刘栋,高守亭. 2003. 饱和湿大气Brunt-V3/4is3/4l3/4频率及修正的相当位温[J]. 气象学报, 61(3):379-383, doi:10.11676/qxxb2003.037
饱和湿大气Brunt-V3/4is3/4l3/4频率及修正的相当位温
THE BRUNT-VAISALA FREQUENCY IN A SATURATED ATMOSPHERE AND THE REVISED EQUIVALENT POTENTIAL TEMPERATURE
投稿时间:2002-12-20  修订日期:2003-02-19
DOI:10.11676/qxxb2003.037
中文关键词:  饱和湿空气  Brunt-V3/4is3/4l3/4频率  相当位温
英文关键词:Saturated atmosphere  Brunt-V3/4is3/4l3/4 frequency  Equivalent potential temperature
基金项目:中国科学院知识创新工程项目(KZCX3SW213及KZCX2208)
作者单位
刘栋 中国科学院大气物理研究所, 北京, 100029
中国科学院研究生院, 北京, 100039 
高守亭 中国科学院大气物理研究所, 北京, 100029 
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中文摘要:
      实际大气中受扰动的饱和气块发生凝结后,凝结水会部分脱离气块。以前研究饱和湿大气的Brunt-V3/4is3/4l3/4频率(Nm2)没有考虑凝结水的部分脱离,相当位温(θe)也忽略了饱和气块的混合比的作用。文中针对这些不足,在假设饱和空气中只存在气液转换条件下,推导出液态水部分脱离气块的、更符合实际情况的Nm2表达式和修正的饱和湿大气θe表达式。新的Nm2表达式增加了部分脱离气块的液态水的作用项,新的θe表达式中包含有饱和气块的混合比,并对有关的表达式分别作了讨论和比较。
英文摘要:
      If a parcel of air is displaced slightly upward in an unsatured atmosphere, it will cool by adiabatic expansion. If the atmosphere is saturated, upward displacements are also accompanied by condensation and latent heating. After an infinitesimal perturbation, the condensed liquid water will drop partially out of the parcel. This phenomenon was not described in the Brunt-V3/4is3/4l3/4 frequency(Nm2) in previous studies, although they have been studied in many aspects, especially in the stability reduction quantified by deriving an expression for the saturat ed Brunt-V3/4is3/4l3/4 frequency(Nm2). At the same time, deriving an expression for equivalent potential temperature(θe) in previous studies also omits a term, mixing ratio of saturated vapor in air parcel. For simplicity, we consider only liquid-vapor phase transitions during derivation. A new formula of expressing Nm2, according to an air parcel change in a saturated at mosphere, is derived, discussed, and compared with original expression. It contains an additional term: the liquid water dropping partially out of the parcel, so that the new formula of expressing Nm2 accurately describes an air parcel change in a saturated atmosphere, it is useful in theory. In Section 3, an accurate formula of expressing θe is derived under the condition that no neglecting the mixing ratio of saturated vapor. Results are estimated and compared with two other θe formulas. Results of the new equivalent potential temperature (θe) are showed the less error in middle and high at mosphere. These two revised formulas Nm2 and θe describing the stability of a saturated atmosphere are reasonably accurate and applicable for the dynamic diagnosis.
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