A Preliminary Study On The Measurements Of Boundary Layer Height And Rainfall Particle Phase Using Wind Profile Radar

The particle identification is the key and optimal difficulty of study of precipitation, which has the vital significance in serving weather warning. Besides, the boundary layer height, atmosphere structure parameter, is of optimal meaning to atmosphere dynamics and air pollutant dispersion.Wind profile radar(WPR), measuring the atmosphere efficiently, not only in clear, but also in raining days can detect the signal from atmosphere turbulence and rainfall precipitation particles.A study of macro and micro structure of weather process of rain turned into snow was presented in this paper, by using data obtained from wind profile radar in Yanqing, Beijing, China. Results showed that the products of intensity and velocity field of wind profile radar were good at diagnosing and distinguishing the evolution of phase change of precipitation from rainfall into snowfall. Features of reflectivity, signal to noise ratio(SNR), spectral width and other factors showed discontinuous before the rain; With bright band disappeared, rainfall turned into snow. In the ground rainfall stage, the figure of the echo intensity spectra had a clear hierarchical structure, showing solid above1300m and liquid below700m, respectively. There was a close relationship between stratification height and temperature, where had a melting layer with temperature of274-275k, and with the most obvious change of echo intensity spectra. Besides, statistics of radial velocity and SNR show that, radial velocity is from3to6m/s and SNR is from15to25dB when the rain; while0-1.5m/s and3-15dB when the snow, respectively.In addition, a comparison study of merit and demerit of calculating boundary-layer height (BLH), under three different weather conditions of clear, altostratus and stratus, from different methods which are GPS sounding, Wind profiler, Micro-pulse Lidar, is presented in this paper, by using the data obtained from ARM experiment from Sep. to Dec.2008in Shouxian, Anhui, China. Results show that (1) Wind profile radar seems to be a very promising device for direct and continuous measurement of the mixing height in daytime, which determines BLH with the refractive index structure constant (Cn2) accurately. However, in nighttime, limited in the lowest range and the weak signal extraction problem, the wind profiler radar cannot work well in determining the nocturnal boundary layer height.(2) the mixing layer height was caught by WPR revealing diurnal change of boundary layer in Shouxian, which reaching the highest height-1200m. the stable layer was detected by Lidar and Sonde. Whereas, this method underestimates the height of boundary layer. And this method is failed to work in cloudy conditions, due to the influence of water vapor.