Abstract
Ice nuclei are very important factors as they significantly affect the development and evolvement of convective clouds such as hail clouds. In this study, numerical simulations of hail processes in the Zhejiang Province were conducted using a mesoscale numerical model (WRF v3.4). The effects of six ice nuclei parameterization schemes on the macroscopic and microscopic structures of hail clouds were compared. The effect of the ice nuclei concentration on ground hailfall is stronger than that on ground rainfall. There were significant spatiotemporal, intensity, and distribution differences in hailfall. Changes in the ice nuclei concentration caused different changes in hydrometeors and directly affected the ice crystals, and, hence, the spatiotemporal distribution of other hydrometeors and the thermodynamic structure of clouds. An increased ice nuclei concentration raises the initial concentration of ice crystals with higher mixing ratio. In the developing and early maturation stages of hail cloud, a larger number of ice crystals competed for water vapor with increasing ice nuclei concentration. This effect prevents ice crystals from maturing into snow particles and inhibits the formation and growth of hail embryos. During later maturation stages, updraft in the cloud intensified and more supercooled water was transported above the 0°C level, benefitting the production and growth of hail particles. An increased ice nuclei concentration therefore favors the formation of hail.
Highlights
Statistics show that over 50% of mid-latitude precipitation is caused by the melting of large ice particles produced during the ice-phase transformation process; this ratio is slightly lower (∼30%) in the tropics [1]
The results showed that microphysical processes in clouds are affected by changes in the atmospheric thermodynamic environment through artificially propagating ice nuclei (IN) that can grow into ice crystals
Sensitivity tests of the IN concentration of strong convective clouds showed opposite effects. van den Heever et al [9] and Carrioet al. [10] discussed the effects of IN on strong convective clouds in Florida using the Regional Atmospheric Modeling System (RAMS), a highly versatile numerical code developed by scientists at Colorado State University to simulate and forecast meteorological phenomena [11]
Summary
Statistics show that over 50% of mid-latitude precipitation is caused by the melting of large ice particles produced during the ice-phase transformation process; this ratio is slightly lower (∼30%) in the tropics [1]. The microphysical process of ice-phase transformation in clouds plays a distinct role in the formation of precipitation particles. The results showed that microphysical processes in clouds are affected by changes in the atmospheric thermodynamic environment through artificially propagating IN that can grow into ice crystals. This affects the latent heat release rates, dynamic processes of strong convective clouds, and resultant precipitation particles [5]. [10] discussed the effects of IN on strong convective clouds in Florida using the Regional Atmospheric Modeling System (RAMS), a highly versatile numerical code developed by scientists at Colorado State University to simulate and forecast meteorological phenomena [11]. It is meaningful to use observatory IN parameterization to explore the role of IN in the development of severe precipitation
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