CMI Historical Data (v2.1)
| Domain | Resolution | Time Span | Download |
|---|---|---|---|
| Global | 0.5°x0.5° | 1961-2025 | 
|
| Global (deserts removed) |
0.5°x0.5° | 1961-2025 |
|
CMI Operational Data (Monthly Updated)
| Domain | Resolution | Time Span | Download |
|---|---|---|---|
| Global | 0.5°x0.5° | 1961-present |
|
| Global (deserts removed) |
0.5°x0.5° | 1961-present |
|
Data Description:
- Time scales combined: 3-, 6-, and 12-month
- Data Format: netCDF, FillValue: -9999
- Reference period: 1961-2020
- CMI Historical Data: The CMI historical dataset is constructed using precipitation and potential evapotranspiration (PET) data retrieved from CRU TS. This dataset remains static and will only be updated when the source CRU data are officially refreshed.
- CMI Operational Data (Monthly Updated): The CMI operational dataset extends the time series to present through monthly updates. Current operational data from FEWS (potential evapotranspiration) and CPC (precipitation) are integrated with the CRU baseline using z-score normalization methods, enabling continuous monthly monitoring.
- Methodological Updates:The algorithm has been refined compared to the original BAMS publication, with the primary improvement being the adoption of parametric methods replacing the original non-parametric approaches in CMI calculations. However, users can be assured that the spatial-temporal patterns remain consistent across different versions, with only marginal numerical differences that do not affect the overall drought characterization.
- Desert Mask: Major global desert regions are excluded.
Release history:
- v2.1: updated to span 1961-2025 based on CRU TS4.10 [2026-7-5]
- v2.0: The CMI index is now synthesized from 3-, 6-, and 12-month timescales, replacing the previous composite that included 3-, 6-, 12-, 24-, and 48-month timescales. In addition, the masking method was changed from GlobCover gridded data for bare land exclusion to a vector shapefile-based mask of major global deserts. [2025-11-20]
- v1.1: intermediate version [2025-11-03]
- v1.0: Major release with operational data capability and methodological improvements [2025-9-25]
- v0.5: updated to span 1961-2024 based on CRU TS4.09 [2025-4-10]
- v0.4: updated to span 1961-2023 based on CRU TS4.08 [2024-7-9]
- v0.3: updated to span 1961-2022 based on CRU TS4.07 [2023-7-8]
- v0.2: updated to span 1961-2021 based on CRU TS4.06 [2023-4-13]
- v0.1: Initial release based on CRU TS4.05 [2023-3-29]
