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气象:2021,47(9):1156-1161
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两种气象常用坐标系中涡度和散度物理意义的比较
吴洪
(中国气象局气象干部培训学院,北京 100081)
Comparison of the Vorticity and Divergence in Two Common Meteorological Coordinate Systems
WU Hong
(China Meteorological Administration Training Centre, Beijing 100081)
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投稿时间:2020-10-14    修订日期:2021-07-12
中文摘要: 气象常用的涡度、水平散度(简称散度)是天气系统、天气现象演变的重要诊断物理量。依据坐标转换的观点,分别推导出气象中常用的局地直角坐标系(“z”坐标系)和等压坐标系(“p”坐标系)中涡度之间、散度之间的关系表达式。讨论表明,在两种坐标系中,涡度、散度的定义式形式完全相同,但本质有所差异,“p”坐标系中涡度不仅表示空气微团绕天顶方向的旋转程度,还反映大气的斜压性强弱。同样,“p”坐标系中散度不仅表示空气微团水平面积的相对变化率大小程度,也反映大气的斜压性强弱。只有大气在正压状态的情况之下,“p”坐标系中涡度、散度才表示纯粹的旋转和辐散辐合。“p”坐标系中涡度、散度不仅具有大气动力特征,同时还具有大气热力特征。
Abstract:The vorticity and divergence are two basic and important diagnostic physical quantities for the evolution process of the synoptic systems and phenomena in the common meteorological coordinate systems. In this paper, the formula between the vorticity in the isobaric coordinates (“p” coordinate) and one in the local rectangular coordinates (“z” coordinate) is obtained via coordinate transformation method. So done for the divergence. The results show that the expression forms of the vorticity and the divergence are exactly same in both coordinates, but they have essential differences. The vorticity in the “p” coordinate not only indicates the rotation of the air parcel around the vertical axis, but also implies the atmospheric baroclinity. Similarly, the divergence in the “p” coordinate not only expresses the relative variable ratio of the horizontal area of the air parcel, but also indicates the atmospheric baroclinity. In the area of the front, the difference of the vorticity is very obvious in “p” coordinate and “z” coordinate, and the same difference is found for the divergence. If the atmosphere is barotropic, the vorticity in the “p” coordinate equals that in the “z” coordinate. The same is true for the divergence. The vorticity and divergence both have the dynamic and thermodynamic natures of the atmosphere in the “p” coordinate.
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引用文本:
吴洪,2021.两种气象常用坐标系中涡度和散度物理意义的比较[J].气象,47(9):1156-1161.
WU Hong,2021.Comparison of the Vorticity and Divergence in Two Common Meteorological Coordinate Systems[J].Meteor Mon,47(9):1156-1161.