Threading the Atmosphere and the Space Environment: Global Effects by Small Scale Gravity Waves | 9am PT Tues, May 14, 2024

[Grigory Bronevetsky]

Modeling Talks

Threading the Atmosphere and the Space Environment: Global Effects by Small Scale Gravity Waves Hanli Liu, High Altitude Observatory,  National Center for Atmospheric Research Tues, May 14 | 9:00 am PT Meet | Youtube Stream Hi all, The presentation will be via Meet and all questions will be addressed there. If you cannot attend live, the event will be recorded and can be found afterward at https://sites.google.com/modelingtalks.org/entry/threading-the-atmosphere-and-the-space-environment Abstract: Atmospheric gravity waves are buoyancy waves that are excited by meteorological processes, such as deep convection, tropical cyclones, jet streams, and flow over topography. These waves become dynamically important, or even dominant, at the Earth's upper atmosphere and in its space environment. This is because of their global distribution, their exponential growth with altitudes as the air density decreases, and their contribution to the momentum and energy budgets. They are therefore thought to play a key role in connecting the terrestrial atmosphere with the space environment. However, it has been challenging for observations and numerical models alike to quantify their global effects because of the large scale range--from km to global scale--required to resolve them in a whole atmosphere context. In this talk, I will discuss our recent efforts to address this challenge by developing the high-resolution Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X). WACCM-X is one of the atmosphere components of the NCAR’s Community Earth System Model (CESM). It is a first-principle model that simulates processes from the Earth surface to the upper thermosphere, including radiative, physical, chemical, dynamical, and electrodynamical processes. With this newly developed capability, we can now assess the wave effects on the circulation, transport and composition of the whole atmosphere system. At the same time, the high-resolution simulations also reveal the importance of unresolved, smaller scale waves in the global momentum budget. We will explore innovative ways to account for such wave impacts.    Bio: Dr. Hanli Liu is a senior scientist at the High Altitude Observatory, National Center for Atmospheric Research. He received a B.S. in Fluid Mechanics from the University of Science and Technology of China, and a Ph.D. in Atmospheric and Space Physics from the University of Michigan. He came to the Observatory in 1997 as a postdoctoral researcher, and joined the scientific staff in 1999. His research includes: theoretical, numerical, and interpretive studies of the dynamics, structure, and variability of the Earth's middle and upper atmosphere; coupling of different atmospheric regions on global and regional scales, including impacts of lower atmospheric forcing on space weather; atmospheric waves and geophysical turbulence. He is leading the thermosphere/ionosphere extension of the Whole Atmosphere Community Climate Model (WACCM-X). More information on previous and future talks: https://sites.google.com/modelingtalks.org/entry/home

[Grigory Bronevetsky]

Video Recording: https://youtu.be/ktx8zFkMfcg

Slides: https://docs.google.com/presentation/d/1XQ6xKYkhBXpteTIAALSSS1-KZeLRwP9w/edit?usp=sharing&ouid=110584304018462442605&rtpof=true&sd=true

Summary:

• Focus: simulating the Earth’s atmosphere

  • WACCM-X: Whole Atmosphere Community Climate Model with Thermosphere/Ionosphere extension

  • Gravity waves, their propagation and effects

• Atmosphere has many layers

  • Top layers: low earth satellites, drag from air

  • Ionosphere: blocks high energy solar/space particles

  • Middle/lower atmosphere transport processes transport gasses vertically and laterally

• Challenges in modeling the atmosphere

  • Climate/global weather

  • Deep vertical domain: 0-700km, 10% of Earth radius, 

  • Change in physical processes at different depths

    • 1013 change in density from surface to edge

    • Surface: wind, heat, transport

    • Edge: radiation

  • Ion-neutral coupling

  • Short temporal/spatial sacles

    • Winds: 300m/s

    • Acoustic: 800m/s

• NCAR Community Earth System Model (CESM)

  • Couples different domain-specific sub-models: Land, Ocean, Ice, Atmosphere

  • Atmosphere

    • CAM: lower atmosphere

    • WACCM: lower to mesosphere

    • WACCM-W: all layers, including space boundary

  • Components

    • Chemistry

    • Neutral physics

    • Iconosphere Physics

    • Variable resolution management

• Current WACCM model incorporates many physical processes but has a number of key limitation

• Motion of waves through the atmosphere

  • Carry momentum and energy fluxes

  • Gravity waves: caused by vertical movements in the atmosphere

    • Wind blowing up over mountain 

    • Deep convective system pushing air up

    • 20-2000km

  • Planetary waves: horizontal direction

    • E.g. Coriolis

    • ~104km

  • Tides: motion due to day-night heating

    • ~104km

  • Ocean tides: move atmosphere up and down

• SIMA: System for Integrated Modeling of the Atmosphere

  • Models: WACCM-X, WACCM, CAM, MPAS, MUSICA

  • Currently can represent Local to Regional Scales

  • Not enough to represent gravity waves, which are global-scale

  • Doesn’t properly model: quasi-biennial oscillation (QBO), polar vortex

  • Need high-resolution whole atmosphere climate models

    • Sub-grid parameterizations effective to phenomena that depend on average effects (e.g. energy deposition)

    • Need a fine-grid model to capture phenomena where directionality matters

  • SIMA/WACCM-X development focused on high-resolution

    • Cube-sphere grid

    • 25km, horizontal .1 scale vertical 

    • 200km / .25  for comparison

  • Fine-grained model captures fine-grained wave perturbations not visible from coarse model

    • Affects ionosphere and flow of plasmas in the upper atmosphere

    • Can model 

      • Plasmasphere ducts

      • Thermosphere composition in southern vs northern hemisphere

      • Chemical composition in mesosphere/upper stratosphere polar regions

  • 100km horizontal resolution: can resolve waves > 800km

  • ~25km horizontal resolution: can resolve waves > 200km

  • Makes it possible to capture the mesa-alpha scale, but not yet the finer beta scale

  • Still many important waves at the unresolved finer scale

• For climate models we need good sub-scale parameterizations for modeling gravity waves

  • Gravity wave impacts have a scale invariance, so we can extrapolate to finer scales

  • Enables a statistical approximation of the effect: ongoing work

• Working on global models on convection-permitting scales

  • <5km / .05 scale global models

  • Will need ~1.25 ExaFlops, GPU enablement