Laboratory study on ice nucleation and growth mechanisms in the early stage of cirrus clouds

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K05558
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: Japan, Meteorological Research Institute
• Principal Investigator: Orikasa Narihiro 気象庁気象研究所, 気象予報研究部, 主任研究官 (50354486)
• Co-Investigator(Kenkyū-buntansha): 田尻 拓也 気象庁気象研究所, 気象予報研究部, 主任研究官 (40414510)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 氷晶発生 / 氷晶核 / 雲凝結核 / 巻雲 / ダスト粒子

Outline of Final Research Achievements

From in situ measurements of ice crystals in cirrus which has been associated with synoptic-scale disturbances, it is suggested that the ice crystals were generated from the type of in situ origin cirrus, which is characterized by the direct formation of ice with slow updraft. We speculate from the comparison between the measurements and simulation results that the ice crystals would be nucleated from heterogeneous mode only or from both heterogeneous and homogeneous modes. Based on the observations in terms of IN ability of atmospheric aerosols, their ability was lower than that of mineral dust particles. The IN ability of metal oxide particles was investigated, indicating that their ability was comparable to those of surrogates of mineral dust. Based on the observations in terms of CCN ability, the comparison of hygroscopicity suggested that the atmospheric aerosols were composed of external and/or internal mixtures of various types of aerosols which had a size dependency.

Free Research Field

気象学、雲物理学

Academic Significance and Societal Importance of the Research Achievements

対流圏上部に出現する巻雲の氷晶核形成モードや環境条件を特定するのは現在も極めて困難で限定的であるが、各種エアロゾルの物理化学特性やその氷晶核能・雲核能に関する室内実験データのほか、これまで得られた野外観測データから推察を行った。特に総観規模の擾乱で形成された巻雲は不均質核形成が卓越していることが示唆され、各種エアロゾルのうちダストのような有効な氷晶核能を持つ粒子の氷晶核能・雲核能を様々な環境条件（温度・湿度・冷却率など）で精度良く定式化することは、巻雲の発生維持の予測には重要な情報であることが分かる。