Observational Characteristics of Wintertime Extreme Surface Turbulent Heat Flux Events in the North Pacific Subtropical Region. Issue 6 (23rd March 2022)

• Record Type: Journal Article
• Authors: Huang, Jing; Zhang, Yang; Hu, Haibo; Yang, Xiu‐Qun; Ren, Xuejuan
• Is Part Of: Journal of geophysical research. Volume 127:Issue 6(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-23
• Subjects: surface turbulent heat flux -- extreme events -- North Pacific subtropical region -- subtropical high -- precipitation; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2021JD035778
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Surface turbulent heat flux is the most direct variable denoting air‐sea interactions. In wintertime North Pacific, in addition to the Kuroshio‐Oyashio extension (KOE) region, high‐resolution observations show that the North Pacific subtropical region (NPSR) is also characterized with high surface heat flux, whose characteristics need systematic investigation. In this study, the extreme surface turbulent heat flux events in the NPSR are investigated using daily observational data. Our results show that the extreme events exhibit dipolar changes of surface flux over NPSR and KOE regions, lasting for several days. Though with a spatially correlated pattern, the occurrence of extreme events in NPSR and KOE is found greatly independent. In the extreme events, both surface sensible and latent heat fluxes display evident changes in north NPSR, while in south NPSR the change in surface latent heat flux dominates. The formation of extreme events in the NPSR is mainly determined by anomalous atmospheric circulation. Changes in the intensity of subtropical high influence the surface air wind speed, humidity, and temperature, contributing to the formation of extreme events in the NPSR. Our results further suggest that the processes through which the extreme events affect the atmospheric precipitation may be different in south and north NPSR. In south NPSR, the change of precipitation in extreme events is very likely attributed to the change of surface latent heat flux. In north NPSR, the change of water vapor transport by atmospheric circulations is found to play a major role. Plain Language Summary: Surface turbulent heat flux in the North Pacific, especially its extreme events, is important for the local and downstream weather system. Most of the previous studies focused on the surface turbulent heat flux in the Kuroshio‐Oyashio extension (KOE). This study investigates the wintertime extreme surface turbulent heat flux events in the North Pacific subtropical region (NPSR), which also exhibits high value with the subtropical oceanic front but has not been systematically studied. This study delineates the characteristics, formation, and atmospheric impacts of the wintertime extreme surface turbulent heat flux in the NPSR. We show that though with a spatially correlated pattern, the occurrence of extreme events in NPSR and KOE is almost independent. Different from the extreme events in the KOE region, the change in subtropical high is most responsible for the extreme change of surface flux in NPSR by affecting the surface air wind speed, humidity, and temperature. Our results also suggest that the extreme events may affect the atmospheric precipitation via different processes in south and north NPSR. The above results highlight the importance of subtropical air‐sea interaction to the wintertime extratropical variabilities of the atmosphere. Key Points: The extreme events are characterized with dipolar heat flux anomalies over North Pacific subtropical region (NPSR) and Kuroshio‐Oyashio extension regions sustaining for several days Intensity change of subtropical high, by affecting surface air wind, temperature, and humidity, is responsible for the extreme event in NPSR Processes associated with the anomalous precipitation in the extreme events are found different in south and north NPSR