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Using observational and reanalysis data, the cloud-shortwave radiation-sea surface temperature (SST) feedback in the Ningaloo Nino/Nina region off the west coast of Australia is examined. It is found that this feedback operates as a negative feedback for positive SST anomalies and as a positive feedback for negative SST anomalies. This asymmetry is due to variation in the dominant cloud amount with SST. For positive SST anomalies, a decrease in the shortwave radiation resulting from an increase in high cloud amount associated with deep convection prevails, because SSTs in this region are relatively high compared to other eastern boundary regions and close to the convective threshold. Conversely, the region is under the influence of the subtropical high, and a decrease in the surface shortwave radiation associated with an increase in low cloud amount is dominant for negative SST anomalies.

Plain Language Summary Ningaloo Nino is an El Nino-like phenomenon that occurs off the west coast of Australia and causes marine heatwave. This study investigates the feedback between shortwave radiation reaching the sea surface, cloud, and sea surface temperature (SST) that plays an important role in the development of this phenomenon. When the SST off the western Australia warms anomalously, the feedback acts as a negative feedback because increased high cloud amount reduces shortwave radiation reaching the sea surface. Conversely, when the SST cools anomalously, the feedback further cools the SST because the amount of low cloud increases and less shortwave radiation can reach the ocean surface. Dependence of the sign of the feedback to that of SST anomalies is a unique feature that has not been identified in other regions. This study enhances our understanding of local ocean-atmosphere interaction associated with Ningaloo Nino and may help us to better predict this phenomenon in advance and mitigate its detrimental influences..