A52F-03
Positive dust and low cloud feedbacks help to generate tropical north atlantic Multidecadal variability
Friday, 18 December 2015: 10:50
3012 (Moscone West)
Tianle Yuan1, Lazaros Oreopoulos1, Mark D Zelinka2, Hongbin Yu3, Joel R Norris4, Mian Chin1, Steven E Platnick1 and Kerry Meyer5, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)Lawrence Livermore National Laboratory, Livermore, CA, United States, (3)University of Maryland College Park, College Park, MD, United States, (4)University of California San Diego, La Jolla, CA, United States, (5)Universities Space Research Association Greenbelt, Greenbelt, MD, United States
Abstract:
The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many impacts, it is either too weak or absent in most climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is critical in generating the tropical arm of AMO. The feedbacks can be understood in a consistent dynamical framework, where the response of tropical surface wind to a warm North Atlantic SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic. This in turn helps to generate the tropical arm of AMO. Most climate models miss both feedbacks and the wind speed response, though realistic simulations of them may be essential for many climatic studies related to the AMO.
