Simulation of the North Atlantic Oscillation in a general circulation model

1991 ◽  
Vol 18 (5) ◽  
pp. 841-844 ◽  
Author(s):  
Iqbal I. Pittalwala ◽  
Sultan Hameed
Keyword(s):  
North Atlantic Oscillation ◽  
General Circulation Model ◽  
North Atlantic ◽  
General Circulation ◽  
Circulation Model ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

scholarly journals European Climate Extremes and the North Atlantic Oscillation

2008 ◽  
Vol 21 (1) ◽  
pp. 72-83 ◽  
Author(s):  
Adam A. Scaife ◽  
Chris K. Folland ◽  
Lisa V. Alexander ◽  
Anders Moberg ◽  
Jeff R. Knight
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Extreme Weather Events ◽  
The North ◽  
Weather Events ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract The authors estimate the change in extreme winter weather events over Europe that is due to a long-term change in the North Atlantic Oscillation (NAO) such as that observed between the 1960s and 1990s. Using ensembles of simulations from a general circulation model, large changes in the frequency of 10th percentile temperature and 90th percentile precipitation events over Europe are found from changes in the NAO. In some cases, these changes are comparable to the expected change in the frequency of events due to anthropogenic forcing over the twenty-first century. Although the results presented here do not affect anthropogenic interpretation of global and annual mean changes in observed extremes, they do show that great care is needed to assess changes due to modes of climate variability when interpreting extreme events on regional and seasonal scales. How changes in natural modes of variability, such as the NAO, could radically alter current climate model predictions of changes in extreme weather events on multidecadal time scales is also discussed.

scholarly journals North Atlantic Oscillation Response to Anomalous Indian Ocean SST in a Coupled GCM

2005 ◽  
Vol 18 (24) ◽  
pp. 5382-5389 ◽  
Author(s):  
Jürgen Bader ◽  
Mojib Latif
Keyword(s):  
Indian Ocean ◽  
North Atlantic Oscillation ◽  
General Circulation Model ◽  
North Atlantic ◽  
General Circulation ◽  
Circulation Model ◽  
Atlantic Sector ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic

Abstract The dominant pattern of atmospheric variability in the North Atlantic sector is the North Atlantic Oscillation (NAO). Since the 1970s the NAO has been well characterized by a trend toward its positive phase. Recent atmospheric general circulation model studies have linked this trend to a progressive warming of the Indian Ocean. Unfortunately, a clear mechanism responsible for the change of the NAO could not be given. This study provides further details of the NAO response to Indian Ocean sea surface temperature (SST) anomalies. This is done by conducting experiments with a coupled ocean–atmosphere general circulation model (OAGCM). The authors develop a hypothesis of how the Indian Ocean impacts the NAO.

Granger Causality of Coupled Climate Processes: Ocean Feedback on the North Atlantic Oscillation

2006 ◽  
Vol 19 (7) ◽  
pp. 1182-1194 ◽  
Author(s):  
Timothy J. Mosedale ◽  
David B. Stephenson ◽  
Matthew Collins ◽  
Terence C. Mills
Keyword(s):  
Time Series ◽  
North Atlantic Oscillation ◽  
Granger Causality ◽  
North Atlantic ◽  
General Circulation ◽  
Careful Examination ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract This study uses a Granger causality time series modeling approach to quantitatively diagnose the feedback of daily sea surface temperatures (SSTs) on daily values of the North Atlantic Oscillation (NAO) as simulated by a realistic coupled general circulation model (GCM). Bivariate vector autoregressive time series models are carefully fitted to daily wintertime SST and NAO time series produced by a 50-yr simulation of the Third Hadley Centre Coupled Ocean–Atmosphere GCM (HadCM3). The approach demonstrates that there is a small yet statistically significant feedback of SSTs on the NAO. The SST tripole index is found to provide additional predictive information for the NAO than that available by using only past values of NAO—the SST tripole is Granger causal for the NAO. Careful examination of local SSTs reveals that much of this effect is due to the effect of SSTs in the region of the Gulf Steam, especially south of Cape Hatteras. The effect of SSTs on NAO is responsible for the slower-than-exponential decay in lag-autocorrelations of NAO notable at lags longer than 10 days. The persistence induced in daily NAO by SSTs causes long-term means of NAO to have more variance than expected from averaging NAO noise if there is no feedback of the ocean on the atmosphere. There are greater long-term trends in NAO than can be expected from aggregating just short-term atmospheric noise, and NAO is potentially predictable provided that future SSTs are known. For example, there is about 10%–30% more variance in seasonal wintertime means of NAO and almost 70% more variance in annual means of NAO due to SST effects than one would expect if NAO were a purely atmospheric process.

scholarly journals Seasonal Predictions of Tropical Cyclones Using a 25-km-Resolution General Circulation Model

2013 ◽  
Vol 26 (2) ◽  
pp. 380-398 ◽  
Author(s):  
Jan-Huey Chen ◽  
Shian-Jiann Lin
Keyword(s):  
Tropical Cyclones ◽  
General Circulation Model ◽  
North Atlantic ◽  
Intensity Distribution ◽  
North Pacific ◽  
General Circulation ◽  
Circulation Model ◽  
Geophysical Fluid Dynamics Laboratory ◽  
The North ◽  
The North Atlantic

Abstract Retrospective seasonal predictions of tropical cyclones (TCs) in the three major ocean basins of the Northern Hemisphere are performed from 1990 to 2010 using the Geophysical Fluid Dynamics Laboratory High-Resolution Atmospheric Model (HiRAM) at 25-km resolution. Atmospheric states are initialized for each forecast, with the sea surface temperature anomaly (SSTA) “persisted” from that at the starting time during the 5-month forecast period (July–November). Using a five-member ensemble, it is shown that the storm counts of both tropical storm (TS) and hurricane categories are highly predictable in the North Atlantic basin during the 21-yr period. The correlations between the 21-yr observed and model predicted storm counts are 0.88 and 0.89 for hurricanes and TSs, respectively. The prediction in the eastern North Pacific is skillful, but it is not as outstanding as that in the North Atlantic. The persistent SSTA assumption appears to be less robust for the western North Pacific, contributing to less skillful predictions in that region. The relative skill in the prediction of storm counts is shown to be consistent with the quality of the predicted large-scale environment in the three major basins. It is shown that intensity distribution of TCs can be captured well by the model if the central sea level pressure is used as the threshold variable instead of the commonly used 10-m wind speed. This demonstrates the feasibility of using the 25-km-resolution HiRAM, a general circulation model designed initially for long-term climate simulations, to study the impacts of climate change on the intensity distribution of TCs.

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