fnctId=thesis,fnctNo=367
Characteristics of Global Monsoon Precipitation in a Warm Climate: Extremes and Rainy Season
- 작성자
- 기후시스템전공
- 저자
- Suyeon Moon
- 발행사항
- 발행일
- 2022-02
- 저널명
- 국문초록
- 영문초록
- Global monsoon precipitation is expected to change in a warm climate. How much precipitation changes in the monsoon domain, which is home to billions of people worldwide, is a critical issue to prepare for proper policies for climate change. This study aims to understand the global and regional monsoon precipitation changes in a warm climate. I have investigated (1) the robustness of future monsoon precipitation in response to a warm climate, (2) the impact of anthropogenic forcing on future precipitation and potential impacts on human society, and (3) the role of soil moisture-atmosphere interaction in terms of a precursor of monsoon onset.
Firstly, the global monsoon domain is newly defined based on the harmonic analysis. In addition, precipitation changes in a warm climate are quantified in diverse aspects. Changes in monsoon precipitation are expected to increase, but this has been challenged due to substantial regional uncertainties. I have tried to understand the variations in the amount of summertime precipitation, the change in length of the rainy season, and the factors modulating precipitation changes over the regional monsoon domain. The sensitivity of precipitation depends on the regional monsoon. The Asian monsoon, especially Indian and East Asian, is vulnerable in both seasonal mean and extreme precipitation. In general, changes in precipitation intensity in warm climates are mainly affected by the thermodynamic component. However, over Indian, and East Asian monsoon, the dynamic component also modulates the future precipitation intensity. In addition, the length of the rainy season is expanded over most monsoon domains, except over the American monsoon. The regions where the precipitation sensitivity is expected to enhance in the future are likely to have a more extended monsoon season. Longer rainy seasons might affect people’s lives in additional ways than those discussed so far.
Secondly, the intensity of precipitation is controlled in a warm climate, resulting from the combined effects of internal variability and anthropogenic forcing. An increase in moisture leads to the enhancement of extreme precipitation. Numerous previous studies have examined the extreme precipitation affected by human-induced changes. But there are few studies for extreme detection of the anthropogenic signal based on large ensemble simulations. Moreover, it is also necessary to identify when anthropogenic forcing influences the mean and extreme precipitation regionally. Extreme precipitation is strongly affected by anthropogenic forcing over most global monsoon regions. The emerging time for extremely heavy rainfall, when the anthropogenic signal overtakes natural variability, is expected to expand rapidly from 2024 and appear in 88% of the global monsoon region within 2100. The emerging time for the length of a dry spell is fatal over American, southern African, and Asian, primarily East Asian monsoon. Furthermore, the socio-economic impacts of climate change are also investigated using projected future population and GDP. Among the global monsoon domain, the African monsoon is vulnerable mainly due to population increase, but the economic growth rate is slow. The highly vulnerable and less resilient regions require urgent plans for climate change.
Finally, I investigated the role of soil moisture and atmosphere interaction on monsoon onset. The onset date of the monsoon influences society directly. Therefore, advancing the predictable time for monsoon onset is essential. As a precursor of monsoon onset, I used the soil moisture dataset, which has a long memory and provides leading impacts on the summer monsoon onset by modulating the surface energy budget. In the case of the Indian monsoon, the low surface soil moisture during spring over the Iranian region can induce warm air by enhancing the sensible heat flux. The land-ocean thermal contrast is strengthened from spring, resulting in increasing the vertical wind shear, which influences the monsoon onset. In other words, the low (high) soil moisture over the Iranian region can induce the early (late) monsoon onset. The role of spring soil moisture in the Iranian region plays as a precursor of Indian monsoon onset under the low emission scenario. However, the relationship weakens under high emission scenarios due to a decrease in the strength of soil moisture-atmosphere interaction. Under high emission scenarios, “dry soil” and “impact of dry soil on the atmosphere” are not linear relationships. This study helps in understanding the relationship between the present and future soil moisture-atmosphere interaction in more detail.
In conclusion, gaining a better knowledge of future changes in regional monsoon precipitation can raise awareness of precipitation risk and aid in the development of appropriate mitigation strategies. Furthermore, understanding the present and future relationships in climatic systems, particularly the interaction of soil moisture and atmosphere, helps to understand the global hydrological system.
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