Long-Range Measurement Technology and Application of Doppler Wind Lidar for Wind Field Detection for Forest Fires
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Abstract:
Global climate warming leads to an increase in the frequency and intensity of forest and grassland fires. During the rescue process of forest and grassland fires, wind is the most important meteorological factor affecting the spread of the fire. It determines not only the speed of the fire’s spread but also the area and direction of the fire’s spread. Moreover, the changeable wind field information under complex terrain conditions further increases the risks for firefighting efforts and the safety guarantee of rescue workers. The wind lidar, which has the capabilities of high spatial and temporal resolution and non-contact measurement, is of great significance for the prevention and control of forest fires and the on-site rescue command. However, the detection range of the existing wind lidar is difficult to meet the demand for long-distance wind field monitoring at the forest and grassland fire site, which restricts the precise monitoring and early warning of secondary disasters at the forest fire rescue site. Therefore, The study conducts research from two aspects: high-power laser emission technology and clear-sky weak signal algorithm, and comprehensively improves the detection range from both hardware technology and data processing aspects. The high-power laser emission technology mainly includes low-noise narrow linewidth technology, multi-stage pump source amplification technology, and Brillouin scattering suppression technology, so as to achieve high-power output as a whole and ensure the measurement accuracy, sensitivity, and reliability of the lidar system. In terms of data processing, the maximum likelihood discrete spectrum peak estimation algorithm and the optimised power spectrum frequency shift estimation algorithm are used to improve the detection ability of the lidar for weak signals. The research results show that after adopting the above technologies and algorithms, the wind lidar achieves large-scale wind field measurement over a range of 15 km. The data acquisition rate exceeds 90% at 12,600 metres, reaches more than 80% at 14,400 metres, and is above 75% at 15,000 metres, with a significant improvement in detection ability. In terms of detection accuracy, there is a high degree of consistency when compared with the data from the wind measurement tower. The determination coefficients of the horizontal wind speed and wind direction at the two heights of 77 metres and 103 metres between the wind lidar and the wind measurement tower are all above 0.99, the deviation of the linear regression fitting degree is all below 0.005, the average deviation of the wind speed is below 0.05 m/s, and the average deviation of the wind direction is below 2 degrees.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.