TH scores update: TROPICAL CYCLONES

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Hazard Processing Method

• Data Source: 4 return periods (RP50, RP100, RP1000, RP10000) - wind speed rasters
• Unit: m/s
• Default Value Thresholds:
  • RP50=36
  • RP100=36
  • RP1000=30
  • RP10000=26
• Default Area Threshold: 5%

Workflow:

1. Extract all pixel values for each RP raster within each admin unit
2. Calculate mean (for reporting) and area percentage (% of pixels > value threshold)
3. Check if area threshold % met per RP
4. Score = count of RPs meeting threshold (0-4)
5. Special case: If NO pixels exceed threshold in ALL RPs → Score -1 (not affected)

Scoring Logic:

• 4 RPs meet threshold → Score 3
• 3 RPs meet threshold → Score 2
• 2 RP meets threshold → Score 1
• 1 RPs meet threshold → Score 0
• No pixels > threshold in any RP → Score -1 (not affected by cyclones)

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Comparison

Comment: new scores (from new source) are less dramatic and extend less inland - which was previously exagerated. Now includes hazard on the east atlantic.

New score distribution:

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Original (2019) vs. 2025 Update

Data Overview

• Original Dataset: 38,229 administrative regions (ADM2 level)
• 2025 Dataset: 39,370 administrative regions (ADM2 level)
• High-Quality Matches: 33,207 regions (90%+ matching confidence)
• Unmatched Original: 5,022 regions
• Unmatched 2025: 6,268 regions

Technical Notes

• Hazard ranks: -1 = N/A, 0 = Very Low, 1 = Low, 2 = Medium, 3 = High
• Original data used text codes (VLO, LOW, MED, HIG), converted to numeric for easier comparison (delta)
• Matching threshold: 90% similarity required for inclusion in analysis
• Medium-quality matches (70-90%) available in separate sheet for manual review

Matching Method

Fuzzy string matching using hierarchical location names (Country | Admin1 | Admin2).
Only high-quality matches (≥90% similarity) were used for hazard comparison.

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• Regions Compared: 6,107
• Agreement: 11.5% (705 unchanged) ⚠️ LOW AGREEMENT
• Net Trend: Strong Downgrades (5,315 downgrades vs 87 upgrades)
• Average Change: -1.82 ranks
• Notable Shifts:
  • High → Low: 2,674 regions
  • High risk regions dropped from 4,164 to 306 (major reassessment)

Comment

The combination of new dataset (STORM), new approach and new boundaries introduce a significant change in the scores. The most relevant is the number of unaffected regions far from the coast, whereas the original scores propagated much more inland, up to Mongolia (which is way off the tropical area; it is exposed to cyclones, but entirely of extra-tropical origin).
New data fixes the data gap for the NE Atlantic.
Strange high-low-high patterns are also fixed (see SE-China in original scores).