Multi-model analysis of Northern Hemisphere winter blocking: Model biases and the role of resolution
Journal of Geophysical Research Atmospheres 118:10 (2013) 3956-3971
Abstract:
Blocking of the tropospheric jet stream during Northern Hemisphere winter (December-January-February) is examined in a multi-model ensemble of coupled atmosphere-ocean general circulation models (GCMs) obtained from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The CMIP5 models exhibit large biases in blocking frequency and related biases in tropospheric jet latitude, similar to earlier generations of GCMs. Underestimated blocking at high latitudes, especially over Europe, is common. In general, model biases decrease as model resolution increases. Increased blocking frequency at high latitudes in both the Atlantic and Pacific basins, as well as more realistic variability of Atlantic jet latitude, are associated with increased vertical resolution in the mid-troposphere to lowermost stratosphere. Finer horizontal resolution is associated with higher blocking frequency at all latitudes in the Atlantic basin but appears to have no systematic impact on blocking near Greenland or in the Pacific basin. Results from the CMIP5 analysis are corroborated by additional controlled experiments using selected GCMs. Key PointsCMIP5 models have large blocking biases and associated jet biasesIncreased spatial resolution is associated with reduced blocking and jet biasesVertical and horizontal resolution give blocking changes in different regions ©2013. American Geophysical Union. All Rights Reserved.Multi-model analysis of Northern Hemisphere winter blocking: Model biases and the role of resolution
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 118:10 (2013) 3956-3971
Recent variability of the solar spectral irradiance and its impact on climate modelling
Atmospheric Chemistry and Physics European Geosciences Union (2013)
A mechanism for lagged North Atlantic climate response to solar variability
Geophysical Research Letters 40:2 (2013) 434-439
Abstract:
Variability in solar irradiance has been connected to changes in surface climate in the North Atlantic through both observational and climate modelling studies which suggest a response in the atmospheric circulation that resembles the North Atlantic Oscillation or its hemispheric equivalent the Arctic Oscillation. It has also been noted that this response appears to follow the changes in solar irradiance by a few years, depending on the exact indicator of solar variability. Here we propose and test a mechanism for this lag based on the known impact of atmospheric circulation on the Atlantic Ocean, the extended memory of ocean heat content anomalies, and their subsequent feedback onto the atmosphere. We use results from climate model experiments to develop a simple model for the relationship between solar variability and North Atlantic climate. © 2013. American Geophysical Union. All Rights Reserved.Recent variability of the solar spectral irradiance and its impact on climate modelling
ATMOSPHERIC CHEMISTRY AND PHYSICS 13:8 (2013) 3945-3977