scholarly journals Global Warming and Western North Pacific Typhoon Activity from an Observational Perspective

2004 ◽  
Vol 17 (23) ◽  
pp. 4590-4602 ◽  
Author(s):  
Johnny C. L. Chan ◽  
Kin Sik Liu
Keyword(s):  
Global Warming ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Climate Model ◽  
El Nino ◽  
Interannual Variations ◽  
Model Simulations ◽  
Climate Model Simulations

Abstract Based on results from climate model simulations, many researchers have suggested that because of global warming, the sea surface temperature (SST) will likely increase, which will then lead to an increase in the intensity of tropical cyclones (TCs). This paper reports results of a study of the relationship between SST and observed typhoon activity (which is used as a proxy for the intensity of TCs averaged over a season) over the western North Pacific (WNP) for the past 40 yr. The average typhoon activity over a season is found to have no significant relationship with SST in the WNP but increases when the SST over the equatorial eastern Pacific Ocean is above normal. The mean annual typhoon activity is generally higher (lower) during an El Niño (La Niña) year. Such interannual variations of typhoon activity appear to be largely constrained by the large-scale atmospheric factors that are closely related to the El Niño–Southern Oscillation (ENSO) phenomenon. These large-scale dynamic and thermodynamic factors include low-level relative vorticity, vertical wind shear, and moist static energy. Such results are shown to be physically consistent with one another and with those from previous studies on the interannual variations of TC activity. The results emphasize the danger of drawing conclusions about future TC intensity based on current climate model simulations that are not designed to make such predictions.

scholarly journals Contributions of Different Time-Scale Variations to Tropical Cyclogenesis over the Western North Pacific

2018 ◽  
Vol 31 (8) ◽  
pp. 3137-3153 ◽  
Author(s):  
Xi Cao ◽  
Renguang Wu ◽  
Mingyu Bi
Keyword(s):  
El Niño ◽  
North Pacific ◽  
Time Scale ◽  
Western North Pacific ◽  
Large Scale ◽  
El Nino ◽  
Vertical Wind Shear ◽  
Specific Humidity ◽  
Interannual Variations ◽  
Intraseasonal Variations

Abstract The present study investigates relative contributions of different time-scale variations of environmental factors to the tropical cyclone (TC) genesis over the western North Pacific (WNP) during July–August–September–October (JASO). Distinct from previous studies that are concerned with large-scale spatial patterns during a certain period, the present study focuses on local and instantaneous conditions of the TC genesis. Analysis shows that the contribution of convection and lower-level vorticity to the TC genesis is mainly due to intraseasonal and synoptic variations. The contribution of vertical wind shear is largely related to synoptic variations. The contribution of midlevel specific humidity is almost 2 times more from intraseasonal variations than from synoptic variations. The contribution of sea surface temperature (SST) to the TC genesis is mainly due to interannual and intraseasonal variations. The barotropic energy for synoptic-scale disturbances during the TC genesis comes mainly from climatological mean flows over the southwest quadrant and from intraseasonal wind variations over the northeast quadrant of the WNP, respectively. The contribution of interannual variations to the TC genesis is enhanced over the southeast quadrant of the WNP. More TCs form under weak easterly and westerly vertical shears, respectively, during El Niño developing and decaying JASO. The contribution of interannual variations of SST tends to be larger during El Niño decaying than during developing JASO.

scholarly journals Interannual Variability of Summer Tropical Cyclone Rainfall in the Western North Pacific Depicted by CFSR and Associated Large-Scale Processes and ISO Modulations

2018 ◽  
Vol 31 (5) ◽  
pp. 1771-1787 ◽  
Author(s):  
Jau-Ming Chen ◽  
Pei-Hua Tan ◽  
Liang Wu ◽  
Hui-Shan Chen ◽  
Jin-Shuen Liu ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Interannual Variability ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Trough ◽  
Tropical Eastern Pacific

This study examines the interannual variability of summer tropical cyclone (TC) rainfall (TCR) in the western North Pacific (WNP) depicted by the Climate Forecast System Reanalysis (CFSR). This interannual variability exhibits a maximum region near Taiwan (19°–28°N, 120°–128°E). Significantly increased TCR in this region is modulated by El Niño–Southern Oscillation (ENSO)-related large-scale processes. They feature elongated sea surface temperature warming in the tropical eastern Pacific and a southeastward-intensified monsoon trough. Increased TC movements are facilitated by interannual southerly/southeasterly flows in the northeastern periphery of the intensified monsoon trough to move from the tropical WNP toward the region near Taiwan, resulting in increased TCR. The coherent dynamic relations between interannual variability of summer TCR and large-scale environmental processes justify CFSR as being able to reasonably depict interannual characteristics of summer TCR in the WNP. For intraseasonal oscillation (ISO) modulations, TCs tend to cluster around the center of a 10–24-day cyclonic anomaly and follow its northwestward propagation from the tropical WNP toward the region near Taiwan. The above TC movements are subject to favorable background conditions provided by a northwest–southeasterly extending 30–60-day cyclonic anomaly. Summer TCR tends to increase (decrease) during El Niño (La Niña) years and strong (weak) ISO years. By comparing composite TCR anomalies and correlations with TCR variability, it is found that ENSO is more influential than ISO in modulating the interannual variability of summer TCR in the WNP.

scholarly journals Intensification of the Western North Pacific Anticyclone Response to the Short Decaying El Niño Event due to Greenhouse Warming

2016 ◽  
Vol 29 (10) ◽  
pp. 3607-3627 ◽  
Author(s):  
Wei Chen ◽  
June-Yi Lee ◽  
Kyung-Ja Ha ◽  
Kyung-Sook Yun ◽  
Riyu Lu
Keyword(s):  
Global Warming ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
Climate Models ◽  
El Nino ◽  
Coupled Model ◽  
Precipitation Anomaly ◽  
Historical Period ◽  
Central Pacific

Abstract Two types of El Niño evolution have been identified in terms of the lengths of their decaying phases: the first type is a short decaying El Niño that terminates in the following summer after the mature phase, and the second type is a long decaying one that persists until the subsequent winter. The responses of the western North Pacific anticyclone (WNPAC) anomaly to the two types of evolution are remarkably different. Using experiments from phase 5 of the Coupled Model Intercomparison Project (CMIP5), this study investigates how well climate models reproduce the two types of El Niño evolution and their impacts on the WNPAC in the historical period (1950–2005) and how they will change in the future under anthropogenic global warming. To reduce uncertainty in future projection, the nine best models are selected based on their performance in simulating El Niño evolution. In the historical run, the nine best models’ multimodel ensemble (B9MME) well reproduces the enhanced (weakened) WNPAC that is associated with the short (long) decaying El Niño. The comparison between results of the historical run for 1950–2005 and the representative concentration pathway 4.5 run for 2050–99 reveals that individual models and the B9MME tend to project no significant changes in the two types of El Niño evolution for the latter half of the twenty-first century. However, the WNPAC response to the short decaying El Niño is considerably intensified, being associated with the enhanced negative precipitation anomaly response over the equatorial central Pacific. This enhancement is attributable to the robust increase in mean and interannual variability of precipitation over the equatorial central Pacific under global warming.

scholarly journals Changes in Intensity and Variability of Tropical Cyclones over the Western North Pacific and Their Local Impacts under Different Types of El Niños

Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 59
Author(s):  
Yuhang Liu ◽  
Sun-Kwon Yoon ◽  
Jong-Suk Kim ◽  
Lihua Xiong ◽  
Joo-Heon Lee
Keyword(s):  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
El Nino ◽  
Pearl River Basin ◽  
Regional Variability ◽  
Central Pacific ◽  
El Niño Events ◽  
El Nino Events

This study investigated the effects of El Niño events on tropical cyclone (TC) characteristics over the western North Pacific (WNP) region. First, TC characteristics associated with large-scale atmospheric phenomena (i.e., genesis position, frequency, track, intensity, and duration) were investigated in the WNP in relation to various types of El Niño events—moderate central Pacific (MCP), moderate eastern Pacific (MEP), and strong basin-wide (SBW). Subsequently, the seasonal and regional variability of TC-induced rainfall across China was analyzed to compare precipitation patterns under the three El Niño types. When extreme El Niño events of varying degrees occurred, the local rainfall varied during the developmental and decaying years. The development of MEP and SBW was associated with a distinct change in TC-induced rainfall. During MEP development, TC-induced rainfall occurred in eastern and northeastern China, whereas in SBW, TC-induced heavy rainfall occurred in southwest China. During SBW development, the southwestern region was affected by TCs over a long period, with the eastern and northeastern regions being affected significantly fewer days. During El Niño decay, coastal areas were relatively more affected by TCs during MCP events, and the Pearl River basin was more affected during SBW events. This study’s results could help mitigate TC-related disasters and improve water-supply management.

scholarly journals Analysis of upper-tropospheric humidity in tropical descent regions using observed and modelled radiances

2013 ◽  
Vol 13 (4) ◽  
pp. 10547-10560
Author(s):  
V. O. John ◽  
D. E. Parker ◽  
S. A. Buehler ◽  
J. Price ◽  
R. W. Saunders
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Model Simulations ◽  
Multiple Observations ◽  
Major Mode ◽  
Upper Tropospheric Humidity ◽  
Water Vapour Feedback ◽  
Climate Model Simulations

Abstract. We use multiple observations and climate model simulations to study upper tropospheric humidity (UTH) in tropical descent regions. A satellite simulator is used to generate UTH from model fields to ensure a like-to-like comparison. We have shown that HadGEM2 is generally able to reproduce the patterns and magnitude of UTH in these regions. In both models and observations, the major mode of UTH variability in these regions is associated with El Nino and Southern Oscillation (ENSO); a negative UTH anomaly is seen during El Nino years. There is no significant trend in UTH in these regions, where even a small negative trend would lead to an important reduction of the positive water vapour feedback on global warming.

scholarly journals The Influence of ENSO Flavors on Western North Pacific Tropical Cyclone Activity

2018 ◽  
Vol 31 (14) ◽  
pp. 5395-5416 ◽  
Author(s):  
Christina M. Patricola ◽  
Suzana J. Camargo ◽  
Philip J. Klotzbach ◽  
R. Saravanan ◽  
Ping Chang
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Equatorial Pacific ◽  
Atmospheric Variability ◽  
Central Pacific ◽  
Model Simulations ◽  
Eastern Equatorial Pacific

El Niño–Southern Oscillation (ENSO) is a major source of seasonal western North Pacific (WNP) tropical cyclone (TC) predictability. However, the spatial characteristics of ENSO have changed in recent decades, from warming more typically in the eastern equatorial Pacific during canonical or cold tongue El Niño to warming more typically in the central equatorial Pacific during noncanonical or warm pool El Niño. We investigated the response in basinwide WNP TC activity and spatial clustering of TC tracks to the location and magnitude of El Niño using observations, TC-permitting tropical channel model simulations, and a TC track clustering methodology. We found that simulated western North Pacific TC activity, including accumulated cyclone energy (ACE) and the number of typhoons and intense typhoons, is more effectively enhanced by sea surface temperature warming of the central, compared to the eastern, equatorial Pacific. El Niño also considerably influenced simulated TC tracks regionally, with a decrease in TCs that were generated near the Asian continent and an increase in clusters that were dominated by TC genesis in the southeastern WNP. This response corresponds with the spatial pattern of reduced vertical wind shear and is most effectively driven by central Pacific SST warming. Finally, internal atmospheric variability generated a substantial range in the simulated season total ACE (±25% of the median). However, extremely active WNP seasons were linked with El Niño, rather than internal atmospheric variability, in both observations and climate model simulations.

Response of western North Pacific anomalous anticyclone in the summer of decaying El Niño to global warming: Diverse projections based on CMIP6 and CMIP5 models

2021 ◽  
pp. 1-41
Author(s):  
Chao He ◽  
Zhenyuan Cui ◽  
Chunzai Wang
Keyword(s):  
Global Warming ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Indian Ocean ◽  
Cmip5 Models ◽  
Kelvin Wave ◽  
Anomalous Anticyclone

AbstractThe anomalous anticyclone over the western North Pacific (WNPAC) is a key atmospheric bridge through which El Niño-Southern Oscillation (ENSO) affects East Asian climate. In this study, the response of the anomalous WNPAC to global warming under the high-emission scenario is investigated based on 40 models from CMIP6 and 30 models from CMIP5. Despite low inter-model consensus, the multi-model median (MMM) of CMIP6 models projects an enhanced anomalous WNPAC but the MMM of CMIP5 models projects a weakened anomalous WNPAC, both of which reach about 0.5 standard deviation of the decadal internal variability derived from the pre-industrial control experiment. As consistently projected by CMIP6 and CMIP5 models, a same magnitude of sea surface temperature anomaly (SSTA) over the tropical Indian Ocean (TIO) stimulates a weaker anomalous WNPAC under a warmer climate, and this mechanism is responsible for the weakened anomalous WNPAC based on the CMIP5-MMM. However, the above mechanism is overwhelmed by another mechanism related to the changes in tropical SSTA based on the CMIP6-MMM. As a result of the enhanced warm SSTA over the TIO and the eastward shift of the warm SSTA over the equatorial Pacific during the decaying El Niño, the warm Kelvin wave emanating from the TIO is enhanced along with the stronger zonal SSTA gradient based on the CMIP6-MMM, enhancing the anomalous WNPAC. The diverse changes in the zonal SSTA gradient between the TIO and the equatorial western Pacific also explain the inter-model diversity of the changes in anomalous WNPAC.

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