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青藏高原东南部昌都地区近地层湍流输送的观测研究
TURBULENT MEASUREMENT OVER THE SOUTHEASTERN TIBETAN PLATEAU
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摘要: 利用我国1998年第2次青藏高原气象科学试验 (TIPEX) 昌都的湍流观测资料, 初步分析了三维风速、温度和湿度湍流谱、归一化方差与稳定度的关系、湍流通量和整体输送系数.结果表明, 白天标准化的湍流谱大多数满足2/3次方定律.风速方差与稳定度的关系在不稳定条件下基本服从1/3次方定律, 但水平风速方差比垂直速度方差与稳定度的关系离散.中性层结下的A、B值比平原地区大, 与起伏地形的值接近, C值与平原地区和起伏地区的差异不大.温度和湿度方差与不稳定层结的关系基本满足1/3次方定律, 而在稳定层结下的关系均无明显规律.湍流通量在干湿期转换中有突变现象, 干期的动量和热量通量均大于湿期, 热源强度以感热为主, 占80%.湿期热源强度明显增大, 其中以潜热为主, 占热源强度的60%.整体输送系数与稳定度的关系明显, 拟合得到的中性层结条件下的CDN和CHN分别为4.40×10-3和4.70×10-3, 其结果大于高原中、西部的同期观测值.
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关键词:
- 第2次青藏高原气象科学试验 (TIPEX);
- 涡旋相关法;
- 湍流结构;
- 整体输送系数
Abstract: Based on the second Tibetan Plateau Meteorological Experiment (TIPEX) turbulent data from Changdu, the turbulent structure and transportation characteristics in the near-surface layer for summer time are analyzed by using the eddy correlation technique. The main results show that the relation between the normalized variance of 3D winds and z/L satisfies the similarity law under both unstable and stable stratification. The relations of normalized variances of temperature and specific humidity to z/L obey the law of 1/3 fractional power only under the unstable condition. In the case of stable stratification, their relations to z/L are disperse. The sensible heat dominates in the dry period, making up 80% of the total heating; while in the wet period the heating is intensified to great degree, in which latent (sensible) heat constitutes 60% (40%). The relations of drag coefficients (Cd and Ch) to z/L are quite close and the fitted Cdn (4.40×10-3) Chn (4.70×10-3) are obtained in a neutral case, which are bigger than those for the middle and western parts of the plateau in the same period.-
Key words:
- TIPEX;
- Eddy correlation;
- Turbulent structure;
- Drag coefficient
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图 1 (a) 超声风温仪DA 600的水平合成风速Vc与风洞风速Vt的比较, (b) E009B红外水汽测量仪输出电压 (V) 与比湿 (q) 的关系
(图中1和2为测试点)
图 5 三维风速归一化的标准方差与z/L的关系[a, b: y=3.45 (1-3z/L) 1/3; c, d: y=3.15 (1-3z/L) 1/3; e, f: y=1.30 (1-3z/L) 1/3]
表 1 湍流测量系统传感器的主要技术指标
表 2 近中性条件无因次风速方差值
表 3 昌都的平均热源强度
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