Physics Colloquium: Scale Decomposition and Kinetic Energy Cascade in the Atmosphere

Physics Colloquium
Scale Decomposition and Kinetic Energy Cascade in the Atmosphere

Dr. Pejman Hadi Sichani
Postdoctoral Researcher, Department of Mechanical Engineering
University of Rochester

Event Details:
The nonlinear dynamics of atmospheric circulation covers a range of length scales spanning several orders of magnitude, presenting a complex system with nonlinear coupling across scales. Analyzing the distribution and transfer of kinetic energy (KE) at various scales is crucial for understanding and predicting atmospheric evolution. Traditionally, such analysis relied on spherical harmonics, which are inherently global and cannot provide local information connecting scales with circulation patterns geographically. To address this, the coarse-graining (CG) framework is introduced to analyze multi-scale dynamics on the sphere. This is made possible by generalizing the definition of convolution to ensure that for arbitrary kernel shapes, including wavelets, the filtering operator and spatial derivatives on the sphere commute, thereby allowing us to derive the partial differential equations (PDEs) governing any set of scales. The approach is very general, allows for probing the dynamics simultaneously in scale and in space, and is not restricted by usual assumption of homogeneity. Applying the CG scale-analysis framework to atmospheric reanalysis data, derived from satellites and high-resolution models, enables us to create global geographic maps of the KE cascade at any scale. In this work, we present the spatial distribution of KE cascade at different pressure levels (throughout troposphere and stratosphere) and different scales for the first time. Analyzing the spatial distribution of the atmospheric KE cascade reveals its relationship with distinct atmospheric circulation patterns.

Bio:
Pejman Hadi Sichani earned his M.S. and Ph.D. in Mechanical Engineering from the Vienna University of Technology, Austria, where he conducted research on the interaction of thermal and solutal stratification with turbulence in wall-bounded flows using Direct Numerical Simulations (DNS) under the supervision of Prof. Alfredo Soldati. His Ph.D. research focused on DNS of thermally stratified wall-bounded turbulence, exploring the dynamics of internal gravity waves, energetics, and irreversible mixing in stably stratified turbulence. In 2022, he joined the University of Rochester, NY, as a Postdoctoral Associate in the Department of Mechanical Engineering. His current research involves investigating atmospheric flow dynamics using scale-by-scale analysis, with a focus on energy transfer across various length scales in the troposphere and stratosphere. His primary research interests include computational fluid dynamics, theory of turbulence, environmental and geophysical fluid dynamics, and high-performance computing.

Intended Audience:
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