雷暴云内电场力对起电和电荷结构的反馈作用
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摘要
利用美国国家强风暴实验室(NSSL)发展的耦合了详细起电机制和放电过程的中尺度电耦合数值模式WRF(weather research forecasting)-Elec,在NSSL云微物理双参数化方案中增加了电场力对霰、雹粒子降落末速度的影响,完善了WRF-Elec模式的物理过程,建立了双向耦合WRF-Elec模式.利用改进后的WRF-Elec模式,通过敏感性数值实验,定量分析了雷暴云内电场力对起电和电荷结构的反馈作用.结果发现:雷暴云发展旺盛阶段,由于电场力作用,霰、雹粒子质量加权平均降落末速度的瞬时变化极值可以超过4 m/s,但这种情况仅出现在雷暴云内局部区域,并且维持时间较短;电场力对直径小且数浓度较低的霰和雹粒子影响较大,但这种影响不是由单一物理量决定,而是由电场强度和霰、雹粒子的电荷密度、极性以及粒子的直径与数浓度共同决定;电场力通过对霰、雹粒子降落末速度的调整,增强了雷暴云内感应、非感应起电率,且前者远大于后者,云内局部产生-0.6—1.2 n C/m~3总电荷密度的变化,从而使电荷结构重新分布,局部垂直电场强度增强5 k V/m,总闪电数增加,与此同时,雷暴云内降水粒子的微观增长过程也发生改变.总体上,电场力对雷暴云起电过程的作用为正反馈,电场力对雷暴云电荷结构的反馈作用不可忽略.
The electrification within the thunderstorm, caused mainly by inductive and noninductive charging mechanism,can produce strong local electric field inside the thundercloud. Due to the resulting electric field force, the vertical velocity of the graupel and hail particles which are the main in-cloud charge carriers, would change. As a feedback, this variation could affect the original electrification and charge structure of the thunderstorm. In order to investigate such a feedback effect, a weather research forecasting(WRF) model coupled with explicit lightning physics including charging and discharge lightning scheme(hereafter WRF-Elec) is employed and modified in this study. We derive the formulas for calculating the mass-weighted mean terminal velocities of graupel and hail under the balance among gravity, resistance and electric field force. Then, the National Sever Storm Laboratory(NSSL) two-moment bulk microphysics scheme is modified by adding the calculating code with consideration of electric field force(EFF) acting on the fall speed of graupel and hail particles. Eventually, the two-coupled WRF-Elec is developed successfully.Based on this modified WRF-Elec, sensitivity tests are conducted to quantitatively investigate the influences of EFF on the thunderstorm electrification and the corresponding charge structure in an idealized supercell case. The results show that during the rapid enhancement of the thunderstorm, the grid-scale mass-weighted mean fall speed of graupel and hail vary significantly in consideration of EFF, with the maximum values both exceeding 4 m/s, although this situation occurs within a local area and lasts a short time. The action of EFF tends to enhance the falling of graupel and weaken the falling of hail. The influences of EFF on those graupel and hail particles with smaller-size and lower number concentration are stronger, as determined by composite factors of the strength and polarity of electric field, the diameter and number concentration of graupel and hail, and their charge density and polarity as well. The adjustment of the terminal velocity of the graupel and hail in consideration of EFF, eventually results in increasing the rate of both inductive and noninductive charge separation, where the inductive charging is the much more significant one. This leads to a grid-scale total charge density variation of-0.6–1.2 n C/m~3 and a redistribution of the charge structure in the thunderstorm, and correspondingly, an increase of the local vertical electric field by 5 k V/m, thus producing stronger lightning eventually. In addition, due to the effect of electric field force, the mass mixing ratio of four precipitation particles including graupel, hail, ice crystal and snow is changed in the ranges of-0.09–0.24,-0.16–0.04,-0.04–0.05,and-0.01–0.006 g/kg, respectively. Therefore, the electric field force in thunderstorm affects not only the electrification and charge structure, but also the microphysical process. Generally, the overall influence of EFF on electrification tends to be positive, and the feedback effect of EFF on the charge structure should not be neglected.
The electrification within the thunderstorm, caused mainly by inductive and noninductive charging mechanism,can produce strong local electric field inside the thundercloud. Due to the resulting electric field force, the vertical velocity of the graupel and hail particles which are the main in-cloud charge carriers, would change. As a feedback, this variation could affect the original electrification and charge structure of the thunderstorm. In order to investigate such a feedback effect, a weather research forecasting(WRF) model coupled with explicit lightning physics including charging and discharge lightning scheme(hereafter WRF-Elec) is employed and modified in this study. We derive the formulas for calculating the mass-weighted mean terminal velocities of graupel and hail under the balance among gravity, resistance and electric field force. Then, the National Sever Storm Laboratory(NSSL) two-moment bulk microphysics scheme is modified by adding the calculating code with consideration of electric field force(EFF) acting on the fall speed of graupel and hail particles. Eventually, the two-coupled WRF-Elec is developed successfully.Based on this modified WRF-Elec, sensitivity tests are conducted to quantitatively investigate the influences of EFF on the thunderstorm electrification and the corresponding charge structure in an idealized supercell case. The results show that during the rapid enhancement of the thunderstorm, the grid-scale mass-weighted mean fall speed of graupel and hail vary significantly in consideration of EFF, with the maximum values both exceeding 4 m/s, although this situation occurs within a local area and lasts a short time. The action of EFF tends to enhance the falling of graupel and weaken the falling of hail. The influences of EFF on those graupel and hail particles with smaller-size and lower number concentration are stronger, as determined by composite factors of the strength and polarity of electric field, the diameter and number concentration of graupel and hail, and their charge density and polarity as well. The adjustment of the terminal velocity of the graupel and hail in consideration of EFF, eventually results in increasing the rate of both inductive and noninductive charge separation, where the inductive charging is the much more significant one. This leads to a grid-scale total charge density variation of-0.6–1.2 n C/m~3 and a redistribution of the charge structure in the thunderstorm, and correspondingly, an increase of the local vertical electric field by 5 k V/m, thus producing stronger lightning eventually. In addition, due to the effect of electric field force, the mass mixing ratio of four precipitation particles including graupel, hail, ice crystal and snow is changed in the ranges of-0.09–0.24,-0.16–0.04,-0.04–0.05,and-0.01–0.006 g/kg, respectively. Therefore, the electric field force in thunderstorm affects not only the electrification and charge structure, but also the microphysical process. Generally, the overall influence of EFF on electrification tends to be positive, and the feedback effect of EFF on the charge structure should not be neglected.
引文
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[2]Saunders C P R,Keith W D,Mitzeva R P 1991 J.Geophys.Res.96 11007
[3]Li W L,Liu D X,Qie X S,Fu S M,Duan S,Chen Y C 2012 Acta Phys.Sin.61 059202(in Chinese)[李万莉,刘冬霞,郄秀书,傅慎明,段树,陈羿辰2012物理学报61059202]
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[8]Tan Y B,Liang Z W,Shi Z,Zhu J R,Guo X F 2014Sci.China:Earth Sci.57 2125
[9]Xu L T,Zhang Y J,Liu H Y,Zheng D,Wang F 2016Sci.China:Earth Sci.59 1414
[10]Zhao Y,Qie X S,Kong X Z,Zhang G S,Zhang T,Yang J,Feng G L,Zhang Q L,Wang D F 2009 Acta Phys.Sin.58 6616(in Chinese)[赵阳,郄秀书,孔祥贞,张广庶,张彤,杨静,冯桂力,张其林,王东方2009物理学报586616]
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[13]Jiang R B,Qie X S,Wang C X,Yang J,Zhang Q L,Wang J F,Liu D X 2011 Acra Phys.Sin.60 079201(in Chinese)[蒋如斌,郄秀书,王彩霞,杨静,张其林,王俊芳,刘冬霞2011物理学报60 079201]
[14]Cao D J,Qie X S,Duan S,Xuan Y J,Wang D F 2012Acta Phys.Sin.61 069202(in Chinese)[曹冬杰,郄秀书,段树,宣越建,王东方2012物理学报61 069202]
[15]Wang C X,Qie X S,Jiang R B,Yang J 2012 Acta Phys.Sin.61 039203(in Chinese)[王彩霞,郄秀书,蒋如斌,杨静2012物理学报61 039203]
[16]Wang J F,Qie X S,Lu H,Zhang J L,Yu X X,Shi F2012 Acta Phys.Sin.61 159202(in Chinese)[王俊芳,郄秀书,卢红,张吉龙,于晓霞,石峰2012物理学报61159202]
[17]Liu D X,Qie X S,Wang Z C,Wu X K,Pan L X 2013Acta Phys.Sin.62 219201(in Chinese)[刘冬霞,郄秀书,王志超,吴学珂,潘伦湘2013物理学报62 219201]
[18]Vonnegut B 1963 Meteorol.Monogr.27 24
[19]Willams E R,Lhermitte R M 1983 J.Geophys.Res.8810984
[20]Latham J,Saunders C P R 1967 J.Glaciol.6 505
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[22]Schlamp R J,Grover S N,Pruppacher H R,Hamielec A E 1976 J.Atmos.Sci.33 1747
[23]Rawlings F 1982 Quart.J.Roy.Meteor.Soc.108 779
[24]Sun A P,Zhang Y J,Yan M H 2004 Plateau Meteorol.23 26(in Chinese)[孙安平,张义军,言穆弘2004高原气象23 26]
[25]Zhang Y J,Sun A P,Yan M H,Guo F X,Qie X S,Huang M Y 2004 Chin.J.Geophys.47 25(in Chinese)[张义军,孙安平,言穆弘,郭凤霞,郄秀书,黄美元2004地球物理学报47 25]
[26]Zhou Z M,Guo X L,Cui C G,Li X Y,Xu G R,Zhao Y C 2011 Acta Meteorol.Sin.69 830(in Chinese)[周志敏,郭学良,崔春光,李兴宇,徐桂荣,赵玉春2011气象学报69 830]
[27]Brooks I M,Saunders C P R,Mitzeva R P,Peck S L1997 Atmos.Res.43 277
[28]Saunders C P R,Peck S L 1998 J.Geophys.Res.10313949
[29]Dendy J E 1987 SIAM J.Sci.Stat.Comput.8 673
[30]Dwyer J R 2003 Geophys.Res.Lett.30 2055
[31]Ziegler C L,Mac Gorman D R 1994 J.Atmos.Sci.51833
[32]Mac Gorman D R,Strake J M,Ziegler C L 2001 J.Appl.Meteorol.40 459
[33]Mansell E R,Ziegler C L 2013 J.Atmos.Sci.70 2032
[34]Weisman M L,Klemp J B 1982 Mon.Wea.Rev.110504
[35]Connolly P J,Saunders C P R,Gallagher M W,Bower K N,Flynn M J,Choularton T W,Whiteway J,Lawson R P 2005 Quart.J.Roy.Meteor.Soc.131 1695.
[36]Lawson R P,Baker B A,Pilson B L 2003 30th International Symposium on Remote Sensing of Environment Honolulu,Hawaii,November 10–14,2003 p707
[37]Pedernera D A,ávila E E 2018 J.Geophys.Res.1231244
[2]Saunders C P R,Keith W D,Mitzeva R P 1991 J.Geophys.Res.96 11007
[3]Li W L,Liu D X,Qie X S,Fu S M,Duan S,Chen Y C 2012 Acta Phys.Sin.61 059202(in Chinese)[李万莉,刘冬霞,郄秀书,傅慎明,段树,陈羿辰2012物理学报61059202]
[4]Fierro A O,Mansell E R,Mac Gorman D R,Ziegler C L2013 Mon.Wea.Rev.141 2390
[5]Mansell E R,Mac Gorman D R,Ziegler C L,Straka J M2005 J.Geophys.Res.110 D12101
[6]Mansell E R,Ziegler C L,Bruning E C 2010 J.Atmos.Sci.67 171
[7]Guo F X,Li Y,Huang Z C,Wang M F,Zeng F H,Lian C H,Mu Y J 2017 Sci.China:Earth Sci.60 2204
[8]Tan Y B,Liang Z W,Shi Z,Zhu J R,Guo X F 2014Sci.China:Earth Sci.57 2125
[9]Xu L T,Zhang Y J,Liu H Y,Zheng D,Wang F 2016Sci.China:Earth Sci.59 1414
[10]Zhao Y,Qie X S,Kong X Z,Zhang G S,Zhang T,Yang J,Feng G L,Zhang Q L,Wang D F 2009 Acta Phys.Sin.58 6616(in Chinese)[赵阳,郄秀书,孔祥贞,张广庶,张彤,杨静,冯桂力,张其林,王东方2009物理学报586616]
[11]Yang J,Qie X S,Wang J G,Zhao Y,Zhang Q L,Yuan T,Zhou Y J,Feng G L 2008 Acta Phys.Sin.57 1968(in Chinese)[杨静,郄秀书,王建国,赵阳,张其林,袁铁,周筠珺,冯桂力2008物理学报57 1968]
[12]Mac Gorman D R,Straka J M,Ziegler C L 2001 J.Appl.Meteor.40 459
[13]Jiang R B,Qie X S,Wang C X,Yang J,Zhang Q L,Wang J F,Liu D X 2011 Acra Phys.Sin.60 079201(in Chinese)[蒋如斌,郄秀书,王彩霞,杨静,张其林,王俊芳,刘冬霞2011物理学报60 079201]
[14]Cao D J,Qie X S,Duan S,Xuan Y J,Wang D F 2012Acta Phys.Sin.61 069202(in Chinese)[曹冬杰,郄秀书,段树,宣越建,王东方2012物理学报61 069202]
[15]Wang C X,Qie X S,Jiang R B,Yang J 2012 Acta Phys.Sin.61 039203(in Chinese)[王彩霞,郄秀书,蒋如斌,杨静2012物理学报61 039203]
[16]Wang J F,Qie X S,Lu H,Zhang J L,Yu X X,Shi F2012 Acta Phys.Sin.61 159202(in Chinese)[王俊芳,郄秀书,卢红,张吉龙,于晓霞,石峰2012物理学报61159202]
[17]Liu D X,Qie X S,Wang Z C,Wu X K,Pan L X 2013Acta Phys.Sin.62 219201(in Chinese)[刘冬霞,郄秀书,王志超,吴学珂,潘伦湘2013物理学报62 219201]
[18]Vonnegut B 1963 Meteorol.Monogr.27 24
[19]Willams E R,Lhermitte R M 1983 J.Geophys.Res.8810984
[20]Latham J,Saunders C P R 1967 J.Glaciol.6 505
[21]Saunders C P R,Wahab N M A 1975 J.Met.Soc.Japan53 121
[22]Schlamp R J,Grover S N,Pruppacher H R,Hamielec A E 1976 J.Atmos.Sci.33 1747
[23]Rawlings F 1982 Quart.J.Roy.Meteor.Soc.108 779
[24]Sun A P,Zhang Y J,Yan M H 2004 Plateau Meteorol.23 26(in Chinese)[孙安平,张义军,言穆弘2004高原气象23 26]
[25]Zhang Y J,Sun A P,Yan M H,Guo F X,Qie X S,Huang M Y 2004 Chin.J.Geophys.47 25(in Chinese)[张义军,孙安平,言穆弘,郭凤霞,郄秀书,黄美元2004地球物理学报47 25]
[26]Zhou Z M,Guo X L,Cui C G,Li X Y,Xu G R,Zhao Y C 2011 Acta Meteorol.Sin.69 830(in Chinese)[周志敏,郭学良,崔春光,李兴宇,徐桂荣,赵玉春2011气象学报69 830]
[27]Brooks I M,Saunders C P R,Mitzeva R P,Peck S L1997 Atmos.Res.43 277
[28]Saunders C P R,Peck S L 1998 J.Geophys.Res.10313949
[29]Dendy J E 1987 SIAM J.Sci.Stat.Comput.8 673
[30]Dwyer J R 2003 Geophys.Res.Lett.30 2055
[31]Ziegler C L,Mac Gorman D R 1994 J.Atmos.Sci.51833
[32]Mac Gorman D R,Strake J M,Ziegler C L 2001 J.Appl.Meteorol.40 459
[33]Mansell E R,Ziegler C L 2013 J.Atmos.Sci.70 2032
[34]Weisman M L,Klemp J B 1982 Mon.Wea.Rev.110504
[35]Connolly P J,Saunders C P R,Gallagher M W,Bower K N,Flynn M J,Choularton T W,Whiteway J,Lawson R P 2005 Quart.J.Roy.Meteor.Soc.131 1695.
[36]Lawson R P,Baker B A,Pilson B L 2003 30th International Symposium on Remote Sensing of Environment Honolulu,Hawaii,November 10–14,2003 p707
[37]Pedernera D A,ávila E E 2018 J.Geophys.Res.1231244