京津冀城市群地区夏季低层大气风速谱特征分析

利用京津冀城市群地区6个观测站风廓线雷达夏季一个月同步观测资料,对其进行了风功率谱和小波分析.越接近地面,测站之间风的周期变化特征差异越明显,离地面越远,差异不显著.各站大于1天周期的频谱特征差异小,而小于1天周期的频谱特征差异大.各站频谱在几百米高度有明显日变化.不同位置的测站其日变化周期信号随高度分布表现为不同程度的地形影响效应.部分测站1 km高度以下风功率谱在大于1天高频区近似满足-5/3幂分布规律.降水过程风频谱在低层普遍有小于1天的高频周期,这与降水过程高低空风速起伏和变化密切相关.各站平均风矢量日变化在5:00—6:00、20:00—21:00有明显风速变化和风向转换,1500 m以下风向变化差异显著,偏南风出现时间及影响高度与该地区的山谷风和海陆风相联系.各站之间风速相关系数随高度分布呈现出低层低、上层高的特点.最后还给出了风廓线雷达布网建议.

Analysis of spectral characteristics for wind velocity in the low layer of the atmosphere in the Beijing-Tianjin-Hebei city cluster area during summer

Power spectrum and wavelet were used to analyze data from 6 wind profiler stations in the Beijing-Tianjin-Hebei city cluster area during summer 2010. The results show the differences of frequencies among 6 stations are smaller closer to the ground, and bigger farther away from the ground. The differences of frequencies greater than 1-day are smaller than the frequencies less than 1-day. Obvious diurnal oscillations, which are different with locations of stations and effects by topography, are identified at hundreds meters level for all of stations. The spectra of some stations below 1 km indicate -5/3 power-law scaling regions for the frequencies higher than diurnal. High frequencies, less than 1 day, at lower level usually are accompanied with rainfall, during which upper and lower winds oscillate and interact. Diurnal mean wind vectors show two wind transitions, which are 05~06 h LST and 20~21 h LST. More pronounced differences of wind directions are identified below 1500 m. Southerly winds occurrence and its depth are associated with mountain-valley breeze and sea breeze in this area. Wind speed correlation coefficients between stations increase with height. Suggestions for deploying wind profiler radars are given in this paper.