鄂西北两次强降雪的滴谱特征和积雪深度预估方法

Droplet Spectrum Characteristics and Depth Forecast Method of Two Snowstorms in Northwest of Hubei

利用丹江口站Thies Clima激光雨滴谱仪(TCLPM)和地面人工加密观测资料对2010年12月14—15日和2012年1月20—22日两次强降雪天气滴谱演变特征及预估积雪深度方法进行了分析探讨,结果表明:(1)激光雨滴谱仪能自动识别降水相态,结合地面人工加密观测结果,气温高于0.7℃,降水相态为雨,低于0.7℃为雨夹雪,低于-0.5℃为纯雪,同时发现地面温度低于0.5℃,地面开始有积雪,且这两次过程地面风速比较低有利于地面积雪;(2)激光雨滴谱仪还可以很好地监测强降雪天气滴谱特征演变规律,回波强度(Z)、平均直径(D_m)、降雪粒子水含量(W)、数浓度(N)随降雪强度增强而增大,且两次过程中D_m、Z、N、W均与地面积雪速率(VSD)均有不同程度的正相关性,W与VSD相关性更好,分别达到了0.844和0.926;(3)选取降雪粒子水含量W与地面积雪速率进行一阶拟合,得出地面积雪速率预估方程,通过纯雪阶段地面积雪速率预估值(VSDF)和地面积雪深度预估值(SDF)与利用雨滴谱仪实测资料反演的VSD、SD两者进行比较,发现它们两者非常接近,说明通过这种方法可以较好地预估地面积雪速率和积雪深度,其结果可以再现地面积雪跃增的主要时段。

The droplet spectrum variation characteristics and snow depth forecast of the two snowstorms in 14-15 December 2010 and 20-22 January 2012 are studied by using Thies Clima laser precipitation moni-tor (TCLPM)and artificial observation data from Danjiangkou Station.The results show that:(1 )the TCLPM can automatically identify the precipitation phase state.Combined with surface artificial dense ob-servations,the temperature higher than 0.7℃ is for precipitation phase state,less than 0.7℃ is for sleet, below -0.5℃ is for pure snow.At the same time,when the surface temperature is below 0.5℃,snow begins to accumulate.The surface wind speeds in the two processes are relatively slow,conducive to snow accumulation on the ground;(2)the TCLPM can monitor the variation of droplet spectrum characteristics of heavy snowfall weather,the echo intensity (Z),average diameter (Dm ),water content (W ),snowfall particle number concentration (N)which increases with the enhancement of snowfall intensity.During the two snowstorm events,there are different levels of positive correlations among Dm ,Z,N,W and VSD, better correlation between W andVSD,respectively reaching 0.844 and 0.926;(3)Selecting the first-or-der fitting snow particles in water content W and surface snow rate,the snow rate forecast equation is de-rived compare surface snow rate forecast (VSDF)in the pure snow stage and the surface snow depth fore-casts (SDF)to VSD,SD retrieved with the observation data by TCLPM it is found that they are very close,indicating this method can be used to estimate VSD and SD on the surface snow rate and snow depth,which can reflect the main time period with quick increase of surface snow.