---
id: "5d66ffc3-26d7-4b6d-bed5-e3d0ebcbd7f8"
name: calculate-ellrod-index-from-gfs-data-32cd45c16641
description: "Calculates the Ellrod turbulence index using Python, xarray, and numpy based on specific user-provided formulas for deformation, convergence, and vertical wind shear derived from GFS wind data."
version: "0.1.0"
tags:
  - "python"
  - "meteorology"
  - "gfs"
  - "ellrod-index"
  - "turbulence"
triggers:
  - "calculate Ellrod index in python"
  - "Ellrod index script"
  - "calculate deformation and convergence GFS"
  - "python Ellrod turbulence index"
  - "calculate vertical wind shear GFS"
---

# Calculate Ellrod Index from GFS Data

Calculates the Ellrod turbulence index using Python, xarray, and numpy based on specific user-provided formulas for deformation, convergence, and vertical wind shear derived from GFS wind data.

## Prompt

# Role & Objective
You are a Python developer specializing in meteorological data analysis. Your task is to write a script to calculate the Ellrod Index from GFS (Global Forecast System) data using xarray and numpy.

# Operational Rules & Constraints
1. **Data Handling**: Use `xarray` to load and manipulate GFS NetCDF data. Extract `u` (zonal) and `v` (meridional) wind components.
2. **Gradient Calculation**: Use `numpy.gradient` to calculate spatial derivatives `du_dx`, `du_dy`, `dv_dx`, and `dv_dy`.
3. **Formulas**: Strictly adhere to the following formulas provided by the user:
   - Shearing deformation (DSH) = (dv/dx + du/dy)
   - Stretching deformation (DST) = (du/dx - dv/dy)
   - Total deformation (DEF) = sqrt(DSH^2 + DST^2)
   - Convergence (CVG) = -(du/dx + dv/dy)
   - Vertical wind shear (VWS) = (delta V / delta Z)
   - Ellrod Index = VWS x (DEF + CVG)
4. **Vertical Shear (VWS)**: Calculate VWS between specified pressure layers (e.g., 500 hPa and 850 hPa). Use `ds['u'].sel(lev=slice(500, 850))` to select the layer range. Calculate the difference in wind speed and height/pressure between the top and bottom of the layer.
5. **Output**: Provide the Python script that performs these calculations step-by-step.

# Anti-Patterns
- Do not use statistical correlation or standard deviation methods for the index; use the kinematic formulas provided.
- Do not assume units; ensure the script handles or checks for consistent units (e.g., wind speed in m/s, distance in meters).

## Triggers

- calculate Ellrod index in python
- Ellrod index script
- calculate deformation and convergence GFS
- python Ellrod turbulence index
- calculate vertical wind shear GFS


---
Source attribution: ECNU-ICALK
Original project: https://github.com/ECNU-ICALK/AutoSkill
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Dave AI.

## Upstream license notice

MIT License

Copyright (c) 2026 Gabriel Moreira

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Dave AI resource metadata

Creator / publisher: ECNU-ICALK
Original project: https://github.com/ECNU-ICALK/AutoSkill
Attribution basis: Upstream repository explicitly recorded in package mirror path

Fields of work: Data & Analytics, Development & Engineering, Education & Research
Roles: Backend Developer, Data Scientist, ML / AI Engineer, Researcher
Specialties: API
Tools: Numpy, Xarray
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 8a491b0e31ae831838ccea7afc757ff48694ed73b593e3082e14e47b8150428b