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Frost flower aerosol effects on Arctic wintertime longwave cloud radiative forcing

  • Author(s): Xu, L
  • Russell, LM
  • Somerville, RCJ
  • Quinn, PK
  • et al.
Abstract

Frost flowers are clusters of highly saline ice crystals growing on newly formed sea ice or frozen lakes. Based on observations of particles derived from frost flowers in the Arctic, we formulate an observation-based parameterization of salt aerosol source function from frost flowers. The particle flux from frost flowers in winter has the order of 106 m-2 s-1 at the wind speed of 10 m s-1, but the source flux is highly localized to new sea ice regions and strongly dependent on wind speed. We have implemented this parameterization into the regional Weather Research and Forecasting model with Chemistry initialized for two wintertime scenarios. The addition of sea salt aerosol emissions from frost flowers increases averaged sea salt aerosol mass and number concentration and subsequent cloud droplet number. This change of cloud droplet number concentration increases downward longwave cloud radiative forcing through enhanced cloud optical depth and emissivity. The magnitude of this forcing of sea salt aerosols from frost flowers on clouds and radiation, however, contributes negligibly to surface warming in Barrow, Alaska, in the wintertime scenarios studied here. Key Points We evaluate a parameterization of salt aerosol from frost flowers in WRF-Chem The modeled salt explains half of the observed submicron salt aerosol Longwave cloud forcing increases but does not add to Arctic surface warming ©2013. American Geophysical Union. All Rights Reserved.

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