scholarly journals Intensified Impact of East Indian Ocean SST Anomaly on Tropical Cyclone Genesis Frequency over the Western North Pacific

2014 ◽  
Vol 27 (23) ◽  
pp. 8724-8739 ◽  
Author(s):  
Ruifen Zhan ◽  
Yuqing Wang ◽  
Li Tao
Keyword(s):  
Indian Ocean ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Tropical Cyclone Genesis ◽  
Central Pacific ◽  
East Indian ◽  
The Impact ◽  
East Indian Ocean ◽  
Genesis Frequency

Abstract A recent finding is the significant impact of the sea surface temperature anomaly (SSTA) over the east Indian Ocean (EIO) on the genesis frequency of tropical cyclones (TCs) over the western North Pacific (WNP). In this study it is shown that such an impact is significant only after the late 1970s. The results based on both data analysis and numerical model experiments demonstrate that prior to the late 1970s the EIO SSTA is positively correlated with the equatorial central Pacific SSTA and the latter produces an opposite atmospheric circulation response over the WNP to the former. As a result, the impact of the EIO SSTA on the TC genesis over the WNP is largely suppressed by the latter. After the late 1970s, the area coverage of the EIO SSTA is expanding. This considerably enhances the large-scale circulation response over the WNP to the EIO SSTA and significantly intensifies the impact of the EIO SSTA on TC genesis frequency over the WNP. The results from this study have great implications for seasonal prediction of TC activity over the WNP.

scholarly journals Decadal Transition of the Leading Mode of Interannual Moisture Circulation over East Asia–Western North Pacific: Bonding to Different Evolution of ENSO

2018 ◽  
Vol 32 (2) ◽  
pp. 289-308 ◽  
Author(s):  
Xiuzhen Li ◽  
Zhiping Wen ◽  
Deliang Chen ◽  
Zesheng Chen
Keyword(s):  
Indian Ocean ◽  
East Asia ◽  
North Pacific ◽  
Western North Pacific ◽  
Eastern Pacific ◽  
Enso Cycle ◽  
Central Pacific ◽  
Huai River ◽  
Leading Mode ◽  
The Impact

Abstract The El Niño–Southern Oscillation (ENSO) cycle has a great impact on the summer moisture circulation over East Asia (EA) and the western North Pacific [WNP (EA-WNP)] on an interannual time scale, and its modulation is mainly embedded in the leading mode. In contrast to the stable influence of the mature phase of ENSO, the impact of synchronous eastern Pacific sea surface temperature anomalies (SSTAs) on summer moisture circulation is negligible during the 1970s–80s, while it intensifies after 1991. In response, the interannual variation of moisture circulation exhibits a much more widespread anticyclonic/cyclonic pattern over the subtropical WNP and a weaker counterpart to the north after 1991. Abnormal moisture moves farther northward with the enhanced moisture convergence, and thus precipitation shifts from the Yangtze River to the Huai River valley. The decadal shift in the modulation of ENSO on moisture circulation arises from a more rapid evolution of the bonding ENSO cycle and its stronger coupling with circulation over the Indian Ocean after 1991. The rapid development of cooling SSTAs over the central-eastern Pacific, and warming SSTAs to the west over the eastern Indian Ocean–Maritime Continent (EIO-MC) in summer, stimulates abnormal descending motion over the western-central Pacific and ascending motion over the EIO-MC. The former excites an anticyclone over the WNP as a Rossby wave response, sustaining and intensifying the WNP anticyclone; the latter helps anchor the anticyclone over the tropical–subtropical WNP via an abnormal southwest–northeast vertical circulation between EIO-MC and WNP.

scholarly journals A Region-Dependent Seasonal Forecasting Framework for Tropical Cyclone Genesis Frequency in the Western North Pacific

2019 ◽  
Vol 32 (23) ◽  
pp. 8415-8435 ◽  
Author(s):  
Chao Wang ◽  
Bin Wang ◽  
Liguang Wu
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Prediction Models ◽  
Temporal Correlation ◽  
Tropical Cyclone Genesis ◽  
Regional Variability ◽  
Empirical Prediction ◽  
Genesis Frequency

ABSTRACT It has been a common practice to predict total tropical cyclone (TC) genesis frequency over the entire western North Pacific (WNP). Here we show that TC genesis (TCG) exhibits distinct regional variability and sources of predictability. Therefore, we divide the WNP into four quadrants with 140°E and 17°N being dividing lines plus the South China Sea (SCS) to predict five subregional TCG frequencies as well as the entire WNP TCG frequency. Besides the well-known ENSO-induced seesaw relationship between the TCGs in the southeast and northwest quadrants, we found that 1) an enhanced TCG in the northeast WNP is associated with a pronounced anomalous cyclonic circulation, which is maintained through its interaction with the underlying sea surface temperature (SST) anomalies; 2) an active TCG in the southwest WNP is accompanied by a zonally elongated positive vorticity anomaly and SST warming over the equatorial eastern Pacific; and 3) the SCS TCG is influenced by the upper-level South Asia high through modulating large-scale environmental parameters. Physically meaningful predictors are identified and a set of empirical prediction models for TCG frequency is established for each subregion. Both the cross-validated reforecast for 1965–2000 and independent forecast for 2001–16 show significant temporal correlation skills. Moreover, the sum of the predicted TCG frequency in five subregions yields a basinwide TCG frequency prediction with a temporal correlation skill of 0.76 for the independent forecast period of 2001–16. The results indicate its potential utility to improve the TC forecasting in the WNP.

scholarly journals Absence of Tropical Cyclone Genesis Over the Western North Pacific in July 2020 and Its Prediction by CFSv2

2021 ◽  
Vol 9 ◽  
Author(s):  
Baoqiang Tian ◽  
Ke Fan
Keyword(s):  
North Atlantic ◽  
Environmental Conditions ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Walker Circulation ◽  
Feedback Mechanism ◽  
North Indian Ocean ◽  
Tropical Cyclone Genesis ◽  
The Impact

There were no TCs generated in July 2020 over the western North Pacific (WNP), which was the first time this had happened during since 1980. This study attempts to understand the cause of there having been no TCs generated in July 2020, and evaluates the prediction skill for the large-scale environmental conditions associated with the TC genesis number (TCGN). Results show that the main causes were the abnormal warming of sea surface temperature (SST) in the North Indian Ocean (NIO) and North Atlantic in July and the abnormal decrease in SST from April and May in the Niño4 region. The NIO SST can affect the large-scale environmental conditions via the SST–precipitation–wind feedback mechanism. Through the interaction between the tropical North Atlantic and the NIO, the abnormally warm North Atlantic SST further strengthened the impact of the NIO SST on the environmental conditions. The monthly difference (MD) of the Niño4 index from April to May is significantly correlated with the TCGN in July. Not only can the Niño4 MD in May affect the environmental conditions by affecting the WNP anticyclone, but it can also affect the NIO SST and precipitation anomalies through a shift in the position of the Walker circulation. Besides, the activity of the MJO also had a certain impact on the absence of TC genesis in July 2020. Although CFSv2 can successfully predict the local feedback affecting the July TCGN, it fails to forecast the large-scale environmental conditions associated with the absence of TC genesis over the WNP in July 2020.

scholarly journals Impact of SSTA in the East Indian Ocean on the Frequency of Northwest Pacific Tropical Cyclones: A Regional Atmospheric Model Study

2011 ◽  
Vol 24 (23) ◽  
pp. 6227-6242 ◽  
Author(s):  
Ruifen Zhan ◽  
Yuqing Wang ◽  
Chun-Chieh Wu
Keyword(s):  
Indian Ocean ◽  
Atmospheric Model ◽  
Western Pacific ◽  
Northwest Pacific ◽  
East Indian ◽  
Regional Atmospheric Model ◽  
The Impact ◽  
East Indian Ocean ◽  
The Western Pacific ◽  
Genesis Frequency

Abstract The impact of the sea surface temperature anomaly (SSTA) in the East Indian Ocean (EIO) on the tropical cyclone (TC) frequency over the western North Pacific (WNP) and the involved physical mechanisms are examined using the International Pacific Research Center (IPRC) Regional Atmospheric Model (iRAM) driven by the reanalysis and the observed SSTs. The model reproduces generally quite realistic climatic features of the WNP TC activity, including the interannual variability of the WNP TC genesis frequency, the geographical distributions of TC genesis and frequency of occurrence. In particular, the model reproduces the observed statistical (negatively correlated) relationship between the WNP TC frequency and the EIO SSTA, as recently studied by Zhan et al. The experiments with artificially imposed SSTA in the EIO in the year 2004 with normal EIO SST and WNP TC activity confirm that the EIO SSTA does affect the TC genesis frequency in the entire genesis region over the WNP by significantly modulating both the western Pacific summer monsoon and the equatorial Kelvin wave activity over the western Pacific, two major large-scale dynamical controls of TC genesis over the WNP. Additional sensitivity experiments are performed for two extreme years: one (1994) with the highest and one (1998) with the lowest TC annual frequencies in the studied period. The results reveal that after the EIO SSTAs in the two extreme years are removed, the TC frequency in 1998 is close to the climatological mean, while the excessive TCs in 1994 are still simulated. The model results suggest that the warm EIO might be a major factor contributing to the unusually few TCs formed over the WNP in 1998, but the cold EIO seemed to contribute little to the excessive WNP TCs in 1994.

scholarly journals Possible Cause of Seasonal Inhomogeneity in Interdecadal Changes of Tropical Cyclone Genesis Frequency over the Western North Pacific

2021 ◽  
Vol 34 (2) ◽  
pp. 635-642
Author(s):  
Minhee Chang ◽  
Doo-Sun R. Park ◽  
Chang-Hoi Ho
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Tropical Cyclone Genesis ◽  
Easterly Wind ◽  
Sst Warming ◽  
Cyclone Genesis ◽  
Interdecadal Changes ◽  
Genesis Frequency

AbstractAn abrupt decrease in annual tropical cyclone genesis frequency (TCGF), which is statistically significant only from October to December (OND), has been noticed over the western North Pacific Ocean. However, the seasonal inhomogeneity of interdecadal changes in TCGF between OND and the other seasons (from January to September) and the associated mechanisms are not clearly documented. This study examines and compares the different interdecadal changes in OND and in January–September from 1979 to 2018. According to our analysis, the TCGF decrease in OND (2.2) accounts for 79% of the total decrease (2.8) in annual TCGF after 1998, whereas the TCGF in January to September remains unchanged. The key differences in large-scale environment are found from the extension of equatorial easterly wind anomalies and attendant anticyclone anomalies in the subtropics. Under similar sea surface temperature (SST) warming pattern in the tropical Indo-Pacific region (i.e., the La Niña–like SST warming), tropical precipitation is significantly enhanced over the area where its seasonal peak occurs: the tropical Indian Ocean in OND and the tropical western Pacific in January–September. Thus, the equatorial easterly wind anomalies extend westward to 110°E in OND and to 145°E in January–September. Different extension of easterly wind anomalies results in different expansion of attendant large-scale anticyclone anomaly over the subtropical western Pacific, which dominates the entire main development region in OND but not in January–September. To summarize, the different extensions of easterly wind anomalies under similar La Niña–like SST warming are responsible for the seasonal inhomogeneity of interdecadal changes in TCGF.

scholarly journals Multi-model Projection of Tropical Cyclone Genesis Frequency over the Western North Pacific: CMIP5 Results

SOLA ◽  
2012 ◽  
Vol 8 (0) ◽  
pp. 137-140 ◽  
Author(s):  
Satoru Yokoi ◽  
Chiharu Takahashi ◽  
Kazuaki Yasunaga ◽  
Ryuichi Shirooka
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Tropical Cyclone Genesis ◽  
Model Projection ◽  
Cyclone Genesis ◽  
Genesis Frequency
Sign in / Sign up

Export Citation Format

Share Document