Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session L26: Geophysical Fluid Dynamics: Atmospheric II |
Hide Abstracts |
Chair: Marco Giometto, Department of Cilvil Engineering Mechanics, Columbia University, New York, NY 10027, USA Room: 251 D |
Monday, November 25, 2024 8:00AM - 8:13AM |
L26.00001: Droplet nucleation in a rapid expansion cloud chamber Ilian Ahmed, Martin Aleksandrov Erinin, Cole Sagan, Nadir Jeevanjee, Marissa Weichman, Luc Deike We present experiments conduced in a new aerosol-cloud chamber at Princeton University. Experiments are performed with precise control over the thermodynamic properties (humidity, temperature, pressure) and air quality (aerosol concentration) to study nucleation processes relevant to cloud microphysics. Rapid expansions allow for the nucleation of water droplets either in an homogeneous way, or on submicron aerosol particles. We characterize the time evolution of the pressure and temperature during the experiments, and compare the temperature evolution with classic adiabatic expansion in dry and moist environment. We employ optical diagnostics to track droplet nucleation and growth and characterize the size and total number of droplets being formed as a function of initial relative humidity and aerosol particles concentration and compare our experimental results to various theoretical prediction from the cloud microphysics literature. |
Monday, November 25, 2024 8:13AM - 8:26AM |
L26.00002: Forcing stratocumulus clouds with internal gravity waves Arun Balakrishna, Hao Fu, Parviz Moin, Morgan E O'Neill Stratocumulus clouds extensively cover Earth’s surface and subtropical oceans resulting in a net-cooling effect through reflection of sunlight. Previous studies have shown that reductions in stratocumulus lead to significant warming akin to that of greenhouse gases. Thus, it is important to understand factors that can cause the cloud deck to dissipate. |
Monday, November 25, 2024 8:26AM - 8:39AM |
L26.00003: Abstract Withdrawn
|
Monday, November 25, 2024 8:39AM - 8:52AM |
L26.00004: Cold pools and mesoscale organization of shallow cumulus convection Oumaima Lamaakel, Georgios Matheou, Joao Teixeira Clouds forming in the atmospheric boundary layer, typically the lowermost 4 km of the atmosphere, have a large impact on the Earth's energy balance and are one of the largest sources of uncertainty in climate projections. The development of precipitation in shallow cumulus clouds changes the spatial structure of convection and creates large-scale organization affecting the boundary layer energy balance. |
Monday, November 25, 2024 8:52AM - 9:05AM |
L26.00005: The long road to equilibrium: Temporal scaling of marine boundary layers Georgios Matheou, OBAIDULLAH KHAWAR, Joao Teixeira Clouds forming in the atmospheric boundary layer play a crucial role in the Earth's energy balance. Climate projections are sensitive to the amount of low-cloud cover and small variations in stratocumulus area coverage can produce energy-balance changes comparable to those due to greenhouse gases. The response of the marine atmospheric boundary layer to the large-scale circulation is investigated using idealized large-eddy simulations (LES). The effects of the large-scale circulation are modeled by variations in the sea surface temperature and large-scale divergence, which span a typical subtropical-value parameter space. All simulations are initialized with a balanced free troposphere and a stratocumulus-topped mixed layer. The boundary layers are time-integrated until a statistically steady state is attained. The vertically integrated liquid water potential temperature equation is used to investigate the contribution to the energy balance of the various physical processes. In cloud regimes with a high area fraction stratiform cloud the dominant balance is between cloud long wave cooling and subsidence warming. In cloud regimes with little or no stratiform cloud the key processes are cloud long wave cooling, subsidence warming, and the surface heat flux. The column integrated energy budget is used to study the boundary layer approach to equilibrium. Subsidence warming has the longest time scale during the boundary layer approach to steady state. For boundary layers with significant stratiform cloud the time adjustment is exponential. The LES model results support theoretical estimates that the adjustment time scale is proportional to the inverse of the large-scale divergence. |
Monday, November 25, 2024 9:05AM - 9:18AM |
L26.00006: Fundamental Measurements of Ice Particle Growth Rates at Cirrus-like Temperatures and Improved Microphysics Parameterizations Gwenore Pokrifka, Alfred Moyle, Jerry Y Harrington Cirrus clouds cover about 30% of Earth's surface, and their impact on Earth's radiative balance is one of the largest sources of uncertainty in climate prediction. Much of this uncertainty originates from a lack of information regarding fundamental cirrus microphysics. The vapor growth rates of the ice particles contained within cirrus clouds control the particle shapes, their fall speeds, and the rate of vapor depletion. However, there are few measurements of ice particle growth rates at temperatures relevant to cirrus clouds (< -40 C), and almost none for the tropical tropopause (down to -90 C). Presented here are mass and dimensional growth rate time series of ice crystals grown within thermal-gradient diffusion chambers at temperatures from -67 to -40 C. From these data, we derive parameterizations to describe the growth of ice more realistically than the capacitance theory that is currently used in cloud models. The capacitance theory treats small cirrus particles as solid spheres that grow from vapor with perfect efficiency, but these data show that the particles develop complex, faceted shapes. At high supersaturation, hollowed columnar polycrystals are common, whose growth cannot be described by capacitance theory, but can be modeled with faceted growth theory. To match the data, processes on the crystal surface must be accounted for, otherwise the remaining microphysics will be misrepresented in models. |
Monday, November 25, 2024 9:18AM - 9:31AM |
L26.00007: Flux Uncertainty Quantification in Heterogeneous Turbulent Boundary-Layer Flows Thomas D Wright, Eric R Pardyjak, Marc Calaf The effects of surface heterogeneity on turbulent boundary-layer flows are complex and not well understood. Practical constraints often limit atmospheric studies to no more than one data collection tower. However, surface heterogeneities introduce significant variability in both surface momentum and sensible heat fluxes, indicating a strong need for multiple observation sites to capture the full statistics of a flow. We investigate a novel method for quantifying uncertainty in surface momentum and sensible heat fluxes as a function of the number of observations. Data from a 1 km × 1 km region were acquired over the desert playa at the Surface Layer Turbulence and Environmental Science Test (SLTEST, Dugway, UT, USA) facility as part of the Idealized Planar Array experiment for Quantifying Spatial heterogeneity (IPAQS 2019) field campaign to determine surface flux variability as a function of flux footprint density. In the idealized terrain at SLTEST, we find variations of over 400% in both momentum and sensible heat fluxes when comparing measurements to spatially averaged data. Additional tests have been conducted to understand the impact of atmospheric conditions on flux variability. These findings will inform the development of new numerical wall models and field experiment design. |
Monday, November 25, 2024 9:31AM - 9:44AM |
L26.00008: Ring-integrated horizontal velocity spectra in the convective atmospheric surface layer: theory and measurements Kirill Barskov, Chenning Tong The Multipoint Monin-Obukhov Similarity Theory (MMO) for the convective atmospheric boundary layer (Tong and Nguyen JAS 2015 and Tong and Ding JFM 2019) predicts that at heights much smaller than the Obukhov length ($-z/L\ll 1$) and for scales larger than the height from the surface the turbulence spectra have a convective range and a dynamic range. Large-eddy simulation results have provided general support to the prediction. To use field data to further validate the theory, we conducted a field campaign, Multipoint Monin-Obukhov Horizontal Array Turbulence Studies (M$^2$HATS) in the summer/fall of 2023 in Tonopah NV. A 250 m long array consisting of 50 sonic anemometers, a Doppler lidar with the beam along the sonic array, and an aerosol lidar were deployed to measure the horizontal velocity components of scales ranging from 5 m to approximately 2000 m. Taylor's hypothesis is applied to the sonic and Doppler lidar data, enabling calculation of two-dimensional spectra and ring-integrated spectra. Preliminary comparisons between the measurement results and the theoretical prediction will be presented. |
Monday, November 25, 2024 9:44AM - 9:57AM |
L26.00009: Surface heterogeneities and the structure of the turbulent flow: a puzzle of timescales Marc Calaf, Mohammad Hassan Allouche, Khaled Ghannam, Joseph Fogarty, Elie Bou-Zeid Flow over surface heterogeneities has been mostly investigated through the lenses of internal boundary layers, to understand how much, or over how long, the characteristics of the flow over a certain surface patch transport over to the neighboring patches. Interestingly, there remains a limited understanding on whether the resulting flow presents a roll-type structure due to persistent shear with the surface, or instead is characterized by a cell-type structure resulting from the strong land-atmosphere coupling. Furthermore, little differentiation has been made on whether the land-atmosphere convective forcing leads to stationary, or transient convective cells. Here, we investigate the flow developed in different land-atmosphere configurations, as well as the controlling mechanisms that enable the transition from one type of flow to the other. We leverage the use of a quadruple flow decomposition in parallel with the definition of four different time scales that characterize each of the processes described by such decomposition. We then hypothesize that a combination of these timescales in a set of non-dimensional Pi-groups allow to determine, a-priori, under what land-atmosphere configurations the different terms of the quadruple decomposition become relevant, and what are the competing flow mechanisms to mixing. For this work, we exploit several existing Large-Eddy Simulation datasets of ABL flows over different types of surface heterogeneity. |
Monday, November 25, 2024 9:57AM - 10:10AM |
L26.00010: Kinetic energy cascade in the atmosphere and its connection to circulation patterns Pejman Hadi Sichani, Benjamin A Storer, Hussein Aluie Atmospheric circulation is characterized by a nonlinear dynamic over a broad range of spatial and temporal scales, spanning several orders of magnitude, presenting a complex system with non-linear kinetic energy (KE) flux across scales. Analyzing the KE cascades across different scales is central to understanding and predicting atmospheric evolution. These KE cascades influence atmospheric circulation patterns and the development of synoptic-scale weather systems. This work employs a coarse graining (CG) scale-analysis framework to compute the KE cascades from ERA5 reanalysis data, derived from satellite and high-resolution model observations. The framework enables us to generate global geographic maps of the KE cascade across all resolved scales and pressure levels. Our analysis reveals a relationship between the KE cascade and distinct atmospheric circulation patterns. |
Monday, November 25, 2024 10:10AM - 10:23AM |
L26.00011: Higher-order mean velocity profile in the convective atmospheric boundary layer Davoud Pourabdollah, Chenning Tong, Kirill Barskov
|
Monday, November 25, 2024 10:23AM - 10:36AM |
L26.00012: Aerosol-induced Radiative Cooling in the Nocturnal Boundary Layer Suryadev P Singh, Mohammad Rafiuddin, Subham Banerjee, Sreenivas Sreenivas Longwave radiative cooling significantly affects the thermal profiles in the Nocturnal Boundary Layer (NBL), influencing mist, fog, dew, Lifted Temperature Minimum (LTM), and pollution dispersion. Current weather forecasting models often overlook aerosols in the longwave (LW) band, leading to inaccurate simulations of LW cooling and temperature profiles in the NBL. Our extensive field experiments at the Kempegowda International Airport, Bengaluru, combined with numerical simulations using a one-dimensional radiation-conduction model that includes aerosol-radiation interactions, reveal that aerosol-induced cooling impacts the temperature profiles several hundred meters into the boundary layer. Notably, this cooling can cause the air layer above the surface to be 2-6 K cooler than the soil surface (LTM), which is contrary to the belief that the ground cools faster than adjacent air layers after sunset. This research highlights the urgent need to incorporate aerosol-induced radiative cooling into numerical weather prediction models to accurately forecast temperature profiles within the NBL. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700