THE VARIATION CHARACTERISTICS OF 10～30 DAYS OSCILLATION INTENSITY OF SPRING OVER THE SOUTH CHINA SEA-WESTERN PACIFIC OCEAN AND THEIR EFFECTS ON THE SOUTH CHINA SEA SUMMER MONSOON ONSET
LI Chun-hui
PAN Wei-juan
LI Xia
LIU Yan
Abstract：Based on the NCEP reanalysis data,the 10～30 days significant sub-seasonal variability period of spring (March-May) convection over the South China Sea-Western Pacific Ocean is revealed.On interannual scale,there exist a negative significant correlation between the intensity variation of the 10～30 days oscillation over the South China Sea-Western Pacific Ocean regions (SCSWP_SISO) and the South China Sea summer monsoon onset.When the sea surface temperature anomalies (SSTA) of the Philippines and the western Pacific Ocean is high,the central and east equatorial Pacific SSTA is low,the crossing equatorial currents of Somali and around 110～120 °E areas and westerly winds from the tropical Indian Ocean will strengthen.Meanwhile,an obvious anomalous cyclonic circulation over the South China SeaWestern Pacific Ocean occurs,along with enhancing vertical ascending motion,increasing water vapor anomalies and strengthening wind vertical shear,which results in enhancing SCSWP_SISO.Due to the SCSWP_SISO increase,propagation of an anomalous cyclone from south to north and west to east leads to early withdrawal of lower subtropical high from the South China Sea and the South China Sea summer monsoon breaks out earlier.And vice versa.Under the background of different decadal,SCSWP_SISO has experienced the change of the weak,the weaker and strong,while the influencing factors are not entirely consistent.In the first stage (1958-1976),the negative SSTA over the South China Sea-Western Pacific and abnormal subsidence,decreasing water vapor-convection play a leading role.In the second stage (1977-1993),the main factors are the abnormal cold SST in the Middle East Pacific and local anomalies reducing vertical shear of wind field.In the third stage (1994-1994),the overall warming SST in the tropical,abnormal increasing vertical shear of wind field and convection are the key factors.But,as the SCSWP SISO increases,its relation with the date of the South China Sea summer monsoon onset is a declining trend.
Keywords：the South China Sea-Western Pacific Ocean10～30 days oscillationthe South China Sea summer monsoon onsetearly and later
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：10( 43-52 )