Journal Article

Improved Atlantic winter blocking in a climate model

Williams, Keith, O'Neill, Alan, Hinton, Tim, Keeley, Sarah, Gordon, Chris, Harris, Chris, Scaife, Adam A., Roberts, Malcolm, Copsey, Dan

2011

Overview

Most climate models underestimate the frequency of Atlantic blocking. Horizontal resolution is often cited as the main culprit due to poorly resolved small‐scale variability whose upscale effects help to maintain blocks. However, recent studies show that blocking errors are also largely attributable to the large scale climatological bias of the model. Furthermore, modest resolution models can contain enough variability to generate greatly improved blocking frequency if they are corrected to account for time‐mean bias. Here we show greatly improved simulations of Atlantic winter blocking frequency in a coupled ocean–atmosphere climate model. A reduction of the mean bias, due to an improved simulation of the Atlantic Ocean, is a key element of the improvement. Key Points Atlantic blocking deficit is caused by Atlantic SST error Atlantic SST errors are corrected in our improved model Atlantic blocking is much improved

• Publisher: Blackwell Publishing Ltd,American Geophysical Union,John Wiley & Sons, Inc
• Subject: Atlantic Ocean / Atmospheric circulation / Atmospheric sciences / Bias / blocking / Climate models / Climate science / Climatology / Computer simulation / Earth sciences / Earth, ocean, space / Error analysis / Exact sciences and technology / General circulation models / Geophysics / Gulf Stream / Marine / model bias / NAC / Ocean-atmosphere interaction / Winter