1998年南海季风爆发期间近海面层大气湍流结构和通量输送的观测研究

Characteristics of Turbulence Structure and Flux Transfer on the Sea Surface during the Onset of SCS Monsoon in 1998

１９９８年５月１４日至６月２２日，在西沙永兴岛近海铁塔上进行了－次海－气通量观测试验，观测期包括了西南季风爆发前、爆发、爆发后风速加强等几个阶段。这次试验获得该年西南季风爆发的天气特征以及由涡度相关法，廓线法计算的动量、感热、潜热通量及湍流强度等一些统计量分布。分析结果表明，观测期湍流强度σｕ、σｖ、σｗ与平均风速之比为０．０９６、０．０６６、０．０４５；在近中性条件下（ｚ／Ｌ≈０），各相似函数基本为常数，σｕ／ｕ≈３，σｖ／ｕ≈２，σｗ／ｕ≈１．２５；在稳定条件下ｕ、ｖ、ｗ三方向σ／ｕ 近似相等；在稳定与不稳定条件下σｔ／Ｊ随稳定度参数ｚ／Ｌ的变化趋势相似，但符号相反。摩擦速度ｕ随风速的变化接近于关系式ｕ＝００２９Ｕ１０＋ ０００６（ Ｕ１０为１０ ｍ高度 ３０ ｍｉｎ平均风速），空气动力粗糙度长度ｚ０变化在０．０１～０．３５ ｍｍ之间。观测期动量通量变化在０．０５～０．３０ Ｎ／ｍ２之间，季风爆发期明显增大；曳力系数ＣＤ平均为 １．１２×１０－３，它随平均风速变化可以表示为关系式１０３ＣＤ＝０．００３Ｕ２１０＋００２０Ｕ１０＋０．８３６或１０３ＣＤ＝ ０．０５６Ｕ１０＋０．７３２。感热通量由海洋输向大气。

Turbulent fluxes have been measured on the marine surface layer from Xisha air-sea flux tower during SCSMEX (The South China Sea Monsoon Experiment) in May 14- June 22, 1998. The preliminary results of fluctuation and gradient measurements of wind velocity, air temperature and moisture at the air-sea flux tower are presented. Intensities of turbulence are estimated to the values of σu / u=0.096, σv / u=0.066 and σw / u=0.045 respectively at about 10 m high during the measured period. The drag coefficient CD of momentum transfer is approximated by the expression 103 CD = 0.003U210+ 0.020U10 + 0.836. And vertical fluxes of momentum, latent and sensible heat obtained from the eddy correlation or profile method are shown with various statistical quantities of turbulence structure such as friction velocity u * and aerodynamic roughness height z0.