A comprehensive parameterization of heterogeneous ice nucleation of dust surrogate: laboratory study with hematite particles and its application to atmospheric models

Abstract

Abstract. A new heterogeneous ice nucleation parameterization that covers a wide temperature range (−36 to −78 °C) is presented. Developing and testing such an ice nucleation parameterization, which is constrained through identical experimental conditions, is important to accurately simulate the ice nucleation processes in cirrus clouds. The ice nucleation active surface-site density (ns) of hematite particles, used as a proxy for atmospheric dust particles, were derived from AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber measurements under water subsaturated conditions. These conditions were achieved by continuously changing the temperature (T) and relative humidity with respect to ice (RHice) in the chamber. Our measurements showed several different pathways to nucleate ice depending on T and RHice conditions. For instance, almost T-independent freezing was observed at −60 °C < T < −50 °C, where RHice explicitly controlled ice nucleation efficiency, while both T and RHice played roles in other two T regimes: −78 °C < T < −60 °C and −50 °C < T < −36 °C. More specifically, observations at T lower than −60 °C revealed that higher RHice was necessary to maintain a constant ns, whereas T may have played a significant role in ice nucleation at T higher than −50 °C. We implemented the new hematite-derived ns parameterization, which agrees well with previous AIDA measurements of desert dust, into two conceptual cloud models to investigate their sensitivity to the new parameterization in comparison to existing ice nucleation schemes for simulating cirrus cloud properties. Our results show that the new AIDA-based parameterization leads to an order of magnitude higher ice crystal concentrations and to an inhibition of homogeneous nucleation in lower-temperature regions. Our cloud simulation results suggest that atmospheric dust particles that form ice nuclei at lower temperatures, below −36 °C, can potentially have a stronger influence on cloud properties, such as cloud longevity and initiation, compared to previous parameterizations.

A new temperature- and humidity-dependent surface site density approach for deposition ice nucleation

“…(14) or (15) was only marginal for the temperature and humidity conditions investigated in this study. Note also that x therm as a linear function in humidity and temperature is assumed to be only strictly valid between 226 and 250 K. Other studies show that the n s isolines for deposition nucleation caused by materials such as hematite are strongly temperature dependent between 223 and 237 K, but not between 223 and 213 K (Hiranuma et al, 2014). Thus, these results suggest that different x therm or other approaches might be needed within different temperature regimes.…”

A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques

“…Hence, comparison of IN efficiencies can be readily performed for multiple types of instruments using n s parameterizations. Moreover, such time-independent and surface-area-scaled n s formulations can be further adapted to comprehensively assess ice nucleation in a wide range of atmospherically relevant temperatures and relative humidities with respect to ice (RH ice ), as was recently presented in Hiranuma et al (2014a). The n s parameterization for both immersion freezing and deposition nucleation can be directly implemented in cloud, weather and climate models to calculate the temperature-dependent abundance of INPs as a function of the aerosol surface area concentration.…”

“…Thus, a negligible size dependency of n s for "submicron" dry illite NX particles for temperatures below −27 • C was found. Previously, Hiranuma et al (2014a) demonstrated the size independence of the n s value using two different sizes of submicron hematite particles (200 and 1000 nm volume equivalent diameter) based on AIDA deposition mode nucleation experiments. Such a similarity might remain true for the immersion mode freezing of mineral dust particles that are smaller than 1 µm diameter.…”

“…The same disperser type was used at both chambers for particle generation, and the upstream cyclone impactors (D 50 ∼ 1 and 2.5 µm) were similarly deployed to filter out any larger particles and safeguard against injecting these particles into the vessel. We note that a linear correction factor of ∼ 2 was applied to convert the optical diameter measured by the welas-OPC to the APS-inferred volume equivalent di-ameter in several studies (Wagner et al, 2011;Hiranuma et al, 2014a).…”

“…Previous laboratory experiments have taken diverse approaches in an attempt to mimic ice nucleation and freezing processes. These heterogeneous ice formation processes include deposition nucleation, immersion freezing, condensation freezing, and contact freezing (Vali, 1985), inside-out contact freezing (i.e., freezing of an immersed INP in contact with the droplet surface from the inside; Durant and Shaw, 2005;Fornea et al, 2009) and surface condensation freezing (i.e., freezing of supercooled water or residual aqueous solution trapped on particle surfaces, e.g., by the inverse Kelvin effect; Christenson, 2013;Hiranuma et al, 2014a;Marcolli, 2014;Welti et al, 2014;Wex et al, 2014). Without INPs, pure cloud water droplets or solution within particles can be supercooled to below −37 • C before freezing (Koop et al, 2000;Murray et al, 2010;Rosenfeld and Woodley, 2000).…”