Hurrell's North Atlantic Oscillation (NAO) Index from NCAR measures the normalized sea level pressure difference between stations in Portugal/Azores and Iceland. The dataset provides extended winter, seasonal, and annual indices starting from the year 1864. It is maintained by SCIOPS using station data from the World Monthly Surface Station Climatology.
Use Cases
- Analyze long-term trends in the NAO index values to study climate variability since 1864.
- Correlate the extended winter (Dec-Mar) NAO index with seasonal weather patterns in Europe and North America.
- Compare seasonal (DJF, MAM, JJA, SON) NAO indices to understand intra-annual atmospheric oscillation changes.
- Validate climate model outputs against the historical annual NAO index based on Ponta Delgada and Stykkisholmur/Reykjavik pressure differences.
- Investigate the impact of normalization base period changes, such as the shift from 1864-1994 to 1864-1983, on index values.
Strengths
- Time series begins in 1864, providing over 150 years of climate data.
- Data includes multiple temporal aggregations: extended winter, four seasons, and annual indices.
- Pressure anomalies are normalized using a long-term (120-year: 1864-1983) standard deviation.
Limitations
- The dataset's exact row count and update frequency are not specified.
- Index values are derived from only two primary station pairs, limiting spatial resolution.
- Differences from the original Hurrell (1995) publication due to data updates may require careful citation.
Provenance
- Source
- NCAR (National Center for Atmospheric Research), based on station data from the World Monthly Surface Station Climatology (ds570.0).
- Collection Method
- Calculated from the difference of normalized sea level pressure anomalies between specified stations in Portugal/Azores and Iceland.
- Time Range
- 1864 to present (continually updated).
- Freshness
- null
- Geography
- North Atlantic region, specifically stations in Lisbon, Portugal; Ponta Delgada, Azores; and Stykkisholmur/Reykjavik, Iceland.