Climate data guide content with tag Circulation
Amundsen Sea Low indices
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The Amundsen Sea Low (ASL) is a climatological low pressure center located over the extreme southern Pacific Ocean, off the coast of West Antarctica. Atmospheric variability in this region is larger than anywhere else in the Southern Hemisphere, and exhibits significant correlations with both the Southern Annular Mode (SAM) and ENSO. Given its linkages to…
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Timestep
- Monthly, Seasonal, Annual
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Collections
- N/A
Experts contributing reviews
- Hosking, Scott
Hurrell North Atlantic Oscillation (NAO) Index (station-based)
Years of record
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The winter (December thru March) station-based index of the NAO is based on the difference of normalized sea level pressure (SLP) between Lisbon, Portugal and Stykkisholmur/Reykjavik, Iceland since 1864. Positive values of the NAO index are typically associated with stronger-than-average westerlies over the middle latitudes, more intense weather systems over…
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Formats
- ascii
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Timestep
- Monthly, Seasonal, Annual
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Domain
- Atlantic Ocean
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Collections
- Climate Analysis Section (CAS) Data Catalog
Experts contributing reviews
- Hurrell, James, Phillips, Adam
Hurrell wintertime SLP-based Northern Annular Mode (NAM) Index
Years of record
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The NAM (or Arctic Oscillation) is defined as the first EOF of NH (20°-90°N) winter SLP data. It explains 23% of the extended winter mean (December-March) variance, and it is clearly dominated by the NAO structure in the Atlantic sector. Although there are some subtle differences from the NAO regional pattern over the Atlantic and Arctic (see Figure 1 below), the main…
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Formats
- ascii
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Timestep
- Seasonal
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Collections
- N/A
Experts contributing reviews
- Phillips, Adam
Marshall Southern Annular Mode (SAM) Index (Station-based)
Years of record
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The station-based index of the Southern Annular Mode (SAM) is based on the zonal pressure difference between the latitudes of 40S and 65S. As such, the SAM index measures a "see-saw" of atmospheric mass between the middle and high latitudes of the Southern Hemisphere. Positive values of the SAM index correspond with stronger-than-average westerlies over the…
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Formats
- ascii
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Timestep
- N/A
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Collections
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Experts contributing reviews
- Marshall, Gareth
MJO: Madden-Julian Oscillation Diagnostics
Years of record
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"The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal (30–90 days) variability in the tropical atmosphere. It is a large-scale coupling between atmospheric circulation and tropical deep convection.[1][2] Rather than being a standing pattern (like ENSO) it is a traveling pattern, propagating eastwards at approximately 4 to 8 m/s, through the…
Main variables and Earth System components
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Domain
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Experts contributing reviews
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North Pacific (NP) Index by Trenberth and Hurrell; monthly and winter
Years of record
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The North Pacific Index (NP index or NPI) is the area-weighted sea level pressure over the region 30°N-65°N, 160°E-140°W. The NP index is defined to measure interannual to decadal variations in the atmospheric circulation. The dominant atmosphere-ocean relation in the North Pacific is one where atmospheric changes lead changes in sea surface temperatures by one to two…
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Formats
- ascii
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Timestep
- Monthly, Seasonal
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Collections
- Climate Analysis Section (CAS) Data Catalog
Experts contributing reviews
- Hurrell, James, Phillips, Adam
QBO: Quasi-Biennial Oscillation
Years of record
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The quasi-biennial oscillation (QBO) is a quasi-periodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. The alternating wind regimes develop at the top of the lower stratosphere and propagate downwards at about 1 km (0.6 mi) per month until they are dissipated at the tropical…
Experts contributing reviews
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Southern Hemisphere westerly jet strength and position
Years of record
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The dynamics of the Southern Hemisphere westerly jet are described in terms of two indices, jet strength and jet latitude. Here, these indices are defined using the ERA-Interim reanalysis, although other datasets, including climate models, could be used. Although closely linked with the Southern Annular Mode (SAM) Index, these indices more precisely capture…
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Formats
- ascii
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Timestep
- Seasonal, Annual
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Collections
- N/A
Experts contributing reviews
- Bracegirdle, Thomas J.
Southern Oscillation Indices: Signal, Noise and Tahiti/Darwin SLP (SOI)
Years of record
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The Southern Oscillation Index (SOI) is a time series used to characterize the large scale sea level pressure (SLP) patterns in the tropical Pacific. Monthly mean SLP at Tahiti [T] and Darwin [D] are used. An optimal SOI can be constructed. It consists of [T-D] which is a measure of the large scale phenomena while [T+D] is a measure of small scale and/or…
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Timestep
- Monthly
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Domain
- Australia, Pacific Ocean, Tropics
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Collections
- Climate Analysis Section (CAS) Data Catalog
Experts contributing reviews
- Trenberth, Kevin