The Indo-Pacific warm pool (IPWP) is enclosed by a 28 °C isotherm and plays a vital role in controlling atmospheric circulations. However, the effects of changes in regional warm pool sea surface temperatures (SSTs) remain unexplored. We divided the IPWP into the Indian and Pacific sectors and distinguished their responses to natural variability and global warming. Furthermore, we examined the impacts of the interannual variability (IAV) in warm pool SST on the tropical Hadley, Walker, and monsoon circulations. The Hadley circulation was affected by warm pool SST warming, i.e., warmer SSTs over the warm pool strengthened the upward branch of Hadley circulation, whereas the downward branch was respectively weakened and strengthened in the Northern and Southern Hemispheres. Walker circulation was strengthened (weakened) in the warming (natural) mode. Consequently, the Walker circulation is weakened since the natural variability of warm pool SST plays a more dominant role rather than the warming trend of SSTs over the warm pool. Furthermore, our analysis displays that warm pool warming has little impact on the monsoon circulation. Our findings highlight the different roles of the IAV of warm pool regions in each tropical circulation as part of the warming trend and natural variability.
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.
<p><span lang="EN-US">The Indo-Pacific warm pool (IPWP) is enclosed by a 28 &#9702;C isotherm and plays a vital role in controlling tropical circulations. However, the effects of changes in regional warm pool sea surface temperatures (SSTs) on the circulations remain unexplored. To do this, we divided the IPWP into the Indian and Pacific sectors and distinguished their responses to natural variability and global warming. And then, we examined the impacts of the interannual variability (IAV) in warm pool SST on the tropical Hadley, Walker, and monsoon circulations. The Hadley circulation was affected by warm pool SST warming, i.e., warmer SSTs over the warm pool strengthened the upward branch of Hadley circulation, whereas the downward branch was weakened and strengthened in the Northern and Southern Hemispheres. Walker circulation was strengthened (weakened) in the warming (natural) mode. Consequently, the Walker circulation is weakened since the natural variability of warm pool SST plays a more dominant role than the warming trend of SSTs over the warm pool. It is notable that warm pool warming has little impact on monsoon circulation. Our findings highlight the different roles of the IAV of warm pool regions in each tropical circulation as part of the warming trend and natural variability. Furthermore</span><span lang="EN-US">, </span><span lang="EN-US">an </span><span lang="EN-US">increase in precipitation is limited up to a specific SST, although SST becomes warmer. We defined this specific SST as Saturation Threshold SST (STT). Under a warming climate, future changes in STT over the IPWP and its mechanism will be shortly shown in this presentation.</span></p>
Climate change has altered the frequency, intensity, and timing of mean and extreme precipitation. Extreme precipitation has caused tremendous socio-economic losses, and severe impacts on human life, livelihood, and ecosystems. In recent years, heavy rainfall events occurred during the boreal summer (June-to-August) frequently and sporadically over South Korea. Given that its severity, a call for an urgent investigation of summer extreme rainfall is needed. Although many previous studies have addressed daily extreme precipitation, hourly extreme rainfall still needs to be thoroughly investigated. Therefore, in this study, we investigated the trends, spatio-temporal variability, and long-term variations in mean and extreme precipitation over South Korea during the boreal summertime using daily and hourly observational data through various analysis methods. During the past 50 years , there has been a notable escalation in maximum hourly precipitation, although the boreal summer mean precipitation has increased only marginally. Regionally, an increase in mean and extreme rainfall occurred in the northern part of the central region and the southern coast of the Korean peninsula. Moreover, the increase in intensity and frequency of extreme precipitation as well as in dry day have contributed more to the total summer precipitation in recent years. Our findings provide scientific insights into the progression of extreme summer precipitation events in South Korea.
Climate change has altered the frequency, intensity, and timing of mean and extreme precipitation events. Extreme precipitation has caused tremendous socio-economic losses and displays strong regional variability. Although many previous studies have addressed daily extreme precipitation, hourly extreme rainfall still needs to be thoroughly investigated. In this study, we investigated the trends, spatio-temporal variability, and long-term variations in mean and extreme precipitation over South Korea using daily and hourly observational data. During the past 50 years (1973–2022), there has been a notable escalation in maximum hourly precipitation, although the boreal summer mean precipitation has increased only marginally. Regionally, an increase in mean and extreme rainfall occurred in the northern part of the central region. Moreover, increased intensity and frequency of extreme precipitation have contributed more to the total summer precipitation in recent years. Our findings provide scientific insights into the progression of extreme summer precipitation events in South Korea.
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