Freshwater input such as runoff and rainfall can enhance stratification in the Bay of Bengal(BOB) through the formation of a "barrier layer",which can lead to the formation of a temperature inversion.The authors focused on the temperature inversion in spring,especially before the onset of the summer monsoon,because previous research has mainly focused on the temperature inversion in winter.Using the hydrographic data from two cruises performed during 24-30 April 2010 and 1-4 May 2011,the authors found that inversions appeared at two out of nine Conductivity-Temperature-Depth Recorder(CTD) stations across the 10°N section and at seven out of 13 CTD stations across the 6°N section in the BOB.In 2010,the inversions(at stations N02 and N05) occurred at depths of approximately 50-60 meters,and their formation was caused by the advection of cold water over warm water.In 2010,the N02 inversion was mainly influenced by the warm saline water from the east sinking below the cold freshwater from the west,while the N05 inversion was affected by the warm saline water from its west sinking below the cold freshwater from its east.In 2011,the inversions appeared at depths of 20-40 meters(at stations S01,S02,S07,S08,and S09) and near 50 m(S12 and S13).The inversions in 2011 were mainly caused by the net heat loss of the ocean along the 6°N section.
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 (>13.8m/s) and very low wind speeds (<1.5m/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.
