Mountain-wave influence on polar stratospheric ice clouds: evidence from MIPAS–ERA5 analysis

Mountain-wave-induced temperature perturbations can locally enable the formation of polar stratospheric clouds (PSCs). We examine a decade-long (2002–2012) record of ice PSCs derived from MIPAS/Envisat measurements. The points with the smallest temperature difference (ΔT_{ice_min}) between the frost point temperature (T_ice) and the environmental temperature along the line of sight have been proposed and shown to provide a better estimate of the location of ice PSC observation from MIPAS. The temperature for the ice PSC observations is analyzed based on ERA5. Following this, we investigated the temperature history of the ice PSCs detected above T_ice at the observation points along 24 h backward trajectories.

We find that 52 % of Arctic and 26 % of Antarctic ice PSCs are detected above Tice, with pronounced clustering over mountainous terrain and in downstream regions. The backward trajectories were calculated by using the MPTRAC model,  initialized at the ΔT_{ice_min}​ locations. Analysis of the temperature evolution along these trajectories shows that the fraction of ice PSCs at a temperature above Tice along the trajectory decreases, with the strongest decrease within the 6 h before observation. Accounting for temperature fluctuations along the air-mass histories, reduces the fractions of too warm ice PSCs at observation to 33 % in the Arctic and 9 % in the Antarctic.

These results demonstrate the substantial role of orographic waves in ice PSC formation and provide observational constraints for chemistry–climate model evaluation. This contribution is based on the published analysis of Zou et al. (2024, Atmos. Chem. Phys., 24, 11759–11774, https://doi.org/10.5194/acp-24-11759-2024) .