scholarly journals Impact of Different ENSO Regimes on Southwest Pacific Tropical Cyclones

2013 ◽  
Vol 26 (2) ◽  
pp. 600-608 ◽  
Author(s):  
Savin S. Chand ◽  
John L. McBride ◽  
Kevin J. Tory ◽  
Matthew C. Wheeler ◽  
Kevin J. E. Walsh
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
El Nino ◽  
Function Analysis ◽  
Vertical Wind Shear ◽  
Relative Vorticity ◽  
La Niña ◽  
Pacific Region ◽  
Southwest Pacific ◽  
La Nina

Abstract The influence of different types of ENSO on tropical cyclone (TC) interannual variability in the central southwest Pacific region (5°–25°S, 170°E–170°W) is investigated. Using empirical orthogonal function analysis and an agglomerative hierarchical clustering of early tropical cyclone season Pacific sea surface temperature, years are classified into four separate regimes (i.e., canonical El Niño, canonical La Niña, positive-neutral, and negative-neutral) for the period between 1970 and 2009. These regimes are found to have a large impact on TC genesis over the central southwest Pacific region. Both the canonical El Niño and the positive-neutral years have increased numbers of cyclones, with an average of 4.3 yr−1 for positive-neutral and 4 yr−1 for canonical El Niño. In contrast, during a La Niña and negative-neutral events, substantially fewer TCs (averages of ~2.2 and 2.4 yr−1, respectively) are observed in the central southwest Pacific. The enhancement of TC numbers in both canonical El Niño and positive-neutral years is associated with the extension of favorable low-level cyclonic relative vorticity, and low vertical wind shear eastward across the date line. Relative humidity and SST are also very conducive for genesis in this region during canonical El Niño and positive-neutral events. The patterns are quite different, however, with the favorable conditions concentrated in the date line region for the positive-neutral, as compared with conditions farther eastward for the canonical El Niño regime. A significant result of the study is the demonstration that ENSO-neutral events can be objectively clustered into two separate regimes, each with very different impacts on TC genesis.

scholarly journals Tropical Cyclone Activity in the Fiji Region: Spatial Patterns and Relationship to Large-Scale Circulation

2009 ◽  
Vol 22 (14) ◽  
pp. 3877-3893 ◽  
Author(s):  
Savin S. Chand ◽  
Kevin J. E. Walsh
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Vertical Wind Shear ◽  
Relative Vorticity ◽  
La Niña ◽  
Factors Affecting ◽  
La Nina

Abstract This study examines the variations in tropical cyclone (TC) genesis positions and their subsequent tracks for different phases of the El Niño–Southern Oscillation (ENSO) phenomenon in the Fiji, Samoa, and Tonga region (FST region) using Joint Typhoon Warning Center best-track data. Over the 36-yr period from 1970/71 to 2005/06, 122 cyclones are observed in the FST region. A large spread in the genesis positions is noted. During El Niño years, genesis is enhanced east of the date line, extending from north of Fiji to over Samoa, with the highest density centered around 10°S, 180°. During neutral years, maximum genesis occurs immediately north of Fiji with enhanced genesis south of Samoa. In La Niña years, there are fewer cyclones forming in the region than during El Niño and neutral years. During La Niña years, the genesis positions are displaced poleward of 12°S, with maximum density centered around 15°S, 170°E and south of Fiji. The cyclone tracks over the FST region are also investigated using cluster analysis. Tracks during the period 1970/71–2005/06 are conveniently described using three separate clusters, with distinct characteristics associated with different ENSO phases. Finally, the role of large-scale environmental factors affecting interannual variability of TC genesis positions and their subsequent tracks in the FST region are investigated. Favorable genesis positions are observed where large-scale environments have the following seasonal average thresholds: (i) 850-hPa cyclonic relative vorticity between −16 and −4 (×10−6 s−1), (ii) 200-hPa divergence between 2 and 8 (×10−6 s−1), and (iii) environmental vertical wind shear between 0 and 8 m s−1. The subsequent TC tracks are observed to be steered by mean 700–500-hPa winds.

scholarly journals Influence of Intraseasonal–Interannual Oscillations on Tropical Cyclone Genesis in the Western North Pacific

2018 ◽  
Vol 31 (12) ◽  
pp. 4949-4961 ◽  
Author(s):  
Jau-Ming Chen ◽  
Ching-Hsuan Wu ◽  
Pei-Hsuan Chung ◽  
Chung-Hsiung Sui
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Southern Oscillation ◽  
Relative Vorticity ◽  
La Niña ◽  
Positive Vorticity ◽  
La Nina

Influences of intraseasonal–interannual oscillations on tropical cyclone (TC) genesis are evaluated by productivity of TC genesis ( PTCG) from the developing (TC d) and nondeveloping (TC n) precursory tropical disturbances (PTDs). A PTD is identified by a cyclonic tropical disturbance with a strong-enough intensity, a large-enough maximum center, and a long-enough lifespan. The percentage value of PTDs evolving into TC d is defined as PTCG. The analysis is performed over the western North Pacific (WNP) basin during the 1990–2014 warm season (May–September). The climatological PTCG in the WNP basin is 0.35. Counted in a common period, mean numbers of PTDs in the favorable and unfavorable conditions of climate oscillations for TC genesis [such as equatorial Rossby waves (ERWs), the Madden–Julian oscillation (MJO), and El Niño–Southern Oscillation (ENSO)], all exhibit a stable value close to the climatological mean [~31 (100 days)−1]. However, PTCG increases (decreases) during the phases of positive-vorticity (negative-vorticity) ERWs, the active (inactive) MJO, and El Niño (La Niña) years. PTCG varies from 0.17 in the most unfavorable environment (La Niña, inactive MJO, and negative-vorticity ERW) to 0.56 in the most favorable environment (El Niño, active MJO, and positive-vorticity ERW). ERWs are most effective in modulating TC genesis, especially in the negative-vorticity phases. Overall, increased PTCG is facilitated with strong and elongated 850-hPa relative vorticity overlapping a cyclonic shear line pattern, while decreased PTCG is related to weak relative vorticity. Relative vorticity acts as the most important factor to modulate PTCG, when compared with vertical wind shear and 700-hPa relative humidity.

scholarly journals Improved Simulation of Tropical Cyclone Responses to ENSO in the Western North Pacific in the High-Resolution GFDL HiFLOR Coupled Climate Model*

2016 ◽  
Vol 29 (4) ◽  
pp. 1391-1415 ◽  
Author(s):  
Wei Zhang ◽  
Gabriel A. Vecchi ◽  
Hiroyuki Murakami ◽  
Thomas Delworth ◽  
Andrew T. Wittenberg ◽  
...  
Keyword(s):  
High Resolution ◽  
Tropical Cyclone ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Walker Circulation ◽  
La Niña ◽  
Sea Surface ◽  
La Nina

Abstract This study aims to assess whether, and the extent to which, an increase in atmospheric resolution of the Geophysical Fluid Dynamics Laboratory (GFDL) Forecast-Oriented Low Ocean Resolution version of CM2.5 (FLOR) with 50-km resolution and the High-Resolution FLOR (HiFLOR) with 25-km resolution improves the simulation of the El Niño–Southern Oscillation (ENSO)–tropical cyclone (TC) connections in the western North Pacific (WNP). HiFLOR simulates better ENSO–TC connections in the WNP including TC track density, genesis, and landfall than FLOR in both long-term control experiments and sea surface temperature (SST)- and sea surface salinity (SSS)-restoring historical runs (1971–2012). Restoring experiments are performed with SSS and SST restored to observational estimates of climatological SSS and interannually varying monthly SST. In the control experiments of HiFLOR, an improved simulation of the Walker circulation arising from more realistic SST and precipitation is largely responsible for its better performance in simulating ENSO–TC connections in the WNP. In the SST-restoring experiments of HiFLOR, more realistic Walker circulation and steering flow during El Niño and La Niña are responsible for the improved simulation of ENSO–TC connections in the WNP. The improved simulation of ENSO–TC connections with HiFLOR arises from a better representation of SST and better responses of environmental large-scale circulation to SST anomalies associated with El Niño or La Niña. A better representation of ENSO–TC connections in HiFLOR can benefit the seasonal forecasting of TC genesis, track, and landfall; improve understanding of the interannual variation of TC activity; and provide better projection of TC activity under climate change.

scholarly journals Statistical Analysis of Tropical Cyclones in the Solomon Islands

2018 ◽  
Author(s):  
Edward Maru ◽  
Taiga Shibata ◽  
Kosuke Ito
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Solomon Islands ◽  
Climatic Variability ◽  
Vertical Wind Shear ◽  
Longwave Radiation ◽  
Relative Vorticity

This paper examines the tropical cyclone (TC) activity in Solomon Islands (SI) using the best track data from Tropical Cyclone Warning Centre Brisbane and Regional Specialized Meteorological Centre Nadi. The long-term trend analysis showed that the frequency of TCs has been decreasing in this region while average TC intensity becomes strong. Then, the datasets were classified according to the phase of Madden-Julian Oscillation (MJO) and the index of El Nino Southern Oscillation (ENSO) provided by Bureau of Meteorology. The MJO has sufficiently influenced TC activity in the SI region with more genesis occurring in phases 6-8, in which the lower outgoing longwave radiation indicates enhanced convective activity. In contrast, TC genesis occurs less frequently in phases 1, 2, and 5. As for the influence of ENSO, more TCs are generated in El Nino period. The TC genesis locations during El Nino (La Nina) period were significantly displaced to the north (south) over SI region. TCs generated during El Nino condition tended to be strong. This paper also argues the modulation in terms of seasonal climatic variability of large-scale environmental conditions such as sea surface temperature, low level relative vorticity, vertical wind shear, and upper level divergence.

scholarly journals Tropical cyclone genesis in the Southern Hemisphere and its relationship with the ENSO

2009 ◽  
Vol 27 (6) ◽  
pp. 2523-2538 ◽  
Author(s):  
Y. Kuleshov ◽  
F. Chane Ming ◽  
L. Qi ◽  
I. Chouaibou ◽  
C. Hoareau ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Geographical Distribution ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Vertical Wind Shear ◽  
La Niña ◽  
The South ◽  
La Nina ◽  
South Indian

Abstract. Tropical cyclogenesis climatology over the South Indian and South Pacific Oceans has been developed using a new tropical cyclone (TC) archive for the Southern Hemisphere, and changes in geographical distribution of areas favourable for TC genesis related to changes in the El Niño-Southern Oscillation (ENSO) phases have been investigated. To explain these changes, large-scale environmental variables which influence TC genesis and development such as sea surface temperatures (SSTs), relative humidity in mid-troposphere, vertical wind shear and lower tropospheric vorticity have been examined. In the South Indian Ocean, reduction of TC genesis in the western part of the basin and its increase in the eastern part as well as displacement of the area favourable for TC genesis further away from the equator during La Niña events compared to El Niño events can be explained by changes in geographical distribution of relative humidity and vorticity across the basin as primary contributors; positive anomalies of SSTs observed during La Niña seasons in the eastern part of the basin additionally contribute to enhanced cyclogenesis near the Western Australia. In the South Pacific Ocean, changes in geographical distribution of relative humidity and vorticity appear to be the key large-scale environmental factors responsible for enhanced TC genesis in the eastern (western) part of the basin as well as for the northeast (southwest) shift of points of cyclogenesis during El Niño (La Niña) events, with vertical wind shear and SSTs as additional contributing large-scale environmental variables.

scholarly journals Different El Niño Types and Tropical Cyclone Landfall in East Asia

2012 ◽  
Vol 25 (19) ◽  
pp. 6510-6523 ◽  
Author(s):  
Wei Zhang ◽  
H.-F. Graf ◽  
Yee Leung ◽  
Michael Herzog
Keyword(s):  
Tropical Cyclone ◽  
East Asia ◽  
El Niño ◽  
El Nino ◽  
The Philippines ◽  
La Niña ◽  
Malay Peninsula ◽  
Cp El Niño ◽  
La Nina ◽  
Ep El Niño

Abstract This study examines whether there exist significant differences in tropical cyclone (TC) landfall between central Pacific (CP) El Niño, eastern Pacific (EP) El Niño, and La Niña during the peak TC season (June–October) and how and to what extent CP El Niño influences TC landfall over East Asia for the period 1961–2009. The peak TC season is subdivided into summer [June–August (JJA)] and autumn [September–October (SO)]. The results are summarized as follows: (i) during the summer of CP El Niño years, TCs are more likely to make landfall over East Asia because of a strong easterly steering flow anomaly induced by the westward shift of the subtropical high and northward-shifted TC genesis. In particular, TCs have a greater probability of making landfall over Japan and Korea during the summer of CP El Niño years. (ii) In the autumn of CP El Niño years, TC landfall in most areas of East Asia, especially Indochina, the Malay Peninsula, and the Philippines, is likely to be suppressed because the large-scale circulation resembles that of EP El Niño years. (iii) During the whole peak TC season [June–October (JJASO)] of CP El Niño years, TCs are more likely to make landfall over Japan and Korea. TC landfall in East Asia as a whole has an insignificant association with CP El Niño during the peak TC season. In addition, more (less) TCs are likely to make landfall in China, Indochina, the Malay Peninsula, and the Philippines during the peak TC season of La Niña (EP El Niño) years.

ENSO-Modulated Cyclogenesis over the Bay of Bengal*

2013 ◽  
Vol 26 (24) ◽  
pp. 9806-9818 ◽  
Author(s):  
Clifford S. Felton ◽  
Bulusu Subrahmanyam ◽  
V. S. N. Murty
Keyword(s):  
Tropical Cyclone ◽  
Relative Humidity ◽  
El Niño ◽  
El Nino ◽  
Tropical Cyclone Activity ◽  
La Niña ◽  
Sea Surface ◽  
Cyclone Activity ◽  
La Nina ◽  
Sst Anomalies

Abstract The role of the El Niño–Southern Oscillation (ENSO) on the modulation of tropical cyclone activity over the Bay of Bengal (BoB) for the 1979–2011 period is examined. It is shown that Niño-3.4 sea surface temperature (SST) anomalies are negatively correlated with the BoB tropical cyclone activity to a statistically significant percentage by a lead time of 5 months. Composites of 10-m zonal winds exhibit greater variance during La Niña events, favoring the development of low-level cyclonic vorticity. Low vertical wind shear over the central and northern BoB also aids in the development of tropical cyclones during La Niña events. Increased relative humidity is the result of enhanced moisture transport and higher precipitable water under La Niña conditions. Furthermore, storm-relative composites of relative humidity show stronger moisture pulses over the BoB during La Niña. The enhanced moisture associated with tropical cyclogenesis likely aids in the development and strengthening of the systems. ENSO forces modulations in oceanic conditions as well. The observed negative (positive) SST anomalies during La Niña (El Niño) could be seen as the result of increased (decreased) net heat flux across the sea surface. Tropical cyclone activity varies between El Niño and La Niña as a result of anomalous wind and moisture patterns during each ENSO phase.

scholarly journals Impacts of ENSO on Philippine Tropical Cyclone Activity

2016 ◽  
Vol 29 (5) ◽  
pp. 1877-1897 ◽  
Author(s):  
Irenea L. Corporal-Lodangco ◽  
Lance M. Leslie ◽  
Peter J. Lamb
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
The Philippines ◽  
Life Cycles ◽  
La Niña ◽  
Cyclone Activity ◽  
La Nina ◽  
The Mean

Abstract This study investigates the El Niño–Southern Oscillation (ENSO) contribution to Philippine tropical cyclone (TC) variability, for a range of quarterly TC metrics. Philippine TC activity is found to depend on both ENSO quarter and phase. TC counts during El Niño phases differ significantly from neutral phases in all quarters, whereas neutral and La Niña phases differ only in January–March and July–September. Differences in landfalls between neutral and El Niño phases are significant in January–March and October–December and in January–March for neutral and La Niña phases. El Niño and La Niña landfalls are significantly different in April–June and October–December. Philippine neutral and El Niño TC genesis cover broader longitude–latitude ranges with similar long tracks, originating farther east in the western North Pacific. In El Niño phases, the mean eastward displacement of genesis locations and more recurving TCs reduce Philippine TC frequencies. Proximity of La Niña TC genesis to the Philippines and straight-moving tracks in April–June and October–December increase TC frequencies and landfalls. Neutral and El Niño accumulated cyclone energy (ACE) values are above average, except in April–June of El Niño phases. Above-average quarterly ACE in neutral years is due to increased TC frequencies, days, and intensities, whereas above-average El Niño ACE in July–September is due to increased TC days and intensities. Below-average La Niña ACE results from fewer TCs and shorter life cycles. Longer TC durations produce slightly above-average TC days in July–September El Niño phases. Fewer TCs than neutral years, as well as shorter TC durations, imply less TC days in La Niña phases. However, above-average TC days occur in October–December as a result of higher TC frequencies.

scholarly journals Changes in Western Pacific Tropical Cyclones Associated with the El Niño–Southern Oscillation Cycle

2012 ◽  
Vol 25 (17) ◽  
pp. 5864-5878 ◽  
Author(s):  
Richard C. Y. Li ◽  
Wen Zhou
Keyword(s):  
Tropical Cyclones ◽  
El Niño ◽  
Wind Shear ◽  
El Nino ◽  
Southern Oscillation ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
La Niña ◽  
El Nino Southern Oscillation ◽  
La Nina

Abstract This study examines the interannual variability of three groups of tropical cyclones (TCs)—super typhoons (STYs), typhoons (TYs), and tropical storms and tropical depressions (TSTDs)—and their relationship with the El Niño–Southern Oscillation (ENSO). Both wavelet analysis and correlation studies of upper-ocean heat content reveal significant differences for the three types of TCs. In particular, an increase (decrease) in the frequency of STYs is usually associated with the mature phase of El Niño (La Niña) events, while the converse is true for TSTDs. In contrast, the frequency of TYs increases (decreases) during the transition period from La Niña to El Niño (El Niño to La Niña) events. The results suggest that the timing with which ENSO impacts STYs, TYs, and TSTDs varies and that their corresponding changes in frequency closely follow the evolution of the ENSO cycle. Empirical orthogonal function analysis is also conducted to investigate the impact of different environmental factors influenced by ENSO on TCs. The vertical wind shear and moist static energy associated with ENSO are identified as the dominant factors that control the frequency of STYs. In comparison, the frequency of TYs is found to be closely related to the relative vorticity and vertical wind shear associated with both the transition phase of ENSO and with other types of climate variability.

scholarly journals Combined effects of ENSO and PDO on Activity of Major Hurricanes in Eastern North Pacific

2021 ◽  
Author(s):  
Chaoming Huang ◽  
Hailong Liu ◽  
Xidong Wang ◽  
Juncheng Zuo ◽  
Ruyun Wang
Keyword(s):  
El Niño ◽  
North Pacific ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Vertical Wind Shear ◽  
Open Ocean ◽  
Hadley Cell ◽  
La Niña ◽  
La Nina

Abstract Major hurricanes (MHs) in the eastern North Pacific (ENP) in 1970-2018 were clustered into 3 categories with different quantity, intensity, lifetime, translation speed, track and large-scale environmental fields. MHs in all three clusters are more active in the Pacific Decadal Oscillation (PDO) warm phase than cold phase period. There are two clusters that their relationship with El Niño Southern Oscillation (ENSO) were modulated by PDO. The first cluster generates and develops in the open ocean and has an increasing trend of annual frequency, which is more active during El Niño years than during La Niña years in the PDO cold phase, but equally active in the PDO warm phase. The second cluster generates in the nearshore and translate rapidly into the ocean, which is more active during La Niña years than during El Niño years in the PDO warm phase, but equally active in the PDO cold phase. The PDO modulation mainly result from that MHs are obviously active during La Niña years in the PDO warm phase, which can be explained by local warming sea surface temperature, lower vertical wind shear, increasing vorticity and weakening sinking branch of circulation like Hadley cell. Therefore, PDO modulation cannot be ignored when predict the activity of tropical cyclone in ENP, especially for MHs that enters the open ocean and threat the islands such as the Hawaiian Islands.

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