Aleutian Low Pressure Index Anomalies 1900-2008

The Aleutian Low Pressure Index (ALPI) measures the intensity of the North Pacific's Aleutian Low pressure system during winter months (December-March). It is calculated as the mean area with sea-level pressure <= 100.5 kPa and expressed as an anomaly from the 1950-1997 mean. The index, regenerated in 2015, provides comparable values for the period 1900-2008.

Use Cases

• Analyze long-term trends in Aleutian Low intensity using the ALPI anomaly values from 1900-2008.
• Correlate the ALPI index with other climate indices to study North Pacific atmospheric dynamics.
• Model the relationship between sea-level pressure area (<= 100.5 kPa) and regional climate patterns.
• Validate the 2015 calculation method against historical climate model outputs using the provided time series.

Strengths

• Provides a continuous, comparable time series from 1900 to 2008.
• Based on a defined calculation method (mean area with sea-level pressure <= 100.5 kPa) documented in a technical report.
• Values are expressed as anomalies from a consistent 1950-1997 baseline period.

Limitations

• Data ends in 2008, lacking recent years for contemporary climate analysis.
• The underlying raw pressure data or spatial grids are not included, only the derived index.
• Limited to the December-March season, not a full annual record.

Provenance

Source

Fisheries and Oceans Canada.

Collection Method

Calculated as the mean area (km²) with sea-level pressure <= 100.5 kPa, expressed as an anomaly from the 1950-1997 mean.

Time Range

1900-2008.

Freshness

The index calculation was last updated in 2015, though the platform record was updated in 2026.

Geography

North Pacific Ocean, focusing on the Aleutian Low region.