edu.ucar.opensky::articles:12514 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T03:51:12.309712 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7mk6dps Sensitivity studies of dust ice nuclei effect on cirrus clouds with the Community Atmosphere Model CAM5 2012-12-19T00:00:00Z publication https://n2t.org/ark:/85065/d7mk6dps https://doi.org/10.5194/acp-12-12061-2012 Liu, X. author Shi, X. author Zhang, K. author Jensen, E. author Gettelman, Andrew author Barahona, D. author Nenes, A. author Lawson, P. author UCAR/NCAR - Library publisher In this study the effect of dust aerosol on upper tropospheric cirrus clouds through heterogeneous ice nucleation is investigated in the Community Atmospheric Model version 5 (CAM5) with two ice nucleation parameterizations. Both parameterizations consider homogeneous and heterogeneous nucleation and the competition between the two mechanisms in cirrus clouds, but differ significantly in the number concentration of heterogeneous ice nuclei (IN) from dust. Heterogeneous nucleation on dust aerosol reduces the occurrence frequency of homogeneous nucleation and thus the ice crystal number concentration in the Northern Hemisphere (NH) cirrus clouds compared to simulations with pure homogeneous nucleation. Global and annual mean shortwave and longwave cloud forcing are reduced by up to 2.0 ± 0.1 W m⁻² (1σ uncertainty) and 2.4 ± 0.1 W m⁻², respectively due to the presence of dust IN, with the net cloud forcing change of -0.40 ± 0.20 W m⁻². Comparison of model simulations with in situ aircraft data obtained in NH mid-latitudes suggests that homogeneous ice nucleation may play an important role in the ice nucleation at these regions with temperatures of 205-230 K. However, simulations overestimate observed ice crystal number concentrations in the tropical tropopause regions with temperatures of 190-205 K, and overestimate the frequency of occurrence of high ice crystal number concentration (> 200 L⁻¹) and underestimate the frequency of low ice crystal number concentration (< 30 L⁻¹) at NH mid-latitudes. These results highlight the importance of quantifying the number concentrations and properties of heterogeneous IN (including dust aerosol) in the upper troposphere from the global perspective. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License. None eng geoscientificInformation