Tropical Cyclones over the Western North Pacific Strengthen the East Asia-Pacific Pattern during Summer

<p>The identification, climatic modulation and hydrological impact of Atmospheric Rivers (ARs) is an emergent scientific topic in recent years. ARs are important and yet understudied for East Asia (EA). We use our new AR identification algorithm (Pan & Lu, 2019), to build up a comprehensive AR catalog for this region for the first time. &#160;Interesting patterns are found: (1) there is a dominant AR route, originating from the Arabian Sea, crossing over the Bay of Bengal and Indochina, South China Sea (SCS) and Southeast China (SEC), and terminating in the western North Pacific; and (2) a nine-stage annual pattern in the climatological frequency is revealed. &#160;Stage 1: mid-Mar to mid-May, the formation of Western North Pacific Subtropical Height (WNPSH) near the SCS steers and confines AR in its northwest flank over SEC. &#160;Stages 2-5: during the monsoon season from mid-May to late-Aug, the evolution of AR follow the intra-seasonal progression of Asia-Pacific monsoon (including South Asian monsoon, East Asian monsoon and western North Pacific monsoon. Stages 6-9: late-Aug to mid-Mar, ARs leave EA and only occur over the North Pacific. Over all stages, we find the contribution of AR grows significantly with more extreme rainfall (i.e., from the annual rainfall, heavy rainfall, persistent heavy rainfall to large spatial extent persistent heavy rainfall), especially in spring and early-monsoon season. This emphasizes ARs&#8217; significant role in extreme or catastrophic rainfall events. Intriguingly, divergence of AR trajectories (also in their characteristics) occurs along the extratropical direction, and such divergent features have spatially heterogenous dependence on the leading modes of a collection of steering atmospheric and regulating climatic signals. Large divergence indicates high sensitivity of AR to transient steering; while small divergence promises high predictability of ARs, thus their associated hydrological impacts.</p>

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Statistical–Dynamical Seasonal Forecast of Western North Pacific and East Asia Landfalling Tropical Cyclones using the GFDL FLOR Coupled Climate Model

Journal of Climate ◽

10.1175/jcli-d-16-0487.1 ◽

2017 ◽

Vol 30 (6) ◽

pp. 2209-2232 ◽

Cited By ~ 27

Author(s):

Wei Zhang ◽

Gabriel A. Vecchi ◽

Gabriele Villarini ◽

Hiroyuki Murakami ◽

Richard Gudgel ◽

...

Keyword(s):

East Asia ◽

Correlation Coefficient ◽

Tropical Cyclones ◽

Hybrid Model ◽

North Pacific ◽

Western North Pacific ◽

Hybrid Models ◽

Predictive Skill ◽

Meridional Mode ◽

Landfalling Tropical Cyclones

Abstract This study attempts to improve the prediction of western North Pacific (WNP) and East Asia (EA) landfalling tropical cyclones (TCs) using modes of large-scale climate variability [e.g., the Pacific meridional mode (PMM), the Atlantic meridional mode (AMM), and North Atlantic sea surface temperature anomalies (NASST)] as predictors in a hybrid statistical–dynamical scheme, based on dynamical model forecasts with the GFDL Forecast-Oriented Low Ocean Resolution version of CM2.5 with flux adjustments (FLOR-FA). Overall, the predictive skill of the hybrid model for the WNP TC frequency increases from lead month 5 (initialized in January) to lead month 0 (initialized in June) in terms of correlation coefficient and root-mean-square error (RMSE). The hybrid model outperforms FLOR-FA in predicting WNP TC frequency for all lead months. The predictive skill of the hybrid model improves as the forecast lead time decreases, with values of the correlation coefficient increasing from 0.56 for forecasts initialized in January to 0.69 in June. The hybrid models for landfalling TCs over the entire East Asian (EEA) coast and its three subregions [i.e., southern EA (SEA), middle EA (MEA), and northern EA (NEA)] dramatically outperform FLOR-FA. The correlation coefficient between predicted and observed TC landfall over SEA increases from 0.52 for forecasts initialized in January to 0.64 in June. The hybrid models substantially reduce the RMSE of landfalling TCs over SEA and EEA compared with FLOR-FA. This study suggests that the PMM and NASST/AMM can be used to improve statistical/hybrid forecast models for the frequencies of WNP or East Asia landfalling TCs.

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Statistical-dynamical seasonal forecast of western North Pacific and East Asia landfalling tropical cyclones using the high-resolution GFDL FLOR coupled model

Journal of Advances in Modeling Earth Systems ◽

10.1002/2015ms000607 ◽

2016 ◽

Vol 8 (2) ◽

pp. 538-565 ◽

Cited By ~ 17

Author(s):

Wei Zhang ◽

Gabriele Villarini ◽

Gabriel A. Vecchi ◽

Hiroyuki Murakami ◽

Richard Gudgel

Keyword(s):

High Resolution ◽

East Asia ◽

Tropical Cyclones ◽

North Pacific ◽

Western North Pacific ◽

Coupled Model ◽

Seasonal Forecast ◽

Landfalling Tropical Cyclones

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Intraseasonal Variability of the East Asia-Pacific Teleconnection and Its Impacts on Multiple Tropical Cyclone Genesis Over the Western North Pacific

Frontiers in Earth Science ◽

10.3389/feart.2020.598043 ◽

2021 ◽

Vol 8 ◽

Author(s):

Xin Lin ◽

Lan Wang ◽

Jianyun Gao ◽

Xiaoxiao Chen ◽

Wei Zhang

Keyword(s):

East Asia ◽

El Niño ◽

North Pacific ◽

Western North Pacific ◽

El Nino ◽

Intraseasonal Variability ◽

Asia Pacific ◽

Boreal Summer ◽

Relative Role ◽

The Impact

A daily East Asia–Pacific teleconnection (EAP) index was constructed to investigate the impact of the intraseasonal variability (ISV) of this index on the genesis of multiple tropical cyclones (MTC) in boreal summer over the western North Pacific (WNP). The result indicates that the EAP index has dominant intraseasonal periods of 10–20 days, 20–40 days and 50–70 days, respectively. The ISV of the EAP during 1979–2019 can be classified into three types, a single-period-domination type (37%), a multiple period coexistence type (24%) and a transition type (39%). It is found that during El Niño (La Niña) summers, the ISV of the EAP is dominated by a higher-frequency (lower-frequency) oscillation with a period of around 20–30 (50–70) days. The distinctive ISV characteristics during the different ENSO years were accompanied with different dynamic and thermodynamic background conditions over the WNP and the South China Sea, which modulated the frequency and location of MTC genesis. By examining the relative contributions of individual environmental variables of the Genesis Potential Index, we found that the low-level absolute vorticity and mid-level relative humidity are two important environmental factors modulating MTC genesis. However, the relative role of these variables tends to change with the EAP ISV phase. The environmental condition over the SCS appears less influenced by ENSO. A more southern location of MTC genesis during El Niño is attributed to the change of the environmental humidity.

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