Low‐Level Ice Clouds–Ice Fog

Abstract

Abstract Ice clouds play an important role in the hydrological cycle and climate change, and their impact on water and heat cycle is crucial depending on their macro‐ and microphysical properties. As ice fog, it also affects weather conditions such as visibility. Ice clouds and ice fog usually form at cold temperatures ( T < 0 °C), and their nucleation processes usually take place at T < −5 °C. They occur extensively at colder T . They are usually composed of only ice crystals although mixed‐phase particle can be found down to −40 °C, and below that T , droplets can freeze up spontaneously. The development of ice clouds needs some level of dynamical activity, e.g. updrafts and thermal instabilities in a lifting moist air layer. Ice fog is composed of many small particles and has less water content compared to ice clouds. Its impact on economy and on Earth's heat budget is still not understood properly. In situ observation of ice cloud and their monitoring using remote‐sensing platforms such as radar, LiDAR, and satellites can improve their predictions and help develop algorithms to retrieve their physical properties. In this article, the physical properties of ice cloud and ice fog are summarized using in situ and remote‐sensing observations, also focusing on the prediction issues related to forecast and climate models.