INVESTIGATING SOURCES OF OBSERVATION-MODEL DISAGREEMENT IN IMMERSION-MODE ICE NUCLEATING PARTICLES AT SEASONAL TIMESCALES IN E3SM

Abstract:

Modeling ice nucleating particle (INP) concentrations is important for estimating cloud phase, lifetime, radiation, and precipitation properties at regional and global scales. Over marine regions, transported dust and organic matter in sea spray aerosol contribute to INP concentrations. Recent INP observations over marine regions from Department of Energy (DOE) ARM ship- and aircraft-based campaigns have improved our understanding of INP concentrations in these regions and provide a resource for the development and evaluation of model parameterizations. In this study, we evaluate simulations of dust and sea spray aerosol by the Energy Exascale Earth System Model (E3SM), as well as the resulting model-predicted total INP number concentrations over different ocean regions. We select field campaigns that provide aerosol and INP observations for understanding the seasonal variability of sources and sinks of marine INPs. In particular, we will use measurements performed during Measurement of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) from 1 September 2017 - 30 April 2018 and Marine Ice nuclei collections (MAGIC) from 1 October 2012 – 30 September 2013 to evaluate various IN parameterizations for dust and marine organic matter INP sources. Long-term measurements and measurements in contrasting seasons are especially useful in understanding how seasonal variations in the sources and sinks of INP interact with seasonal changes in synoptic environments and airmass source regions. We examine the discrepancies between the model INP values and observations at different freezing temperatures and discuss the potential reasons for these differences in terms of uncertainties in aerosol fields in the model, missing marine INP sources, and in situ transformation of aerosols. Quantitative metrics of agreement/disagreement between INP from model and observations will be analyzed along with other variables such as meteorological fields, vertical profiles of aerosols, and cloud phase/cloud water content from the E3SM model.