Changes in the SST-precipitation relationship over the Indo-Pacific warm pool under a warming climate

Abstract

The Indo-Pacific warm pool (IPWP) is a region known for its strong atmospheric convection, which plays a key role in global climate. However, in recent decades, the IPWP has experienced human-induced warming, and it has been observed to have a non-linear relationship between Sea Surface Temperature (SST) and precipitation. Despite the rising SSTs, the increase in precipitation is limited until a specific SST, which is defined as saturation threshold SST (STT). The STT indicates a distinct transition before and after the STT, highlighting the non-linear response of precipitation to SST. Nevertheless, the impact of warmer climates on the SST-precipitation relationship and STT remains uncertain. To investigate future changes in this relationship, we analyzed a joint distribution of SST and precipitation using the historical data and three different Shared Socioeconomic Pathway (SSP) scenarios (SSP2-4.5, SSP3-7.0, and SSP5-8.5). We examined the near future (2041-2060), and far future (2081-2100). Our findings reveal that the STT increases with the shift in mean state due to the involvement of atmospheric stratification. This increase is observed across all three scenarios in both future periods, with the SSP5-8.5 scenario exhibiting the most substantial rise during the far future. The warming climate leads to a more pronounced warming in the upper troposphere than the surface, resulting in tropospheric stabilization. This process contributes to the increase in STT through Moist-Adiabatic Lapse Rate (MALR) adjustment. Additionally, the weakening of vertical motion constrains the increase in precipitation, despite the availability of abundant moisture. This study sheds light on the changing SST-precipitation relationship and provides a possible mechanism for the limited increase in precipitation. Therefore, this study offers a background for a better understanding of the non-monotonic response of precipitation to SST in the context of climate change.

Earth system resilience and tipping behavior

“…The sea surface temperature (SST)-atmospheric convection relationship in the Indo-Pacific warm pool (IPWP) is non-monotonic, with studies indicating intensified convection up to a certain SST threshold, beyond which the relationship breaks down. Kim et al (2023) investigate shifts in the SST-precipitation relationship and the SST threshold for deep convection under a warming climate in the IPWP, addressing the gaps in understanding the non-continuous increase in precipitation with SST warming.…”

Seasonal Diversity of Indo-Pacific Warm Pool Volume Expansion: The Role of Climatological Subsurface Temperature Patterns

“…Under the background of greenhouse warming, the expansion of surface IPWP and its impacts on global climate has become research hotspots nowadays [20][21][22][23][24][25][26][27] . Recent studies have revealed the warming and expansion of the surface IPWP in uences various climatic phenomena, including the Madden-Julian Oscillation 28,29 , tropical cyclones [30][31][32] , East Asian summer monsoon 33 , El Niño warming 34 , Hadley circulation 35,36 ,Walker circulation 19,24,37 ,Western Paci c subtropical high 38 and extreme precipitation and drought 27,[39][40][41] .…”