https://github.com/limeo131/ssw-topography
This project explores the hemispheric asymmetry of Stratospheric Sudden Warmings (SSWs) using climate model simulations and data analysis. It demonstrates that topography plays a dominant role in shaping the frequency and dynamics of SSWs by enhancing eddy heat flux through increased wave amplitude and phase alignment.
https://github.com/limeo131/ssw-topography
climate-model climate-science python
Last synced: about 1 month ago
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This project explores the hemispheric asymmetry of Stratospheric Sudden Warmings (SSWs) using climate model simulations and data analysis. It demonstrates that topography plays a dominant role in shaping the frequency and dynamics of SSWs by enhancing eddy heat flux through increased wave amplitude and phase alignment.
- Host: GitHub
- URL: https://github.com/limeo131/ssw-topography
- Owner: Limeo131
- Created: 2025-04-03T00:37:34.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2025-04-03T05:41:38.000Z (about 1 year ago)
- Last Synced: 2025-04-03T06:26:43.430Z (about 1 year ago)
- Topics: climate-model, climate-science, python
- Language: Jupyter Notebook
- Homepage:
- Size: 26.7 MB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
## 📘 Topography Dominates the Hemispheric Asymmetry of Stratospheric Sudden Warmings
**Author**: Siming Liu
**Affiliations**: The University of Chicago
**Contact**: smliu01@uchicago.edu
### 🔍 Overview
This repository contains the code and analysis for the study:
> **Topography dominates the hemispheric asymmetry of Stratospheric Sudden Warmings**
> Liu, S., Shaw, T. A., & Garfinkel, C. I. (2025). accepted by Geophysical Research Letters.
The study investigates why **Stratospheric Sudden Warmings (SSWs)** occur almost exclusively in the Northern Hemisphere (NH). Using climate model simulations, the paper shows that **topography is the dominant factor** in creating this hemispheric asymmetry through its control of eddy heat flux.
---
### 📄 Paper
- **Main Manuscript**: [`manuscript.pdf`](./result/manuscript.pdf)
- **Supporting Information**: [`supplementary.pdf`](./result/supplementary.pdf)
---
### 📂 Notebooks
The analysis is broken into several Jupyter notebooks:
| Notebook | Description |
|----------|-------------|
| `ssw_onset_dm.ipynb` | Detects the onset of SSW events following the Charlton & Polvani (2007) method. |
| `tropos_ssw_v_t_vint.ipynb` | Calculates and visualizes vertically integrated meridional eddy heat flux (`v*T*`) in both hemispheres. |
| `v.t.daily.ipynb` | Computes and analyzes daily zonal deviations of meridional wind (`v`) and temperature (`T`). |
| `vtpdf_100_ssw.ipynb` | Generates probability distributions of wave amplitudes and phase differences at 100 hPa, 60°N. |
| `vt_amp.phase.pdf.ipynb` | Decomposes `v` and `T` into wave components and calculates amplitude and phase differences. |
| `u_z.lat.ipynb` | Analyzes zonal mean zonal wind structure as a function of height and latitude. |
---
### 📊 Key Findings
- **Topography dominates** the hemispheric asymmetry in SSWs.
- Flattening NH topography nearly eliminates SSWs in climate model simulations.
- Topography amplifies eddy heat flux by:
- Increasing the amplitude of eddy meridional wind and temperature.
- Decreasing their phase difference, enhancing vertical wave propagation.
---
### 🗂️ Data
The analysis uses the following datasets:
- **ECHAM6 Climate Model Simulations**
- ALL: Realistic topography and surface energy fluxes
- FLAT: Flattened topography
- SYMS: Symmetrized surface energy fluxes
- F+S: Flattened topography + symmetrized fluxes
- 60-year integrations with monthly and daily outputs
- Developed in Shaw et al. (2022)
- **ERA5 Reanalysis** (1958–2022)
- Zonal and meridional wind, temperature
- Used to evaluate model performance and calculate SSW frequency
---
### 🛠️ Environment & Dependencies
This project was developed using:
- Python 3.x
- Jupyter Notebook
- Common scientific libraries: `numpy`, `matplotlib`, `scipy`, `xarray`, `cartopy`, `netCDF4`
*Note: You may need to configure access to climate model output or reanalysis datasets used in the analysis.*
---
### 🧑🔬 Reproducibility
If you’d like to reproduce the analysis:
1. Clone the repository.
2. Make sure you have access to the model output files used in the simulations.
3. Run the notebooks in the order listed above, starting with `ssw_onset_dm.ipynb`.
---
### 📘 Citation
If you use this code or analysis in your work, please cite:
```
Liu, S., Shaw, T., & Garfinkel, C. I. (2025). Topography dominates the hemispheric asymmetry of stratospheric sudden warmings. Geophysical Research Letters, 52, e2024GL113051.
https://doi.org/10.1029/2024GL113051
```