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风廓线雷达除能得到风速场资料外,还可以根据信号与噪声强度生成信噪比资料。风廓线雷达信噪比的变化与比湿梯度间具有显著的相关性。而云底是空气饱和与未饱和的临界面,必然有明显的比湿的梯度变化,在风廓线雷达上反映为信噪比的显著增强。本文提出了应用信噪比垂直梯度最大正值(信噪比随高度急剧增大)处的高度来反演云底高度的方法。利用上海浦东机场2015年1月1日-3月4日间风廓线雷达的信噪比资料,通过信噪比垂直梯度最大正值所在高度反演的云底高度与云高仪所测的云底高度间对比,发现两者具有较高的相关性,相关系数达到0.41,并通过了显著水平?(28)0.01的t检验。表明采用风廓线雷达的信噪比资料能有效反演无降水天气的云底高度。
Wind profiler radar can not only get wind speed field data, but also generate signal-to-noise ratio data according to signal and noise intensity. The wind profiler SNR has a significant correlation with the specific humidity gradient. The cloud bottom is the critical surface of saturated and unsaturated air, which obviously has the obvious gradient of specific humidity. It is reflected in the wind profiler radar that the signal-to-noise ratio is significantly enhanced. In this paper, we propose a method of retrieving the height of cloud base using the height of the maximum vertical gradient of signal-to-noise ratio (the ratio of signal to noise increases sharply with height). Using the signal to noise ratio data of wind profiler radars at Shanghai Pudong Airport from January 1 to March 4, 2015, the height of the cloud bottom retrieved from the height at which the vertical gradient of signal-to-noise ratio is maximized is similar to that measured by ceilometer The correlation between the height of the cloud bottom and the height of the cloud was found to be highly correlated, with a correlation coefficient of 0.41 and a significant t-test of (28) 0.01. It shows that the SNR of wind profiler radar can effectively reflect the height of cloud base without precipitation.