A thermodynamic mechanism for the maintenance of the moist-tropical margins

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H01966
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: Nagoya University
• Principal Investigator: Masunaga Hirohiko 名古屋大学, 宇宙地球環境研究所, 准教授 (00444422)
• Co-Investigator(Kenkyū-buntansha): 鈴木 健太郎 東京大学, 大気海洋研究所, 教授 (00396946)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 熱帯気象 / 衛星観測

Outline of Final Research Achievements

A moist large-scale ascent with active cumulus clouds prevails near the equator, while dry subsidence suppresses convective activity in the latitudes where the upper-tropospheric flow turns downward. This well-known picture of the Hadley circulation explains, from the perspectives of atmospheric dynamics, the unique low-latitude climate of the wet and rainy tropics and the dry and sunny subtropics in a consistent manner. On the other hand, the dynamics of the "margin" separating the tropics and subtropics has been a focus of recent research. In this study, we conducted an energy budget analysis using satellite observation data and reanalysis data, offering a physical explanation for the mechanism of the margin between the tropics and subtropics dominated by the variability in water vapor and convective activity. At the same time, related phenomena such as convective self-aggregation and tropical convergence zones were studied.

Free Research Field

気象学・気候学

Academic Significance and Societal Importance of the Research Achievements

熱帯における気象の成り立ちは地球水循環・エネルギー循環の要をなし、その動態を深く理解することは地球温暖化を含む気候変化やエルニーニョ現象などの年々変動の理解にも関連する幅広い影響力がある。本研究課題の成果は、気候モデルや気象予報数値モデルなどの性能評価に有用な観測的知見を与えるものであり、中長期的に気候予測・気象予報の精度向上に資するデータの礎を築く意味で重要である。