Contrasting cloud radiative feedbacks during warm pool and cold tongue El Niños

Abstract

The study presents the contrasting characteristics of cloudradiative feedbacks to the cold tongue (CT) and warm pool (WP) El Niño (EN). The maximum sea surface temperature anomalies (SSTA) of the CT-EN are located in the far-eastern Pacific. However, the maximum responses of the shortwave- and longwavecloud- radiative forcing (SWCRF and LWCRF) to the CT-EN warming are centered near the dateline, showing 70° westward shift relative to the maximum SSTA center of CT-WN. In contrast, the maximum responses of the SWCRF and LWCRF to the WP-EN warming show only slight westward shift relative to the maximum SSTA center. The contrasting cloud-radiative feedbacks to the two types of ENs can be traced back to the contrasting precipitation feedbacks, which is associated with the convection threshold. When the warm SSTA of CT-EN occurs in the relatively cold eastern Pacific, the total SST in-situ may not exceed the convection threshold. Therefore, the induced precipitation anomaly would occur towards the warm western Pacific, and the corresponding cloud cover and cloud-radiative feedbacks would exhibit an apparent westward shift. As the warm SSTA of WP-EN occurs in the relatively warm central Pacific, the corresponding responses of the anomalous fields to the WP-EN show only slight westward displacement.