1,1,2,4,4,5- 1Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ 85721, USA (edgardo@arizona.edu, sylvia@arizona.edu)
- 2Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, USA (sylvia@arizona.edu)
- 3School of Meteorology, The University of Oklahoma, Norman, OK, USA (fengxu@ou.edu)
- 4NASA Goddard Space Flight Center, Climate and Radiation Laboratory, Greenbelt, MD, USA (dong.l.wu@nasa.gov, jie.gong@nasa.gov)
- 5Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ, USA (meredith@optics.arizona.edu)
Ice clouds are a key component in the atmospheric system because of their influence on atmospheric circulation and precipitation. However, studying ice cloud microphysical processes and radiative impact remains a challenge, in part because ice crystal non-sphericity is not well-represented in models. Remote sensing retrievals can help constrain and characterize the ice crystal complexity within high clouds, through measurements of polarized radiance. Although both previous and current satellite instruments have used polarization measurements to achieve this goal, their spectral ranges have been limited to the shortwave (SW) (e.g., POLDER, CALIPSO, and HARP2) or microwave (e.g., GPM-GMI) ranges. Polarization has not previously been remotely sensed in the longwave infrared (LWIR) spectral range, where ice clouds exhibit strong signatures from both emission and scattering.
Development of the CHanneled Infrared Polarimeter (CHIRP) instrument aims to characterize LWIR polarized radiances from ice clouds. Here, we provide a set of LWIR polarized radiative transfer simulations for various ice cloud configurations under tropical conditions. Using a polarized Markov chain radiative transfer model, we compute the polarization difference (PD), defined as the difference between the vertically and horizontally polarized brightness temperatures, at three LWIR wavelengths (8.5, 9.5, and 10.5 µm) and for a wide range of ice cloud optical depths (τ = 0.05–20), cloud-top heights (8.5–15.5 km), view zenith angles (0–70°), effective radii (reff = 5-90 µm), and randomly oriented ice crystal habits (droxtals, plates, solid columns, bullet rosettes, and 8-column aggregates). Relatively small but distinct negative PD signatures (> -1 K, horizontal polarization) are found in ice clouds across different ice habits at τ ~ 5–7 and for the smallest and largest crystals (reff < 20 µm, reff > 40 µm). Non-negligible PD signatures also emerge at oblique viewing angles (vza = 50º–70º) and from clouds at altitudes near the tropopause. Additionally, we discuss preliminary work to run analogous parameter sweeps in the LWIR for oriented ice crystals.
How to cite: Sepúlveda Araya, E. I., Sullivan, S., Xu, F., Wu, D., Gong, J., and Kupinski, M.: Influence of Ice Crystal Morphology on Simulated Longwave Infrared Polarized Radiance of Ice Clouds, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16048, https://doi.org/10.5194/egusphere-egu26-16048, 2026.
