scholarly journals Cluster Analysis of Typhoon Tracks. Part II: Large-Scale Circulation and ENSO

2007 ◽  
Vol 20 (14) ◽  
pp. 3654-3676 ◽  
Author(s):  
Suzana J. Camargo ◽  
Andrew W. Robertson ◽  
Scott J. Gaffney ◽  
Padhraic Smyth ◽  
Michael Ghil
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Vertical Wind Shear ◽  
Longwave Radiation ◽  
Probabilistic Clustering ◽  
Consistent Picture ◽  
Regression Mixture ◽  
Typhoon Tracks

Abstract A new probabilistic clustering method, based on a regression mixture model, is used to describe tropical cyclone (TC) propagation in the western North Pacific (WNP). Seven clusters were obtained and described in Part I of this two-part study. In Part II, the present paper, the large-scale patterns of atmospheric circulation and sea surface temperature associated with each of the clusters are investigated, as well as associations with the phase of the El Niño–Southern Oscillation (ENSO). Composite wind field maps over the WNP provide a physically consistent picture of each TC type, and of its seasonality. Anomalous vorticity and outgoing longwave radiation indicate changes in the monsoon trough associated with different types of TC genesis and trajectory. The steering winds at 500 hPa are more zonal in the straight-moving clusters, with larger meridional components in the recurving ones. Higher values of vertical wind shear in the midlatitudes also accompany the straight-moving tracks, compared to the recurving ones. The influence of ENSO on TC activity over the WNP is clearly discerned in specific clusters. Two of the seven clusters are typical of El Niño events; their genesis locations are shifted southeastward and they are more intense. The largest cluster is recurving, located northwestward, and occurs more often during La Niña events. Two types of recurving and one of straight-moving tracks occur preferentially when the Madden–Julian oscillation is active over the WNP region.

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 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 Cluster Analysis of Typhoon Tracks. Part I: General Properties

2007 ◽  
Vol 20 (14) ◽  
pp. 3635-3653 ◽  
Author(s):  
Suzana J. Camargo ◽  
Andrew W. Robertson ◽  
Scott J. Gaffney ◽  
Padhraic Smyth ◽  
Michael Ghil
Keyword(s):  
Tropical Cyclone ◽  
Mixture Model ◽  
Large Scale ◽  
Clustering Algorithm ◽  
Southern Oscillation ◽  
Companion Paper ◽  
Probabilistic Clustering ◽  
East And Southeast Asia ◽  
Regression Mixture ◽  
Typhoon Tracks

Abstract A new probabilistic clustering technique, based on a regression mixture model, is used to describe tropical cyclone trajectories in the western North Pacific. Each component of the mixture model consists of a quadratic regression curve of cyclone position against time. The best-track 1950–2002 dataset is described by seven distinct clusters. These clusters are then analyzed in terms of genesis location, trajectory, landfall, intensity, and seasonality. Both genesis location and trajectory play important roles in defining the clusters. Several distinct types of straight-moving, as well as recurving, trajectories are identified, thus enriching this main distinction found in previous studies. Intensity and seasonality of cyclones, though not used by the clustering algorithm, are both highly stratified from cluster to cluster. Three straight-moving trajectory types have very small within-cluster spread, while the recurving types are more diffuse. Tropical cyclone landfalls over East and Southeast Asia are found to be strongly cluster dependent, both in terms of frequency and region of impact. The relationships of each cluster type with the large-scale circulation, sea surface temperatures, and the phase of the El Niño–Southern Oscillation are studied in a companion paper.

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.

scholarly journals Analysis and quantification of ENSO-linked changes in the tropical Atlantic cloud vertical distribution using 14 years of MODIS observations

2019 ◽  
Vol 19 (21) ◽  
pp. 13535-13546
Author(s):  
Nils Madenach ◽  
Cintia Carbajal Henken ◽  
René Preusker ◽  
Odran Sourdeval ◽  
Jürgen Fischer
Keyword(s):  
Time Series ◽  
Vertical Distribution ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Cloud Amount ◽  
Cloud Fraction ◽  
Tropical Atlantic ◽  
High Cloud

Abstract. A total of 14 years (September 2002 to September 2016) of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) monthly mean cloud data are used to quantify possible changes in the cloud vertical distribution over the tropical Atlantic. For the analysis multiple linear regression techniques are used. For the investigated time period significant linear changes were found in the domain-averaged cloud-top height (CTH) (−178 m per decade), the high-cloud fraction (HCF) (−0.0006 per decade), and the low-cloud amount (0.001 per decade). The interannual variability of the time series (especially CTH and HCF) is highly influenced by the El Niño–Southern Oscillation (ENSO). Separating the time series into two phases, we quantified the linear change associated with the transition from more La Niña-like conditions to a phase with El Niño conditions (Phase 2) and vice versa (Phase 1). The transition from negative to positive ENSO conditions was related to a decrease in total cloud fraction (TCF) (−0.018 per decade; not significant) due to a reduction in the high-cloud amount (−0.024 per decade; significant). Observed anomalies in the mean CTH were found to be mainly caused by changes in HCF rather than by anomalies in the height of cloud tops themselves. Using the large-scale vertical motion ω at 500 hPa (from ERA-Interim ECMWF reanalysis data), the observed anomalies were linked to ENSO-induced changes in the atmospheric large-scale dynamics. The most significant and largest changes were found in regions with strong large-scale upward movements near the Equator. Despite the fact that with passive imagers such as MODIS it is not possible to vertically resolve clouds, this study shows the great potential for large-scale analysis of possible changes in the cloud vertical distribution due to the changing climate by using vertically resolved cloud cover and linking those changes to large-scale dynamics using other observations or model data.

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 Large-Scale Mode Impacts on the Sea Level over the Red Sea and Gulf of Aden

2019 ◽  
Vol 11 (19) ◽  
pp. 2224 ◽  
Author(s):  
Kamal A. Alawad ◽  
Abdullah M. Al-Subhi ◽  
Mohammed A. Alsaafani ◽  
Turki M. Alraddadi ◽  
Monica Ionita ◽  
...  
Keyword(s):  
Sea Level ◽  
Red Sea ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Positive Phase ◽  
El Nino Southern Oscillation ◽  
Gulf Of Aden ◽  
The Impact

Falling between seasonal cycle variability and the impact of local drivers, the sea level in the Red Sea and Gulf of Aden has been given less consideration, especially with large-scale modes. With multiple decades of satellite altimetry observations combined with good spatial resolution, the time has come for diagnosis of the impact of large-scale modes on the sea level in those important semi-enclosed basins. While the annual cycle of sea level appeared as a dominant cycle using spectral analysis, the semi-annual one was also found, although much weaker. The first empirical orthogonal function mode explained, on average, about 65% of the total variance throughout the seasons, while their principal components clearly captured the strong La Niña event (1999–2001) in all seasons. The sea level showed a strong positive relation with positive phase El Niño Southern Oscillation in all seasons and a strong negative relation with East Atlantic/West Russia during winter and spring over the study period (1993–2017). We show that the unusually stronger easterly winds that are displaced north of the equator generate an upwelling area near the Sumatra coast and they drive both warm surface and deep-water masses toward the West Indian Ocean and Arabian Sea, rising sea level over the Red Sea and Gulf of Aden. This process could explain the increase of sea level in the basin during the positive phase of El Niño Southern Oscillation events.

scholarly journals Tropical Cyclone Climatology of the South Pacific Ocean and Its Relationship to El Niño–Southern Oscillation

2012 ◽  
Vol 25 (18) ◽  
pp. 6108-6122 ◽  
Author(s):  
Andrew J. Dowdy ◽  
Lixin Qi ◽  
David Jones ◽  
Hamish Ramsay ◽  
Robert Fawcett ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
Large Scale ◽  
Critical Line ◽  
El Nino ◽  
Southern Oscillation ◽  
South Pacific ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
The South

Abstract Climatological features of tropical cyclones in the South Pacific Ocean have been analyzed based on a new archive for the Southern Hemisphere. A vortex tracking and statistics package is used to examine features such as climatological maps of system intensity and the change in intensity with time, average tropical cyclone system movement, and system density. An examination is presented of the spatial variability of these features, as well as changes in relation to phase changes of the El Niño–Southern Oscillation phenomenon. A critical line is defined in this study based on maps of cyclone intensity to describe the statistical geographic boundary for cyclone intensification. During El Niño events, the critical line shifts equatorward, while during La Niña events the critical line is generally displaced poleward. Regional variability in tropical cyclone activity associated with El Niño–Southern Oscillation phases is examined in relation to the variability of large-scale atmospheric or oceanic variables associated with tropical cyclone activity. Maps of the difference fields between different phases of El Niño–Southern Oscillation are examined for sea surface temperature, vertical wind shear, lower-tropospheric vorticity, and midtropospheric relative humidity. Results are also examined in relation to the South Pacific convergence zone. The common region where each of the large-scale variables showed favorable conditions for cyclogenesis coincided with the location of maximum observed cyclogenesis for El Niño events as well as for La Niña years.

scholarly journals The Influence of Large-Scale Climate Variability on Winter Maximum Daily Precipitation over North America

2010 ◽  
Vol 23 (11) ◽  
pp. 2902-2915 ◽  
Author(s):  
Xuebin Zhang ◽  
Jiafeng Wang ◽  
Francis W. Zwiers ◽  
Pavel Ya Groisman
Keyword(s):  
North America ◽  
Climate Variability ◽  
El Niño ◽  
Extreme Precipitation ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Statistical Significance ◽  
Winter Season ◽  
The North

Abstract The generalized extreme value (GEV) distribution is fitted to winter season daily maximum precipitation over North America, with indices representing El Niño–Southern Oscillation (ENSO), the Pacific decadal oscillation (PDO), and the North Atlantic Oscillation (NAO) as predictors. It was found that ENSO and PDO have spatially consistent and statistically significant influences on extreme precipitation, while the influence of NAO is regional and is not field significant. The spatial pattern of extreme precipitation response to large-scale climate variability is similar to that of total precipitation but somewhat weaker in terms of statistical significance. An El Niño condition or high phase of PDO corresponds to a substantially increased likelihood of extreme precipitation over a vast region of southern North America but a decreased likelihood of extreme precipitation in the north, especially in the Great Plains and Canadian prairies and the Great Lakes/Ohio River valley.

scholarly journals Use of a Genesis Potential Index to Diagnose ENSO Effects on Tropical Cyclone Genesis

2007 ◽  
Vol 20 (19) ◽  
pp. 4819-4834 ◽  
Author(s):  
Suzana J. Camargo ◽  
Kerry A. Emanuel ◽  
Adam H. Sobel
Keyword(s):  
Tropical Cyclone ◽  
Relative Humidity ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Vertical Wind Shear ◽  
Vertical Shear ◽  
Interannual Variations ◽  
Genesis Potential Index ◽  
Potential Index

Abstract ENSO (El Niño–Southern Oscillation) has a large influence on tropical cyclone activity. The authors examine how different environmental factors contribute to this influence, using a genesis potential index developed by Emanuel and Nolan. Four factors contribute to the genesis potential index: low-level vorticity (850 hPa), relative humidity at 600 hPa, the magnitude of vertical wind shear from 850 to 200 hPa, and potential intensity (PI). Using monthly NCEP Reanalysis data in the period of 1950–2005, the genesis potential index is calculated on a latitude strip from 60°S to 60°N. Composite anomalies of the genesis potential index are produced for El Niño and La Niña years separately. These composites qualitatively replicate the observed interannual variations of the observed frequency and location of genesis in several different basins. This justifies producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology, to determine which among the factors are most important in causing interannual variations in genesis frequency. Specific factors that have more influence than others in different regions can be identified. For example, in El Niño years, relative humidity and vertical shear are important for the reduction in genesis seen in the Atlantic basin, and relative humidity and vorticity are important for the eastward shift in the mean genesis location in the western North Pacific.

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