Opposite Changes in Tropical Cyclone Rain Rate During the Recent El Nino and La Nina Years

摘要

In this paper, we investigate whether the relationship between the El Nino-Southern Oscillation and tropical cyclone (TC) rain rate over the western North Pacific (WNP) changes between the global warming slowdown (2001-2012) and resumption (2013-2020) periods. Using high-resolution satellite rainfall data, we show that the average TC rain rate increases by 9% but decreases by 14% during the recent El Nino and La Nina years (since 2013), respectively. During the El Nino years, the increase is related to higher TC track density at lower latitudes, where more water vapor and stronger convergence are present. On the other hand, the decrease in TC rain rate during the recent La Nina years is mainly related to an increase in track density at higher latitudes and a decrease in TC intensity. These changes in TC track density and intensity are both associated with the strengthening of the subtropical high since 2013. @@@ Plain Language Summary The impacts on various weather phenomena associated with the global surface warming slowdown (or "hiatus": 1998-2012) and its subsequent resumption since 2013 have been extensively investigated. An unresolved issue is whether the tropical cyclone (TC) rain rate over the western North Pacific (WNP) basin has also changed, especially during the El Nino (or La Nina) years. Considering the availability of high-resolution satellite rainfall data, we mainly focus on the period of 2001-2020 (slowdown period: 2001-2012; resumption period: 2013-2020). Our results show that, consistent with the increase in atmospheric water vapor after the global warming resumption, the average TC rain rate has increased by similar to 2%. However, TC rain rate increases in El Nino years but decreases in La Nina years during the resumption period. This opposite change in TC rain rate is mainly influenced by the strengthened WNP subtropical high. Our findings suggest that it is necessary to properly consider the influence of the subtropical high on the projections in TC migration, intensity, and rain rate under global warming.

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