scholarly journals Statistical analysis of satellite-observed trade wind cloud clusters in the western North Pacific

Tellus ◽  
1973 ◽  
Vol 25 (4) ◽  
pp. 313-336 ◽  
Author(s):  
KNOX T. WILLIAMS ◽  
WILLIAM M. GRAY
Keyword(s):  
Statistical Analysis ◽  
North Pacific ◽  
Western North Pacific ◽  
Trade Wind ◽  
Cloud Clusters

Recent decrease in genesis productivity of tropical cloud clusters over the Western North Pacific

2018 ◽  
Vol 52 (9-10) ◽  
pp. 5819-5831 ◽  
Author(s):  
Haikun Zhao ◽  
Shaohua Chen ◽  
G. B. Raga ◽  
Philip J. Klotzbach ◽  
Liguang Wu
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Cloud Clusters

scholarly journals Multidecadal Variability of Tropical Cyclone Rapid Intensification in the Western North Pacific

2015 ◽  
Vol 28 (9) ◽  
pp. 3806-3820 ◽  
Author(s):  
Xidong Wang ◽  
Chunzai Wang ◽  
Liping Zhang ◽  
Xin Wang
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Wind Shear ◽  
Western North Pacific ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Trade Wind ◽  
Rapid Intensification ◽  
Multidecadal Variability ◽  
Heat Potential

Abstract This study investigates the variation of tropical cyclone (TC) rapid intensification (RI) in the western North Pacific (WNP) and its relationship with large-scale climate variability. RI events have exhibited strikingly multidecadal variability. During the warm (cold) phase of the Pacific decadal oscillation (PDO), the annual RI number is generally lower (higher) and the average location of RI occurrence tends to shift southeastward (northwestward). The multidecadal variations of RI are associated with the variations of large-scale ocean and atmosphere variables such as sea surface temperature (SST), tropical cyclone heat potential (TCHP), relative humidity (RHUM), and vertical wind shear (VWS). It is shown that their variations on multidecadal time scales depend on the evolution of the PDO phase. The easterly trade wind is strengthened during the cold PDO phase at low levels, which tends to make equatorial warm water spread northward into the main RI region rsulting from meridional ocean advection associated with Ekman transport. Simultaneously, an anticyclonic wind anomaly is formed in the subtropical gyre of the WNP. This therefore may deepen the depth of the 26°C isotherm and directly increase TCHP over the main RI region. These thermodynamic effects associated with the cold PDO phase greatly support RI occurrence. The reverse is true during the warm PDO phase. The results also indicate that the VWS variability in the low wind shear zone along the monsoon trough may not be critical for the multidecadal modulation of RI events.

scholarly journals The Role of Trade Wind Surges in Tropical Cyclone Formations in the Western North Pacific

2010 ◽  
Vol 138 (11) ◽  
pp. 4120-4134 ◽  
Author(s):  
Lung-Yao Chang ◽  
Kevin K. W. Cheung ◽  
Cheng-Shang Lee
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Mesoscale Convective Systems ◽  
Trade Wind ◽  
Convective Systems ◽  
Short Period ◽  
Mesoscale Convective ◽  
Wind Surge

Abstract A total of 40 out of 531 tropical cyclones that formed in the western North Pacific during 1986–2005 have accompanied trade wind surges located 5°–15° latitude to the north of the pretropical cyclone disturbance centers. Composite and empirical orthogonal function analyses indicate that the trade wind surges are related to a midlatitude eastward-moving high pressure system often found during the East Asian winter monsoon. Therefore, these trade wind surge tropical cyclones tend to occur in late season (with one-third of them in December), and at lower latitudes (7° latitude lower than the climatological average formation position). The evolution of mesoscale features during formation of trade wind surge tropical cyclones is examined. Various satellite datasets show similar mesoscale patterns during their formations. A few convective lines form by convergence between the trade wind surges and the strengthening cyclonic circulation associated with incipient vortex within the 24 h before formation. Some mesoscale convective systems are embedded in the convective line with lifetimes of about 5 h, and these are illustrated through case studies. Formations usually occur when the trade winds start to decrease in magnitude and a short period after the major episodes of convection in the convective lines and mesoscale convective systems. The relationships between the temporal variability of synoptic-scale trade wind surges, the mesoscale features, and associated tropical cyclone formations are discussed.

scholarly journals A Statistical Analysis of Tropical Upper-Tropospheric Trough Cells over the Western North Pacific during 2006–15

2018 ◽  
Vol 57 (11) ◽  
pp. 2469-2483 ◽  
Author(s):  
Dian Wen ◽  
Ying Li ◽  
Da-Lin Zhang ◽  
Lin Xue ◽  
Na Wei
Keyword(s):  
Surface Layer ◽  
Statistical Analysis ◽  
Pacific Ocean ◽  
Life Span ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Peak Frequency ◽  
Cyclonic Vorticity ◽  
Mature Phase

AbstractA statistical analysis of tropical upper-tropospheric trough (TUTT) cells over the western North Pacific Ocean (WNP) during 2006 to 2015 is performed using the NCEP Final reanalysis. A total of 369 TUTT-cell events or 6836 TUTT cells are identified, with a peak frequency in July. Most TUTT cells form to the east of 150°E and then move southwestward with a mean speed of 6.6 m s−1 and a mean life span of 4.4 days. About 75% of the TUTT cells have radii of <500 km with 200-hPa central heights of <1239.4 dam. In general, TUTT cells exhibit negative height anomalies above 450 hPa, with their peak amplitudes at 200 hPa, pronounced cold anomalies in the 650–200-hPa layer, and significant cyclonic vorticity in the 550–125-hPa layer. A comparison of the composite TUTT cells among the eastern, central, and western WNP areas shows the generation of an intense cold-cored vortex as a result of the southward penetration of a midlatitude trough into a climatological TUTT over the eastern WNP region. The TUTT cell with pronounced rotation is cut off from the midlatitude westerlies after moving to the central WNP region, where it enters its mature phase, under the influence of northeasterly flow. The TUTT cell weakens in rotation and shrinks in size, diminishing within the TUTT after arriving at the western WNP region. Results suggest that, although most TUTT cells may diminish before reaching the western WNP, their vertical influences may extend to the surface layer and last longer than their signals at 200 hPa.

scholarly journals Tropical Cyclogenesis Detection in the North Pacific Using the Deviation Angle Variance Technique

2015 ◽  
Vol 30 (6) ◽  
pp. 1663-1672 ◽  
Author(s):  
Kimberly M. Wood ◽  
Oscar G. Rodríguez-Herrera ◽  
Elizabeth A. Ritchie ◽  
Miguel F. Piñeros ◽  
Ivan Arias Hernández ◽  
...  
Keyword(s):  
False Alarm ◽  
False Alarm Rate ◽  
Tropical Cyclones ◽  
Median Time ◽  
North Pacific ◽  
Western North Pacific ◽  
Tropical Cyclogenesis ◽  
Deviation Angle ◽  
Variance Technique ◽  
Cloud Clusters

Abstract The deviation angle variance technique (DAV-T) for genesis detection is applied in the western and eastern North Pacific basins. The DAV-T quantifies the axisymmetric organization of cloud clusters using infrared brightness temperature. Since axisymmetry is typically correlated with intensity, the technique can be used to identify relatively high levels of organization at early stages of storm life cycles associated with tropical cyclogenesis. In addition, the technique can be used to automatically track cloud clusters that exhibit signs of organization. In the western North Pacific, automated tracking results for the 2009–11 typhoon seasons show that for a false alarm rate of 25.6%, 96.8% of developing tropical cyclones are detected with a median time of 18.5 h before the cluster reaches an intensity of 30 knots (kt; 1 kt = 0.51 m s−1) in the Joint Typhoon Warning Center best track at a DAV threshold of 1750°2. In the eastern North Pacific, for a false alarm rate of 38.0%, the system detects 92.9% of developing tropical cyclones with a median time of 1.25 h before the cluster reaches an intensity of 30 kt in the National Hurricane Center best track during the 2009–11 hurricane seasons at a DAV threshold of 1650°2. A significant decrease in tracked nondeveloping clusters occurs when a second organization threshold is introduced, particularly in the western North Pacific.

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