【摘要】 构成卷云的冰晶粒子主要呈六棱柱状和片状。Heymsfield的研究表明,卷云冰晶的粒径分布可用分段Junge分布律描述,并且Junge分布律中的参数与卷云的环境温度有关。本文着重研究了环境温度为-20—-25℃时,不同光学厚度的卷云在4种太阳辐射波长的通量反射率和透射率。文中有关粒径谱平均的单次散射参量是用近年来作者完善和改进后的六角冰晶单次散射的射线追综模式计算的;卷云的辐射传输则是用本文给出的离散累加方法求解。其次,由于冰晶粒子具有非常强的前向散射,容易导致辐射传输数值计算的病态化,本文在冰晶单次散射计算中扣除了造成相函数中强前向散射峰值的衍射场,并且在辐射传输计算中对有关冰晶单次散射参量采用δ-M等效法进行订正。最后,为研究不同环境温度下冰晶粒径分布的差异对卷云辐射特性的影响,本文也计算了环境温度为-55—-60℃的卷云通量反射率和透射率,并与-20—-25℃环境温度下的结果进行了对比讨论。更多还原

【Abstract】 The ice crystals in cirrus cloud layers are predominantly in the form of hexagonal columns and plates; and according to the investigation of Heymsfield, the size-distribution of the ice particles may be described in terms of Junge’s formula with the parameters depending on ambient temperature. The presented studies focus on the albedo and transmissivity of cirrus with different optical depth under ambient temperature of -20-25℃ at four solar radiative wavelength. With the corresponding size distribution, the single scattering of ice crystals are solved by ray-tracing method proposed by the authors previously. Next, a discretely mathematical expression of doubling principle is presented and used to compute the radiative transfer through cirrus layers. Moreover, in the radiative transfer calculation, the strong forward-peaks of scattering phase function of the ice particles are truncated by taking away the diffraction part in single scattering, and the corresponding parameters of single scattering are adjusted according to Delta-M "equivalent" method. Finally, to evaluate the impacts of size-distribution of the ice particles under diffferent ambient temperature, the radiative transfer computation is also carried out for the cirrus with ambient temperature of-55-更多还原