Role of Interhemispheric Heat Transport and Global Atmospheric Cooling in Multidecadal Trends of Northern Hemisphere Precipitation

Abstract

Changes in the hydrological cycle in the northern hemisphere (NH) have a significant socioeconomic impact. Thus, quantifying past changes and projecting future changes in this cycle are important. We analyzed the positive and negative multidecadal trends in the NH mean precipitation since the 1950s that were accurately reproduced by a state-of-the-art Earth system model. Results showed that changes in the interhemispheric heat transport play a major role in the NH atmospheric heat budget, accounting for 59% of the negative-to-positive trend change in NH precipitation through a north–south shift in the tropical precipitation zone, and were strongly linked to Hadley circulation anomaly. The remaining 41% corresponded to changes in atmospheric cooling with small interhemispheric differences, which were primarily related to clear-sky longwave radiation. These findings quantitatively agreed with the results from a multimodel analysis.