| 摘要: |
| 为了进一步揭示大气边界层低层动量通量逆梯度输运的观测事实, 本文利用福建南部赤湖 镇海边100m 铁塔上观测得到的超声风温仪资料, 采用诊断方法分析了2010 年13 号“鲇鱼”台风影响 过程中近海面边界层大气中动量垂直通量逆梯度输送特征。结果表明: 在逐小时时间尺度上台风近 海面边界层大气中湍流动量垂直通量输送以沿梯度方向为主, 但也存在一定比例的逆梯度方向输送 现象, 且越往高层该现象越明显, 本文中其百分比最高不超过16%.并且这一现象出现的频率在台 风环流的不同区域存在差别: 在台风环流的内核区域最多, 其次是登陆以后残余环流区, 而在早期 的台风外围环流中较少。湍流低频扰动的相干结构也是影响因素, 当水平扰动与垂直扰动出现同位 相变化时容易出现动量垂直通量逆梯度输送。大气动量通量逆梯度的水平和垂直平均空间尺度分别 为258m 和35m, 平均时间尺度分别为123s 和13s, 均小于通常的顺梯度湍流低频扰动的时空尺度的 1-3 倍。 |
| 关键词: 台风 边界层 动量通量 逆梯度输送 相干结构 |
| DOI：10.11693/hyhz20150700186 |
| 分类号: |
| 基金项目:国家重点基础研究计划(973)项目, 2013CB430305 号; 上海市科委项目, 14DZ1205200 号。 |
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| OBSERVATION ON COUNTER-GRADIENT TRANSPORT OF MOMENTUM FLUX IN LOW ATMOSPHERE BOUNDARY LAYER DURING TYPHOON MEGI |
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ZHENG Yun-Xia, LI Yong-Ping, DUAN Zi-Qiang
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Shanghai Typhoon Institute, CMA, Shanghai 200030, China
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| Abstract: |
| To explain the observational data of counter-gradient transport of momentum flux in lower atmospheric boundary layer, we studied very-high-frequency data measured by ultrasonic wind instruments that installed on a multilayer tower (N24°2'9.6", E117°54'; 100m tall on 29m base above sea level) near sea shore by diagnostic method. A case of landfall typhoon Megi in 2010 was selected. Result show that the counter-gradient transport of momentum occurred in a small proportion (<16%) in lower boundary layer of the typhoon, although it moved along the gradient direction on longer time scale, e.g., one hour. The phenomenon in higher layers was more obvious than that in lower ones, stronger in the area of typhoon core and weakened away from it, and less in early and outskirt of typhoon. The vertical counter-gradient flux of momentum is closely related to the coherent structure of low-frequency disturbance. When wind disturbance in horizontal and vertical directions was in-phase, the counter-gradient flux of momentum would occur easier due to loose coherence structure between the disturbances in the two directions. The averaged spatial scales were 258m and 35m and the temporal scales were 123s and 13s in horizontal and vertical directions respectively, both are smaller than those of common ones of low-frequency disturbances in low layer boundary atmosphere of typhoon. |
| Key words: typhoon boundary layer counter-gradient flux of momentum coherent structure |
