2006年夏季珠江口外海域船基海气通量观测资料质量评估

Quality assessment of shipboard air-sea flux measurements off Zhujiang River mouth

2006年夏季在珠江口外海域进行了143个站位的海气通量船基观测。设计了一个剔除船速的滤波器及资料处理程序,对观测资料进行了处理。通过对垂向观测风速的平均值、湍流功率谱、观测通量值的计算,得出该次观测方法是不可取的。设备安置在船舷外,气流绕过船体时形成上升气流并干扰了湍流场,测得的垂向平均风速不为零,一般存在0.2—1.0m.s-1的垂向平均风速,无量纲湍流功率谱在惯性次区不符合f-2/3次律,通过涡动相关法计算的动量通量远大于块体动力学公式的计算结果。今后的船基通量观测需要选取好设备安装位置及安装高度。

In the summer of 2006, the shipboard air-sea flux measurements at 143 survey stations were carried out off the Zhujiang River mouth. A band stop filter is designed and a set of data processing program is developed to eliminate the vessel motion and to process the measured data. By calculating the mean ver tical winds, turbulence power spectrums and air-sea fluxes, it is concluded that the measuring methods of this cruise are not feasible. During this cruise, the observational equipments were fixed outside the right shipboard. When air flow passed through the vessel, the air was lifted and the turbulences around the ship were enhanced. Consequently, the measured mean vertical winds were non-zero, but with a speed of 0.2 1.0m·s^-1 , the non-dimensional spectral energy densities at the frequencies of inertial subrange were not proportional to f ^-2/3, and the momentum fluxes estimated by direct eddy covariance method were much larger than those by bulk aerodynamic formulae. The present measurements suggest that the installation position of turbulence sensor on the vessel and its installation height above the deck should be well chosen and tested.