EFFECTS OF GRAUPEL WITH DIFFERENT DENSITIES ON SIMULATION OF PERSISTENT AUTUMN RAINSTORMS OVER HAINAN ISLAND IN 2008
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摘要: 利用WRF模式对海南2008年秋季持续强降水进行月尺度模拟,并基于WDM6微物理方案研究不同密度霰对强降水模拟及其云微物理过程的影响。结果表明:(1)不同密度霰对降水强度模拟影响较大,LDG(小密度霰)试验海南东部和北部两个降水中心强度减小,HDG(大密度霰)试验东部降水中心强度减小,北部降水强度增大。(2)随着霰密度增大,强降水时期高层霰含量减少,0 ℃层以下霰含量增多。雨水主要来自霰和雪向雨水的转化,其中霰向雨水转化量最大,对降水贡献最大,并随着霰密度增大霰向雨水转化量增多。(3)随着霰密度增大,暴雨及以下降水范围减小、大暴雨及以上降水范围增大;单位格点降水率增大,大暴雨及以上降水贡献增大。随着降水强度增大,小密度霰收集雨水量增多,霰向雨水净转化量减少,对降水贡献减小;大密度霰融化量明显增多,霰收集雨水量增幅较小,霰向雨水净转化量增大,对降水贡献增大。Abstract: In this paper, the WRF model was used to simulate the persistent autumn rainstorms over Hainan Island (HNI) in 2008. The effects of graupel with different densities on the process of heavy rainfall was studied using sensitivity test based on the WDM6 microphysical scheme. The results showed that: (1) Graupel with different densities had significant influence on precipitation intensity. Low-density graupel (LDG) weakened precipitation in the east and north of HNI. High-density graupel (HDG) weakened precipitation in the east of HNI and strengthened precipitation in the north of HNI. (2) As graupel density increased, the amount of graupel decreased in the high altitude area and increased below the 0℃ layer. The top two sources of rainwater in these simulations were the conversion of graupel into rainwater and the conversion of snow into rainwater, and the conversion of graupel into rainwater made the largest contribution to precipitation. As graupel density increased, more graupel was converted into rainwater. (3) As graupel density increased, the range of precipitation less than 100mm decreased, and the range of precipitation greater than 100mm increased. As precipitation intensity enhanced, the amount of rainwater collected by LDG increased, the net conversion of graupel into rainwater decreased and its contribution to precipitation decreased. The melting of HDG increased significantly, and the amount of rainwater collected by graupel increased slightly. The net conversion of HDG into rainwater increased, and its contribution to precipitation increased.
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Key words:
- autumn precipitation in Hainan /
- WRF model /
- cloud microphysical process /
- graupel
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表 1 试验具体设置
表 2 WDM6方案中云微物理转化项和含义
转化项 含义 aacw 云水被雪/霰收集 cact 云凝结核生成 cond 水汽凝结为云水 cevp 云水蒸发为水汽 gaci 云冰被霰收集 gacr 雨水被霰收集 gacs 雪被霰收集 gacw 云水被霰收集 gaut 雪自动转化成霰 gdep 霰的凝华 gsub 霰的升华 geml 霰的增强融化 gevp 融化的霰蒸发 gfrz 雨水冰冻成霰 gmlt 霰的融化 ihmf 云冰的均质增长 ihtf 云冰的异质增长 imlt 云冰融化 raci 云冰被雨水收集 racs 雪被雨水收集 racw 云水被雨水收集 raut 云水自动转化为雨水 rcond 水汽凝结成雨水 revp 雨水蒸发为水汽 revp_rc 雨水蒸发为云水 saci 云冰被雪收集 sacr 雨水被雪收集 sacw 云水被雪收集 saut 云冰自动转化为雪 sdep 雪的凝华 smlt 雪的融化 表 3 2008年10月12日不同强度降水的网格百分比(PGN)
试验名称 0~100(暴雨及以下) 0~25 (小雨-中雨) 25~100 (大雨-暴雨) ≥100 (大暴雨及以上) 100~250(大暴雨) >250(特大暴雨) LDG 97.8% 68.9% 28.9% 2.2% 2.2% 0.0% CNTL 92.5% 76.4% 16.1% 7.5% 5.9% 1.6% HDG 88.8% 70.7% 18.1% 11.2% 9.5% 1.7% 表 4 2008年10月12日不同强度降水格点平均降水量(MP,单位:mm)
试验名称 0~100 (暴雨及以下) 0~25 (小雨-中雨) 25~100 (大雨-暴雨) ≥100 (大暴雨及以上) 100~250(大暴雨) >250(特大暴雨) LDG 19.51 5.37 53.26 116.43 116.43 - CNTL 12.03 3.31 53.52 191.93 156.50 320.30 HDG 14.17 3.88 54.36 181.01 159.92 294.96 表 5 2008年10月12日单位格点降水率(单位:mm)和不同强度降水贡献率
试验名称 0~100 (暴雨及以下) 0~25 (小雨-中雨) 25~100 (大雨-暴雨) ≥100 (大暴雨及以上) 100~250(大暴雨) >250(特大暴雨) 单位格点降水率(mm) LDG 88.0% 17.1% 70.9% 12.0% 12.0% - 21.68 CNTL 43.5% 9.9% 33.6% 56.5% 36.1% 20.4% 25.59 HDG 38.2% 8.3% 29.9% 61.8% 46.1% 15.7% 32.91 -
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