Development of a Polar Stratospheric Cloud Model Within the Community Earth System Model: Assessment of 2010 Antarctic Winter. Issue 19 (12th October 2017) - Zhu, Yunqian
Abstract: To simulate polar stratospheric clouds (PSCs) during the Antarctic winter of 2010, we have developed a PSC model within the Community Earth System Model framework that includes detailed microphysics of sulfuric aerosols and three types of PSCs: supercooled ternary solution (STS), nitric acid trihydrate (NAT), and ice. Our model includes two major NAT formation mechanisms, both of which are essential to reproduce the PSC and gas phase chemical features in the 2010 Antarctic winter. Homogeneous nucleation of NAT from STS produces NAT particles with sizes near 8 μm, which are important to properly simulate denitrification and the gas phase HNO3 observed by the Microwave Limb Sounder (MLS). Heterogeneous nucleation of NAT on ice particles or ice particles on NAT and subsequent evaporation of the ice produces NAT particles with sizes from submicrometers to a few micrometers. These particles account for the large backscattering ratio from NAT observed by the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations satellite, especially in the midwinter season. Adding temperature fluctuations from gravity waves is important to produce larger number density and higher backscattering ratio from ice and NAT particles. However, our model needs a better representation of waves to improve the backscattering ratio and gas phase HNO3 compared with observations. Our model also includes homogeneous nucleation of ice from STS and heterogeneous nucleation of ice on NAT. The model reproduces the gas phase H2 O during the winter within the uncertainty of the MLS observations. Key Points: The 3‐D modeling of polar stratospheric clouds simulates two size modes of NAT that are inferred over Antarctica NAT nucleated from STS produces NAT particles with sizes near 8 μm, but NAT released from ice produces small NAT particles Adding temperature fluctuations is important to produce larger number densities and higher backscattering ratios from ice and NAT particles