Dynamics and Characteristics of Climatic Extremes over East Asia Monsoon region

In this talk, I will highlight our recent advances and findings in changes in climatic extremes over east Asia monsoon region. I will focus specifically on monsoon duration, intensity, rainfall extremes changes, and mechanism, with dynamic and thermodynamic factors controlling rainfall extremes over East Asia in late summer. Moreover, I will present our latest research on climatic extremes such as heatwaves based on dry conditions and stationary waves. Despite increasing future rainfall, rainfall extremes and rainfall variability in many areas, our recent studies suggest also an increase in drought risk over eastern Asia as a result of changes in evapotranspiration. However, the underlying mechanisms of heat waves and potential atmospheric and land feedbacks are still not fully understood. Through feedback attribution analysis, we found that there are dry and hot heat waves with very different underlying physical processes and feedbacks. The increasing global warming is expected to exacerbate atmospheric water demand, worsening future conditions of extreme droughts and heatwaves. Compound drought and heatwaves (DHW) events have much attention due to their notable impacts on socio-ecological systems. However, studies on the mechanisms of DHW related to land-atmosphere interaction are not still fully understood in regional aspects. Here, we investigate drastic increases in DHW from 1980 to 2019 over northern East Asia, one of the strong land-atmosphere interaction regions. Heatwaves occurring in severely dry conditions have increased after the late 1990s, suggesting that the heatwaves in northern East Asia are highly likely to be compound heatwaves closely related to drought. Moreover, the soil moisture–temperature coupling strength increased in regions with strong increases in DHW through phase transitions of both temperature and heat anomalies that determine the coupling strength. As the soil moisture decreases, the probability density of low evapotranspiration increases through evaporative heat absorption. This leads to increase evaporative stress and eventually amplify DHW since the late 1990s. Focusing on changes in stomatal conductance due to CO2 changes, our research results reveal an increase in surface resistance with CO2 elevation. Particularly under drought conditions, potential evapotranspiration tends to overestimate drought severity in the East Asian region by approximately 17% when scenarios considering vegetation are not taken into account. Additionally, intensified land-atmosphere interactions due to soil moisture deficiency lead to more frequent and amplified occurrences of compound heatwaves and droughts over northern East Asia. Understanding the relationship between soil moisture and vegetation can contribute to comprehending future severe droughts and heatwaves under diverse surface conditions with warming and moistening.