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Impact of North Pacific Meridional Mode Diversity on Western North Pacific Tropical Cyclone Genesis.

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Titel: Impact of North Pacific Meridional Mode Diversity on Western North Pacific Tropical Cyclone Genesis.
Autoren: Song, Jinjie1,2 (AUTHOR) songjinjie@qq.com, Klotzbach, Philip J.3 (AUTHOR), Jiang, Sulin1,2,4 (AUTHOR), Duan, Yihong4 (AUTHOR)
Quelle: Geophysical Research Letters. 11/28/2025, Vol. 52 Issue 22, p1-11. 11p.
Schlagwörter: *TROPICAL cyclones, *MODES of variability (Climatology), *OCEAN temperature, *WEATHER, *CLIMATE feedbacks
Geografische Kategorien: NORTH Pacific Ocean, PACIFIC Ocean
Abstract: This study investigates the diversity of the impact of the North Pacific Meridional Mode (NPMM) on western North Pacific (WNP) tropical cyclone (TC) genesis during June–November from 1961 to 2024. We consider preceding springtime NPMM events driven by tropical and extratropical forcings, and classify them as successive and stochastic events, respectively. In successive positive NPMM years, TC genesis changes only slightly over the entire WNP. In successive negative NPMM years, significant increases (decreases) in TC genesis are observed over a region spanning 20°–140°E, 0°–20°N (140°–160°E, 0°–20°N). In stochastic NPMM years, there are significant increases in TC genesis over a region spanning 135°–160°E, 5°–25°N. These changes in TC genesis can be explained by the anomalous environmental conditions in different NPMM years, which can be further linked to the NPMM's strength as well as sea surface temperature anomalies over the tropical western Pacific. Plain Language Summary: Previous publications have documented a notable interannual relationship between basinwide tropical cyclone (TC) frequency over the western North Pacific (WNP) and the North Pacific Meridional Mode (NPMM). Springtime NPMM events can be classified into successive and stochastic events, driven by tropical and extratropical forcings, respectively. This study compares the responses of June–November WNP TC genesis from 1961 to 2024 to different NPMM events and investigates their related mechanisms. NPMM‐induced changes in basinwide TC frequency vary based on the forcing mechanism, with a significant increase in stochastic positive NPMM years but only weak changes in successive positive or negative NPMM years. In successive positive NPMM years, there are almost no significant changes in TC genesis and environmental conditions over the entire WNP. In successive negative NPMM years, favorable (unfavorable) environmental conditions induce significant increases (decreases) in TC genesis over the western (eastern) portion of the WNP. In stochastic NPMM years, a basinwide enhancement of TC genesis is observed, driven by favorable environmental conditions over most of the WNP. These changes can be further linked to the NPMM's strength and sea surface temperature anomalies over the tropical western Pacific. Key Points: A stochastic positive North Pacific Meridional Mode (NPMM) induces a basinwide increase in western North Pacific tropical cyclone (TC) genesisA successive positive or negative NPMM causes only weak changes in basinwide TC frequencyDifferent NPMM flavors are characterized by different NPMM strengths and sea surface temperature changes over the tropical western Pacific [ABSTRACT FROM AUTHOR]
Datenbank: Academic Search Index
Beschreibung
Abstract:This study investigates the diversity of the impact of the North Pacific Meridional Mode (NPMM) on western North Pacific (WNP) tropical cyclone (TC) genesis during June–November from 1961 to 2024. We consider preceding springtime NPMM events driven by tropical and extratropical forcings, and classify them as successive and stochastic events, respectively. In successive positive NPMM years, TC genesis changes only slightly over the entire WNP. In successive negative NPMM years, significant increases (decreases) in TC genesis are observed over a region spanning 20°–140°E, 0°–20°N (140°–160°E, 0°–20°N). In stochastic NPMM years, there are significant increases in TC genesis over a region spanning 135°–160°E, 5°–25°N. These changes in TC genesis can be explained by the anomalous environmental conditions in different NPMM years, which can be further linked to the NPMM's strength as well as sea surface temperature anomalies over the tropical western Pacific. Plain Language Summary: Previous publications have documented a notable interannual relationship between basinwide tropical cyclone (TC) frequency over the western North Pacific (WNP) and the North Pacific Meridional Mode (NPMM). Springtime NPMM events can be classified into successive and stochastic events, driven by tropical and extratropical forcings, respectively. This study compares the responses of June–November WNP TC genesis from 1961 to 2024 to different NPMM events and investigates their related mechanisms. NPMM‐induced changes in basinwide TC frequency vary based on the forcing mechanism, with a significant increase in stochastic positive NPMM years but only weak changes in successive positive or negative NPMM years. In successive positive NPMM years, there are almost no significant changes in TC genesis and environmental conditions over the entire WNP. In successive negative NPMM years, favorable (unfavorable) environmental conditions induce significant increases (decreases) in TC genesis over the western (eastern) portion of the WNP. In stochastic NPMM years, a basinwide enhancement of TC genesis is observed, driven by favorable environmental conditions over most of the WNP. These changes can be further linked to the NPMM's strength and sea surface temperature anomalies over the tropical western Pacific. Key Points: A stochastic positive North Pacific Meridional Mode (NPMM) induces a basinwide increase in western North Pacific tropical cyclone (TC) genesisA successive positive or negative NPMM causes only weak changes in basinwide TC frequencyDifferent NPMM flavors are characterized by different NPMM strengths and sea surface temperature changes over the tropical western Pacific [ABSTRACT FROM AUTHOR]
ISSN:00948276
DOI:10.1029/2025GL119126