P1.11 Forest fires detected by using doppler weather radar

Tuesday, 23 October 2007
Wingwood (Atlantic Oakes Resort)
Kehui Huang, Wenzhou Meteorological Bureau, Wenzhou City, Zhejiang, China; and F. Gu, F. Zhao, J. Zhu, B. Zhou, H. Xie, and J. Zhong

Ten cases of forest and grass fires which took place in the south of Zhejiang province China, were detected efficiently by CINRAD-SA Doppler Weather Radar earlier 2007. The distances between the fires spots and radar station were from 30 to 108 km, and the burned areas were from 1 to 100 ha. The CINRAD-SA Doppler Weather Radar (WSR-98D S Band Fully Coherent Doppler Weather Radar) is the new generation of the WSR-88D Weather Surveillance Radar of USA, with higher sensitivity detector of aerosol. The radar analysis result revealed that the radar performed well in tracking the smoke plume produced by forest and grass fires, with the low elevation (0.5°) radar products of base reflectivity and base velocity, and then detected the fires indirectly. The Doppler radar echoes of the fires, nearly share the same characteristics with clutter echoes, with small horizontal scale, low echo heights and high echo intensity. The echo heights were from 1 to 2.4 km in altitude, 0.3 to 1.7 km higher than the altitude of radar station, which were lower than the echoes of regular precipitation, much lower than the ones of the thunderstorms and hail clouds. The strongest echo intensity could reach from 43 to 58 dBz near the fire spots, which were stronger than the echoes of stratiformis precipitation, and even nearly as strong as the echoes of severe convection. The distinct characteristic could distinguish from the clutter echoes easily, were the appearance of the velocity couplet in the radial velocity charts, which indicated the divergence appears upon the fire spots. The fires showed different echo characteristics with rains, which has large horizontal scales and has higher echo heights. It was worth point out that the forest fires always took place in continuous dry, clear weather conditions, which almost had no echoes on the radar. So fires echoes were easy to distinguish. According to the strongest echo position, the fire spots would be determined. With the aid of GIS system, the accurate address of the fire spots could be read. Two of the fires took place on two islands of the East China Sea, which located 30 and 38 km east of the radar, had different echo characteristics from the ones on the mainland. Thanks to the effect of higher wind speed and lower terrain heights on the islands, the echo characteristics of forest fires occurred on the islands had a weaker radar signals, and sometimes had no echo at all while the wind speed increased. On the other hand, the echoes could be detected during the whole process of the other eight fires on the mainland, with rare absence of echoes. As to polar satellites, sometimes could not monitor the fire efficiently under the overcast or cloudy weather conditions, or especially the real-time forest fires, because of their restrictions of temporal (scans twice a day) and special resolutions. The Doppler radar, on the other hand, could observe the forest fires efficiently with near real-time (scans every 6 min) temporal and special resolutions. On the basis of wind speed, wind direction near the fire spots and the accurate position of the fire spots provided by the Doppler radar, and assisted by the data of mesoscale automatic weather stations, the forest fire management office could make scientific schedules of anti-forest fires in time, and would greatly decrease the lose of the fires.
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