逸入 (气象学)

对流云周围的空气流动示意图
逸入是指大气中的扰流捕捉到附近非扰流的过程。通常用在对流发展时，附近较干气块进入对流气柱中，与湿空气混和的过程。
逸出则是与逸入相反，为对流气柱中空气离开气柱、进入环境的过程。通常发生在对流气柱的顶端。

**理论**
上图显示出不同积雨云中逸入率 ()对云内垂直温度的影响。逸入率越高，则云内温度越倾向环境温度(T)的分布。
逸入是环境中的空气与气柱里或云里的空气混和的作用，部分环境中的空气性质会进入到云内。由于逸入作用会改变云的性质，进而影响到降水、辐射...等，因此云内的逸入系数设定对气候模式的模拟影响相当大。
逸入作用可分成同质及异质混和过程。同质混和过程是一个假设云内混和作用的时间尺度小于蒸发的时间尺度的模式。这意味着当环境里的未饱和干空气在使云水蒸发之前，已有足够的时间逸入到云内，并与云内空气混和。透过同质混和过程的逸入作用，并不影响云内的云滴数量，只会使云滴的部分液态水蒸发。 与同质混和相对应的是异质混和过程，其云滴蒸发的时间尺度短于混和的时间尺度，因此云内的饱和气块会在逸入作用的区域被完全蒸发，使总云滴数量减少。
这两种模式的差距主要在于云滴粒径谱上的表现。在同质混和中，由于大、小云滴的过饱和水气压并不相同，改变了粒径分布曲线的形状，因此同质混和后的云滴粒径分布将会变窄，而异质混和则不影响云滴粒径分布。

**逸入率**
积云在大气中扮演着传输能量和水气的重要角色，也影响着地球的气候，但是在大尺度的模式当中，积云无法直接被模拟而需要参数化。逸入率的决定又牵动着积云内的性质，因此这个参数对积云参数化来说相当重要。相关的研究中以Henry Stommel为积云内逸入系数研究的先锋科学家。

**参考资料**

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 Lu C., S. Niu, Y. Liu, A. Vogelmann, 2013:  Empirical relationship between entrainment rate and microphysics in cumulus clouds date=20170202052115 . Geophys. Res. Lett., 40, 2333-2338.- Lu C., Y. Liu, and S. Niu, 2013:  A method for distinguishing and linking turbulent entrainment mixing and collision-coalescence in stratocumulus clouds. Chin. Sci. Bull., 58, 545-551.- Lu C., Y. Liu, S. Niu, A. Vogelmann, 2012:  Lateral entrainment rate in shallow cumuli: Dependence on dry air sources and probability density functions date=20170109144321 . Geophys. Res. Lett., 39, L20812. - Lu C., Y. Liu, S. Yum, S. Niu, S. Endo, 2012:  A new approach for estimating entrainment rate in cumulus clouds date=20150629052058 . Geophys. Res. Lett., 39, L04802. - Lu C., Y. Liu, and S. Niu, 2014:  Entrainment mixing parameterization in shallow cumuli and effects of secondary mixing events date=20200211052719 . Chinese Sci. Bull., 59(9), 896-903.- Lu C., Y. Liu, and S. Niu, 2011:  Examination of turbulent entrainment-mixing mechanisms using a combined approach date=20150330045614 . J. Geophys. Res., 116, D20207. - Burnet, F., and J.L. Brenguier, 2007: Observational Study of the Entrainment-Mixing Process in Warm Convective Clouds. J. Atmos. Sci., 64, 1995–2011.- Chosson, F., J.L. Brenguier, and L. Schüller, 2007: Entrainment-Mixing and Radiative Transfer Simulation in Boundary Layer Clouds. J. Atmos. Sci., 64, 2670–2682.- Hill, A.A., G. Feingold, and H. Jiang, 2009: The Influence of Entrainment and Mixing Assumption on Aerosol–Cloud Interactions in Marine Stratocumulus. J. Atmos. Sci., 66, 1450–1464.- Hicks, E., C. Pontikis, and A. Rigaud, 1990: Entrainment and Mixing Processes as Related to Droplet Growth in Warm Midlatitude and Tropical Clouds. J. Atmos. Sci., 47, 1589–1618.- Pontikis, C.A., and E.M. Hicks, 1993: Droplet Activation as Related to Entrainment and Mixing in Warm Tropical Maritime Clouds. J. Atmos. Sci., 50, 1888–1896.- Baker, B.A., 1992: Turbulent Entrainment and Mixing in Clouds: A New Observational Approach. J. Atmos. Sci., 49, 387–404.- Paluch, I.R., 1979: The Entrainment Mechanism in Colorado Cumuli. J. Atmos. Sci., 36, 2467–2478.- Baker, M., and J. Latham, 1979: The Evolution of Droplet Spectra and the Rate of Production of Embryonic Raindrops in Small Cumulus Clouds. J. Atmos. Sci., 36, 1612–1615.- Baker, M.B., R.G. Corbin, and J. Latham, 1980, The influence of entrainment on the evolution of cloud droplet spectra: I. A model of inhomogeneous mixing. Quarterly Journal of the Royal Meteorological Society, 106, 581-598.