Spaceborne Insights into Wildfire-Induced Cirrus Cloud Formation

The dominant ice nucleation regime, whether homogeneous or heterogeneous, governs the microphysical structure and radiative properties of cirrus clouds. While ground-based observations demonstrate that the long-range transport of wildfire smoke can effectively trigger heterogeneous nucleation in the upper troposphere and lower stratosphere, these studies remain spatially limited. A systematic, global-scale approach is required to identify the broader impacts of smoke on cirrus occurrence and properties.

In this study, we perform a closure analysis by linking potential ice-nucleating particles (INPs) with in-cloud ice crystal number concentrations (ICNC) using spaceborne remote sensing. We retrieve potential smoke INPs from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) level 2 V4.51 data products and compare them with in-cloud ICNC derived from the DARDAR-Nice (liDAR–raDAR-Number concentration of ICE particles) product. By examining the consistency between these two independent datasets across a decade of observations, we can evaluate the extent to which wildfire smoke triggers heterogeneous ice nucleation across different latitudes and seasons. This research provides a global dataset offering the large-scale observational constraints necessary to bridge the gap between local process studies and the representation of smoke-cirrus interactions in global climate models.