Testable hypotheses

1
Testable hypotheses natural ice processes

1. The nuclei for homogeneous ice nucleation are
   salt CCN
2. The nuclei for heterogeneous ice nucleation are
   salt CCN
3. In convective clouds, the greatest number of ice
   particles are produced by secondary processes
4. In convective clouds, initial ice formation
   occurs primarily at updraft edges
5. Ice formation in most convective clouds is
   produced during entrainment processes
6. Ice formation in most convective clouds is
   produced on entrained aerosols
7. Cloud electrification does not directly affect
   ice formation processes
8. Measurements of ice nuclei, cloud dynamics and
   thermodynamics can be used to predict ice
   concentrations
9. First ice forms differently in maritime versus
   continental clouds.
10. Dust events produce a major impact on the ice
    budget in affected clouds.

2
Testable hypotheses natural ice processes

1. Liquid water and primary ice nucleation are more
   transient in maritime than continental
   convection.
2. Models can accurately predict homogeneous ice
   nucleation with accurate knowledge of particle
   chemistry and thermodynamic forcing.
3. Deposition nucleation is important in
   dust-perturbed cloud environments.
4. The first initiation of ice in clouds is
   tractable to a population of nuclei whose source
   is known and can be quantified (lab and field)
5. Precipitation in most cumulus clouds ensues only
   following secondary ice formation processes that
   can also be quantified (field and modeling,
   perhaps lab).
6. Local depletion of ice forming nuclei affects
   variability of cloud water, ice and precipitation
   in layered supercooled clouds (field and
   modeling).
7. Mineral dusts are the primary source of ice
   nuclei in the atmosphere. Alternately, biological
   materials are not (lab, field).
8. Homogeneous freezing nucleation usually occurs in
   deeper convective clouds and dominates ice
   particle distributions in anvils.

3
Testable hypotheses natural ice processes

• We may need to extend hypotheses to include more
  of a climate-scale context.
• A steady stream of papers is appearing these
  days addressing the issue of cosmic ray
  modulation of precipitation and cloud cover, with
  a hand-waving attribution to "electrofreezing" as
  one of the links in the chain. We may want to
  include a hypothesis related to this area of
  work.
• .. unusual aspects are the mode of cirrus
  particle nucleation, presumably involving the
  lofting of sea salt nuclei in strong thunderstorm
  updrafts into the upper troposphere.
• The following distinct cirrus cloud ice
  nucleation and growth processes are dominated by
  the following
• homogeneous freezing of sulfate of ammonia
  droplets, probably the normal mode of midlatitude
  cirrus ice crystal production
• homogeneous freezing of aqueous sulfuric acid
  droplets in tropopause-topped cirrus, or along
  tropopause folds, apparently associated with the
  uncommon cirrus corona display
• heterogeneous freezing via biogenic and other IN
  of solution droplets through the
  condensationfreezing process, but also dependent
  on the aqueous phase chemistry
• the effect of dust on cloud properties is to
  inhibit precipitation.