Overview
The Observed Rainfall module provides retrospective precipitation observations at three timescales:
- Dekad (10-day) — Data aggregated every 10 days.
- Monthly — Calendar-month totals.
- Seasonal — Aggregated over multi-month seasons.
Data Layers
- Total — Observed rainfall in mm.
- LTM (Long-Term Mean) — Climatological average for the same period, used as the reference baseline.
- SPI (Standardised Precipitation Index) — A statistical measure of rainfall deficit or surplus relative to the long-term distribution. Negative SPI values indicate drought conditions.
Interpreting SPI
| SPI Value | Category |
|---|---|
| ≥ 2.0 | Extremely wet |
| 1.5 to 1.99 | Very wet |
| 1.0 to 1.49 | Moderately wet |
| -0.99 to 0.99 | Near normal |
| -1.0 to -1.49 | Moderately dry |
| -1.5 to -1.99 | Severely dry |
| ≤ -2.0 | Extremely dry |
Data Source
Observed rainfall data is sourced from GeoTIFF rasters (FTP) and processed with zonal statistics. Files are stored under media/geodata/rain/observed/.