttps://us04web.zoom.us/j/72403319998?pwd=jbHqp0tDgWjv6utYWoBohzFuMkAGwt.1Meeting ID: 724 0331 9998Passcode: 8EQg28

room B0.14, Pasteura 5 at 13:15

prof. dr hab. Szymon Malinowski, prof. dr hab. Hanna Pawłowska (IGF UW)

Uroczyste Seminarium Środowiskowe Fizyki Atmosfery z okazji jubileuszu 90 lecia urodzin prof. Krzysztofa Hamana

Zapraszamy serdecznie na specjalne uroczyste Seminarium Środowiskowe Fizyki Atmosfery z okazji jubileuszu 90 lecia urodzin Profesora Krzysztofa Hamana, które odbędzie się 23 Lutego 2024 roku o godzinie 13:15 w sali B0.14 Wydziału Fizyki UW przy ul. Pasteura 5, 02-093 Warszawa. Seminarium będzie transmitowane online. Program: Laudacja i krótkie przypomnienie zasług Jubilata dla nauki a także dla polskiej fizyki atmosfery, meteorologii i geofizyki - Szymon Malinowski, Hanna Pawłowska. Wspomnienia wychowanków i współpracowników Profesora, m. in. Hanny Pawłowskiej, Wojciecha Grabowskiego, Piotra Smolarkiewicza, Piotra Flatau. Wspomnienia czcigodnego Jubilata. Zapraszamy wszystkich, którzy mieli przyjemność współpracy z prof. Hamanem, cenią jego dorobek lub po prostu chcą być z nami w tym uroczystym dniu.

Seminarium jest otwarte, jednak ze względów organizacyjnych będziemy wdzięczni za zgłoszenie uczestnictwa w spotkaniu towarzyskim po seminarium do dnia 15 lutego 2024 na adres: dabrowka.stepniewska@fuw.edu.pl.

room 1.02, Pasteura 5 at 13:15

mgr Emeka Ugboma (IGF UW)

Satellite observations showed a negligible reduction in NO2 pollution due to COVID-19 lockdown over Poland

This study analyzed tropospheric NO2 levels in Poland from 2010 to 2020, focusing on major cities and the impact of COVID-19 lockdowns in 2020. During the lockdown, notable pollution sources were identified in Katowice, Warszawa, and Bełchatów. While NO2 pollution decreased during the lockdown, this reduction was consistent with typical monthly and annual variations. Kraków exhibited the highest reduction in March 2020, while Gdańsk, Wrocław, and Warszawa also showed decreases throughout the lockdown. Meteorological conditions affected NO2 dispersion, but anthropogenic emissions remained the primary driver of NO2 concentrations. Ultimately, the study found that COVID-19 restrictions had a negligible impact on NO2 pollution in Poland, confirming the importance of reduced traffic in urban pollution reduction.

https://uw-edu-pl.zoom.us/j/92088590567?pwd=RXJ2T2JVY0VJVis0TmppeXJTN1VpUT09Meeting ID: 920 8859 0567Passcode: 917936

room B4.58, Pasteura 5 at 13:15

prof. Lian-Ping Wang (Southern University of Science and Technology, Shenzhen, P.R. China)

Can acoustic waves be used to promote collisional growth of cloud droplets?

Acoustic precipitation enhancement technology uses strong low-frequency sound waves to enhance the relative motion and thus the collisional growth of cloud droplets, leading to increased rainfall. As a forward-looking technology, acoustic precipitation enhancement is viewed to be low-cost, environmentally friendly, simple to operate, and easy to promote. However, the science behind this technology, namely, turbulent cloud microphysics and dynamics under the action of sound waves, is a challenging multi-scale, multi-physics, and interdisciplinary research topic. In this talk, I will first review previous theoretical understanding on the mechanisms of acoustic agglomeration and related collision kernels, and discuss how the magnitude of these collision kernels compared to collision kernels due to gravitational settling motion and turbulent air fluctuations. We then solve the stochastic collection equation under the combined actions of gravity and acoustic waves, to study how acoustic waves affect the collisional growth of cloud droplets. In particular, we study how the growth rate depends on the frequency, the applied duration, and intensity of sound waves. It is found that an optimal wave frequency exists and its value depends on the initial droplet size distribution, applied duration, and wave intensity. We also compare our findings with previous experimental observations and theoretical results. >>> Join Zoom Meeting >>>https://uw-edu-pl.zoom.us/j/94443885713?pwd=MFk1bERoaVhaY2pJQW1hZWdaTlg4Zz09Meeting ID: 944 4388 5713Passcode: 330254

room 1.02, Pasteura 5 at 13:15

prof. dr hab. Wojciech W. Grabowski (MMM Laboratory, NCAR, Boulder, Colorado, USA)

Reversed Twomey effect: fact or fiction?

Atmospheric aerosols play an important role in modulating properties of warm (ice-free) clouds. For the same liquid water path (LWP), an increase of aerosol concentration leads to the decrease of the cloud droplet size. This impacts cloud radiative properties and cloud capability to develop precipitation. The former is typically referred to as the Twomey or first aerosol indirect effect. However, recent satellite observation in highly polluted regions near the Indian subcontinent suggest a reversal of the Twomey effect, with extremely polluted clouds showing larger cloud droplets (larger droplet effective radii to be exact) than clouds that develop in less polluted environments. This has been referred to as the reversed Twomey effect. According to satellite observations, the reversal is seen in shallow clouds with relatively low liquid water path, below 100 g m2. One possibility suggested in the literature is that competition for the water vapor during cloud droplet formation (i.e., activation of cloud condensation nuclei, CCN) leads to a situation where lower droplet concentrations are possible in higher CCN concentrations. This hypothesis is tested in series of numerical simulations using an adiabatic parcel model, two-dimensional kinematic (prescribed flow) model, and a three-dimensional cloud model applying Lagrangian particle-based microphysics. Simulated droplet spectra and the effective radius dependence of on LWP are compared for simulations with CCN spectra representing observed polluted and extremely polluted conditions. Overall, all simulations fail to show the reversed Twomey effect. Possible ways to reconcile satellite observations and model simulations will be discussed.

https://uw-edu-pl.zoom.us/j/96657964798?pwd=UDBLRlVmUnI4eWxFREh6c3pUTjJCdz09Meeting ID: 966 5796 4798Passcode: 075262

room B4.58, Pasteura 5 at 13:15

dr hab. Krzysztof Markowicz (IGF UW)

Zmiany czasowe budżetu energetycznego nad Polską w ubiegłych czterech dekadach

W ramach seminarium zaprezentowane będą wyniki badań nad budżetem energetycznym obszaru Polski w okresie od 1980 do 2021 r. W tym celu wykorzystano dane z re-analizy MERRA-2 oraz wyniki symulacji wykonanych modelem radiacyjnym Fu-Liou sprzężonym z klimatycznymi bazami danych.Średnia temperatura powietrza w Polsce rośnie w ostatnich dekadach w tempie ok. 0,5 stopnia na dekadę. Równocześnie zmiana się saldo energii zarówno na powierzchni ziemi, jak i na górnej granicy atmosfery. Wynika to głównie ze zmian koncentracji gazów cieplarnianych, ale również ze zmian niektórych wielkości fizycznych opisujących aerozole i chmury. Dane wskazują na znaczny wzrost współczynnika transmisji promieniowania krótkofalowego wynikający z redukcji aerozolu oraz zachmurzenia. Prowadzi to do wzrostu salda energii na powierzchni ziemi oraz redukcji ujemnego strumienia netto energii na górnej granicy atmosfery. Równolegle wzrost temperatury przy powierzchni ziemi powoduje coraz silniejsze wypromieniowanie energii w postaci długofalowego promieniowania elektromagnetycznego. Zmiany promieniowania długofalowego na górnej granicy atmosfery są tylko częściowo kompensowane poprzez spadek transmisji promieniowania w zakresie termalnym, który wynika ze wzrostu koncentracji gazów cieplarnianych. W ramach seminarium dyskutowane będą również zmiany czasowe podstawowych wielkości atmosferycznych, które wpływają na budżet energetyczny.

https://us05web.zoom.us/j/85860171835pwd=lwjaFJwk9nsAhGZXF3ubpw51Z48Puc.1Identyfikator spotkania: 858 6017 1835Kod dostępu: r6pK40

room B4.58, Pasteura 5 at 13:15

dr Dariusz B. Baranowski (IGF PAN)

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/94843514675?pwd=QThsdlh5dE1wUlA1N3hwOWxRRXNndz09Meeting ID: 948 4351 4675Passcode: 162517

room B4.58, Pasteura 5 at 13:15

prof. dr hab. Wojciech W. Grabowski (MMM Laboratory, NCAR, Boulder, Colorado, USA)

Reversed Twomey effect: fact or fiction?

Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/96657964798?pwd=UDBLRlVmUnI4eWxFREh6c3pUTjJCdz09Meeting ID: 966 5796 4798Passcode: 075262