Turbulent fluxes were measured on the Xisha air-sea flux research tower in May 14-June 22, 1998 and May 7-June 17,2000.The observational period can be divided into some synoptic stages:prior to onset,onset period,mons...Turbulent fluxes were measured on the Xisha air-sea flux research tower in May 14-June 22, 1998 and May 7-June 17,2000.The observational period can be divided into some synoptic stages:prior to onset,onset period,monsoon break,cold air and southwesterly period.The observational results show that corresponding to the onset of SCS monsoon the air-sea fluxes indicate considerable changes.This paper presented the preliminary analysis results of fluctuation and gradient measurements of wind velocity,air temperature and moisture at the air-sea flux tower.The wind spectrum and some parameters including latent and sensible heat obtained from the eddy correlation or profile method are shown with various statistical quantities of scaling parameters such as intensities of turbulence and friction velocity u<sup>*</sup>.Intensities of turbulence are estimated to the values of σ<sub>u</sub>/■=0.096,■=0.066 and ■=0.045 respectively at about 10 m high during the measured period in 1998.Momentum flux is about 0.1 N/m<sup>2</sup>.The drag coefficient C<sub>D</sub> of momentum transfer is approximated by the statistical relationship 10<sup>3</sup>C<sub>D</sub>=0.003u<sub>10</sub><sup>2</sup>+ 0.020u<sub>10</sub>+0.836.Furthermore,the analyzed results of four synoptic stages are compared and the special characteristics of flux transfer during the different stages around onset of SCS monsoon are discussed.Finally,through comparison of the Xisha fluxes with those obtained from Indian Ocean and western Pacific Ocean,we can see their differences and a possible link between the moisture fluxes and rainfall in continent areas.展开更多
Based on height and wind data of NCEP/NCAR and OLR data, patterns of upper air circulation from April to October have been analyzed, and the South China Sea (SCS) Summer Monsoon Onset (SMO) and retreat have been defin...Based on height and wind data of NCEP/NCAR and OLR data, patterns of upper air circulation from April to October have been analyzed, and the South China Sea (SCS) Summer Monsoon Onset (SMO) and retreat have been defined. The empirical formula fitting to the onset index of the SCS SMO has been established, and the onset and ending time of monsoon, together with the intensity index sequence during 1953-1999 are given by the analysis of characteristics of thermodynamic and dynamic factors during the process of SMO. The emergence and development of symmetric vortex pair at both sides of the equator in tropical East Indian Ocean, which may excite the SCS SMO, can be taken as a short-term prediction indicator of SMO.展开更多
基金State Key Project for Basic Research"South China Sea Monsoon Experiments"Nationai Natural Science Foundation of China 40075003
文摘Turbulent fluxes were measured on the Xisha air-sea flux research tower in May 14-June 22, 1998 and May 7-June 17,2000.The observational period can be divided into some synoptic stages:prior to onset,onset period,monsoon break,cold air and southwesterly period.The observational results show that corresponding to the onset of SCS monsoon the air-sea fluxes indicate considerable changes.This paper presented the preliminary analysis results of fluctuation and gradient measurements of wind velocity,air temperature and moisture at the air-sea flux tower.The wind spectrum and some parameters including latent and sensible heat obtained from the eddy correlation or profile method are shown with various statistical quantities of scaling parameters such as intensities of turbulence and friction velocity u<sup>*</sup>.Intensities of turbulence are estimated to the values of σ<sub>u</sub>/■=0.096,■=0.066 and ■=0.045 respectively at about 10 m high during the measured period in 1998.Momentum flux is about 0.1 N/m<sup>2</sup>.The drag coefficient C<sub>D</sub> of momentum transfer is approximated by the statistical relationship 10<sup>3</sup>C<sub>D</sub>=0.003u<sub>10</sub><sup>2</sup>+ 0.020u<sub>10</sub>+0.836.Furthermore,the analyzed results of four synoptic stages are compared and the special characteristics of flux transfer during the different stages around onset of SCS monsoon are discussed.Finally,through comparison of the Xisha fluxes with those obtained from Indian Ocean and western Pacific Ocean,we can see their differences and a possible link between the moisture fluxes and rainfall in continent areas.
基金Supported by Climbing Programme under Ministry of Science and Technology of China:The South China Sea Monsoon Experiment(SCSMEX)the Operational Development Subject/NCC.
文摘Based on height and wind data of NCEP/NCAR and OLR data, patterns of upper air circulation from April to October have been analyzed, and the South China Sea (SCS) Summer Monsoon Onset (SMO) and retreat have been defined. The empirical formula fitting to the onset index of the SCS SMO has been established, and the onset and ending time of monsoon, together with the intensity index sequence during 1953-1999 are given by the analysis of characteristics of thermodynamic and dynamic factors during the process of SMO. The emergence and development of symmetric vortex pair at both sides of the equator in tropical East Indian Ocean, which may excite the SCS SMO, can be taken as a short-term prediction indicator of SMO.
