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This study investigates the impact of the intraseasonal oscillation (ISO) on tropical cyclone (TC) tracks in the South China Sea (SCS) during 1970-2010. About one third of TCs in the SCS move eastward, while the other two thirds move westward. In the TC genesis peak seasons of June-October (JJASO), the westward moving TCs are controlled by the background TC steering flow of easterly, and the eastward moving TCs by the TC steering flow induced by the ISO. The outgoing longwave radiation and wind fields show that the eastward moving TCs were mostly along the main axis of strong TC steering flow anomaly of westerly associated with the ISO, while the westward moving TCs were only weakly associated with the ISO. An experiment performed with a simple two-level model further confirmed the result. The interannual variation of TC tracks in the SCS is also discussed. It is found that the steering flow anomalies in the SCS mostly favor eastward moving TCs in central Pacific (CP) El Niño and eastern Pacific (EP) El Niño years. However, the eastward flow anomalies are too weak to have strong influence on the majority of the TCs. During La Niña years, TCs in the SCS tend to move westward, possibly related to the westward steering flow anomalies. [ABSTRACT FROM AUTHOR]

Tropical cyclone (TC) genesis in the South China Sea (SCS) during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994-2008, about twice that during 1979-1993 (27). During the TC peak season (July-September, JAS), there were 43 TCs from 1994-2008, but only 17 during 1979-1993. For July in particular, 13 TCs formed from 1994-2008, but there were none during 1979-1993. The change in TC number is associated with changes of key environmental conditions in atmosphere and ocean. Compared to 1979-1993, the subtropical high was significantly weaker and was displaced more eastward during 1994-2008. In the former period, a stronger subtropical high induced downward flow, inhibiting TC formation. In the latter period, vertical wind shear and outgoing longwave radiation all weakened. Mid-level (850-500 hPa) humidity, and relative vorticity were higher. Sea surface temperature and upper layer heat content were also higher in the area. All these factors favor TC genesis during the latter period. The decadal change of TC genesis led to more landfalling TCs in Southern China during the period 1994-2008, which contributed to an abrupt increase in regional rainfall. [ABSTRACT FROM AUTHOR]

In the past 10 years (2004-2013), annual open cruise during late summer provided new opportunities for comprehensive studies in the Northern South China Sea (NSCS). The 10-year field investigation program was carried out by the South China Sea Institute of Oceanology, Chinese Academy of Sciences (SCSIO, CAS). Measurements included water mass property, ocean circulation, atmospheric structure, and chemical and biological elements. The observation data collected during these open cruises have been intensively used in the studies of marine oceanographic, meteorological, chemical, and biological processes in the NSCS. In this study, comprehensive assessment of data application in oceanographic and meteorological studies is provided: (1) the property and variability of water masses in different layers; (2) the distribution of main currents and three-dimensional structure of mesoscale eddies; and (3) atmospheric structure and its feedback to the ocean. With the continuance of open cruises, it is feasible to construct high-quality, gridded climatological marine meteorological datasets in the NSCS in the near future. [ABSTRACT FROM AUTHOR]

Wind measurements derived from QuikSCAT data were compared with those measured by anemometer on Yongxing Island in the South China Sea (SCS) for the period from April 2008 to November 2009. The comparison confirms that QuikSCAT estimates of wind speed and direction are generally accurate, except for the extremes of high wind speeds (>13.8 m/s) and very low wind speeds (<1.5 m/s) where direction is poorly predicted. In-situ observations show that the summer monsoon in the northern SCS starts between May 6 and June 1. From March 13, 2010 to August 31, 2010, comparisons of sea surface temperature (SST) and rainfall from AMSR-E with data from a buoy located at Xisha Islands, as well as wind measurements derived from ASCAT and observations from an automatic weather station show that QuikSCAT, ASCAT and AMSR-E data are good enough for research. It is feasible to optimize the usage of remote-sensing data if validated with in-situ measurements. Remarkable changes were observed in wind, barometric pressure, humidity, outgoing longwave radiation (OLR), air temperature, rainfall and SST during the monsoon onset. The eastward shift of western Pacific subtropical high and the southward movement of continental cold front preceded the monsoon onset in SCS. The starting dates of SCS summer monsoon indicated that the southwest monsoon starts in the Indochinese Peninsula and forms an eastward zonal belt, and then the belt bifurcates in the SCS, with one part moving northeastward into the tropical western North Pacific, and another southward into western Kalimantan. This largely determined the pattern of the SCS summer monsoon. Wavelet analysis of zonal wind and OLR at Xisha showed that intra-seasonal variability played an important role in the summer. This work improves the accuracy of the amplitude of intra-seasonal and synoptic variation obtained from remote-sensed data. [ABSTRACT FROM AUTHOR]