부산대학교 도서관

Mixed‐phase clouds (MPCs) have been identified as significant contributors to uncertainties in climate projections, attributable to model representation of processes controlling the formation and loss of supercooled water droplets and ice particles from the atmosphere. Arctic MPCs are commonly widespread and long‐lived, with sustained ice crystal formation processes that challenge current understanding. This study examines the ice‐nucleating particle (INP) reservoir dynamics governing immersion‐mode heterogeneous freezing in an observed case of Arctic MPCs using a simplified 1D aerosol‐cloud model. The model setup includes prescribed dynamical forcings and thermodynamic profiles, and represents INPs as multicomponent and polydisperse particle size distributions. Diagnostic and prognostic approaches to immersion freezing parameterization are compared, including time‐independent (singular) number‐ and surface area‐based descriptions and a time‐dependent description following classical nucleation theory (CNT). The choice of freezing parameterization defines the size of the INP reservoir. The CNT‐based description yields an orders of magnitude larger INP reservoir than the singular parameterizations, which is the dominant factor for sustained ice crystal formation. The efficiency of the freezing process and cloud cooling are of secondary importance. A diagnostic treatment neglecting INP loss is only accurate when the INP reservoir size is large and INP depletion weak. Since a larger INP reservoir sustains ice crystal formation substantially longer, and ice water path scales with ice crystal concentrations for the conditions considered, resolving the source of differences in INP reservoir dynamics due to model implementation is a high priority for advancing climate model physics. Plain Language Summary: Knowledge gaps regarding long‐lived Arctic mixed‐phase clouds, wherein supercooled droplets and ice crystals coexist, lead to significant uncertainties when assessing Earth's surface warming from increasing greenhouse gases. The longevity of such clouds, sustaining both liquid and ice crystal formation over many hours, is poorly represented across global climate models. Application of a simplified column model shows that the underlying freezing parameterization defines the number of ice‐nucleating particles (INPs) available for ice formation, termed INP reservoir in this work. A time‐dependent freezing description yields a substantially greater INP reservoir than time‐independent approaches, and therefore greater ice formation over 10 hr, whereas other factors are less important. Future work will extend to additional environmental conditions and modeling approaches. Key Points: A 1‐D model informed by a large‐eddy simulation allows detailed study of immersion ice‐nucleating particles (INPs)Stochastic immersion freezing yields a greater INP reservoir and more sustained ice formation than singular approachesThe efficiency of the freezing process and cloud cooling are of secondary importance for the sustenance of ice crystal formation [ABSTRACT FROM AUTHOR]