Diurnal Variation of Overshooting Tops in Typhoons Detected by Himawari‐8 Satellite. Issue 21 (1st November 2021)

• Record Type: Journal Article
• Authors: Sun, Liangxiao; Tang, Xiaodong; Zhuge, Xiaoyong; Tan, Zhe‐Min; Fang, Juan
• Is Part Of: Geophysical research letters. Volume 48:Issue 21(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-01
• Subjects: typhoon -- overshooting top -- diurnal cycle -- Himawari‐8 satellite -- intensity -- intensity change; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL095565
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Overshooting top (OT), a proxy for deep convection with an intense updraft that can penetrate the tropopause, has an important influence on typhoon intensification. Using 9003 Himawari‐8 satellite images and a unique OT detection algorithm, the diurnal variation of OTs within 45 western North Pacific typhoons were analyzed. We examined the distribution of OTs in different types of typhoons in terms of both intensity and intensity change and the relationship between the OTs and typhoon intensification on a diurnal scale. Our results show that a greater OT density (OTD) occurs in strong typhoons and rapid intensification (RI) typhoons. Moreover, RI typhoons showed greater diurnal variation than non‐RI typhoons. The diurnal cycle of OTD in RI typhoons was in phase with the intensification of the typhoon, with the maximum in the early morning. Therefore, OTD can become a potentially effective indicator to estimate diurnal changes in typhoon intensity. Plain Language Summary: Typhoons are often topped by flat anvil‐shaped clouds. Under the correct conditions, the region with the greatest upward motion can penetrate the cloud anvil, leading to an overshooting top (OT). Previous studies have suggested that OTs behave differently from anvil clouds and that the warming induced by OT is important in the intensification of typhoon. Although a higher rate of typhoon intensification during the night is well established, it remains unknown whether there is relationship between the frequency and density of OT and the intensity and intensity change of typhoon over the course of each day. Observations from the Himawari‐8 satellite showed that there are more OTs occur in strong typhoons and rapid intensification typhoons. Rapid intensification typhoons have the greater diurnal variations of OT occurrence, with the maximum in the early morning and the minimum in the afternoon. This is consistent with the diurnal variations of the intensification rate of typhoon and provides direct observational evidences of the relationship between tropical cyclone intensification and deep convection. OT frequency per unit area in typhoon can be a potentially reliable indicator to estimate diurnal changes of typhoon intensity and could be used to improve forecasting of typhoon intensity in the future. Key Points: A greater overshooting top density (OTD) appears in stronger typhoons within six times the radius of maximum wind of the typhoon center A greater OTD and diurnal variation occur in rapid intensification (RI) typhoons than in non‐RI typhoons The maximum (minimum) OTD in the early morning (afternoon) in RI typhoons is related to the diurnal phase of intensification