Analysis on detection characteristics of two forest fires using dual-polarization radars
Two forest fires occurred in Yantai and Qingdao,Shandong on 17 March and 23 April 2020,respectively,and the detection data using dual-polarization radars are analyzed.The results are as follows.(1)Ashes from forest fires rise up into the air and drift downstream to form a smoke plume,whose radar reflectivity is around 20 dBZ,with a maximum of 36 dBZ in the small range above the fire spot.(2)The farthest distance of the two wildfires'floating objects spreading downstream in the environmental wind direction is 65 km and 94 km,respectively,and the highest rising height reaches 3.7 km and 4.8 km,respectively.(3)The environmental wind speed of corresponding altitude can be estimated by tracking the plume's front edge.Both wildfires occur on sunny days,the environmental wind speed is not large,and except for the large velocity spectrum width at the plume's edge,the velocity spectrum width is very small,mostly at 1-2 m·s-1.(4)The ranges detected by correlation coefficient(Cc),differential reflectivity(ZDR)and differential phase shift(ΦDP)are close to the evolution and area of the radar reflectivity,and also increase gradually along with the diffusion of the plume.The value of C is very small with the values of most sites less than 0.9 and the values of a few range bins under 0.5.There is a part of relatively small ZDR over the fire spot between 2 dB and 3 dB,while in the downwind direction,ZDR is large,mostly over 5 dB.(5)The detection characteristics of the two forest fires using dual-polarization radars show that the reflectors of generating echoes are mainly non-spherical particle reflectors with large horizontal scale produced by ashes such as hay and pine needles.
smoke plume of wildfiredual-polarization radarcorrelation coefficient(Cc)differential reflectivity(ZDR)detection characteristics
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