卷云数值模式和对流性卷云数值模拟

A CIRRUS CLOUD MODEL AND THE SIMULATIONS OF A CIRRUS CONVECTIVE CELL

本文建立了两线面对称、滞弹、非静力平衡,包含有水汽、云水、云冰、雪晶和霰五种水元间各种微物理过程的卷云模式。运用该模式对卷云对流胞的典型环境作无切变和有4×10^(-3)s^(-1)的风切变两种情况模拟表明,风切变环境下的对流较弱,但最大上升气流仍达2.71m/s。无风切变环境下卷云对流易于向两边传播,而当存在强风切变作用时,对流向上风方传播。模拟卷云的宏、微观结构及其演变特点与国外飞机穿云、卫星和地面遥感等观测结果十分一致。模拟表明卷云对流的下沉气流及下落冰粒子的蒸发冷却激发出的新的上升气流是卷云多核心结构和对流卷云向层状卷云演变的重要机制;卷云中过饱和度对冰晶核化的依赖和抑制是卷云冰晶浓度远低于FLETCHER浓度的一个主要原因。

A two-dimensional, slab-symmetry, anelastic and non-hydrostatic cirrus model was developed in which a bulk-microphysical parameterization of the moist processes among water vapor, cloud water, cloud ice crystals, snow and graupels was included. The model was very flexible for the sake of the changible domain, the stretched grid length and its applicability for various cold clouds. With the model, an idealized case of cirrus convective cell was simulated with or without environment wind shear (4×10-3s-1). The results were analysed and compared with observations. It was indicated that the macro structures (in-cloud updrafts, multi-core structure, cloud life and so on) and micro-characteristics (ice crystal concentration and supercool liquid water distribution) of the modeling cirrus were consistent with observations.