Comparison of Madden–Julian Oscillation Modulation on tropical-cyclone genesis over the South China Sea and Western North Pacific under different El Niño Southern Oscillation conditions

2020 ◽  
Author(s):  
Chengyao Ye ◽  
Liping Deng ◽  
Wan-Ru Huang ◽  
Jinghua Chen
Keyword(s):  
Tropical Cyclone ◽  
South China Sea ◽  
South China ◽  
North Pacific ◽  
Western North Pacific ◽  
Southern Oscillation ◽  
The South China Sea ◽  
Dominant Factor ◽  
The South ◽  
China Sea

<p>This paper explores the modulation by Madden–Julian Oscillation (MJO) on tropical-cyclone (TC; hereafter, MJO TC) genesis over the Western North Pacific (WNP) and the South China Sea (SCS) under different El Niño Southern Oscillation (ENSO) conditions. Analyses used Joint Typhoon Warning Center (JTWC) Best Track data, the Real-Time Multivariate MJO (RMM) index, and European Center for Medium-Range Weather Forecasts (ECMWF) Interim (ERA-Interim) reanalysis data. Results showed that MJO has significant modulation on both SCS and WNP TC genesis in neutral years, with more (fewer) TCs forming during active (inactive) MJO phases. However, during El Niño and La Niña years, modulation over the two regions differs. Over the SCS, the modulation of TC genesis is strong in La Niña years, while it becomes weak in El Niño years. Over the WNP, MJO has stronger influence on TC genesis in El Niño years compared to that in La Niña years. Related Genesis Potential Index (GPI) analysis suggests that midlevel moisture is the primary factor for MJO modulation on SCS TC genesis in La Niña years, and vorticity is the secondary factor. Over the WNP, midlevel moisture is the dominant factor for MJO TC genesis modulation during El Niño years. The main reason is increased water-vapor transport from the Bay of Bengal associated with the active MJO phase related westerly wind anomalies; these features are a significant presence over the SCS during La Niña years, and over the WNP during El Niño years.</p>

scholarly journals Climatological analysis of passage-type tropical cyclones from the Western North Pacific into the South China Sea

2017 ◽  
Vol 28 (3) ◽  
pp. 327-343 ◽  
Author(s):  
Jau-Ming Chen ◽  
Pei-Hua Tan ◽  
Liang Wu ◽  
Jin-Shuen Liu ◽  
Hui-Shan Chen
Keyword(s):  
South China Sea ◽  
Tropical Cyclones ◽  
South China ◽  
North Pacific ◽  
Western North Pacific ◽  
The South China Sea ◽  
The South ◽  
China Sea

scholarly journals Two Distinctive Processes for Abnormal Spring to Summer Transition over the South China Sea

2017 ◽  
Vol 30 (23) ◽  
pp. 9665-9678 ◽  
Author(s):  
Renguang Wu ◽  
Zhuoqi He
Keyword(s):  
South China Sea ◽  
South China ◽  
North Pacific ◽  
Western North Pacific ◽  
The South China Sea ◽  
The South ◽  
Maritime Continent ◽  
China Sea ◽  
Tropical Western North Pacific ◽  
Sst Anomalies

The period from April to June signifies the transition from spring to summer over the South China Sea (SCS). The present study documents two distinct processes for abnormal spring to summer transition over the SCS. One process is related to large-scale sea surface temperature (SST) anomalies in the tropical Indo-Pacific region. During spring of La Niña decaying years, negative SST anomalies in the equatorial central Pacific (ECP) and the southwestern tropical Indian Ocean (TIO) coexist with positive SST anomalies in the tropical western North Pacific. Negative ECP SST anomalies force an anomalous Walker circulation, negative southwestern TIO SST anomalies induce anomalous cross-equatorial flows from there, and positive tropical western North Pacific SST anomalies produce a Rossby wave–type response to the west. Together, they contribute to enhanced convection and an anomalous lower-level cyclone over the SCS, leading to an advanced transition to summer there. The other process is related to regional air–sea interactions around the Maritime Continent. Preceding positive ECP SST anomalies induce anomalous descent around the Maritime Continent, leading to SST increase in the SCS and southeast TIO. An enhanced convection region moves eastward over the south TIO during spring and reaches the area northwest of Australia in May. This enhances descent over the SCS via an anomalous cross-equatorial overturning circulation and contributes to further warming in the SCS. The SST warming in turn induces convection over the SCS, leading to an accelerated transition to summer. Analysis shows that the above two processes are equally important during 1979–2015.

scholarly journals Climate shift of the South China Sea summer monsoon onset in 1993/1994 and its physical causes

2019 ◽  
Vol 54 (3-4) ◽  
pp. 1819-1827
Author(s):  
Ailan Lin ◽  
Renhe Zhang
Keyword(s):  
South China Sea ◽  
South China ◽  
North Pacific ◽  
Early Onset ◽  
Western North Pacific ◽  
The South China Sea ◽  
The South ◽  
Climate Shift ◽  
China Sea ◽  
Zonal Winds

AbstractThe characteristics of anomalous circulations during spring associated with the climate shift of the South China Sea summer monsoon (SCSSM) onset in 1993/1994 and its physical causes are investigated. It is found that the interdecadal shift of SCSSM onset happened in 1993/1994 is related closely to the 850 hPa zonal wind anomalies over the area around Kalimantan Island. Easterly (westerly) anomalies over Kalimantan Island enhance (weaken) subtropical high over the western North Pacific, leading to the late (early) onset of SCSSM in 1979–1993 (1994–2013). The sea surface temperature anomalies (SSTAs) in the key region 140°–150° E, 5° S–2.5° N influence the interdecadal change of zonal winds over Kalimantan Island. The positive SSTAs over this key region in 1994–2013 force convergence toward the region at low-level and form significant westerly anomalies near Kalimantan Island located to the west of the key region. The negative anomalies of meridional gradient of zonal winds over the South China Sea region increase the atmospheric vorticity over there significantly and result in the weakening and retreating eastward of the subtropical high over the western North Pacific, which is conducive to the early onset of SCSSM.

scholarly journals Evaluation of the ability of the Chinese stalagmite δ<sup>18</sup>O to record the variation in atmospheric circulation during the second half of the 20th century

2014 ◽  
Vol 10 (3) ◽  
pp. 975-985 ◽  
Author(s):  
S. Nan ◽  
M. Tan ◽  
P. Zhao
Keyword(s):  
Water Vapor ◽  
South China Sea ◽  
South China ◽  
Bay Of Bengal ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
The South China Sea ◽  
The South ◽  
China Sea

Abstract. The Chinese stalagmite δ18O (δ18Ocs) has provoked debate worldwide over the past few years due to its lack of quantitative calibration, leading us to questions of whether δ18Ocs records a local or large-scale signal and whether δ18Ocs records the signal of a single remote water vapor source or multiple water vapor sources. In this study, we observe all of the δ18Ocs trends within the instrumental period to verify whether they possess a common trend, which could be used as a basis to determine whether the trends reflect the large-scale signal together or whether each trend reflects the local signal. The results show that most of the δ18Ocs experienced a linear increase from 1960 to 1994, which may indicate that the δ18Ocs could record a trend occurring in large-scale atmosphere circulations. We then quantitatively describe the proportion of water vapor transport (WVT) from different source regions. Using the NCEP/NCAR (National Centers for Environmental Protection/National Center for Atmospheric Research) reanalysis data from 1960 to 1994, the ratios of the intensities of three WVTs from the Bay of Bengal, the South China Sea, and the western North Pacific during the summer are calculated. We define RSCS/BOB as the ratio of the WVT intensities from the South China Sea to those from the Bay of Bengal, RWNP/BOB as the ratio of the WVT intensities from the western North Pacific to those from the Bay of Bengal, and RWNP/SCS as the ratio of the WVT intensities from the western North Pacific to those from the South China Sea. The significant decadal increase occurs in the time series of RWNP/BOB and RWNP/SCS, most likely resulting from the strengthening of the WVT from the western North Pacific in the late 1970s due to the western Pacific subtropical high that extended westward. Further analysis indicates that when the equatorial central and eastern Pacific is in the El Niño phase, the sea surface temperature (SST) in the tropical Indian Ocean, the Bay of Bengal, and the South China Sea is high, and the SST at the middle latitudes in the North Pacific is low, then the RWNP/BOB and RWNP/SCS values tend to be high. After the late 1970s, the equatorial central and eastern Pacific have often been in the El Niño phase. Therefore, we confirm that the δ18Ocs primarily records the variation in atmospheric circulation during the second half of the 20th century.

scholarly journals The Philippines–Taiwan Oscillation: Monsoonlike Interannual Oscillation of the Subtropical–Tropical Western North Pacific Wind System and Its Impact on the Ocean

2012 ◽  
Vol 25 (5) ◽  
pp. 1597-1618 ◽  
Author(s):  
Y.-L. Chang ◽  
L.-Y. Oey
Keyword(s):  
South China Sea ◽  
South China ◽  
North Pacific ◽  
Western North Pacific ◽  
The Philippines ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Interannual Oscillation ◽  
Tropical Western North Pacific

Tide gauge and satellite data reveal an interannual oscillation of the ocean’s thermoclines east of the Philippines and Taiwan, forced by a corresponding oscillation in the wind stress curl. This so-called Philippines–Taiwan Oscillation (PTO) is shown to control the interannual variability of the circulation of the subtropical and tropical western North Pacific. The PTO shares some characteristics of known Pacific indices, for example, Niño-3.4. However, unlike PTO, these other indices explain only portions of the western North Pacific circulation. The reason is because of the nonlinear nature of the forcing in which mesoscale (ocean) eddies play a crucial role. In years of positive PTO, the thermocline east of the Philippines rises while east of Taiwan it deepens. This results in a northward shift of the North Equatorial Current (NEC), increased vertical shear of the Subtropical Countercurrent (STCC)/NEC system, increased eddy activity dominated by warm eddies in the STCC, increased Kuroshio transport off the northeastern coast of Taiwan into the East China Sea, increased westward inflow through Luzon Strait into the South China Sea, and cyclonic circulation and low sea surface height anomalies in the South China Sea. The reverse applies in years of negative PTO.

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