Phenology Analysis Code

This Google Earth Engine (GEE) script performs comprehensive analysis of global 
vegetation phenology trends using MODIS MCD12Q2 Collection 6.1 data from 2001 
to 2023. The code calculates temporal trends in Start of Season (SOS), End of 
Season (EOS), and Growing Season Length (GSL) with robust quality filtering and 
dual-cycle detection algorithms.

Key Features:
- Automated phenological metric extraction (SOS, EOS, GSL)
- Dual-cycle analysis for regions with multiple growing seasons
- Quality filtering using MODIS QA flags (QA_Overall_1 ≤ 1)
- Linear trend analysis (2001-2023) with R² calculation
- Regional time series generation for multiple biomes
- Latitudinal gradient analysis (-60° to 70°N)
- Interactive visualizations (maps and charts)

Technical Specifications:
- Platform: Google Earth Engine (JavaScript API)
- Input Dataset: MODIS/061/MCD12Q2
- Spatial Resolution: 500m
- Temporal Coverage: 2001-2023
- Geographic Extent: Global (-180° to 180°E, -60° to 75°N)

Usage:
Copy the code to Google Earth Engine Code Editor (https://code.earthengine.google.com/). 
No authentication or data downloads required - all analysis runs in the cloud. Results 
are displayed in the console and map interface.

Related Publication:
This code supports the research described in: Salhi, A. et al. (in review). 
Threshold-driven phenological divergence reshapes global ecosystems.