Topic: Postponement of tropical rainy season cycle

Speaker: Professor Song Fengfei

Center for Frontier Science in the Abyssal Sphere and Earth System, Ocean University of China | Key Laboratory of Physical Oceanography, Ministry of Education

Time: 10:00-12:00, December 21, 2021 (Tuesday)

Forms of participation: Online live streaming/Tencent Meeting

Live Streaming at Official Weibo of the Department of Earth System Science, Tsinghua University Tencent Conference (ID: 100 217 700)

Introduction to the Lecture:

Against the backdrops of global warming, the seasonal cycle of tropical rainfall will change significantly, including amplitude enhancement and phase delay. The former is more obvious in the ocean, while the latter mainly occurs on land. Interestingly, both of the changes are related to the increase of water vapor under global warming. In the rainy season, the upward movement of the atmosphere is robust, and more water vapor means more precipitation, while in the dry season, the opposite is true. Therefore, the enhancement of seasonal cyclic amplitude of tropical rainfall mainly comes from the "wet-get-wet" mechanism. However, exploration about the reason for the phase delay has been going on for a long time. It is not until recently that how the increase of water vapor causes the seasonal delay under global warming is clarified by applying the framework of atmospheric energetics. In spring of the northern hemisphere, due to the seasonal increase of solar radiation, the atmosphere warms rapidly. Against the background of global warming, the increase of water vapor increases the effective specific volume of the atmosphere, and then the response to solar radiation slows down, that is, the seasonal warming of the atmosphere slows down. Similarly, the seasonal cooling of the atmosphere in the southern hemisphere also slows down. Therefore, the difference of energy between the northern and southern hemispheres makes tropical rainfall stay in the southern hemisphere to transport more energy to the northern hemisphere. Although the mechanism of seasonal delay of tropical rainfall is clear in the context of global warming, still many questions remain to be answered. For example, why is the seasonal delay of tropical rainfall more significant only on land? Has the intensification of global warming over the last four decades caused the seasonal delay of tropical rainfall? What climatic effects will the seasonal delay of tropical rainfall lead to? We would like to share our latest reflections on these problems.

Profile of the Speaker:

Song Fengfei, PhD, Young Scholar of the "Overseas Talent Introduction Program" of the Organization Department of the Central Committee of the CPC in 2020. Since November 2021, he has been Professor and Doctoral Supervisor of the Center for Frontier Science in the Abyssal Sphere and Earth System, Ocean University of China | Key Laboratory of Physical Oceanography, Ministry of Education. His current main research directions and interests include: (1) The role of the ocean in the changes of tropical and subtropical rainfall (including monsoon and inter-tropical convergence zone (ITCZ); (2) Tropical air-sea interaction and its influence on climate variability and climate change; (3) Impact of climate change on the ocean and the role of the ocean in climate change. Up to now, he has published over 40 papers, with 18 papers as the first author, including one highly cited paper and two papers published in Nature Climate Change. The total citation is 1335 and H-index is 18 based on Google Scholar.