Call for Papers
American Geophysical Union (AGU) 2005 Fall Meeting
Session A 21: Mixed-Phase Clouds and Their Impact on Weather and Climate
CoSponsor: Global Environmental Change
5-9 December 2005
San Francisco, California
Abstract Submission Deadline: Thursday, 8 September 2005
For further information on the AGU 2005 Fall Meeting, please go to:
http://www.agu.org/meetings/fm05/
Dear Colleagues,
We would like to draw your attention to a special session at this year's
AGU fall meeting:
A 21: Mixed-Phase Clouds and Their Impact on Climate and Weather
Session Description:
Mixed-phase clouds are found in the polar regions and mid-latitudes
throughout the year. In the Arctic, mixed-phase stratocumulus dominate
the cloud cover through much of the year. Low-level precipitating
mixed-phase clouds have been observed to persist for weeks at a time in
the Arctic, and thus, are vitally important players in climate through
their influence on the polar energy budget and hydrologic cycle.
Long-lived mixed-phase stratocumulus are less frequently found in
mid-latitudes. Here, mixed-phase clouds are more commonly associated
with cloud systems that make our weather: winter snowstorms and
summertime convection. The properties of mixed-phase clouds result from
a complex interaction of processes representing a large range of scales.
The properties of long-lived mixed-phase arctic stratocumulus clouds are
determined by a delicate balance of cloud and aerosol microphysics,
radiative cooling, surface and large scale-moisture fluxes and
turbulence/entrainment. In deep convection, interactions between
dynamics and cloud microphysics determine the structure,
electrification, and evolution of the cloud. In winter storms, the
precipitation amount and type (e.g., freezing drizzle) is influenced by
storm dynamics (perhaps most importantly mesoscale organization),
thermodynamic, and microphysics. The properties of more quiescent
supercooled cloud layers with or without ice may be more dependent on
aerosol properties, radiative cooling, and turbulent mixing.
Despite an increase in the number of researchers studying these cloud
systems, a basic understanding of the properties and processes of these
clouds is still lacking owing to measurement difficulties and the
complexity of the microphysical processes. The goal of this session is
to survey current work related to observing (in situ and remote) and
simulating mixed-phase clouds to better understand their role in
determining weather and climate. A key aspect of these clouds, that is
not well understood, is: At what scales are these various cloud types
mixed (i.e., containing supercooled water and ice) and how does the
distribution of supercooled liquid and ice affect radiative transfer,
precipitation development, cloud electrification, and the subsequent
evolution of cloud-scale circulations and boundaries (dynamic -
outflows, thermodynamic - ice/supercooled water interface).
Papers are solicited for both poster and oral presentation in all areas
relevant to the above discussion with particular emphasis on
observational analyses and theory related to the colloidal stability of
mixed-phase clouds and understanding the scales at which supercooled
liquid water and ice coexist in nature and the laboratory as well as
studies addressing how mixed-phase clouds impact weather and climate.
Conveners:
James Pinto, NCAR/RAL
E-mail: pinto [at] ucar.edu
John Hallett, Desert Research Institute
E-mail: hallett [at] dri.edu