THE IMPACT OF DIFFERENT CLOUD MICROPHYSICS PARAMETERIZATION SCHEMES ON THE SIMULATION OF A HEAVY RAINFALL EVENT OVER THE TIBETAN PLATEAU
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摘要: 利用WRF模式中三种云微物理参数化方案(Lin、Eta和WSM6)对青藏高原一次强降水过程进行模拟试验,将模拟降水结果与实测资料进行对比,以评估不同云微物理参数化方案对该区域降水过程的模拟性能。结果表明:三种方案均能够模拟出此次降水天气过程的发生,但在主要降水区域和降水强度两方面仍与实测资料存在偏差;在水凝物方面,三种方案对冰粒子的模拟较接近,Lin和WSM6方案模拟的雪粒子差异较大,但霰粒子无明显差异。进一步对比分析了Lin和WSM6方案模拟的云微物理转化过程,结果表明:这两种方案都表现出了霰向雨水转化的特点。在Lin方案中,通过水汽向霰粒子凝华、霰碰并水汽凝华生成的雪粒子以及霰碰并云水这三种过程生成的霰粒子最终融化为雨水。而在WSM6方案中,一方面水汽凝结成云水,云水被雪和霰粒子碰并收集转化为霰,之后霰融化为雨水;另一方面水汽凝华为冰粒子,一部分冰转化为雪,雪直接融化为雨水或转化为霰融化为雨水,另一部分冰转化为霰,霰融化为雨水。Abstract: In the present study, a heavy rainfall event over the Tibetan Plateau was simulated using the WRF model with three different cloud microphysics parameterization schemes, i. e., the Lin scheme, the Eta scheme and the WSM6 scheme. To evaluate the performance of different cloud microphysics parameterization schemes in this simulation, the simulated data and the observed were compared. The results showed that all three simulations could reproduce the event, but there were significant deviations between the simulated and observed main precipitation area and precipitation intensity. All three simulations showed similar results in terms of ice particles. Lin and WSM6 schemes showed great difference in the simulation of snow particles but had no significant difference when simulating graupel particles. Comparison between the cloud microphysical transformation processes simulated by using Lin and WSM6 schemes showed that both of the two schemes managed to show the characteristics of graupelto-rain conversion. In the Lin scheme, graupel particles were generated by deposition of water vapor, collision and coalescence of snow particles generated by deposition of water vapor, and collision and coalescence of cloud water. These graupel particles eventually melted into rain. In the WSM6 scheme, on the one hand, water vapor condensed into cloud water, which was accreted by snow and graupel particles and formed graupel. Eventually, graupel melted to be rain. On the other hand, water vapor condensed into ice particles; some transformed into snow, which melted directly to be rain or transformed into graupel and then melted to be rain, and the rest transformed directly into graupel which melted to be rain afterwards.
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Key words:
- numerical simulation /
- cloud microphysical process /
- Tibetan Plateau /
- heavy rainfall
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图 2 Lin方案(a)、Eta方案(b)、WSM6方案(c)模拟的雷达反射率
单位:dBZ。黑色线段为图 4中提到截面位置。
图 4 Lin方案模拟(a、d),Eta方案(b、e),WSM6方案(c、f)的相当位温(等值线,单位:K)、绝对涡度(阴影,单位:10-5 s-1)和垂直风速(矢量,单位:m/s)沿图 2所示线段的剖面
图 6 同图 5,但为Lin方案(a、c)模拟、WSM6方案(b、d)模拟
表 1 Lin方案云微物理转化过程
缩写 描述 Pracw 雨水碰并云水造成雨水增长 Praci 雨水碰并冰造成雨水增长 Pracs 雨水碰并雪造成雨水增长 Prevp 雨水蒸发为水汽 Praut 云水自动转化为雨水 Pidw 冰碰并云水造成冰增长 Pimlt 冰融化生成云水 Pihom 云水同质冻结生成冰 Piacr 冰碰并雨水造成冰增长 Psfw 云水通过贝吉龙过程生成雪 Psfi 冰通过贝吉龙过程生成雪 Psacw 雪碰并云水造成雪增长 Psacr 雪碰并雨水造成雪增长 Psaci 雪碰并冰造成雪增长 Psaut 冰自动转化为雪 Psdep 水汽凝华为雪 Pssub 雪升华为水汽 Psmlt 雪融化生成雨水 Psmltevp 雪融化后蒸发为水汽 Pgfr 雨水冻结为霰 Pgaut 雪自动转化为霰 Pgacw 霰碰并云水造成霰增长 Pgacr 霰碰并雨水造成霰增长 Pgaci 霰碰并冰造成霰增长 Pgacs 霰碰并雪造成霰增长 Pgdep 水汽凝华为霰 Pgsub 霰升华为水汽 Pgmlt 霰融化为雨水 Pgmltevp 霰融化后蒸发为水汽 表 2 WSM6方案云微物理转化过程
缩写 描述 Pcond 水汽与云水间转化(水汽凝结/云水蒸发) Pracw 雨水碰并云水造成雨水增长 Praci 雨水碰并冰造成雪或霰增长 Pracs 雨水碰并雪造成霰增长 Prevp 水汽与雨水间转化(水汽凝结/雨水蒸发) Praut 云水自动转化为雨水 Pidep 水汽凝华为云冰 Pigen 水汽核化为冰 Piacr 冰碰并雨水造成雪或霰增长 Psdep 水汽凝华为雪 Psevp 雪融化后蒸发为水汽 Psacw 雪碰并云水造成雨水或霰增长 Psacr 雪碰并雨水造成雪或霰增长 Psaci 雪碰并冰造成雪增长 Psmlt 雪融化为雨水 Pseml 增大的雪融化为雨水 Psaut 冰自动转化为雪 Pgdep 水汽凝华为霰 Pgevp 霰融化后蒸发为水汽 Pgacw 霰碰并云水造成雨水或霰增长 Pgacr 霰碰并雨水造成霰增长 Pgaci 霰碰并冰造成霰增长 Pgacs 霰碰并雪造成霰增长 Pgmlt 霰融化为雨水 Pgeml 增大的霰融化为雨水 Pgaut 雪自动转化为霰 -
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