Empirically derived climate predictability over the extratropical northern hemisphere

Abstract. A novel application of a technique developed from chaos theory is used in describing seasonal to interannual climate predictability over the Northern Hemisphere (NH). The technique is based on an empirical forecast scheme - local approximation in a reconstructed phase space - for time-series data. Data are monthly 500 hPa heights on a latitude-longitude grid covering the NH from 20° N to the equator. Predictability is estimated based on the linear correlation between actual and predicted heights averaged over a forecast range of one- to twelve.month lead. The method is capable of extracting the major climate signals on this time scale including ENSO and the North Atlantic Oscillation.

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How Predictable Are the Arctic and North Atlantic Oscillations? Exploring the Variability and Predictability of the Northern Hemisphere

Journal of Climate ◽

10.1175/jcli-d-17-0226.1 ◽

2018 ◽

Vol 31 (3) ◽

pp. 997-1014 ◽

Cited By ~ 19

Author(s):

Daniela I. V. Domeisen ◽

Gualtiero Badin ◽

Inga M. Koszalka

Keyword(s):

Time Scales ◽

Northern Hemisphere ◽

North Atlantic ◽

Prediction Models ◽

The Arctic ◽

Ensemble Prediction ◽

Atmospheric Conditions ◽

Short Term ◽

The North ◽

The North Atlantic Oscillation

ABSTRACT The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) describe the dominant part of the variability in the Northern Hemisphere extratropical troposphere. Because of the strong connection of these patterns with surface climate, recent years have shown an increased interest and an increasing skill in forecasting them. However, it is unclear what the intrinsic limits of short-term predictability for the NAO and AO patterns are. This study compares the variability and predictability of both patterns, using a range of data and index computation methods for the daily NAO and AO indices. Small deviations from Gaussianity are found along with characteristic decorrelation time scales of around one week. In the analysis of the Lyapunov spectrum it is found that predictability is not significantly different between the AO and NAO or between reanalysis products. Differences exist, however, between the indices based on EOF analysis, which exhibit predictability time scales around 12–16 days, and the station-based indices, exhibiting a longer predictability of 18–20 days. Both of these time scales indicate predictability beyond that currently obtained in ensemble prediction models for short-term predictability. Additional longer-term predictability for these patterns may be gained through local feedbacks and remote forcing mechanisms for particular atmospheric conditions.

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On the Role of Atmospheric Teleconnections in Climate

Journal of Climate ◽

10.1175/2007jcli1907.1 ◽

2008 ◽

Vol 21 (12) ◽

pp. 2990-3001 ◽

Cited By ~ 82

Author(s):

Anastasios A. Tsonis ◽

Kyle L. Swanson ◽

Geli Wang

Keyword(s):

Northern Hemisphere ◽

North Atlantic ◽

Recent Application ◽

The North ◽

The Pacific ◽

Atmospheric Teleconnections ◽

The North Atlantic ◽

The North Atlantic Oscillation ◽

The Tropics

Abstract In a recent application of networks to 500-hPa data, it was found that supernodes in the network correspond to major teleconnection. More specifically, in the Northern Hemisphere a set of supernodes coincides with the North Atlantic Oscillation (NAO) and another set is located in the area where the Pacific–North American (PNA) and the tropical Northern Hemisphere (TNH) patterns are found. It was subsequently suggested that the presence of atmospheric teleconnections make climate more stable and more efficient in transferring information. Here this hypothesis is tested by examining the topology of the complete network as well as of the networks without teleconnections. It is found that indeed without teleconnections the network becomes less stable and less efficient in transferring information. It was also found that the pattern chiefly responsible for this mechanism in the extratropics is the NAO. The other patterns are simply a linear response of the activity in the tropics and their role in this mechanism is inconsequential.

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