东亚副热带高空急流短时间尺度增强的机理研究
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摘要
本文利用中尺度非静力模式WRF输出的高时空分辨率模拟资料研究了东亚副热带高空急流(EASJ)短时间尺度强度变化特征,并结合大气运动方程解释了EASJ增强的可能机制。结果表明,在6 h时间间隔内,急流区纬向风增量的水平尺度大于2 000 km。急流轴北侧高频扰动较少,南侧出现大量高频扰动,相应地,急流轴北侧纬向风大尺度整体增强,而急流轴南侧纬向风增量正值区中还存在水平尺度为几百公里的负值区。高频扰动的周期约为1～6 h,向东传播速度为20～40 m·s-1,与惯性重力波相似。造成EASJ短时间尺度增强的主要物理因子为水平平流作用和非地转效应。水平平流项和非地转项量级相同,但变化趋势几乎相反。两者之和的量值与纬向风局地加速度项相近。此外,垂直平流作用对EASJ强度变化也有一定贡献。
In this paper,the characteristics of the short-time scale variation of the East Asian Subtropical Upper-level Jet Stream( EASJ) were studied by use of the high spatial-temporal resolution simulation data output of the nonhydrostatic mesoscale model WRF. The possible mechanism for the EASJ intensification is explained in light of the atmospheric motion equation. The results indicate that the horizontal scale of zonal wind increment is greater than 2 000 km in the 6 h time interval. Few highfrequency disturbances occur to the north side of EASJ axis, while many occur to the south.Correspondingly,the intensity of zonal wind on the north side of the EASJ axis increases in a large scale,while a negative value area with a horizontal scale of several hundred kilometers still exits in the positive value area of zonal wind increment on the south side of the EASJ axis. The period of high frequency disturbance is about 1—6 h,and the eastward propagation speed is 20—40 m·s-1,which is similar with that of the inertial gravity wave. The main physical factors that contribute to the short-term scale increase of EASJ are horizontal advection and ageostrophic effects. The magnitude of the horizontal advection term is the same as that of the ageostrophic term. However,the variation trends of those two factors arebasically opposite. The magnitude of the sum of the two is similar to the local acceleration term of the zonal wind. In addition,the vertical advection also contributes to the change in EASJ intensity.
In this paper,the characteristics of the short-time scale variation of the East Asian Subtropical Upper-level Jet Stream( EASJ) were studied by use of the high spatial-temporal resolution simulation data output of the nonhydrostatic mesoscale model WRF. The possible mechanism for the EASJ intensification is explained in light of the atmospheric motion equation. The results indicate that the horizontal scale of zonal wind increment is greater than 2 000 km in the 6 h time interval. Few highfrequency disturbances occur to the north side of EASJ axis, while many occur to the south.Correspondingly,the intensity of zonal wind on the north side of the EASJ axis increases in a large scale,while a negative value area with a horizontal scale of several hundred kilometers still exits in the positive value area of zonal wind increment on the south side of the EASJ axis. The period of high frequency disturbance is about 1—6 h,and the eastward propagation speed is 20—40 m·s-1,which is similar with that of the inertial gravity wave. The main physical factors that contribute to the short-term scale increase of EASJ are horizontal advection and ageostrophic effects. The magnitude of the horizontal advection term is the same as that of the ageostrophic term. However,the variation trends of those two factors arebasically opposite. The magnitude of the sum of the two is similar to the local acceleration term of the zonal wind. In addition,the vertical advection also contributes to the change in EASJ intensity.
引文
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[15] ZHONG Zhong,TANG Xiaozhi,LU Wei,et al. The relationship of summertime upper level jet over East Asia and the Pacific-Japan teleconnection. J. Meteor. Sci.,2015,35(6):672-683.
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[17] CHANG E K M,LEE S,SWANSON K L. Storm track dynamics.J. Climate,2002,15(15):2163-2183.
[18]覃卫坚,寿绍文,高守亭,等.一次冰雹过程的惯性重力波观测及数值模拟.地球物理学报,2010,53(5):1039-1049.QIN Weijian,SHOU Shaowen,GAO Shouting,et al. Numerical study of the dynamical mechanism of inertial gravity waves in hail storm process. Chinese Journal of Geophysics(in Chinese),2010,53(5):1039-1049.
[19]王文,程攀.“7.27”陕北暴雨数值模拟与诊断分析.大气科学学报,2013,36(2):174-183.WANG Wen,CHENG Pan. Numerical simulation and diagnostic analysis of heavy rainstorm on 27 July 2012 in North Shaanxi.Transactions of Atmospheric Sciences(in Chinese),2013,36(2):174-183.
[20]沈桐立,田永祥,葛孝贞,等.数值天气预报.北京:气象出版社,2003:82.SHEN Tongli,TIAN Yongxiang,GE Xiaozhen,et al. Numerical Weather Forecast. Beijing:China Meteorological Press(in Chinese),2003:82.
[21] SLATER T P,SCHULTZ D M,VAUGHAN G. Acceleration of near-surface strong winds in a dry,idealised extratropical cyclone.Quart. J. Roy. Meteor. Soc.,141(689):1004-1016.
[22]全美兰,刘海文,朱玉祥,等.高空急流在北京“7.21”暴雨中的动力作用.气象学报,2013,71(6):1012-1019.QUAN Meilan,LIU Haiwen,ZHU Yuxiang,et al. Study of the dynamic effects of the upper-level jet stream on the Beijing rainstorm of 21 July 2012. Acta Meteorologica Sinica(in Chinese),2013,71(6):1012-1019.
[23]孙一昕,方娟. 2010年5月6日重庆强对流过程的天气学分析.气象科学,2012,32(6):609-621.SUN Yixin,FANG Juan. Synoptic analysis of the severe convection event on 6 May 2010 in Chongqing. Journal of the Meteorological Sciences(in Chinese),2012,32(6):609-621.
[24]程胡华,钟中,岑瑾,等.估算大气重力波参数的垂直扰动廓线获取新方法.物理学报,2012,61(18):189201.CHENG Huhua,ZHONG Zhong,CEN Jin,et al. A new method of obtaining perturbation vertical profiles in estimating the atmosphere gravity wave parameters. Acta Physica Sinica(in Chinese),2012,61(18):189201.
[2] FEUDALE L,KUCHARSKI F. A common mode of variability of African and Indian monsoon rainfall at decadal timescale. Climate Dyn.,2013,41(2):243-254.
[3]字冉,管兆勇,李明刚.东亚上空急流位置经向变化及其与东亚夏季气候异常的联系.大气科学学报,2015,38(1):55-65.ZI Ran,GUAN Zhaoyong,LI Minggang. Meridional shifting of upper-level East Asian jet stream and its impacts on East Asian climate variations in boreal summer. Transactions of Atmospheric Sciences(in Chinese),2015,38(1):55-65.
[4] SUN Yuan,ZHONG Zhong,WANG Yuan. Kinetic energy budget of typhoon Yagi(2006)during its extratropical transition. Meteor.Atmos. Phys.,2012,118(1-2):65-78.
[5]陈宪,钟中,卢伟,等.东亚副热带高空急流区中尺度扰动分布特征及可能机理.地球物理学报,2014,57(8):2455-2464.CHEN Xian, ZHONG Zhong, LU Wei, et al. Distribution characteristics and the possible mechanism of mesoscale disturbance in the subtropical upper-level jet stream over East Asia. Chinese Journal of Geophysics(in Chinese),2014,57(8):2455-2464.
[6]舒斯,韩芳蓉,许建玉.一次暴雨过程中湖北西北部和东北部降水差异的成因分析.大气科学学报,2015,38(2):249-258.SHU Si, HAN Fangrong, XU Jianyu. Cause analysis of precipitation difference between Northwest and Northeast Hubei in a torrential rain process. Transactions of Atmospheric Sciences(in Chinese),2015,38(2):249-258.
[7] CHEN S C,TRENBERTH K E. Forced planetary waves in the northern hemisphere winter:wave-coupled orographic and thermal forcing. J. Atmos. Sci.,1988,45(4):682-704.
[8] REN Xuejuan,ZHANG Yaocun,XIANG Yang. Connections between wintertime jet stream variability,oceanic surface heating,and transient eddy activity in the North Pacific. J. Geophys. Res.,2008,113(D21):D21119.
[9] LIAO Zhijie,ZHANG Yaocun. Concurrent variation between the East Asian subtropical jet and polar front jet during persistent snowstorm period in 2008 winter over southern China. J. Geophys.Res.,2013,118(12):6360-6373.
[10]元慧慧,钟中,李杰,等.副热带高空急流的非地转平衡特征.大气科学学报,2011,34(4):484-489.YUAN Huihui, ZHONG Zhong, LI Jie, et al. Ageostrophic characteristics of subtropical upper-level jet. Journal of Nanjing Institute of Meteorology(in Chinese),2011,34(4):484-489.
[11]邓少格,钟中,程胡华.一次暴雨过程中重力波参数演变特征的模拟结果.地球物理学报,2012,55(6):1831-1843.DENG Shaoge, ZHONG Zhong, CHENG Huhua. Evolution characteristics of gravity-wave parameters in a simulated rainstorm process. Chinese Journal of Geophysics(in Chinese),2012,55(6):1831-1843.
[12]钟中,元慧慧,李杰,等.一次高空急流增强过程中的中尺度扰动和动量输送特征.气象科学,2010,30(5):639-645.ZHONG Zhong,YUAN Huihui,LI Jie,et al. Characteristics of the meso-scale perturbations and momentum transportation associated with an intensification process of upper-level jet.Scientia Meteorologica Sinica(in Chinese), 2010, 30(5):639-645.
[13]刘鸣彦,朱伟军,高洁,等.冬季北半球极涡强度对北太平洋风暴轴的影响.大气科学学报,2013,36(3):297-308.LIU Mingyan,ZHU Weijun,GAO Jie,et al. Effects of northern polar vortex intensity on North Pacific storm track during winter.Transactions of Atmospheric Sciences(in Chinese),2013,36(3):297-308.
[14] LI Li,ZHANG Yaocun. Effects of different configurations of the East Asian subtropical and polar front jets on precipitation during the Mei-Yu season. J. Climate,2014,27(17):6660-6672.
[15] ZHONG Zhong,TANG Xiaozhi,LU Wei,et al. The relationship of summertime upper level jet over East Asia and the Pacific-Japan teleconnection. J. Meteor. Sci.,2015,35(6):672-683.
[16] SKAMAROCK W C,KLEMP J B,DUDHIA J,et al. A description of the advanced research WRF version 3. NCAR Technical Note NCAR/TN-475+STR,2008:113-117. doi:10.5065/D68S4MVH.
[17] CHANG E K M,LEE S,SWANSON K L. Storm track dynamics.J. Climate,2002,15(15):2163-2183.
[18]覃卫坚,寿绍文,高守亭,等.一次冰雹过程的惯性重力波观测及数值模拟.地球物理学报,2010,53(5):1039-1049.QIN Weijian,SHOU Shaowen,GAO Shouting,et al. Numerical study of the dynamical mechanism of inertial gravity waves in hail storm process. Chinese Journal of Geophysics(in Chinese),2010,53(5):1039-1049.
[19]王文,程攀.“7.27”陕北暴雨数值模拟与诊断分析.大气科学学报,2013,36(2):174-183.WANG Wen,CHENG Pan. Numerical simulation and diagnostic analysis of heavy rainstorm on 27 July 2012 in North Shaanxi.Transactions of Atmospheric Sciences(in Chinese),2013,36(2):174-183.
[20]沈桐立,田永祥,葛孝贞,等.数值天气预报.北京:气象出版社,2003:82.SHEN Tongli,TIAN Yongxiang,GE Xiaozhen,et al. Numerical Weather Forecast. Beijing:China Meteorological Press(in Chinese),2003:82.
[21] SLATER T P,SCHULTZ D M,VAUGHAN G. Acceleration of near-surface strong winds in a dry,idealised extratropical cyclone.Quart. J. Roy. Meteor. Soc.,141(689):1004-1016.
[22]全美兰,刘海文,朱玉祥,等.高空急流在北京“7.21”暴雨中的动力作用.气象学报,2013,71(6):1012-1019.QUAN Meilan,LIU Haiwen,ZHU Yuxiang,et al. Study of the dynamic effects of the upper-level jet stream on the Beijing rainstorm of 21 July 2012. Acta Meteorologica Sinica(in Chinese),2013,71(6):1012-1019.
[23]孙一昕,方娟. 2010年5月6日重庆强对流过程的天气学分析.气象科学,2012,32(6):609-621.SUN Yixin,FANG Juan. Synoptic analysis of the severe convection event on 6 May 2010 in Chongqing. Journal of the Meteorological Sciences(in Chinese),2012,32(6):609-621.
[24]程胡华,钟中,岑瑾,等.估算大气重力波参数的垂直扰动廓线获取新方法.物理学报,2012,61(18):189201.CHENG Huhua,ZHONG Zhong,CEN Jin,et al. A new method of obtaining perturbation vertical profiles in estimating the atmosphere gravity wave parameters. Acta Physica Sinica(in Chinese),2012,61(18):189201.